Crustacean die off

In October 2021, dead and dying crabs and lobsters were washed ashore in high numbers along parts of the North East coast.

The Environment Agency led the initial emergency response, with Defra launching an investigation in December 2021 working with partners including CEFAS, NEIFCA, MMO, FSA and UKSHA which concluded in March 2022. This investigation considered a range of potential causes including licensed dredging activity, chemical contamination, offshore windfarm activity and presence of algal blooms and aquatic animal disease. Independent scientific and Government findings pointed to algal blooms as the most likely cause.

Despite Teesworks not undertaking any dredging up to the time in question, there was some  inaccurate reports that maintenance dredging work conducted by PD Ports as the Statutory Harbour Authority on the Tees had been carried out in respect of the Teesside Freeport and/or other work at Teesworks. This was despite repeated statements continuing to underline that no dredging had yet been carried out regarding the Teesworks South Bank Quay Project.

In May 2022, Defra published a summary of its findings from a comprehensive, multi-agency, scientific investigation into this issue, with the key findings below. It states dredging and chemical pollution – including pyridine – were highly unlikely to be the cause.

POTENTIAL CAUSE:

• No single, consistent causative factor was identified, however a harmful algal bloom present in the area coincident with the event was identified as of significance
• There was consistent detection of algal toxins in washed up dead crab and lobsters, confirming they had been exposed to algal toxins

OTHER FACTORS CONSIDERED:

• Licenced Activities (including dredging)
• The MMO reviewed marine licenced activities within the area which supported the conclusion the licenced activities (including cabling, offshore windfarm activity and dredging/disposal of sediment to designated grounds) was not likely to be the cause of the mortalities
• EA tested environmental media for a wide range of contaminants including those routinely tested to support applications of disposal of dredged material. Screening supports the conclusion disposal of dredged sediment not likely to be the cause.
• CEFAS (Centre for Environment, Fisheries and Aquaculture Science) completed an indicative 2D tracking model of sediment plume from the disposal site. This indicated any plume would be relatively confined and did not have the same geographic extent consistent with the mortalities

Chemical Pollution

• Analysis of water, sediment and biological tissue samples detected no indicative chemical cause that could explain the scale of the impact. EA did not consider chemical pollution or sewage as a likely cause
• A range of possible sources of contamination were considered, such as industrial and wastewater discharges or dredging
• No abnormal site activities or non-conformance with permit conditions were  noted
• No significant sewage or surface water outfall incidents were reported to EA
• Due to special scale and timescale, it was deemed highly improbable there was a point source contaminant cause
• EA analysed water, surface sediment and blue mussel and crab tissue considering more than 1,000 chemicals
• Extensive testing, research and analysis was undertaken during the initial investigation by the Environment Agency (EA) and CEFAS, supported by the Marine Management Organisation (MMO). This included testing for chemicals and other pollutants including pyridine; dredging activity; disease; and seismic activity.
• No chemicals tested were identified at levels which would consistently explain the cause over the space and time seen.
• Pyridine was identified in crab soft tissue however concentrations could not initially be put into context as analysis had not previously been carried out and background levels were unknown.
• On the assumption it was causal, a potential source was sought, including a formal water discharge sample from a possible industrial source
• Using validated, fully quantifiable tests, no pyridine was present in water samples. No source could be identified
• It is also thought pyridine forms naturally post-mortem in crab tissue
• The findings could not support the hypothesis that pyridine was the cause

Aquatic Animal Disease

• It was concluded an infectious disease agent was not responsible

Harmful Algal Blooms and Toxins

• Routine sampling data showed HAB were occurring in September in high densities
• Satellite data appeared to indicate an algal bloom occurring along the coast in question from September 20 to 26, 2021
• There are limitations of satellite data surrounding uncertainties of interpretation near shore waters where it can be hard to identify species and density
• A separate report from the University of Plymouth showed an elevated risk of HAV in the region at different times through September and October
• Harmful algae, albeit at low concentrations, were identified in November 2021
• Algal biotoxins were detected in dead and moribund animal tissues sampled during, but not after, the event
• Concentrations, in some instances, exceeded FSA regulatory limits applied for bivalve molluscs

Scientists carried out extensive testing for chemicals and other pollutants including pyridine but concluded a naturally occurring algal bloom was the most likely cause. The amount of any chemical needed to cause a mortality event of this scale would have had to be huge and could not have escaped detection in the extensive sampling carried out at the time.

A link to the full report can be found here.

Not limited to the Tees or the UK 

This is not a situation that is unique to the North East or even the UK, with other similar instances taking place around the world.

https://news.sky.com/story/unprecedented-red-tide-kills-thousands-of-fish-in-san-francisco-bay-area-12686396

https://www.theguardian.com/world/2022/aug/19/rare-golden-algae-may-have-caused-fish-deaths-in-oder-river-says-minister

https://www.bbc.com/news/world-europe-49557804

https://www.washingtonpost.com/nation/2021/07/12/red-tide-st-petersburg-dead-fish/

https://www.gazettelive.co.uk/news/teesside-news/numbers-seal-pups-born-teesside-24963243

Select Committee

A letter released by the cross-party Environment, Food and Rural Affairs Select Committee after hearings into crustacean deaths found dredging can continue.

Autumn 2022

A die-off of small crustaceans was reported to the Environment Agency at Hartlepool. Defra has said there is no evidence of a similar event occurring since the crustacean death incident in late 2021. The MMO and the Environment Agency are monitoring the North East coast carefully they have found no evidence of a similar event occurring – including since September 2022 when the Teesworks capital dredging started.

British Ports Authority

The British Ports Association represents the interests of over 100 port members, covering more than 400 ports, terminal operators and port facilities.

The BPA wrote to the Parliamentary select committee to express some concerns about recommendations on future dredging – and has called on Defra to continue to defend robust procedures already in place to assess and approve hundreds of dredge disposal licences.

It has also raised concerns about a report by a group of university researchers into dredging and sealife mortality stating:

Having reviewed a copy of the paper, which has not been formally published, the BPA is concerned that recommendations that could have far-reaching consequences for the ports industry are being made based on its conclusions. The BPA does not believe the conclusions reached in the paper are credible or even reflective of the results found by the researcher. The results in the paper suggest that over 5,000 dredge disposal events would have had to occur in a single day to have the impact stated in the report. The paper also contains a number of factual errors.

Link here: BPA: No New Restrictions on Dredging Without Credible Evidence – British Ports Association