Research and analysis

Investigation into Teesside and Yorkshire coast crab and lobster mortalities

Updated 15 November 2022

Applies to England

This note is intended to preface the data and ancillary reports which formed part of the investigation into Crustacean Mass Mortality Event of Autumn 2021. These data and reports were published on GOV.UK and Cefas data repositories in Autumn 2022.

The dossier of information presented here comprises the outputs of work undertaken by the Cefas group during the Northeast crustacean mass mortality event in the autumn 2021. This mortality event comprised the death of thousands of crustacea (crabs and lobsters) and their subsequent wash up on beaches around the mouth of the Tees estuary and further south along towards Whitby between October and December 2021. This dossier also includes reports from a small number of follow up examinations in the spring and summer of 2022, after the close of the formal Defra led investigation into the most likely causes of the event. Taken together - with investigations undertaken across the Defra group - this information was used to inform advice on most probable cause of the mortality event, and to suggest initial avenues for further investigations commissioned by Defra.

Mass mortalities in the marine environment are not uncommon and their causes are frequently multi-factorial and complex. In this instance, no single causative agent was identified during the initial investigations. However, data showed that algal blooms occurred in the area at the time of the event. Algal blooms have previously been implicated in mass mortality events (e.g. Gravinese et al., 2020). The detection of toxins responsible for Diarrhetic Shellfish Poisoning (DSP) in crustacea originating from the area, coupled with the potential for anoxic conditions at the seabed following the rapid decomposition of another algal bloom, suggested a possible linkage. Whilst the mechanisms for this potential causation are not fully understood they are currently under further scientific investigation.

During the initial emergency response phase, the Environment Agency undertook rapid testing of affected crustacea tissues using a method designed and accredited for the quantitation of pyridine in water. Whilst it is known that pyridine is toxic to marine crustacea, chemical modelling predicted that it was highly unlikely that a source of pyridine could be present in concentrations likely to impact crustacea at the seabed. No pyridine was detected in water samples taken at the time of the incident. Though indications of pyridine or its derivatives were determined in a small number of crustacea from both inside and outside the impacted area. Pyridine is a chemical with a range of uses in industry, but importantly pyridine and its derivatives are key components of many biological processes. Because of its physiochemical properties, pyridine has not been considered a contaminant of concern for the marine sediment, and this is reflected through the OSPAR Convention for the Protection of the Northeast Atlantic. The qualitative detection of pyridine in crustacea tissues in the absence of its detection (using validated and accredited methodology) in water was considered important and required the development of a robust, validated fully quantitative method suitable for application in crustacea tissues. This work is being undertaken as part of Defra commissioned studies.

As further data and findings become available, all information generated by the Defra group will be made available in the public domain.

References

Gravinese, P.M., Munley, M.K., Kahmann, G., Cole, C., Lovko, V.J., Blum, P., Pierce, R.H. 2020. The effects of prolonged exposure to hypoxia and Florida red tide (Karenia brevis) on the survival and activity of stone crabs. Harmful algae. 98, 101897