The long-term recovery of the bioindicator species Nucella lapillus from tributyltin pollution

Bray, Simon (2005) The long-term recovery of the bioindicator species Nucella lapillus from tributyltin pollution. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

In an attempt to control marine biofouling, a co-polymer paint system was developed containing the biocide tributyltin (TBT) in the 1960s. TBT was found to be highly toxic to non-target organisms, particularly to female common dogwhelk (Nucella lapillus) in the UK. TBT blocks hormone conversion of testosterone to oestradiol, resulting in the development of a penis and vas deferens (imposex). Females die as male sex organs overgrow the oviduct, leaving them unable to deposit eggs and so suffer internal rupture. The toxicity of TBT led to legislation controlling its use from the mid 1980s and the intention for a total ban by 2008.

Long-term monitoring of N. lapillus populations in Plymouth, UK south coast and Isle of Wight has showed recovery from TBT effects since the 1980s, although imposex in some populations has recently increased. Imposex has reduced at sites directly affected by shipping and population recovery has been seen at some sites from where N. lapillus had previously been absent. At some sites close to spoil dumping grounds, imposex has risen and may have been adversely affected by TBT associated with dredged harbour sediments. At some south coast sites N. lapillus population fluctuations reflected barnacle abundance, highlighting the uncertainty associated with elucidation of cause-effect relationships.

Recovery from TBT impacts through recolonisation and colonisation at some sites has been achieved despite N. lapillus’ lack of a pelagic stage. Study of man-made groynes at Highcliffe, Dorset, indicated that recruitment may occur due to passive transport from inshore subtidal populations. Reintroduction trials at a formerly occupied site showed that N. lapillus were robust enough to survive translocation, but TBT levels prevented re-establishment of a viable population through severe imposex effects. Passive transport may facilitate the use of artificial sites with viable habitat and tolerable TBT levels as stepping-stones for recolonisation of isolated sites that have suffered local extinction.

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