title: Imposex and organotin concentrations in Buccinum undatum and Neptunea antiqua from the North Sea: relationship to shipping density and hydrographical conditions.
abstract: The presence and the development of imposex were investigated in the common whelk (Buccinum undatum) and the red whelk (Neptunea antiqua) from the open North Sea and the Skagerrak. Imposex development was related to levels of organotins in snails and in the fine fractions (< 63 microm) of the sediments they inhabit. The sampling locations were classified according to three levels of traffic densities of ships of > or = 100 gt per day passing within 15 Nautical miles of the sampling station, shipping levels being: high (> 10 ships day(-1)), intermediate (5--10 ships day(-1)), and low (< 5 ships day(-1)). Sampling stations were also classified according to presence or absence of a vertically stratified water column. In the snails the body levels of the butyltin metabolites MBT and DBT and the parent phenyltin compound TPT, were higher than those of TBT and PT metabolites. In the sediment, the parent compounds and the mono-substituted metabolites MBT and MPT were present in the highest concentrations. The highest body levels of all organotin compounds and the highest imposex indices for the common whelk were found at those locations in the Southern Bight and the German Bight that had a high shipping density as well as a homogeneously mixed water column during the whole year. At these locations sediment levels of organotins were also higher than at other sites. In contrast, the body levels of organotins were low and imposex was sometimes even completely absent in snails from stratified deep-water stations in the Skagerrak, despite a very high shipping density in the entrance area of the Baltic. In sediments from stratified locations with low or intermediate shipping densities, organotin compounds were below or close to their respective limits of detection. These stations were located in areas with a stratified water column during the whole year. The results can be explained by postulating a much higher resistance for dissolved organotins to migrate through a pycnocline. Organotins could only transgress through a pycnocline when adsorbed to settling particles that manage to transgress the boundary between layers. N. antiqua could only be obtained in sufficient numbers from deeper water stations, which almost all had a stratified water column. At stations where both snail species were obtained and imposex was present, the imposex index was higher in the red whelk. Hence N. antiqua seems to be the more sensitive species of the two. In the red whelk, imposex development increased with shipping density too, though in the smaller samples the trend was not significant. Average biota-sediment accumulation factors (BSAFs; normalised for lipid content in snails and TOC content in the fraction < 63 microm in sediments) for Buccinum ranged from 0.4 to 1.0 for butyltins and were similar to literature values reported for TBT in other marine species. Higher average BSAF values were found for phenyltins 1.5 (MPT) to 17 (TPT). The high values for TPT match the ranges expected from equilibrium partitioning concepts of persistent hydrophobic compounds. The ratio of live snails to the total number of live snails plus empty shells ranged between 2.5 and 93%. This parameter might be a useful indicator to compare past and present densities of populations of both species in different areas of the North Sea.
authors.affiliation: Royal Netherlands Institute für Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands. cato@nioz.nl
authors.forename: Cato C
authors.initials: CC
authors.lastname: ten Hallers-Tjabbes
authors.forename: Jan-Willem
authors.initials: JW
authors.lastname: Wegener
authors.forename: Bert  A G M
authors.initials: B
authors.lastname: Van Hattum
authors.forename: John F
authors.initials: JF
authors.lastname: Kemp
authors.forename: Embartus
authors.initials: E
authors.lastname: ten Hallers
authors.forename: Tarren J
authors.initials: TJ
authors.lastname: Reitsemae
authors.forename: Jan P
authors.initials: JP
authors.lastname: Boon
mesh_terms: D000327:Adsorption; D000818:Animals; D003132:Commerce; D012734:Disorders of Sex Development / Q000139:chemically induced*; D004784:Environmental Monitoring; D005260:Female; D019015:Geologic Sediments / Q000737:chemistry; D008297:Male; D009659:North Sea; D009947:Organotin Compounds / Q000009:adverse effects*; D011157:Population Dynamics; D012767:Ships; D012908:Snails / Q000502:physiology*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000009:adverse effects*
chemical_list: D009947:Organotin Compounds; D014874:Water Pollutants, Chemical