The detrimental effects of tributyltin (TBT) have been recorded on many marine organisms. As a result the UK Government imposed a partial ban on the use of organotin antifouling paints on boats less than 25 m in length, in 1987. In 1988 the Isle of Man Government followed suit introducing a licensing procedure restricting all uses of organotins. At concentrations less than 0.5 ng Sn/I female Nucella lap/Nus develop imposex - the superimposition of male sexual characteristics. To date there have been few studies measuring the recovery of Nucella populations after the introduction of restrictions. This study produces evidence of the extent of recovery in Nucella populations from sites in the south-west of England and on the Isle of Man. The recovery observed was measured by decreasing values of relative penis size, vas deferens sequence and the percentage of sterile adult females in the population. Following the 1987 ban the recovery of Nucella populations in the south-west has shown a linear response allowing predictions to be made for the time scale of complete recovery. In addition concentrations of TBT in the water and tissues of selected indicator organisms also showed decreases. Around the Isle of Man the illegal use of TBT paints was identified and later discouraged by the Marine Administration which was followed by a reduction in TBT concentrations in the water at sites around the Isle of Man. Levels of imposex in dogwhelk populations around the Isle of Man have decreased. Although effects of TBT on Nuce/la have been well documented at the cellular and individual level, the knock on effects on the community have not been investigated. Manipulative field experiments were used to demonstrate the role of Nucella lapd/us in structuring shore communities to allow predictions of the effect of TBT to be made. Rather than using the traditional approach of fences and cages, dogwhelks were removed by hand on regular visits to experimental sites creating treatments with reduced abundances of dogwhelks akin to shores affected by TBT. The role of Nucel/a was examined at different stages of a cycle existing on moderately exposed Manx shores where Fucus vesiculosus and Semibe/anus balanoides fluctuate in abundance. The removal of dogwhelks increased the abundance of Semibalanus ba/anoides on the shore and as a result likelihood of algal escapes from grazing by Patella vulgate also increased. In addition the removal of Nucela increased the size and longevity of newly established Fucus vesiculosus clumps. In a factorial experiment the role of Patella vulgate and Nucella lapillus were examined simultaneously. Nuce/la was found to have an significant effect but less than that of Patella. The presence of Nucella did, however, mediate the effect of Patella. In addition Nucella was found to have a direct effect on the level of Semibalanus balanoides settlement in the field with the number of barnacles settling in cleared areas being reduced on areas which had been previously occupied by Nucella.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:260333 |
| Date | January 1994 |
| Creators | Proud, Sarah Victoria |
| Publisher | University of Liverpool |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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