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MBA research that led to legislation banning TBT

This week NERC published its annual Impact Report which highlighted a surge in shellfish production and recovery of marine ecosystems.

The report says: “The UK has seen £908m in positive net impacts as a result of a ban on anti-fouling chemicals. The bans were based on evidence produced by NERC researchers into the effects of chemicals such as tributyltin on shellfish.”

Since the early 1980s research has been carried out at the MBA into the impacts of tributyl tin (TBT), a widely-used anti-fouling chemical, on marine and estuarine ecosystems. The first and probably the most dramatic warning sign was the development of imposex (a toxicity effect of certain pollutants that causes females of marine snails to develop male sex organs) in dog whelks (see Figure 1) and other stenoglossan gastropods and a resultant decline in populations, particularly where TBT was heavily used (N.B. antifouling paints on ships’ hulls).

Dog whelks, Nucella lapillus

Fig. 1. Dog whelks, Nucella lapillus One of the species affected by TBT

This led to early legislation which banned the use of TBTs on small boats (the leisure fleet). Subsequent work showed the importance of sediments as reservoirs of TBT and effects on deposit-feeding species such as clams, for example the peppery furrow shell – see Fig. 2.. This contributed to the evidence and need for further legislation. A total ban on the use of TBT on the global fleet (including commercial and naval vessels) was subsequently introduced in 2008.

Work on the persistence of TBT on the marine environment and recovery following TBT legislation is ongoing, for example a large-scale study on English Channel ecosystems has been published recently [Link to Mar Poll Bull article]

This is one of the most clear-cut examples of effects linked to a known pollutant and it is important to complete the study of recovery as this may have important lessons on the extent, timescale and management of future pollution scenarios.

The peppery furrow shell (Scrobicularia plana).  found in estuarine and intertidal conditions and is able to tolerate low salinities in thick mud or muddy sand. It burrows up to 20 cm deep in sediments and can be identified when buried by the characteristic star-shaped markings made at the surface by its inhalant siphon.

Fig. 2. The peppery furrow shell (Scrobicularia plana).burrows up to 20 cm deep in sediments and can be identified when buried by the characteristic star-shaped markings made at the surface by its inhalant siphon.

Read a recent update on recovery from TBT pollution in English Channel environments in: W.J. Langston, N.D. Pope, M. Davey, K.M. Langston, S.C.M. O’ Hara, P.E. Gibbs, P.L. Pascoe (2015)  Recovery from TBT pollution in English Channel environments: A problem solved? Mar Poll Bull, 95, 551–564.

MBA research in this area has been led by Bill Langstonhead of the MBA’s ecotoxicology laboratory.