Crabs and lobster deaths: University researchers find ‘poisoning by industrial toxins’ may be the cause

The crustaceans have been washing up dead on beaches in Yorkshire and the North East since October, and an investigation led by the Department for Environment, Food and Rural Affairs (Defra), found a naturally occuring algal bloom is “the most likely cause”.

However, a group of fishermen, known as the North East Fishing Collective (NEFC) and academics from Durham, Hull, York and Newcastle Universities have published a report which stated the deaths may be linked to harmful chemicals disturbed by dredging in the River Tees.

Defra has defended the findings of its investigation and said there is no evidence to suggest that dredging or chemical pollution caused the mass die off.

Fishermen also claim their livelihoods are at risk because catches have been decimated, but the Government said there are no plans to provide compensation as it is a naturally occurring event.

Researchers said preliminary evidence suggests the crab deaths are “more consistent with poisoning by industrial toxins than by natural algal toxins” and more analysis of sediment and water samples must be done “as a matter of urgency”.

They agreed satellite imaging does show a marine algal bloom appeared off the coast in October but evidence supporting the theory that it caused the deaths is “incomplete and contradictory”, as the metabolites detected were not from the algal species normally associated with die-offs.

The researchers said harmful algal blooms “usually kill a broad range of organisms”, including fish, but this event “disproportionately affected crabs and lobsters”.

Scientists from the University of Newcastle conducted experiments to analyse the effects of the pyridine exposure on crabs, as the common industrial chemical was found in crustaceans during Defra’s investigation.

They found that half the crabs exposed to just 0.49 milligrams per litre died within 72 hours and according to the report, this “would be broadly equivalent to a single droplet of pyridine in a litre of seawater”.

The report stated pyridine is “highly toxic to crabs even at low levels” and at least one Teesside industrial plant (Vertellus) “is known to have handled large amounts” of the industrial chemical before 2019.

The researchers ran computer simulations which found that if 1,000 litres of pyridine were released from a known dredging site at the River Tees, it “would have been sufficient” to kill approximately 10 per cent of the crab population in Whitby and more than half the crabs in Redcar.

University of York researchers took water and sediment samples along the Tees Estuary in May and found no pyridine in the water but it was detected in eight of the 12 sampling areas

The report stated “the results support the suggestion that pyridine and dredging could have played a major part in the observed mass mortality events”.

Defra said the chemical can form naturally in crustaceans after death but it did not kill them and “varying amounts” have been found in crabs in other parts of the UK.

A Defra spokesman said: “A comprehensive investigation last year included extensive testing for chemicals and other pollutants such as pyridine. It concluded a naturally occurring algal bloom was the most likely cause.

“We recognise the concerns in regards to dredging, but we found no evidence to suggest this was a likely cause. There have been no materials licensed for disposal at sea in the area which would fail to meet international standards.

This is a complex scientific issue, which is why we took a thorough, evidence based approach.

"We welcome research carried out by universities and will continue to work with them, including studying this report carefully. We are aware there have been some localised reductions in catch rates and we are continuing to monitor shellfish populations in the area.”