Oral evidence: Sealife Mortality off the North-East Coast, HC 796

Oral evidence, 25 October 2022.

Witnesses

Rachel Hartnell, Jerry Hopkinson, Trudi Wakelin and Mark Rice.

Chair

Welcome to the sitting of the EFRA Select Committee looking at this very serious issue—certainly in my part of the world—of sea life mortality off the east coast. I thank the public for their interest in this session. A lot of people have contacted the Committee with evidence. The purpose of this session is to hear that evidence, and it will be an opportunity to test the arguments and the possible causes of the mass mortality of crustaceans, and to hear about the impact on local communities. The Committee is not a scientific body, although we do have scientists as members of the Committee, so we will not be able to come to a definitive view on the cause, but at the end of the session we will consider what action we think appropriate, which may involve contacting statutory bodies, Ministers and so on. Starting with Trudi on my left, I will ask you to introduce yourself and to state your role and who you represent.

Trudi Wakelin

I am Trudi Wakelin. I am the director of Marine Planning, Licensing and Global Marine with the Marine Management Organisation. We are the body responsible for the regulation and consenting of marine development in English marine waters.

Mark Rice

My name is Mark Rice. I am deputy director for Water and Land Quality with the Environment Agency. Our role is to take out pollution investigations, and to work with our colleagues on environmental monitoring.

Rachel Hartnell

My name is Rachel Hartnell. I am a science director at CEFAS, the Centre for Environment, Fisheries and Aquaculture Science. My role here is to represent some of the science investigations.

Jerry Hopkinson

Good afternoon, everyone. My name is Jerry Hopkinson. I am the chairman of PD Ports. PD Ports is the port operator on the River Tees and the statutory harbour authority for the river and the estuary.

Chair

You are all very welcome indeed. I will start the questioning with Rachel from CEFAS. The DEFRA-led joint investigation concluded that “no single consistent causative factor was identified for the mass deaths of crabs and lobsters, although a harmful algal bloom in autumn 2021 was identified as of significance”—I think that was the word used. What evidence points to an algal bloom as the likely cause?

Rachel Hartnell

In the area at the time, there is good evidence to suggest algal blooms, plural. The first bloom, as we understand it, identified both by satellite data and through some testing in and around the areas, is proposed to be something called Karenia mikimotoi. This is a bloom that forms very large, dense blooms. It was almost certainly present in the area at the time. The data that we have showed that the bloom appeared to persist up until around about a week into the incident, whereupon the temperature of the water dropped and we believe that the bloom disappeared, potentially crashing. When such blooms crash, they can cause oxygen depletion on the sea floor, which may well have been implicated in the incident. There are at least 10 peer-reviewed publications that describe the health impacts on crustacea from blooms and it is recognised that about 22 species of harmful algae can impact crustacea. We have reviewed the literature, and worldwide, including in the UK and the south of Ireland, there are at least 23 incidents of something similar happening in the past, including one in the UK and one in the south-west of Ireland. That alone does not constitute cause, but at the same time we know in the area that there was another type of algal bloom—the type that you cannot see from satellite data but is the cause of something called diarrhetic shellfish poisoning, which is a regulated suite of toxins that we regulate for bivalve molluscs from a human health perspective. We tested impacted crabs for those toxins and we found quite high levels of the toxic compound okadaic acid in the crab tissue. We suspect that there was a large Karenia mikimotoi bloom in the area, which the evidence that we have suggests crashed around the time of the mortality.

Chair

That one is not a toxic algal bloom?

Rachel Hartnell

No, that is correct.

Chair

When it dies and falls to the bottom it causes—

Rachel Hartnell

The blooms will die as a result of perhaps a temperature drop in this case. We cannot be certain of any of this, but this is the hypothesis. When the blooms crash to the bottom of the sea, they take out the oxygen, which causes this localised anoxic condition. We postulate that, coupled with the diarrhetic shellfish poisoning toxins, okadaic acid is the most likely cause of this mass mortality event.

Chair

How closely did the area identified through satellite imagery correspond to the area where shellfish were killed?

Rachel Hartnell

The resolution of the satellite imagery very close to the shore is not perfect, but it was corresponding with the area.

Chair

Some have argued that algal blooms are unlikely to target only crustaceans, and deaths of other sea creatures would be expected. Why do you think this algal bloom mainly seemed to affect crabs and lobsters, not fish or seals or seabirds?

Rachel Hartnell

In other instances of this type that have impacted predominantly crustacea, it is theorised that other benthic life that can move away from those oxygen-depleted conditions do that. Fish swim away; the crabs and lobsters have less opportunity to do so. Here, though, we are also saying that the presence of an additional toxin from this second bloom that was in the area at the time, and I think that is what makes it unusual, had an additive impact upon those species.

Chair

Understood. We have also heard that larger algal blooms have occurred in the North Sea without causing the associated mass die-offs. Why do you think this particular algal bloom in and after September 2021 was so deadly?

Rachel Hartnell

Again, we are not certain about this and we are certainly trying to test this hypothesis at CEFAS at the moment. It is the oxygen-depleted conditions on the seabed, coupled with the presence of the toxin from the diarrhetic shellfish poisoning bloom, the okadaic acid. That is what we are focusing our work on, going forward.

Chair

Could the discolouration of the sea water picked up by the satellites be picking up, for example, material associated with the dredging of the River Tees that was washing down the coast?

Rachel Hartnell

Yes, there is certainly some uncertainty around the satellite data. From our collaboration with the Plymouth Marine Laboratory, who have a model that looks particularly for Karenia mikimotoi, the Karenia bloom is what we suspect was present here. Our colleagues at the Plymouth Marine Laboratory also corroborated this.

Barry Gardiner

Ms Hartnell, my understanding is that in September to October, the bloom reached levels of 15 micrograms per litre, but in general, isn’t it the case that a bloom is considered dangerous around 30 micrograms per litre—double that?

Rachel Hartnell

Absolutely. We do not have our readings of cells from the area at the time, so we cannot be certain of the levels, but there is certainly evidence that is consistent with a bloom. We cannot be certain about the density of it.

Barry Gardiner

I am not quite clear what your response to that question was. Is it correct that normally it would be considered dangerous at 30 micrograms per litre?

Rachel Hartnell

Yes.

Barry Gardiner

The evidence, such as we have it, shows that the blooms on this occasion may have reached up to 15 micrograms per litre.

Rachel Hartnell

We don’t have good evidence of the bloom concentration predicted at the time, because we don’t have cell counts when we predict the bloom.

Barry Gardiner

You believe that the submission from the Plymouth Marine Laboratory on that point is otiose.

Rachel Hartnell

What I would have to do for the Committee, if you do not mind, is to go back and check those data. We can submit that at a later date.

Barry Gardiner

Thank you very much; that would be helpful. The image phenomenon seemed to centre on the Tees mouth area, rather than the whole affected area—is that correct?

Rachel Hartnell

Yes, although the bloom did spread down the coast to an extent.

Barry Gardiner

You would confirm that blooms usually occur in bays or inlets, rather than in the open sea; is that correct?

Rachel Hartnell

Usually, yes.

Barry Gardiner

In this case, that is not the case.

Rachel Hartnell

Well, the weather conditions were very calm. It was very warm.

Barry Gardiner

I understand that although sea temperatures were higher than normal, blooms such as this are very rare at that time of year, and an historical record of the temperatures in the area shows that they are far below the optimal temperatures for a bloom. Is that not also correct?

Rachel Hartnell

Although you are right that this was towards the end of the bloom season, we have good evidence to suggest that there was a bloom of Karenia in the area at the time. That is consistent with the seawater temperatures, which dropped quite suddenly by around 2 degrees. It then crashed, or certainly disappeared from the satellite.

Barry Gardiner

Why was the joint investigation declared closed, given that the findings were not conclusive?

Rachel Hartnell

Is that a question for me?

Barry Gardiner

I assume you were part of the closing of the investigation, but I am very happy if anybody else feels better qualified to address it.

Rachel Hartnell

Not at all. The investigation was closed because there was no further evidence to suggest that anything else could have been causal. At the time the investigation had closed, we had been investigating for around six months. It was very difficult then to go back to that environment and test anything else.

Barry Gardiner

The findings at that stage were not conclusive, but equally you had no further evidence to proceed on.

Rachel Hartnell

On the balance of probabilities, it was felt that it was the most likely cause. As I have said, we are testing that hypothesis going forward.

Barry Gardiner

In effect, the investigation has been reopened?

Rachel Hartnell

I would not say reopened. I would say that we were testing a hypothesis.

Chair

Mark, could you maybe add to that, in terms of the extent that you were involved?

Mark Rice

The Environment Agency was involved in the initial incident response, doing the water quality sampling and supporting the investigation, yes. As we did not find evidence that water quality caused this issue, then that was handed over, in terms of investigation, to DEFRA back in December 2021, and the Environment Agency supports that investigation.

Barry Gardiner

If I could throw a curveball to Mr Hopkinson, on the BBC documentary recently, you said that, on the subject of the Orca dredger, only virgin sands from the Tees mouth were taken. Is that correct?

Jerry Hopkinson

Yes, it is.

Barry Gardiner

That is not true, is it? The sand always contained background levels of contamination even while the infamous south bank wharf was derelict. There is evidence in the document known as SLAB 5, which measured contamination levels of sediment in dredging drop zones around the country, that the highest levels were found in Tees Bay; that was last reported in 2014. It is not the case that it has always been just virgin sand, is it?

Jerry Hopkinson

While I would not claim that I was seeking some form of licence in my description of the material, what I was trying to make explicit to the viewers of the documentary was that the materials that we had picked up and taken out to the designated spoil ground were materials that, by the action of the sea, we had previously removed and repeatedly removed on the cycle of climate action, which continuously frustrates our attempts to maintain the navigable channels into and out of the port.

Chair

We are going to come back to dredging later in a future question.

Barry Gardiner

I will leave the dredging issue there, then, for you to dredge up later, Chair. Ms Hartnell, how likely is it that the further investigations that you are now doing, which are due to conclude in March of next year, are able to come up with a more definitive conclusion? Is the data that you need to draw further conclusions still available?

Rachel Hartnell

The hypothesis that we are testing through our experimental work is that the action of okadaic acid—the toxin we know was in the crabs, because we measured it—coupled with anoxic conditions on the seafloor, which we can reproduce in our laboratory, are likely to cause the clinical signs we saw in the animals at the event. We can do that experimentally. It is quite a difficult set of experiments to run, but we can test that hypothesis experimentally. Therefore, we will, I am assured, by the end of March be able to give very much greater clarity on whether or not this hypothesis—and I stress it is a hypothesis, in the absence of anything else that anyone could determine—was likely to be implicated here.

Barry Gardiner

If I can summarise, you are saying that you are creating in the laboratory a cocktail of Karenia mikimotoi and its collapse, and you are then overlaying that, or undergirding that, with the other toxin, monitoring if it has the effect that was evinced in the crustaceans.

Rachel Hartnell

Almost, but not quite; but, yes, the principle is the same. What we are doing is recreating anoxic conditions, the conditions that were modelled. If we go back to your question about the likelihood of Karenia causing the oxygen depletion via crashing, that has been modelled using previously published work. With the bloom densities, we have a predicted oxygen-depleted level at the seafloor at the time of the incident. The experimental protocol recreates that oxygen depletion condition. We do not use Karenia to absorb the oxygen from the water, but we do introduce okadaic acid and the Dinophysis toxin—these toxins that we know were there—into the animals through exposure and feeding. The answer is: yes, but we artificially deplete the oxygen in the water, rather than using a crashed algal bloom to do so.

Barry Gardiner

Is that because you are convinced that a crashed algal bloom would have no material difference on the anoxic state of the water?

Rachel Hartnell

In experimental science, you have to really try to control as many variables as possible, as I am sure you know. We are interested in anoxic conditions, so we are testing anoxic conditions.

Barry Gardiner

If an algal bloom was the chief cause, has human activity such as sewage or pollution and climate change made algal blooms more likely? Can anything be done to reduce the likelihood of further such conditions being prevalent?

Rachel Hartnell

Algal blooms are natural, but they are influenced by human activity. They are influenced by warming water temperatures, so there are potentially linkages with climate change. They are also linked to changes in nitrogen phosphate ratios in the water from eutrophication conditions, so run-off and human activity. Therefore, yes, but they are also a naturally occurring event.

Barry Gardiner

It is possible, in the circumstances that we are looking back at, that there were other factors that could have influenced the crash and the subsequent decline of the crustaceans?

Rachel Hartnell

Absolutely, but I will defer to my Environment Agency colleague with respect to potential sewage contamination, which I believe was ruled out as part of the investigation early on.

Barry Gardiner

Forgive me—no discourtesy intended to the panel—but I was due in another Select Committee three minutes ago, and I have to leave.

Robbie Moore

I want to focus a little bit on the ruled-out causes. Mark, will you pick this up to start with? Then we will come to the others. The joint investigation ruled out potential causes, including sewage, animal diseases, seismic activity, windfarms, undersea cabling, temperature fluctuations and severe storms. The report explains why diseases were ruled out but says little about the other factors. Putting aside dredging and pyridine, how confident are you about safely ruling out other causes?

Mark Rice

The Environment Agency’s job is to respond to major incidents like this. Obviously, this was a serious concern to the community, and we responded immediately to the reports of dead and dying crabs. It was a risk-based and hopefully proportionate investigation looking for a cause of pollution. That is the presumption you start with: a cause of pollution, and that you will be able to find someone who has caused that pollution and potentially take enforcement action. The water quality work indicated that we were not able to establish a cause of pollution. We looked at lots of different lines of enquiry. We looked at previous reports of pollution incidents in the area. We checked water-treatment works and associated infrastructure. We have regulated industry teams. They looked at permit compliance on Teesside with an emphasis on those sites that discharge into the Tees Estuary. We have talked about agriculture. We checked around the area to look for agriculture and other diffuse pollution sources, visual observations on the coastline to see if there was anything unusual. Odour is a good way of picking up potential chemical pollution. We also undertook a desktop type of study to identify any industrial sources of pyridine. This was once we had identified pyridine in the crab tissue. None of that indicated the levels of pollution that would cause the type of incident that occurred.

Chair

If I could interrupt briefly, are you talking about a level that would precipitate an algal bloom through eutrophication or a pollution incident, where the pollutant itself would have been toxic and caused animals to die?

Mark Rice

That is right, yes. One that would cause that kind of significant impact on the environment, yes.

Robbie Moore

You were going through potential sources there and ways in which you carried out your investigation. Did you consider potential industrial sources?

Mark Rice

Yes, we certainly did. As I said, we have a regulated industry team based up in the north-east area that regularly monitor and ensure compliance with our permits. We specifically looked into permit compliance by industry on Teesside with a focus on those sites that discharge into the estuary. We found no evidence of pollution to back up any of the issues that occurred.

Robbie Moore

From your position, what measures are in place at the moment to ensure that construction works do not pollute watercourses or, indeed, the sea? Are you confident those are sufficient?

Mark Rice

That might be something that Trudi can answer.

Trudi Wakelin

In respect of the construction that is happening terrestrially, the MMO does not have any involvement in that activity. Dredging works per se—I am conscious the Committee may wish to come back with more specific questions—is an activity that statutory harbour authorities have the ability or statutory power to undertake under their own legislation. However, there are circumstances in which conditions are placed on licences to protect water columns from impacts of surplus materials, and then consider how the dredged material is disposed of. During the time of this incident, maintenance dredging was being carried out under the port’s permissions. The licence that was regulating that work was for the disposal out to the permitted site offshore.

Robbie Moore

Is the EA reassured enough that those measures are sufficient?

Mark Rice

The EA has consulted on these issues, but our primary role is incident response and regulating onshore sources of pollution as opposed to offshore.

Robbie Moore

Rachel, do you mind if I go back to the original question? The report explains that diseases were ruled out but says very little about other factors. Putting aside dredging and pyridine, how confident are you that we can safely rule out other causes?

Rachel Hartnell

My organisation carried out testing for aquatic animal diseases and we are very confident that animal diseases can be ruled out.

Robbie Moore

Mark and Rachel, I don’t know who wants to come to this first. Have you investigated whether the deaths of other animals in the area could have been linked to these pollutants?

Chair

There was a big thing about dogs dying and people getting ill at the time, you may remember.

Rachel Hartnell

I do remember that. Previously dog deaths have been linked to algal toxins. There was no evidence to suggest that in this case any of the dogs or other animals dying were in any way associated with this event. That was backed up by veterinary evidence at the time. There were sick dogs that had not been in any way associated with the shoreline.

Robbie Moore

I know the report is obviously inconclusive, but do you think several factors could have led to what has happened, rather than just a single cause?

Rachel Hartnell

The environment is a hugely complex thing. Algal blooms are the most likely cause, but even there we are not talking about perhaps just one. We are talking about algal blooms plural, the potential for anoxic conditions on the seafloor and the cumulative effect of another toxin of which we do not know the impact upon crustacean physiology.

Robbie Moore

Mark, on the same question?

Mark Rice

Could you repeat the question?

Robbie Moore

Around multiple causes or a single source, what is your view on that?

Mark Rice

As I said, our job is to provide the data and the monitoring in terms of water quality and so on. Therefore, I do not think I am qualified to answer that.

Robbie Moore

Jerry, anything you wanted to add to those questions or any other points?

Jerry Hopkinson

No. I am happy to talk about the dredging and the mechanics of what was undertaken in due course, thank you.

Chair

Dr Neil Hudson, who is a scientist.

Dr Neil Hudson

Thank you, Chair. Can I go to Rachel Hartnell first on the potential multifactorial nature? It is very hard in science to prove definitively causation, as opposed to association. You mentioned that in the tissue samples of some of the crustaceans there were high levels of some of these algal biotoxins. Did you look at control animals, taken from fishing vessels outside this region, to see what the normal baseline was for some of these toxins and some of these other elements you were testing?

Rachel Hartnell

No. We were looking for algal toxins—specifically those indicated by the clinical signs in the animals, so neurotoxins in the first instance. In the UK, we have no baseline monitoring programme for algal toxins in crustaceans, so we do not have baseline information.

Dr Neil Hudson

In that sense, it is quite hard to compare control animals that are not showing clinical signs with animals that are showing clinical signs.

Rachel Hartnell

That is absolutely right. Therefore, we are not making that claim. What we are observing in the tests that we did on affected animals, and some animals that were not affected, is that there does seem to be high levels in affected animals. We are yet to demonstrate the statistical significance of that.

Dr Neil Hudson

In answer to my colleague, Mr Gardiner, you were saying that you are going to be testing some of these hypotheses moving forward in the laboratory.

Rachel Hartnell

Yes.

Dr Neil Hudson

In follow-up to my colleague Mr Moore’s question about the multifactorial nature, have you looked in the literature for other variables so that you can then say, in a multifactorial analysis, whether they are involved or not, or whether it is just one particular factor? You have said, “We are looking at this one. There seems to be a strong association, so our studies will close.”

Rachel Hartnell

In the first instance, we are looking at anoxic conditions and okadaic acid because there is a reasonably compelling theory that suggests that could be causal. When we get to the end of those studies we will of course publish that data, take stock and see what else we need to do.

Dr Neil Hudson

Are people working with the university sectors, and academics in this field, as well?

Rachel Hartnell

We have had a series of meetings now with our academic colleagues. Absolutely, everybody wants to get to the bottom of this. We stand ready and are collaborating with our academic partners.

Dr Neil Hudson

Thank you, that is encouraging to hear. Mr Rice, analysis based on Freedom of Information requests from the Environment Agency suggests that some crab tissue samples from affected areas contained much higher concentrations of the harmful chemical pyridine than baseline samples taken elsewhere. I have asked about baseline in terms of some of the other studies. Do you accept that analysis?

Mark Rice

We certainly carried out analysis of crab tissue. The test that we carried out was not accredited for testing crab flesh for chemicals; it was adapted from a water quality test. Therefore, essentially that test cannot be relied on to give figures on the levels of pyridine found—it just tests the absence or presence of the chemical. If you did look at the levels from the test, the levels of pyridine found in crabs in affected and non-affected areas was fairly well spread, so picking the highest and lowest tends to misrepresent the data. Yes, it is true that we certainly did identify pyridine levels in affected crabs, but the technique we used is not really designed to assess the level in the tissue.

Dr Neil Hudson

You detected levels both in the affected area but also in crustaceans sampled from areas outside the affected area. Both the experimental side and the control side had levels of pyridine, but you are not able to say that there were statistically significant higher levels in the affected area. Is that right?

Mark Rice

That is right. We found that a healthy crab from the Norfolk Wash had nearly 10 times the concentration measured in an impacted crab from Runswick. Therefore, yes, there is quite a spread in the environment of pyridine levels in crabs.

Dr Neil Hudson

You are talking one crab there?

Mark Rice

Yes.

Dr Neil Hudson

You do not have huge numbers, in terms of statistical analysis, in either the affected area or in areas where you are not seeing crustaceans showing these clinical signs, or not seeing death?

Mark Rice

That is correct, yes.

Dr Neil Hudson

I guess more work needs to be done, then. Would you conclude that?

Rachel Hartnell

Yes. Could I pick that up? I am conscious from the very beginning that when we are making really important decisions on the basis of test results, the methods that you apply should be very well validated and, if possible, accredited. That was the case for the methods in water and not, as Mark describes, for the methods that were applied to the crab tissue for pyridine testing. One of the most important elements of the CEFAS work commissioned by DEFRA post-investigation is to develop such a method for pyridine in crab tissue. Once we understand the performance characteristics of that method, we will be able to understand the variability. We will be able to apply those tests to animals that were impacted at the time, healthy animals now, and really explore what this finding—which suggests that there are levels of pyridine in crabs post-mortem—really means. That hypothesis is part of what we are testing at CEFAS, where the presence of pyridine in the tissues of these animals after death is associated with endogenous production of pyridine as part of the breakdown process, the disruption of cellular processes after death.

Dr Neil Hudson

Thank you. It is interesting that there is a slight difference between the EA and CEFAS. In the EA’s studies of pyridine, you are looking at pyridine levels in the affected area but, also, you are sampling crustaceans in different areas. With the algal biotoxins, what you have said to us is that you have sampled it in the area, but you do not have baselines outside. Is that something that CEFAS will start to look at in the future, to get a baseline in other areas?

Rachel Hartnell

Certainly, baseline information in any sort of environmental testing is really important.

Dr Neil Hudson

Thank you. Why was pyridine ruled out by the joint investigation as a potential cause of the mass mortalities, then? Is that a fair comment? Has it been ruled out, or are you still open to testing that hypothesis?

Mark Rice

In terms of Environment Agency water quality monitoring, both at the time and since, we did not detect pyridine in the water. We have not detected pyridine in the River Tees since 2018. We can detect it in extremely low levels now, down to 0.01 micrograms per litre. The highest levels we detected in the Tees was back in 2012, which was at 2.4 milligrams per litre. I suppose we did not find evidence of pyridine in our water monitoring.

Dr Neil Hudson

The low levels made you rule it out, then?

Mark Rice

That is right, yes.

Dr Neil Hudson

Would you agree with that?

Rachel Hartnell

I would. There did not appear to be any credible source of pyridine in the environment. The other thing that perhaps I could add is that the chemical properties of pyridine do not predict that it absorbs well in sediments, or that it bio-accumulates in animals.

Dr Neil Hudson

Further to that, can pyridine accumulate in sediments and damage sealife on the seafloor?

Rachel Hartnell

There is no evidence of that, to the extent that pyridine is excluded from the European Chemical Agency compounds required for bio-accumulation tests. Therefore, it is not considered at the moment—we are always mindful that new evidence can come to the fore—to be a chemical of concern.

Dr Neil Hudson

That tees me up for my final question of this section. Do you think that further research is needed to better understand the impact of pyridine on the wider ecosystem?

Rachel Hartnell

The short answer would be yes. However, perhaps one of the most interesting elements here is to understand whether or not the pyridine was produced from within the animal itself as a product of cellular breakdown processes after death, which is very interesting. If I could elaborate on that slightly, pyridine is a molecule that is in many biological processes. If we think back to our O-level biology, when we learnt about cellular respiration, pyridine nucleotides are the coenzymes that help to produce energy at the cellular level. It is possible, and predicted perhaps, that pyridine is generated to the point where we can detect it and its derivatives after death. That hypothesis is supported by the use of pyridine nucleotides as markers of post mortem.

Dr Neil Hudson

Finally, are you monitoring the presence of pyridine and also some of these algal biotoxins in animals that prey on crabs and lobsters, and other animals, in the marine ecosystem? When you pick up seals and marine mammals on strandings or in bycatch, are you monitoring both pyridine and algal biotoxins?

Rachel Hartnell

Let me take one at a time. First, there is no monitoring programme for algal biotoxins outside the official control testing for bivalve shellfish, which is a piece of UK-retained legislation. When we hear of incidences that are potentially connected with accumulation through the food chain of biotoxins, we test as part of our own investigative work.

Dr Neil Hudson

Do you test any animals—seals, dead porpoises or anything—in the area?

Rachel Hartnell

Not as part of this investigation, but we have done in the past. As I say, there is no routine monitoring outside that of bivalve shellfish. In CEFAS we do not monitor for pyridine. The development of the validated test method pointed out in that crab matrix, which is quite complex compared to water, will enable us to look further and more for that in the future.

Dr Neil Hudson

Mark, would you suggest that there could be some routine monitoring of pyridine in bycatch or in dead animals and so on?

Mark Rice

In terms of the Environment Agency’s responsibility for water quality and land-based sources of pyridine, yes, we do monitor for presence in the environment. As I said, we have not detected it in recent years in the Tees Estuary. As part of the investigation, we also looked at potential sources of pyridine from land-based sources and where it was previously discharged. Neither of those discharges are currently producing pyridine and releasing it into the environment. In terms of a regulatory role for the Environment Agency, we did that work as part of our investigation.

Dr Neil Hudson

Thank you. Back to you, Chair.

Chair

Before we move on to Rosie Duffield, you said you picked up very low levels of pyridine in 2012?

Mark Rice

yes.

Chair

How regularly do you test the water in the Tees?

Mark Rice

We have a monthly monitoring programme of water quality in the Tees.

Chair

Rachel, if you are comparing pyridine levels in a crab that has been dead for some time with pyridine levels in a crab that had been landed as a healthy crab to go into the food chain, could those two tests be seen as comparable, or could things that happen after the crab dies change the amount of chemicals in the crab?

Rachel Hartnell

The important thing here is to have a method that we can be certain about in terms of its reliability. That is really what the focus of part of the work in CEFAS is at the moment: to produce a method that is the same level and standard as those that we would use in regulatory testing, so that we can have confidence in the quantities that method returns. Once we have that, we will be able to examine freshly dead animals, long-dead animals, and animals that may or may not be environmentally contaminated. It is really about having a method where you can be as certain as possible—certainly when there is as much at stake as there is here—that we have reliability in those test results. There are really important decisions being made on the basis of those results and they need to be as robust as possible.

Chair

Thank you; that is helpful.

Rosie Duffield

This is more of a broad question to all the panel. Leaving aside pyridine, could the dredging of polluted sediment lead to death at this scale and geographical extent, as some university computer modelling has suggested?

Trudi Wakelin

Part of the process that the MMO goes through when we receive any marine licence application for dredging activity is, first, that a sample plan is required by the applicant in order to determine and agree the number, location and determinands of samples that need to be taken in order to understand the nature of the material that is proposed for disposal. We use CEFAS as our scientific advisers for that process. They refer to the OSPAR Convention, the list of chemicals for priority action, in order to identify likely chemicals of concern. They also use their knowledge of local historical industrial activity to ensure that the sampling suite is as robust as possible. Having had those samples taken and analysed, we consult again with CEFAS on the likely impacts of the volume of material—things like smothering potential, and sediment plumes that could be created—on the location of where the material is intended to be disposed of. There are a number of licensed disposal sites around the coast. Again, CEFAS holds a significant database with information from previous dredging campaigns and the likely impacts that could be felt from that. All of that is considered on a site-specific and application-specific basis, to ensure that we can be assured that the material is appropriate for disposal at sea and, also, that any potential risks or impacts from that proposed activity can be, if necessary, mitigated through licence conditions—for example, by controlling or restricting the volume of material that is placed, the location or the time of year when it is placed, and how it is spread within the disposal site.

Rosie Duffield

Thank you. Would that have included taking into account the decommissioned coke ovens that produced lots of pyridine? Going back to pyridine again for a second, would that have been a consideration?

Trudi Wakelin

As has already been said, pyridine is not on the list of chemicals of concern. As the UK is a signatory to the OSPAR Convention, we have to act within the regulatory framework in order to be consistent with how other European countries undertake the regulation of this activity. That will have been considered, and samples will have been allocated accordingly. Rachel may wish to follow up with further detail on that.

Rachel Hartnell

To be honest, I cannot give very much more detail than Trudi has provided. The licensing conditions were met. Using the weight-of-evidence approach, the conditions were met.

Rosie Duffield

Does anyone else want to come in on that one? Mark?

Mark Rice

I suppose the key point to make is that dilution, mixing and dispersion from the North Sea and tidal action, on any pollutant and any chemical, would indicate that it would have had to have been a significant release to have had this kind of impact. If it had been such, we would have identified that in our monitoring, both at the time and subsequently. As we have not, we are fairly confident that it was not a pollution source that caused this event.

Rosie Duffield

This particular event was not expected and came out of nowhere. Do you think that it will change the way that that is looked at in the future? Will there be other things taken into consideration from now on?

Trudi Wakelin

As part of our role, in order to ensure that we are enabling sustainable development, the MMO will take the “best available evidence” approach. We are extremely keen and working very closely with our regulatory colleagues, and with DEFRA, through this process to ensure that any additional evidence that comes out of this study informs future considerations. At the moment, from the “weight of evidence” approach that has been identified to date, there is no further reason to add additional controls to the dredging.

Rosie Duffield

This one is for Mark and Trudi. There seem to be conflicting reports about how polluted the Tees seabed is. Do we know much about the material at the bottom of the Tees estuary, and whether the pollution levels are high enough to cause crustaceans to die off? We have kind of covered that, but is there anything else you want to add to that—anything that perhaps has not come under consideration before?

Trudi Wakelin

There are contaminants in the River Tees. What we know from the long-term dataset—and I think we need to remember that maintenance dredging activity has been taking place in the Tees for decades; this is not a new activity—and what we can see from the trend on that long-term dataset is that, overall, the position is improving. Through natural accretion of cleaner sediments that come in and overlay historical deposits, the levels that we are now finding are reducing over time. We have also found, through more recent sampling for activity that is planned, other chemicals of concern. Dredging has been restricted, and the material has to be disposed of at licensed disposal sites on land, because it is not suitable for disposal at sea. There is that ability to take preventative action.

Mark Rice

We will continue to be an active regulator in the Tees area and ensure the very highest standards of environmental protection. We will assess all future reports and respond to those as best we can, in terms of identifying sources of pollution, and taking enforcement action if we find anything.

Rosie Duffield

The next question is for Rachel. Modelling by CEFAS suggests that any plumes of polluted material at the dredge disposal site would be relatively confined and not large enough to cause widespread death. Was any modelling done for the distribution of sediment at the dredging zone, as well as at the disposal site?

Rachel Hartnell

There was plume sediment modelling run using the TELEMAC-2D hydrodynamic model for shallow water. There were two campaigns that were examined, which were focusing on campaigns in late September using data from the MMO. These were the models. I think they were based on the assumption that the material was around about 75% silt. They used data from tidal ellipses and from the National Oceanographic Centre. The model was run for 72 hours. The results showed that the sediment plume would have moved down towards Redcar in a south easterly or southern direction. For the duration of the model, it would have remained in suspension. Yes, we saw the potential for that sediment plume to move down across the affected area.

Rosie Duffield

Jerry, local media has reported that there was some particularly intense dredging before the mass mortality event. Have you looked at whether the timings of dredging match up with the die-off of crustaceans? Also, local media have said that campaigners and fishing groups are absolutely convinced that the pyridine and the dredging were linked.As a result of this event, some fishers are saying they are going to be out of business. Have you looked at those reports in the local media, or addressed them? If you do not believe that is true, how can you reassure the fishers who we will see in a couple of panels’ time?

Jerry Hopkinson

It is a very fair question. When this die-off was initially reported, as a major business on Teesside—we are the largest employer in Redcar—we are hopefully a major driver of providential change in a region that is facing a profound socioeconomic challenge. We view this not simply as an SHA, statutory harbour authority, not simply as a business, but also as a significant player in the local community. In the immediate aftermath of the die-off, we awaited scientific evidence as to precisely what had caused it. The reason why we did so was that we knew that, in terms of the dredging that we had been undertaking, we had, throughout that period and prior to it and in the aftermath of that die-off, been doing what we call maintenance dredging. If I can just explain, we have a licence to dredge in specific areas along the River Tees to specific depths. As long as we do not stray outside those areas or go below those depths, we are licensed to remove that material. The river accretes rapidly. Consequently, we are dredging likely six days a week for quite a protracted period—probably eight to 10 hours a day, six days a week, utilising two dredges.

Chair

Is that material coming from the sea, or does it come from upriver?

Jerry Hopkinson

Both, Chair. The material that is up river is washed down ultimately from the Pennines, and that largely comprises silt. The material that is down river is washed in from the sea, and largely comprises sand. We are essentially, and certainly in the downstream area of the river, picking up material that we have previously picked up, I suspect many, many, many times, and redepositing it back on the dredge disposal site. Sorry, I will now come to your question. We were clear that we were doing nothing more than our normal maintenance dredging. I went and saw the fishermen in the first instance at Hartlepool earlier this year, late spring. It was very clear to me that that community had suffered a very significant issue. You realise any television programme is highly edited, but I expressed my real concern to the guys at that time. The chap said to me, “You brought in a super dredger. You brought in this very big super dredger and you have taken out roughly 40%, 50% of your allowed dredge volumes in the space of 10 days. We watched it. We watched this dredger at work”. The dredger that we brought in was exactly the same size as the two dredgers in our own fleet. In terms of its mechanical operation, it is exactly the same. It is a trailer suction dredger. It is, in effect, a vacuum cleaner. It has a pipe that goes down to a drag head, which empties into a hopper and is pumped into that hopper as the dredger pursues a path.

Chair

Is that the same as each of the other two, or the same as both combined?

Jerry Hopkinson

No, the same as each of the other two. For the avoidance of doubt, a similar LOA, length overall, of about 80 metres, similar beam, similar mechanical operation. The reason that we brought it in was because we had a slippage in that area of the river, and we had outage of one of the dredgers under Lloyd’s inspection. I was asked by our harbour office to sanction the disposition of this dredger, and we did so. We dispelled the myth. It is understandable that people are upset. They are looking for a cause. They are looking for something to blame. It is absolutely understandable. We dispelled the myth objectively that this was some extraordinary dredger that we had brought in. Secondly, we looked at the volumes that we had removed. We are licensed to remove the thick end of 3 million tonnes; 2.9-odd million tonnes of dredge spoil per annum, we can take out. With this dredger, we took out just short of 150,000 tonnes. We did it over a 10-day period. If we had been operating our own dredgers it would have probably taken 20 to 30 days to remove that, as we would have worked much shorter days and not a continuous period. What we also made clear to folk was that the area in which this dredger was working was approximately 2 kilometres out into the River Tees bay. It started its operation within the arms of the River Tees—the two gears that protect the river—then went out in a straight line along the channel that ships come in. We are consented, so we are permitted by statute to dredge to a depth of 15.4 metres. We dredged along that area to a depth of 14.6 metres. How do we know that? Because, first, we monitor both the route and therefore the boundaries of this dredger’s operation throughout its activity, through our harbour office and its VTS—its vehicle tracking and control systems in there—and, secondly, we surveyed the area as soon as we could get out there after the dredger had departed. I think the survey was undertaken about two weeks after the dredger had departed. The reason that the survey was delayed was because of the wave conditions that we were encountering out there, and there was simply the issue of getting the survey craft into position to take the appropriate soundings. I am sorry, that is a long-winded answer to a question. I just want to make it explicit to you how concerned we are about this, and why I personally, as the chair and leader of the business, do not believe that dredging—certainly maintenance dredging—on the River Tees, which is what we have been undertaking, is causal to this.

Rosie Duffield

Thank you for your thorough answer. Rachel, I think you wanted to come in.

Rachel Hartnell

I was going to add something about some of the pyridine modelling carried out at the time by CEFAS. I suppose this is helpful, in terms of us not really understanding how there could have been such a source of pyridine under the circumstances. We have said before that pyridine’s properties mean that it is buoyant; it floats. It is highly volatile and it is soluble. That means that it is not thought to bio-accumulate in the way that we would see with other chemicals, and it is not thought to readily absorb to sediment. That is important here. As I say, there may be other evidence that suggests that internationally the chemical agencies have got this wrong, but certainly that is the thinking at the moment. When we looked at pyridine modelling, to see how a chemical released into the environment might act, that was done at CEFAS at the time using three modelled concentrations of pyridine in the disposal site, from 100 to 10,000 litres of the chemical. The model predicted that over 40% of the compound would evaporate from the surface of the water. The rest of it would be mixed into the water column, and the enormous dilution factors made it very difficult to understand how exposure to pyridine could be singularly causal here. We are not saying that pyridine is not toxic to marine organisms, but we are saying that it is very difficult to see how we could not, with the Environment Agency tests, have picked it up in the water if it was released at the site and dispersed along the coast, as may have happened.

Chair

Even at the disposal site, let alone 25 miles away?

Rachel Hartnell

Yes.

Rosie Duffield

Just a bit more. Are all of you confident that you can rebuild relationships or trust with the fishers? We will get the chance to ask directly in the next couple of panels, but are relations at an all-time low, or do you feel that there are conversations, and that they are at least confident that you are looking at this and listening to them, and hearing their instincts or their belief in an industry that they are absolute experts in? Obviously, you are experts in it too, in your own way, but is there any way of coming together on it?

Jerry Hopkinson

I have had two long sessions with the potters, with representatives from both Hartlepool and Whitby. I absolutely get the issues that these guys have faced. I remember one of these guys, Pinkie, saying to me, “When was the last time you got paid? Because I didn’t get paid last month, and I didn’t get paid the month before.” There is no satisfaction in listening to a man say that to you. You cannot help but question your moral compass if you are going to sit in front of people and seek to mislead them. You are going to hear from one of the guys a little later. He is a guy called Stan Rennie. I would not say that we have got to know one another, but I would say that we have got to know the measure of one another. As relatively old guys in the industry, we both reflected that he cannot recollect anything like this happening in the 48 years that he has been potting off Hartlepool. While I have only been on Teesside for the last 15 years or thereabouts, I cannot remember a similar incident to this in my tenure on Teesside or, indeed, in my time in the port industry. Do I believe that maintenance dredging is the cause of this? No, I do not. Do I believe that the guys encountered an issue? Yes, I do. Have we definitively identified the cause? No. What we have identified is probabilities. Do we need to be extremely cognisant of this going forward? Yes, we certainly do. In respect of maintenance dredging, from my perspective, in terms of the governance of our business, it is absolutely imperative that we totally stick to the remit, both in terms of scope, extent and activity, that we are given under statute. It is a precious privilege, and frankly we should not abuse it. We have plans to undertake capital dredging on the river. We have a great scheme to bring liquified natural gas on to Teesside. We have a fantastic scheme to develop a deep-water container terminal in our port infrastructure. Do we need to look very, very carefully at the permits and consents? Yes, of course we do. Will we join that process? Yes, of course we will. There is absolutely no ideological or logical purpose to operating a business—and we are a successful business—that harms our environment in its operation. That would be my position on this for PD Ports.

Chair

Thanks Rosie. Geraint, we have covered one or two of the points that we discussed you raising.

Geraint Davies

I have a few points to make. Before turning to Jerry on the dredging, I would like to clear a few things up with Rachel on the science. First, can you confirm that pyridine kills crabs?

Rachel Hartnell

Pyridine in certain concentrations is toxic to crustacea.

Geraint Davies

Exactly. You will be aware of emerging evidence from Newcastle University that in very small quantities, pyridine kills crustaceans, in particular crabs and lobsters. That is correct, isn’t it, so that we are clear on this?

Rachel Hartnell

I have heard, through conversations with our academic collaborators in Newcastle and elsewhere, that that is what their results—

Geraint Davies

All right; that is all you have found out before this inquiry, when it has been all over the media—the research that they have done and the tests. You have just said you have heard something.

Rachel Hartnell

If I may, excuse me. We have had presentations from our academic colleagues on the data that they have produced so far.

Geraint Davies

Pyridine kills crabs, yes?

Rachel Hartnell

That certainly is what is being reported. What we have not seen yet—and we are very keen to do so—are the full reports of that work. Certainly, it would be very important to have a thorough peer review of that report. We are very keen to work with the academics on the work that they are doing.

Chair

That has not been published yet.

Geraint Davies

If I can go on, Chair. Secondly, as well as pyridine killing crabs, you would confirm that pyridine dissolves very quickly on contact with oxygen and water. In other words, if it is dredged up, it disperses very quickly. As Jerry mentioned, if you were to test it two weeks later, in all probability, it would no longer be there. The killer would have gone off in the night. That is correct, isn’t it?

Rachel Hartnell

I am going to defer to the Environment Agency on this, if I may, but pyridine does dissolve in water and it is volatile, so, yes, it could.

Geraint Davies

Yes, so it does dissolve in water. I will come back to you, Jerry, in a moment, but I will pursue the scientific questions with Rachel, so that we are clear. We know pyridine is toxic to crabs; we know that if it is churned up, it disappears quickly. We also know from Newcastle University, as I understand it, that they are finding pyridine 20 centimetres below the surface of the sediment. There is concern, therefore, that as you dig deeper, there will be greater concentrations from industrial waste—from coke ovens, from which it is produced. That is true, isn’t it?

Rachel Hartnell

Certainly that is what has been reported so far in the work that has happened at Newcastle, yes, and I know that we will hear more about that later on.

Geraint Davies

Turning to Jerry on the dredging side, if crabs and lobsters tend to walk along the bottom of the ocean, to a certain extent because they do not swim around like fish, and if pyridine is toxic to crabs and lobsters and is found at a 20-centimetre depth and then disappears, you have just testified that you have been digging on your maintenance at 15.4 metres, which is a much greater depth than 20 centimetres. Therefore, would you accept that, given you did your surveys two weeks after dredging, you could have churned up an enormous amount of toxic pyridine, killed enormous numbers of crabs and lobsters, come back two weeks later and said, “Where is it?” The answer is: it had dissolved.

Jerry Hopkinson

First, my apologies. You may not have understood what I said. I said that the depth that we are consented to dredge down to in that particular area where the UKD Orca was operating was 15.4 metres. You have heard the 15.4 correctly.

Geraint Davies

I think you said that you did 14.6. You were consented for 15.4, and you did 14.6 metres. I am saying that at 0.2 metres, there is pyridine being identified by widespread sampling from Newcastle University.

Jerry Hopkinson

I am genuinely not ducking the question. The answer is: I do not know. I know that the material that we took out we are permitted and consented to remove. Coincidentally—and it is coincidental to the completion of that dredge—we surveyed the area to ensure that the depths that we had achieved were what I am telling you. Shortly thereafter, sampling was undertaken by us, which was submitted through the MMO, of the dredge sediment areas, in line with our triannual sampling regime.

Geraint Davies

In that dredge sediment sampling, how much pyridine was found?

Jerry Hopkinson

I would have to defer to the scientists.

Geraint Davies

Who is that? I am not sure who we are talking about. Mark Rice, this is above your pay grade, isn’t it, this level of analysis? You just do water quality, right? I am not trying to be rude. What we want to establish is whether there are concentrations of pyridine in the dredge from coke that has been identified. As I say, Newcastle University, who are experts in this, have found it at just 20 centimetres. If there is a lot more a lot deeper, then obviously it is going to cause a lot more mass death, isn’t it? Is there any further light anyone can shed on this? No.

Chair

Who did you submit the samples to? To MMO or to the Environment Agency?

Jerry Hopkinson

The process is that the samples are gathered and tagged. There is a probity system to ensure the integrity of the samples. They go through to CEFAS or a similar governmental agency for analysis. Those results are submitted to the MMO, and we are given the green light to continue to undertake dredging.

Geraint Davies

In addition to this, my understanding is that there is some sampling—maybe you can tell us a bit more about it—from the Tees itself, but there is not sampling from the licensed dumping site. It is dumped en masse and it is not being sampled there. That is true, isn’t it?

Trudi Wakelin

The material is tested in advance of the dredging being undertaken. We also have an annual monitoring survey, where we review a selection of licensed disposal sites around the country. We tested the inner Tees disposal site in April 2021, and we also tested the outer Tees disposal site in October 2021. The April report is now published. Again, we commissioned CEFAS to undertake that survey work for us, and there were no issues of concern raised during that. The October 2021 report is not yet published, but from the draft report that we have seen, again we have found no indications of any concern about contamination levels at the disposal site.

Geraint Davies

Are you saying to us that the port authorities dredged at 14.6 metres into sediment in which Newcastle University has found pyridine at 20 centimetres; you tested it; and you have not found any pyridine? Do we have that right, so that I am not confused?

Trudi Wakelin

For the purposes of the marine licence application, the sample plan sets out the suite of determinands that are required to be tested, and pyridine is not one of those elements.

Geraint Davies

You do not test for pyridine, so it has not been tested.

Trudi Wakelin

It was not tested ahead of the incident occurring. The sediment has been tested subsequent to the incident occurring, and pyridine was not found.

Geraint Davies

Is that because it dissolves in water and it had been churned up, do you think?

Trudi Wakelin

I would have to defer to the scientists to relate the methodology to you.

Geraint Davies

Therefore, it might have been. Mark, do you have anything to say on that? It does dissolve. It just disappears after killing crabs.

Mark Rice

As I say, we undertake routine monthly surveillance of water quality in the Tees—chemicals, nutrients, dissolved oxygen, chlorophyll and phytoplankton. We have been doing that for years, and we have found no evidence of significant levels of pyridine in the environment. That is what our water-quality monitoring programme demonstrates.

Geraint Davies

The worry and the issue here is that the natural environment, namely the sea, can absorb certain amounts of pyridine in a safe way to crabs. The issue here is that if a sudden bout of dredging occurred—correct me if I am wrong, Jerry; you said that you did 150,000 tonnes in 10 days, where you would normally do it in 30 days—

Jerry Hopkinson

Yes.

Geraint Davies

Yes, you did quite a lot all at once.

Jerry Hopkinson

Twenty to 30.

Geraint Davies

The nature of pyridine is that it will come up and it can kill a lot of crabs, but if you do it more slowly, it will dissolve and it will not be problematic. The concern here is that the speed and depth at which the dredging was occurring was allowing a concentration of pyridine to occur that would lead to mass deaths in crabs. Can I ask about the specific method of dredging? In particular, do you use what is called remediation dredging, which they use in Belgium? You described something akin to it; you said it is a sort of vacuum cleaner attempt to dredge up a material that then is not allowed to dissipate. Do you also use metal fencing—the so-called curtain approach, with sheet-pile walls? The ideas is that you would have walls, and then you would have suction, and you would minimise the prospect of contamination and leakage of pyridine in particular. Do you use those methods? If not, why not?

Jerry Hopkinson

No, we do not use a method of containment around the drag head. Our view is that the amount of disturbance that this causes, in terms of the drag head across the seabed, is minimal. I am certainly more than happy to look at any containment mechanisms but, having talked to colleagues internally about this, they are satisfied that our methodology is in accord with good practice.

Geraint Davies

Finally, the dredged material that you dredge up, which has pyridine in it—is that all put on land, or is some of that simply dumped in the sea?

Jerry Hopkinson

No, the material that we are dredging up in terms of maintenance dredging goes to an offshore disposal site, which is the one mentioned by Trudi. Can I just make one other comment, please, in answer to your suggestion that this intense operation, which replaced an activity that probably would have taken 20 to 30 days for us to undertake, was somehow causal to this? While I would not suggest to the Committee that we are bringing in a dredger to supplant the operation of our own dredgers on a regular basis, it is by no means an irregular activity to bring in dredge support to undertake dredging where we have had significant slippage in the river channels into the River Tees. I can supply the Committee with further information with regard to precisely when we have done this in the past. I would ask you to reflect on my earlier assertion that, in my 48 years undertaking maintenance dredging in accord with the methodology that I have described—without the added sophistication that you have alluded to, but in accord with what we believe to be good practice—we have not had an issue like this on the River Tees. That is why I continue to assert that the maintenance dredging operation on the River Tees has not been causal to this incident. It is coincidental that the dredger arrived at a time when these crustacean mortalities occurred, but frankly I think that we are looking in the wrong direction.

Geraint Davies

So that I am clear here, you do accept that pyridine is toxic to crustaceans, that there is pyridine in the sediment, that it was quickly churned up, and that it dissipates? Are you asserting here that there is no relationship between the dredging up of pyridine and the death of crabs, on the basis that crabs did not die before, so they cannot be dying now?

Jerry Hopkinson

I am asserting that, in terms of the maintenance dredging that we are undertaking, we have done nothing different from what we have been doing for the last 40 to 50 years on the River Tees without these issues occurring.

Geraint Davies

Sorry, I am a bit confused. I thought you said that you did 30 days of work in 10 days—150,000 tonnes. That is different, isn’t it? I am asserting that because pyridine dissipates, if that concentration of work generated an extra concentration of pyridine, that might have tipped it over into a mass-death situation. Something that you were doing differently could explain that. That is true. I know you are saying that it could not, but that is true, isn’t it?

Jerry Hopkinson

I am not going to say, “No, it could not.” This type of relatively intense dredging was not a one-off occurrence. We will have done this many times over the last 40 or 50 years. The issues that we have encountered, in terms of the mortality of crustaceans, have not previously been experienced.

Geraint Davies

In light of what has happened, do you think that there is a case for a precautionary principle from you, namely for doing slower dredging, and for having more mitigation—steel shields or whatever—and using remediation dredging? I know you said that you had looked at it before, but in light of what has happened and the emerging science, do you think that it would be reasonable, from a precautionary point of view, to now do things a bit more slowly and take a more proactive precautionary approach?

Jerry Hopkinson

I think that we are extremely proactive as an organisation. With great respect, I don’t think the Committee should form a view that this is an organisation that does not care about the environment, does not care about the impact that our activities have on people, and does not constantly review the operating methodology that we are following. Can I just illustrate that?

Geraint Davies

I am sure you do care. I am suggesting that you should do more in light of what has happened.

Jerry Hopkinson

Thank you. Can I give you an illustration of that, which is a piece of best practice that we have adopted in the past few years?

Geraint Davies

We are probably running short of time. I am sure there is lots; I am just wondering if you could do a bit more best practice in these things that I have just mentioned in light of what has happened.

Jerry Hopkinson

Sure, we will continue to—

Geraint Davies

Finally, because the Chair will tell me to shut up in a minute, can I ask Rachel a question? There has been a theory put forward that this is an algae bloom killing crustaceans. I accept that algae bloom does cause the death of crustaceans. What has also been said is that a sufficient reason for the deaths could be pyridine. Assuming both of those were true, if there was a conjunction of those two impacts at the same time, would that help explain the level of death that we have seen?

Rachel Hartnell

It is difficult to say. I would draw attention to the huge spatial extent of the impacted area, which is interesting in terms of the pyridine hypothesis, as is the duration over which this very regrettable incident appeared to take place. It was probably over two months plus that we saw animals dying. We do not have evidence of a point source of pyridine that was identifiable in the environment from the EA’s testing. We know the chemical properties of pyridine from the European Chemicals Agency; I will not repeat them now. If pyridine is in the environment at levels that could be toxic to animals—recognising that it is not thought to bio-accumulate, so the crabs would have to be almost actively seeking it out—it is difficult for it to persist for long enough over a wide enough spatial extent to be plausibly linked to the incident.

Geraint Davies

We are not talking about persistence here. We are talking about an explosion of pyridine through dredging. It suddenly gets into the ecosystem, into crabs and lobsters, which then die. We are not talking about a complexity here. That is possible, isn’t it—in fact, very probable?

Rachel Hartnell

I do not have evidence to suggest that it is not possible, no.

Geraint Davies

You do not have evidence that it is not possible. I will leave it there. Case closed.

Chair

On concentration, given that pyridine dissolves, as we have heard, if pyridine were killing crabs 25 miles down the coast, what were the concentration levels likely to be at the dumping point of the dredged material, the dilution?

Rachel Hartnell

I would have to get back to you with a modelled number, but they would have been very high.

Mark Rice

It is worth pointing out that we will be doing additional water-quality sampling around the proposed dredge areas between October and December this year, so we will have a better picture of additional monitoring in response to what has happened.

Geraint Davies

Sorry, but isn’t it the problem that pyridine just sort of leaves the scene of the crime? This is the point about it, isn’t it? If you do your monitoring now of what happened months ago, obviously it will not be there anymore. The issue is what the concentration was at the time of deep dredging on an enormous scale that tipped the balance, in terms of the life expectancy of the concentration. I will leave it there, Chair.

Chair

Thank you. This is the last section with this panel.

Ian Byrne

I want to pick up on something Jerry mentioned about the economic driving factors behind the freeport. I have been on this Committee since 2019, since I got elected, and I have never had so many e-mails from the north-east—the region of concern on this topic. In a lot of the e-mails, the writer feels that the economic and political capital invested in the freeport agenda by certain leaders means that the environmental impact is now a secondary consideration to the rolling out of this project. Is that a fair analysis?

Jerry Hopkinson

I have read very similar articles, Ian, and I have reflected on this quite a lot. I am answering your question as a layperson. I am not a politician. I am an apolitical guy running a business. I know how important the levelling-up agenda has been to people living in the north-east, irrespective of which side of the political divide you sit on. I know the levels of expectation on Teesside have been enormous. I know that the freeport has been projected as a panacea in many ways. You may know that I have gone on both national and local media to say that the evolution of a freeport on Teesside is definitely no silver bullet for the region. As for the suggestion that some kind of collusion has taken place to suppress this issue, on the basis that it could be damaging to a Government agenda, with great respect to my professional colleagues sitting here, that does huge injustice to a lot of very earnest scientists and environmental specialists.

Ian Byrne

There has been a shutting down of evidence. The next panel will be coming along. When they say, in their learned manner, what their research is, it is shut down. People are looking at that as purely political. That is not a good place to be, because if there is evidence, it needs to be accepted. Regardless of where you are with the freeport agenda, we have to protect the environment. I am not casting aspersions on the panel. I am just saying that in my e-mails, there are lots and lots of people who believe that it is this agenda and nothing else matters.

Jerry Hopkinson

Yes, but, Ian, common sense leads me to question this. Bear in mind the whistleblowing policies across the Civil Service and across a business like mine; in my business, there is direct recourse to my owner in Canada. If people feel that they are being coerced or doing something wrong—

Ian Byrne

They would come out and say it?

Jerry Hopkinson

They do. I think so.

Ian Byrne

Thanks very much for that answer. Trudi, how can we be sure that future capital dredging works, particularly for the new freeport on the south bank at Teesside, are safe? For people watching, they have probably been blinded by science in the last hour. What is the difference between maintenance and capital dredging?

Trudi Wakelin

First it is important to remember that the dredging that was undertaken at the time of this incident was maintenance dredging that was not connected to the freeport development. The freeport development was only consented to subsequent to that incident. It is also important to remember that the Marine Management Organisation is a non-departmental body specifically set up to ensure independence around the regulation for marine development. To go back to Ms Duffield’s question relating to relationships, the Marine Management Organisation also has a role as England’s fisheries manager. We work day in, day out managing the activities of fishermen and it is of absolute imperative urgency to us that we understand what has taken place here—indeed, as it is for the whole of the DEFRA group—which is why the investigation was set up and why everybody has worked so hard and so collaboratively to try to understand what is happening here. We all have a role in protecting the marine environment. On the difference between maintenance and capital dredging, to put it simply—because I am not a scientist; I am an engineer by background—in the approaches to a port through the navigable channel, or indeed the berths within a port, there is an accepted depth that needs to be maintained for safe navigation. There must be under-keel clearance, so that, at all states of the tide, vessels can access the port. As the term “maintenance” implies, that level is set. Because of the natural accretion that takes place, both from upriver sources and the sea, those berths—which tend to be slightly deeper than the surrounding area, the berth pockets—need to be regularly maintenance dredged in order to ensure that that depth is maintained. That tends to be the cleaner deposit material that is coming in; the underlying bed is not impacted or affected. As for capital dredging, there are two definitions that we use. It is any dredging that has not been undertaken in the last 10 years, and so cannot be claimed to be routine; and any dredging that increases the overall depth of the approach channel or of the berth pocket. The regulation that is in place to look at capital dredging, therefore, is more thorough. We would look very carefully again at what likely determinands might be required to be sampled, given the historic nature of potential contamination from industries that might have taken place. That would influence the sample plan that the applicant would need to submit and comply with in order for us to be reassured that that material would not be harmful and could be disposed of to licensed disposal facilities at sea. As I mentioned, the OSPAR Convention is the oversight body that looks at material disposed of at sea for the whole of the North Atlantic and the signatories to it. The UK is a signatory to that; accordingly, we have to be compliant and consistent with regulation that is imposed. We also have to provide returns to OSPAR on a six-monthly basis that set out what has been done, where and in what volumes, so that that data can be collected. As part of the sampling process, if any material or any of the samples that are taken exceed what are termed action levels, that prompts further consideration. There are two action levels that are used, not for the full suite of determinands. The first one is action level 1: “This is of concern; we need to consider whether or not it is appropriate in the local environment”. That is where some of the site-specific consideration comes in. Action level 2 would be, “This is too high. It cannot be permitted to go to sea”. That does not mean that it cannot be dredged, but in those circumstances, refusal to dispose of the material at sea results in the need for the material to be taken and disposed of at a licensed disposal facility onshore, which then moves into the terrestrial regulatory regime. That is what is happening at the moment with material that is being dredged.

Ian Byrne

That sounds very comprehensive and exceedingly professional, but we have heard in the last hour and a half undcertainty about what the causes of this could be. You touched on the fact that you had not tested for pyridine, and now you do. Is what is happening here making you review what you are reviewing and what you are testing for? I am worried that nobody knows here what has happened. We will have another panel saying a different thing in a minute, and it has been debunked by Rachel to a degree. My worry is: can we definitively say, with all the uncertainty, that capital dredging is safe in that area?

Trudi Wakelin

With the best available evidence that we currently have, my answer is: yes, it is safe in that area. However, as we have said, we continue to follow up on these lines of inquiry that have been exposed through the work that has been done to date. We are very happy to collaborate on the work being undertaken by the academics, and to share the data that we all hold, so that we can determine whether changes are required, whether to the regulatory framework, the protection, or the action levels required.

Ian Byrne

That is a partial answer, I suppose. You touched on this: there are lots of concerns about dredged material from the south bank escaping back into the Tees. What controls are you putting in place to prevent this, and how will this material be disposed of in the future? Again, there is uncertainty about what is in that material and what it could potentially do to the marine environment, which you have already said it is your priority to protect. How are we going to ensure that that happens?

Trudi Wakelin

There are a number of licensing conditions that are applied to the consent that has been granted to the applicants. As I have said, they control the volume and the location of disposal, where material can be dredged from for disposal at sea, and where it cannot. Our compliance and enforcement local staff monitor the dredging to ensure compliance with those conditions.

Ian Byrne

is that in real time? Obviously, Geraint’s line of questioning was about the instantaneous disappearance. Are we ensuring, with this uncertainty about how long pyridine stays within the water, that we are actually monitoring it?

Trudi Wakelin

For the incident that occurred last year, as part of the DEFRA-led investigation, we reviewed the activity that had been undertaken in order to ensure compliance retrospectively. In the current works, we are working very closely with the contractors so that we know what they are doing and when they are doing it. They are supporting us with the monitoring that we are undertaking, and we are inspecting both the dredging activity and the disposal activity.

Ian Byrne

This is for dredging now, is it?

Trudi Wakelin

Yes.

Ian Byrne

It has been a long session. Jerry, as regards the uncertainty, we know that there are councils that have called for a halt to the capital dredging until we get more evidence and until we get a clear understanding of what has happened. Should a ban on dredging be put in place until we have absolute certainty of what has happened? I mean capital dredging. What are your thoughts on that, Jerry?

Jerry Hopkinson

As Trudi has said, there are processes that these guys are being statutorily forced to follow, in respect of the grab of the material in an enclosed bucket, the movement of the material on to land, and the disposal on land. They also have to stick within the curtilage of the dredge area. As long as they are following those rigorously—I have absolutely no reason to suggest that they are not—I think is questionable. We need a very definitive view as to why it should be stopped. The crustacean die-off did not occur when these guys were undertaking dredging on south bank. There was no dredging activity taking place at that time.

Ian Byrne

When did that start?

Jerry Hopkinson

A couple of months ago.

Ian Byrne

September?

Jerry Hopkinson

Yes, it would be about then.

Ian Byrne

So we are still assessing any impacts?

Jerry Hopkinson

Yes.

Ian Byrne

To finish, what do you see as the main weakness in the dredging arguments that we should put to the next panel? Is there anything that you want me to bring forward to the next panel? That is probably for Trudi and Jerry to finish. If there are not, that is fine.

Trudi Wakelin

No, nothing from me, thank you.

Jerry Hopkinson

I have already told the Committee the historical nature of this, and set out the continuity of the activity that we are undertaking. I realise that I could not give examples of the improvements that we have made, but they are improvements.

Ian Byrne

You can put that in writing, Jerry.

Jerry Hopkinson

I can do, by all means. Thank you very much.

Geraint Davies

Can I ask one very short question?

Chair

We are up against time, because we have overrun by about half an hour already. If it is a short yes-no question.

Geraint Davies

It is a factual question. Jerry, you say the history of dredging has not caused problems. As we move towards the freeport, is the dredging activity going to increase significantly and therefore, in my mind, increase the risk?

Jerry Hopkinson

You ask a great question. The short answer to that is that there will be a peak in the activity that is ongoing at the moment, which is the capital dredging that Trudi has alluded to. Once that capital dredging is undertaken, then we are into maintenance dredging to maintain the navigable channels into and out of the freeport. I think that there could be a minor increase in terms of volumetric amount withdrawn annually. If you asked me to make a guess, I would say circa 100,000 tonnes of material, which is a big number, but it is set within the context of 3 million tonnes.

Geraint Davies

Increase?

Jerry Hopkinson

Yes. Depending on how successful this is, if the freeport, in particular in terms of the offshore wind sector that south bank is focused on, can get some of these big contracts, there could be an increase. These vessels are fairly big and often can be quite deep in terms of the draught. However, this will not be a seismic shift in the volumes that we would anticipate having to dredge. Does that answer your question?

Geraint Davies

Yes.

Chair

Are there any final points any member of the panel wants to make before we finish this session?

Rachel Hartnell

Thank you so much for all your time this afternoon. I want to add one last thing on pyridine, which is being now spoken about as the cause here. We talked at the very beginning about the uncertainty of the test results and, Dr Hudson, you indicated the small sample sizes of the animals that were tested at the Environment Agency initially. I would like to say again that, even with the uncertainty of the test method, pyridine was found, within the range of affected animals, in animals from outside of the site. It is curious that we were able to find evidence of pyridine in animals that were apparently unaffected and a very long way away from the Tees. I just wanted to draw the panel’s attention to that.

Chair

Understood. Thank you for putting that on the record. I thank the panel. This has taken longer than we anticipated, but that is no bad thing, It involves my constituents in Whitby, and it is important that we test the evidence and get as much information as possible. Thank you very much indeed. Examination of witnesses

Witnesses

Dr Gary Caldwell, Dr Rodney Forster and Tim Deere Jones.

Chair

Welcome to our second panel. We have two witnesses here in person and one online. Mr Deere-Jones, can I check that you can hear us and we can hear you?

Tim Deere-Jones

Yes, I can hear you. Can you hear me?

Chair

We can. Wonderful. Can I ask our witnesses to introduce themselves and say what their role is in this matter, maybe starting with Mr Deere-Jones, who has already spoken briefly?

Tim Deere-Jones

Hello. Nice to meet you all, Committee members. I am a marine pollution consultant. I sent a CV, of sorts.

Chair

Yes. We are broadcasting this and not everybody watching will have read the CV.

Tim Deere-Jones

I have been working as a marine pollution consultant since the 1980s. I trained at Cardiff University, where I did a modular degree in maritime sciences, which was aimed at producing managers of marine pollution incidents. I am not a biological chemist or a chemical analyst but I will admit to being a generalist. I was taught research methods as part of my degree course, and there I am. I have a long history of working in the marine environment on pollution issues and a number of dredging issues to boot. Joe Redfern of the Whitby Commercial Fishing Association contacted me in the autumn of 2021 on the basis of having read a document of mine that was lodged in one of the local libraries, where I had done a review of the available data on Tees pollution back in 2007, at which stage it was recognised as possibly the most polluted estuary in England. That is me.

Chair

We will come on to that during the evidence, I am sure. Thanks for that introduction.

Dr Caldwell

Good afternoon. Thank you for the opportunity to speak to you today. My name is Dr Gary Caldwell; I am a senior lecturer in applied marine biology at Newcastle University, where I have been working for the last 18 years. To put my credentials on the table, my specialisms are in marine ecotoxicology, marine poisons and venoms, and naturally occurring toxins. I have a long history of working in the marine systems, and in understanding the nature and risk of toxicity that human activities pose to it.

Chair

I am a science alumnus of Newcastle University, so you are doubly welcome.

Dr Forster

Thank you to the Committee for inviting me to give evidence. Rodney Forster, director of the Hull Marine Laboratory at the University of Hull. My role in this inter-university co-operation, which also includes the universities of York and Durham, who could not be with us, is looking at the algal bloom hypothesis and reworking and looking back at the original images. That is one part of the work. Another is that, with a little bit of funding from the Fishmongers’ Company, we will start fieldwork this year in 2022 out in the North Sea to try to increase our understanding of the north-east coastal system.

Chair

Thanks very much. If you agree with the evidence that one of your colleagues has given in this session, do not be frightened to say, “I agree with him” and move on. We heard in the first session that the joint investigation led by DEFRA concluded that an algal bloom was the likely cause. Do you accept that an algal bloom may have played a role? If so, how central a role? Dr Forster might be the best person to start with.

Dr Forster

Yes and no. Some of my work supports those ideas and some of it contradicts it. First I should say that the number one cause of shellfish mortality events globally is generally algal blooms—red tides—often associated with low-oxygen events, but also with direct toxicity. That is probably the main cause, and that is an indication that we should be looking in this direction. Where I came into the investigation, we saw the first draft of the report from CEFAS and the Environment Agency around about March or April of this year. The first thing that I noticed was that they had a map of chlorophyll concentrations from September last year.

Chair

Was this the Plymouth University satellite image?

Dr Forster

Plymouth was mentioned. I think that came in later on. I looked at the satellite images, and the chlorophyll concentrations were in my view higher than I would expect on the north-east coast. The other thing was that the period just before the event, up until 6 October, was very cloudy, so the satellite image database is not very good. Bear that in mind. It is not a comprehensive view of what has happened. We need clear skies to see the sea surface.

Chair

It is sometimes difficult with these images; when somebody has drawn a line around it, it is hard to tell if it is definitively as clear as is suggested by the line.

Dr Forster

I have gone back to the same information, which is from the Sentinel-3 satellite; it is a European satellite, very high quality and reliable. I have worked with it for quite a long time, and it is the best of the Plymouth and the CEFAS work as well. Through the month of August 2021, we have a very settled situation. It was quite a warm month with very, very low chlorophyll, no sign of any blooms, and I am looking down the north-east coast from about Lindisfarne, Holy Island, south to Scarborough. That is the zone that I am calling the north-east coast. There is no indication of any algal blooms in the first week of September. When we get into the middle of September, there are starts of indications of blooms developing, particularly in the south of the Tees area. In the third week in September there is a distinguishable bloom, not at very high concentrations—not the levels that we talked about, of 15 micrograms per litre. It was probably something up to about 3 or 4 micrograms of chlorophyll, but definite enough to be a bloom of something two weeks before the event. After that it starts to get quite cloudy. There is a major storm on 6 October that brings the material to the shore. That is the reason for the wash-up events, which most of us are quite used to working with. I should say something about wash-ups in general later on, because I did not think much of this, because wash-ups are quite common. Even after that, there was a lot of sediment in the water. You have heard that sediment and chlorophyll in the water compete optically, so it gets more difficult to pick up the situation into October; there are not so many satellite images. However, I am quite confident that throughout September we have enough. I do weekly averaging of the available satellite scenes, and you can see the development of a small bloom.

Chair

The evidence indicates there was a bloom, and it could have crashed, and the dead algae could have sunk to the bottom?

Dr Forster

That is normally what happens. Where I disagree is that it was a large Karenia bloom; I do not think it was. I provided, years ago, some of the field data that feeds into Peter Miller at PML. He is the one who developed the Karenia algorithm on the North Sea. Karenia blooms are quite spectacular events. They dominate, for instance, the western part of the English Channel. In summertime, you get large Karenia blooms easily detectable from space. They are common down the north-east coast in England, particularly in August. Off the Scottish coast, they occur from Aberdeen down to the border. They are quite noticeable events. There is not one off the Tees in September; I am quite sure about that. The chlorophyll levels—well, there might be, but it is not a big bloom.

Chair

Thank you. Dr Caldwell.

Dr Caldwell

Am I answering the same question on the algal bloom?

Chair

Do you think the algal bloom could have been associated with the mass shellfish mortality?

Dr Caldwell

As my colleague was saying, algal blooms are a natural part of the rhythm of the seas at that time of year. It is very common in our temperate seas that you will have large blooms in the springtime and a smaller secondary bloom in the autumn. What we are seeing here in terms of the presence of blooms is entirely expected in the normal pattern of the behaviour of life in the sea. At no point has anyone contested the fact that there was evidence suggesting there was a bloom there. Definitely not; the evidence is clear. There was certainly evidence of a bloom there, but that is pretty much all that can be said about the nature of the bloom. There is evidence that a bloom was there. As CEFAS said earlier, there were no cell counts and there is an awful lot of inference, and I would be very cautious about making definitive conclusions based upon inference. The North Sea system is categorically a stressed system. There are many stressors acting upon it, among them algal blooms, variable oxygen levels and changes in temperature. That is compounded by additional stressors brought about by human activities, whether it is discharge of sewage or potential pollution caused through dredging. All these systems have a certain level of tolerance to them. With anything in life, if you exceed the tolerance of a system, it will break. What we are seeing here is an event that occurred in the autumn of 2021 that caused that system’s tolerance to break, and not just break but break spectacularly. We have seen with our own eyes and from all the evidence that it was the last crustaceans—the decapods, the crabs, the lobsters—that were disproportionately affected by this event. That in and of itself is more than just a curio; that warrants investigation. At this point do you mind if I bridge on to where I think a gap was missed in the investigation?

Chair

We are going to move on to pyridine after, if that is what you are going to talk about.

Dr Caldwell

We will move on to that. To continue on your question, the previous panel put various points that there were toxic algae toxins present in the crabs, and there are, but here I am reading CEFAS’s own report. Its conclusion is: “Overall, there was no clear indications of marine neurotoxins being present in the samples received at the levels that would cause concern.”

Chair

The evidence we got talked about the asphyxiation of the crabs and lobsters because of the breakdown of the algae, rather than them being toxic algae. Am I correct in saying that that is the evidence that they gave us?

Dr Caldwell

Not necessarily. The thing is, if it was predominantly down to deoxygenation, it would not just be the crabs we would be seeing; we would be seeing more or less a complete sterilisation of the benthic form in that system. You have to ask yourself why it is predominantly crabs and lobsters washing up. If it was a mass deoxygenation event, that entire system would be killed. Looking objectively at the picture, it just does not stack up. As I said, this is a complex situation. The North Sea is a very stressed system, there are many things putting stress on organisms and all it takes is one event. Now hopefully this Committee will help us to understand what the nature of that one major event is.

Chair

Dr Forster was nodding his head when I suggested it could be an asphyxiation effect—were you?

Dr Forster

I think it needs looking at seriously, and we are short of evidence on that matter. It is quite interesting that the CEFAS modelling is going down that route. We do not have any in situ evidence of oxygen levels, either surface or benthos, in that part of the world and we need those kinds of measurements. 2021 and 2022 were exceptionally warm, settled summers. In 2022, that broke up earlier. The first storm event was in September this year, but last year, it was quite late. It is quite conceivable, and from our measurement we have certainly shown, that in the north-east coastal system, there is a stratification of the water. There is a warm surface layer and a cold pool below, which effectively is cut off from the surface. We need to find out more about that. There was a study in 2018 from the marine station in Blyth with a glider; an underwater robot set off from shore from there. That studies the oxygen in some detail going off to the Dogger Bank and back. Some work I have been involved with further out shows oxygen levels can get quite low below the thermocline, but at this stage in our part of the world it is just speculation. It could quite easily be something interesting. As for avoidance, herring would avoid areas with oxygen lower than about a 25% concentration. They would simply swim away. Crabs and lobsters are less mobile; they would not be able to escape, and because they are larger animals, with a higher oxygen demand, they might be in the first line of attack and more likely to turn up in a wash-up event. What did not get hit by this event is quite interesting. The anecdotal evidence about birds is also interesting, less so from the oxygen point of view, but there is potentially a link to harmful algae. I was out of Staithes about mid-September last year, and there were dead guillemots and razorbills everywhere belly up. That was before bird flu reached the area. I am not quite sure if there was a proper investigation into that. Most people thought they had come down the coast from further north, but I have never seen so many dead birds, and that would be around about the origin of this event, about that time.

Chair

Understood. Mr Deere Jones, we will move on to your pyridine data later, but your report states that there is an lack of empirical evidence to support the Government’s algal bloom theory. However, the Government did find traces of biotoxins in crab tissue that are associated with algal blooms. Does this, along with satellite imagery and water sampling, not suggest that an algal bloom potentially had an impact, or have you ruled that out completely?

Tim Deere Jones

I was producing the initial reports up until June; they were subsequently superseded by the brilliant work that colleagues on the desk on front you have carried out. The algal bloom hypothesis came to me after I had pointed out the pyridine issue. It seemed like, “Okay, we will have a look at this.” Initially, it was based, as far as I could see, on the satellite imagery. I queried the satellite imagery because I was sent photographs on a page that had been despatched to CEFAS by Plymouth Marine Laboratory. They had the images and they had a few statements. Among the statements put there by Plymouth Marine Laboratory was the fact that the satellite imagery could not define any specific algal species. It could have been any algae, benign or toxic, as far as Plymouth Marine Laboratory were concerned at that stage. I did additional research into satellite imagery and discovered that also, particularly in the US and Australia, it has been remarked that satellite imagery may mistake the chlorophyll-type images for surface suspended sedimentary material, because a lot of the common analytical techniques applied to satellite imagery needed tweaking and enhancing in order to be able to confirm whether or not sediment was present in that imagery. I put that in a report to the Commercial Fisherman’s Association, which I believe made DEFRA aware of that first report in which that was mentioned. I had asked or suggested that those enhanced analytical techniques be applied to the satellite imagery in the context that the satellite imagery was contemporary or nearly contemporary with dredging activity. As I am fully aware, both dredge dumping and dredging activity are likely to create plumes of fine sedimentary material that can rise to the surface and remain suspended for extended periods. The data I have indicates that such blooms may extend, particularly in terms of the fine sediment material, for at least 20 kilometres downstream. I questioned that hypothesis and never got the further responses that I was hoping to get—that is, that additional enhanced research into the imagery was produced and carried out.

Chair

Thank you very much. I will move on to Ian Byrne, who will talk about pyridine, which we have already mentioned.

Ian Byrne

I will direct this to Dr Caldwell. Why did your report identify pyridine as a more likely cause of the mass crustacean deaths than an algal bloom?

Dr Caldwell

Let me first put in context why we came into this study, because I think it is important that the Committee understands why I got involved in it. Whenever I looked at the joint report conclusions from the agencies, it did not make sense that pyridine was dismissed offhand and wasn’t explored any further. If I give you an analogy, it is like if your car breaks down and you take your car to your trusted mechanic who you have faith in. Your mechanic sees there is a warning light for low tyre pressure, concludes you have a puncture and then chooses to ignore the steam and oil pouring out of your engine. Where you have such a significant outlier in terms of a chemical showing up in testing, as a minimum you have to go in with an open mind and say, “Right, I am simply going to look at this to rule it out. Can we clear this from the investigation? If we can, wonderful! We can move on.” That wasn’t done here, and that is the reason why I got involved. From a purely pragmatic, scientific perspective, that would be the first thing you should do. If you see something, any kind of anomaly, any kind of outlier, you must question it. It wasn’t questioned. Second, it does not take any longer than a five-minute search of the scientific literature, even if you are not aware of the nature of pyridine, to think, “This is not something that can be dismissed without looking into it,” because it is a well-known toxin. That is the rationale of why I got involved in this study. The simple question that my laboratory asked is: can we find out whether pyridine is toxic to crabs or not? That was our very simple starting position. Our hope was that we would find it was not toxic, and that would be great; we could conclude that, and then other sources of stress in the system could be found. However, when we undertook our rigorous scientific work that was done to international accredited standards, we found that pyridine was not just toxic, but exceptionally toxic to crabs in two different ways, which I will come on to. Seeing the very powerful nature of the activity of pyridine on crabs triggered us to follow a process that we call STOP, source to outcome pathway, which is an innovative form of risk assessment that we are quite familiar with in our ongoing work in Norway. We decided to apply that approach to this example. In these STOP pathways, you need to try to find out where the likely source of the contaminant in your environment is coming from. You then need to understand whether the source is resident or transitionary. What mechanism will turn that toxin and make it available to the organism? What mechanism will allow the organism to interact with that toxin? Does it accumulate? Is it another mechanism? How does that toxicity express itself in term of the crab? From there, you can extrapolate to population level effects. Before we get on to the source, you need to understand the nature of the toxicity because it is quite striking. We used standard approaches in ecotoxicology. We exposed crabs that we collected outside the impacted area to pyridine of very carefully defined concentrations along a concentration range. We do this to generate what is called a dose response curve. That is a standard protocol in ecotoxicology that allows us to generate valid toxicity data.

Chair

Is that like the LD50?

Dr Caldwell

Exactly. We followed the standard protocols and we assessed all the way down from 100 milligrams per litre to controls and respective steps in between. That allowed us to generate LD50, LD30 and LD10 values. We monitored that over the course of 24, 48 and 72 hours. We were taken aback when we did these experiment; we were very much caught by surprise. We were not expecting pyridine to be as toxic as quickly as we saw, to the extent that we saw crabs die within a matter of hours. You need to understand the nature of how these crabs expressed their toxicity, and how that relates to the reports of dead and moribund crabs and lobsters in the field. Whenever they are exposed to pyridine, first of all, depending on concentration, at the higher end of the concentration, they go into very rapid, aggressive, violent convulsions, to the extent that the best way to describe it is the crabs were doing somersaults in the tank. That lasted for anything up to five or six minutes, whereupon the majority of crabs would come to rest on their back. Then they would enter into a phase of paralysis that lasted anything from 20 to 30 minutes, and that paralysis was progressive. After that period, once paralysis had set in, we could see the crabs were still alive; we could still monitor the movement of their mouth appendages, but they were all dying within the space of six hours. The nature of that response reduced, as you would expect, as the concentration went down, but we were still seeing paralysis and death even at concentrations of 20 milligrams per litre. At really low concentrations, 2 milligrams per litre, at which you would not think you would see any effect, the crabs were surviving the three days, but when you handled them, it was as if they were anesthetised. You would never put your hand into a tank with a crab without being very careful about what you were doing. When crabs were exposed to 2 milligrams per litre, it is as if they were drugged. They were placid and pliable. You could pick them up and handle them without any threat to your safety. That is the smallest concentration we tested. We looked beyond simply the behavioural and the survival data, because that is not enough for us. We wanted to know what was happening inside the tissues. We did that by sampling the gill, the hepatopancreas and the muscle. If I was going to see something, I would have expected to see signals in the gills and hepatopancreas. We were monitoring for signals of cellular stress, a group of chemicals called reactive oxygen species. They are a very natural part of every cell, but under stress, cells produce an awful lot of them, and they cause a great deal of damage. They will attack DNA and proteins; they will damage cell membranes. They are not something you want around in any cell. That is why we take in antioxidants. The job of antioxidants is to mop up those reactive oxygen species before they do harm. I thought we would see a very strong signal in terms of ROS because we have very sensitive measures in the gills and the hepatopancreas versus the control. I was deeply surprised that we did not see any change in ROS levels in those two organs. However, in the muscle tissue, we saw striking change—I mean changes of an order of magnitude. We measured two types of ROS. We measured one called the cellular ROS, which is all the reactive oxygen species put in the cell, and that was a five-fold increase. Then we specifically measured the ROS produced in the mitochondria, which is the power station of the cell. That increased by 20-fold. It is almost off the charts. When you watch those crabs in the tank, they then tend to drop off their legs and their claws. That all coincides with this incredibly powerful stress signal in the muscles that is causing them to drop their limbs. Therefore, you are looking at that range of toxicity from the paralysis. You look at the convulsions. You look at it from the mortality. You look at it from the cellular stress, and you start to put together a picture of what might be happening here. At this point, I need to get a little bit more academic with you. I will try to keep it simple to understand. Faced with these kinds of data, given the low concentrations of pyridine and the fact that the chemistry of the pyridine says it should not accumulate—I agree with CEFAS that it absolutely should not bio-accumulate—whey were we seeing the effects that we were? It took me a while for the penny to drop, but then the penny did drop because it reminded me of something that I teach my own students when I teach them about marine toxins and marine biotoxins. There is a family of toxins produced by a group of marine worms, called the bootlace worms or nemerteans. To you and me they are no great thing. You have to be a marine biologist and spend a lot of time on the shore to see these things, but they are there. They are both prey and predator of crabs, so they have to both protect themselves and have weapons in their arsenal to take down a crab. They do that through chemical warfare. They do that through producing compounds. The interesting thing here is that some of the most potent compounds they produce are pyridine alkaloids, pyridine derivatives. They will pump those into their mucus, so if a crab comes along and grabs the worm, simply by touching the mucus, the crab knows it is dealing with toxins, and it will abandon the worm. That worm can then go around, attack the crab, inject venom and then, once it has done that, what are the symptoms? You have paralysis. You have convulsions. You have death. In fact, when these first venoms were discovered, if you go back to the early French literature, it was initially described as the crab convulsant factor. What we are seeing in the lab is starting to make sense, as is what has been reported by fishers and by members of the public whenever they have seen moribund crabs wash up. The behaviour and presentation of the toxicity all matches. That does not address the question posed by CEFAS that it does not bio-accumulate. If it does not bio-accumulate, how can you see those features taking place? I have to say here that I am grateful to one of the CEFAS colleagues working alongside me—one is a toxicologist—helping us bottom out the actual mechanism for this. The reason why such low concentrations of pyridine and pyridine derivatives can enact such powerful mechanisms on crabs is because crabs have on their legs, outside their body, receptors that have been finely tuned over millions of years to detect pyridine and pyridine analogues. Therefore, it does not need to bio-accumulate. There simply only has to be pyridine in the water or pyridine in the sediment. The crab can only seek to avoid it. To give you an analogy, we all understand that rattlesnakes are poisonous and venomous, and we avoid those by keeping well clear. That is a nice, safe mechanism. What would happen if rattlesnake venom flew to us in a fog that we could not escape from? That is the kind of scenario you are facing here with the crabs. You have an animal that has evolved over millions of years to have receptors for this type of molecule on the outside of its body. When it detects those chemicals it initiates a response in its central nervous system and then, depending on the concentration of the chemical there, you can get a whole range of responses right the way through to what we have seen: convulsions, paralysis and death, so in terms of explaining the toxicity of pyridine, the case is there and clear to be seen. The next step is understanding how pyridine, if it is released during dredging, could then be transported 50 kilometres down the coast and add that toxicity. For that I turned for help to my physical oceanographer colleague, who is an extremely talented marine physicist, and he used the most powerful models and simulations available for the North Sea—more powerful than those that CEFAS has used. He also ran his model for a month, unlike CEFAS’s three days. What is more, we have always taken a conservative—with a small ‘c’—approach to our science. We have always underestimated every chemical we use. We have always underestimated all the parameters we use, so we would never run the risk of making false positives. The same goes for the modelling. We built into the modelling the actual destruction rate of pyridine. As was mentioned by the previous panel, pyridine is both lost to volatilisation and it is also aggressively attacked by oxygen. The US EPA had data for this in the 1980s. It showed that the half-life of pyridine—so losing 50% in water—is eight days. As I said, we have taken a conservative approach in our models. We put that half-life to 90. We would actually remove pyridine from our simulation faster than it would be removed in reality. We modelled based upon the rate of pyridine on the same scale CEFAS used, so a total release of 10,000 litres. We ran the model using the tides and the currents affecting the coast on each given day that the dredging campaign took place and for the following weeks. The model clearly showed that pyridine in water would be transported all the way down to Whitby and Robin Hood’s Bay. From that we could pull out toxicity values based upon what we had generated in my laboratory. We could then make reasonably sound estimates of the extent of population loss from the crabs and lobsters in that given area. Let me start by looking at the epicentre, around about Hartlepool, Redcar and Teesmouth. Based upon our work, we predicted that half of the crab population would have died in the first 24 hours. Moving further down the coast to Runswick Bay, we predicted that 30% would have died within 24 hours. Then moving right the way down to Whitby, we believed that we would have lost 10% as a minimum of the population there. Therefore, we have shown that pyridine is extremely toxic. We have identified the mechanism that means that bio-accumulation is out of the equation. We have identified the way that pyridine will be transported. The next step is then trying to go back to that source to outcome pathway model and trying to come back to: well, where is the source of pyridine? As a professional scientist, I am satisfied that I can explain the toxicity of pyridine. I am completely satisfied that I can defend that. I also need to identify likely sources. You heard from the previous panel that they do not believe there are sources in the Tees estuary. Unfortunately, I have news for them. There are at least three major point sources, two of which are historical, and one of which is much more contemporary. You go right back to—as was mentioned—the coking industry; Redcar is internationally known for that. Pyridine as a by-product, again, is well known throughout the world. It is very well studied and there is a very high risk level with that. I found it very peculiar that pyridine is not monitored routinely in the Tees estuary, given what is known right around the world. You also have a source from when ICI were refining crude oil. Whenever they refine crude oil, there is a fraction called the C5. That is the fraction that has no clear market value, so they would pipe that to another plant in the north of the Tees where that naphtha fraction would undergo a thermal cracking process. In effect, they heat it up to a very high temperature and they make those chemicals in the fraction form other chemicals. They will then extract from that those chemicals that have a market value. Anything that is not worth them selling was discharged directly into the river. Of course, pyridine was one of those chemicals that had no value to them and was discharged. At a more contemporary level, we also have the company called Vertellus, which had its own specific pyridine and pyridine derivative manufacturing plants. It was using that for a range of products: rubber sizers, drugs, herbicides, pesticides, a range of products. There are significant questions to be answered with regards to how it handled its effluent discharge. It was meant to have had a functional wastewater treatment plant on site, and that appears never to have worked properly. It subsequently had to tanker hundreds of thousands of gallons of its wastewater effluent, including pyridine releases, to the Bran Sands water treatment plant run by Northumbrian Water.

Chair

Why didn’t we get dead crabs then when all this stuff was going straight into the river?

Dr Caldwell

I am coming to that. We have three sources: two historical, one much more contemporary, and we must then look at the chemistry of the pyridine. As has been absolutely correctly talked about today, pyridine is unstable. In water it will defuse widely. It will evaporate very quickly into the atmosphere. It will be attacked by oxygen. Therefore, any attempt to measure pyridine in the water is a fool’s errand unless you are literally on top of any kind of release. You are always onto a loser in that kind of scenario. What pyridine does do when it gets into the sediment, if it is protected from oxygen it becomes stable—inert, if you like. In that sediment, it will build up over time. As long as it stays undisturbed in that sediment in an oxygen-free environment, it is fine. No problem. It cannot do any real harm. However, if you have an event that comes along that allows that pyridine to be mobilised from the sediment, and brought back into the system, you have a problem on your hands. As was mentioned in the previous panel, we have measured pyridine in the surface sediments down to a depth of 20 centimetres. It is important for the panel to understand that that 20 centimetres would be regarded as a pyridine destruction zone, so that part of the sediment will be being lost to the atmosphere where it will be diluted, where it will be being attacked by oxygen. Simply by the fact that we are measuring pyridine in the majority of our samples, in the Tees estuary and in the spoil zone, is a significant red flag that must be taken further, because it implies in those deeper sediments, where there is no oxygen present, you have a reservoir of pyridine there. What we believe we were measuring in our surface sediments was effectively the diffusion or the percolation from that pyridine reserve. It was coming to the surface and being interacted with in that destruction zone, and that is what we were measuring. Again, simply the fact that we were measuring pyridine in the sediments, given what we know about the chemistry, is of great concern. That makes it equally puzzling to me why pyridine was not part of the standard risk assessment for any work being undertaken in the Tees estuary—certainly any work that involves any risk to disturbance of the deep sediment. This is where we go on to the dredging. I don’t know whether you picked this up from earlier testimony, but it was pointed out on two occasions that the extra dredging was in response to a slippage in the Tees. That is quite a significant piece of evidence that needs to be explored. How big was that slippage? How deep was it? Was it interacting or interfacing with an aerobic zone? Is that the mechanism whereby pyridine will have been mobilised from that safe reservoir and then been picked up in the maintenance dredging and taken offshore inadvertently? If that was the case, it is just unfortunate that it happened, but that is a tangible mechanism from source to open pathway. You have identified three point sources of pyridine. You have identified the mechanism whereby pyridine would remain stable and resident in the sediment for decades. We have now identified a mechanism whereby an accident, a natural incident, could have caused that sediment to be moved and picked up and transported offshore through the maintenance dredging. We know the discharge of pyridine will have been reaching the whole way down that coast. We have even seen that from the sediment. You speak to the fisheries when they put their pots out at Whitby and they are finding out their pots are being covered in fine sediment. That never happened before. You are not just getting water being transported carrying pyridine; you are also getting the sediment itself. Therefore, the toxicity mechanism is there. The mechanism for crabs to respond to very, very low concentrations is there, as is the explanation for why you are getting this mass mortality within the impacted plume zone and not outside of it. I think you need to understand that. It is a very clear demarcation of where the crabs and lobsters were dying. When you try to trace that timeline of the movement of our simulated plume down the coast, it coincides with when the wash-ups were happening at each given location. Someone mentioned that you are still getting crustations washing up two months after the fact. That can also be addressed. There are in fact two toxicity mechanisms for pyridine and pyridine analogues to crabs. There is one that I have told you about in terms of the thiophene, which is incredibly sharp, incredibly acute, and that would likely have been causing that first major wave of wash-up. However, crabs and lobsters that will have survived that initial exposure—we knew some of them did because we have seen it in our experiments too—then open themselves to a secondary toxic mechanism, because these pyridine compounds interfere with a protein called SARM1. SARM1 has a very important job in maintaining nervous cells, the central nervous system and its function all the way from bacteria right the way through to us. If that SARM1 protein is switched on or damaged or made to function in any kind of way, it switches from its normal function, which is protecting the nerve cells, to switching round and becoming an enemy and it starts attacking and breaking them down, so it is a form of neurodegeneration. Think Alzheimer’s and ALS for crabs, but on a much shorter timescale. Here we are talking about not years for these things to set in but days. With the acute venom response, you are talking scales of hours to days. For the SARM2 protein, you are talking days to weeks. Those two different mechanisms of toxicity explain the really powerful and very disturbing high numbers of crab and lobster being washed up. It also accounts for the later wash-ups and the surviving crabs out there succumbing to the secondary toxicity as a result of the exposure. For us to completely and with confidence say we have a rock-solid explanation of pyridine is the straw that broke the camel’s back in the scenario. We just need to know how much pyridine is in the deep sediment. We cannot get hold of that data. We know boreholes have been drilled. We have not seen this data. We need to see more boreholes being drilled. We need to have an entire pyridine map across the entire depth of sediment in the Tees estuary. There is no point in coming up with any regulatory mechanism based upon monitoring pyridine in the water.

Ian Byrne

Who has done the boreholes, then?

Dr Caldwell

I suspect PD Ports. I don’t know who has done them. We do not have the data. What I am saying is any kind of regulatory monitoring based upon water for pyridine is not going to work because it is not just round long enough for it. For you to understand the nature of the risk of pyridine, and to manage any given system or any given development accordingly, you need to know what is in the sediment to a great deal of detail. That is the case as we have collected and set it out. What we are not saying is that the dredging and the development around the Tees port should be stopped. Far from it. We are not the enemy of development and redevelopment of that site. Far from it. Indeed, my own job title is applied marine biology. My job title is all about extracting value and resource from the sea. What we would like to see by way of a solution is, first, a temporary moratorium on the capital dredge until we understand what is happening and the initial pyridine release is done and dusted, has done its terrible damage, and has moved on through the system. We need to understand whether there is pyridine and other chemicals in the remainder of the sediment that has been earmarked to be dredged out for the south bank.

Ian Byrne

Are you dismissing the algae as the cause of this? Are you absolutely—