Spatial and temporal changes of TBT pollution along the Portuguese coast: inefficacy of the EEC directive 89/677

Nucella lapillus imposex (superimposition of male characters onto prosobranch females) and organotin body burden were surveyed in the Portuguese coast in 1997 and 2000. Time comparisons of the available data on Nucella lapillus imposex in the Portuguese coast indicate a global increase of TBT pollution in recent years, revealing the inefficacy of the 1993 legislation that bans the use of TBT paints on small boats (<25 m). The absence or scarcity of the species inside harbours, which are the most polluted sites in Portugal, is probably a consequence of extinction due to female sterilisation by TBT.     

Recovery from imposex by a population of the dogwhelk, Nucella lapillus (Gastropoda: Caenogastropoda), on the southeastern coast of England since May 2004: A 52-month study

Over a 52-month period beginning in May 2004 and concluding in August 2008, and coinciding with the period over which TBT was banned as a ship anti-foulant globally, a population of the dogwhelk, Nucella lapillus, was studied for changes in population size and structure, and reproduction. During the study period, the size of the population of N. lapillus on the Mewsbrook Groyne at Littlehampton on the southeastern coast of England grew from ∼25 individuals to >500, i.e., a 20-fold increase. Similarly, population structure normalised to reveal a maximum age of up to ∼3 years. The numbers of egg capsules produced by the N. lapillus population also grew over the study, again by a factor of 20, and the length of the breeding season increased from 7 months in 2004-2005 and 2005-2006 to 11 months in 2006-2007 and 2007-2008. Such changes were reflected in the incidence of imposex from Vas Deferens Index Stages 3 and 4 in 2003 to zero commencing in 2008 and continuing into 2009.Due to a lack of confirmatory chemical data, the changes in population size, structure and reproduction herein reported upon for N. lapillus cannot be correlated positively with changes in ambient TBT levels, but they can and are correlated with freedom from imposex. This is the first time such a dramatic recovery from imposex, following the banning of TBT, has been documented.     

Imposex in Three Marine Gastropod Species in Chile and Potential Impact on Muriciculture

A survey of imposex was conducted between the Bay of San Vicente, Concepción, Chile (36° 50′) and the Bay of Renocavi, Puerto Montt, Chile (41° 35′), to determine if imposex is occurring in an area of collection and cultivation of the gastropod, Chorus giganteus. Imposex was recorded in three chilean muricids C. giganteus, Xanthochorus cassidiformis and Nucella crassilabrum complex. Percentage of imposex in females sampled ranged from 0% to 100%. The degree of expression of imposex was not so severe as to elicit sterility in the individuals surveyed. Incidence of imposex was as high as 47% in areas of harvest of C. giganteus for reproductive and cultivation studies for commercial production of this species. A six percent incidence of imposex was observed in Nucella proximal to the facility for cultivation of C. giganteus. Gastropods of the genus Nucella are used in other countries to monitor incidence of imposex and have demonstrated sensitivity toward tributyltin (TBT), the associated causal agent. Since sex of individuals in muriciculture is determined by the presence or absence of a penis, imposex may lead to erroneous classification of males and females. The incidence and severity of imposex in C. giganteus and related species may have a negative impact on sustainable cultivation and harvest of gastropods in Chile.     

Decade-long monitoring reveals a transient distortion of baseline butyltin bioaccumulation pattern in gastropods

Worldwide measures to restrict tributyltin (TBT) in antifouling paints have been legislated for decades, and were upgraded to a total ban on September 2008. With a view to test the response of coastal biota to changing pollution, since 1996 we have determined the concentration of TBT and derivatives di- and mono-butyltin (DBT and MBT) in NW Spain populations of two gastropods of contrasting biology, the rock-snail Nucella lapillus (n = 18) and the mud-snail Nassarius reticulatus (n = 24). TBT pollution in the study area has decreased consistently and considerably over time. In addition, the baseline butyltin (BT) bioaccumulation patterns showed a marked but transient distortion. These field observations are consistent with BT desorption from sediments, a natural phenomenon that is now to be expected in developing countries recently subject to the global TBT ban.     

Re-colonisation and recovery of populations of dogwhelks Nucella lapillus (L.) on shores formerly subject to severe TBT contamination

Dogwhelks Nucella lapillus became locally extinct on some shores adjacent to areas of high shipping/boating activity during the period of high tributyltin (TBT) contamination in the 1980s and early 1990s. However, the species has now re-colonised sites at which extinction occurred on the Isle of Cumbrae, the northeast coast of England, the Shetland Isles and southwest England. There have also been substantial declines in the severity of imposex on adjacent shores where the species has persisted during this period. Re-colonisation and recovery can be attributed to two measures: regulations prohibiting the use of TBT-based paints on vessels < 25 m in length and the development of slow-releasing, self-polishing copolymer paints. Nevertheless, the International Maritime Organisation has now imposed a total ban on the use of TBT-based paints as antifoulants. This is almost certain to result in the use of paints containing alternative biocides and there is widespread concern that there is relatively little information on which to assess their likely environmental impacts. They could cause substantial environmental damage.