Assessment of the environmental health of the Chagos Archipelago

The quality of the environment of the Chagos Archipelago was assessed in terms of the concentration of anthropogenic contaminants or natural elements in enhanced concentrations in surface sediments, selected macrobenthic invertebrates, coral-fish species and birds and bird?s eggs. Polychlorinated biphenyls (PCBs): In surface sediments, in soft body tissue of hermit crabs (Pagurus sp.), in the digestive gland of sea stars (Linkia multiflora and L. laevigata), and in soft-body tissue of clams (Pteria penguin and Lopha folia) the selected chlorinated biphenyl congeners (CBs) could not be identified (limit of detection 0.5 to 3.2 ng g-1 lipid for the several CBs). Organochlorine pesticides: In surface sediments, only traces of the pesticides hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), the DDT-family members o,p'-DDT, p,p'-DDT, p,p'-DDD, and p,p'-DDE, and dieldrin could be identified (limit of detection 4 to 61 pg g-1 lipid for the several pesticides). In a number of samples _-HCH, o,p'-DDT, and p,p'-DDD were quantified, however, in concentrations just above the limits of quantification, at the picogram per gram dry weight level. In certain invertebrate species, HCB and p,p'-DDE in particular could be quantified (limit of quantification 0.4 and 2.8 ng g-1 lipid, respectively). Polyaromatic hydrocarbons (PAHs): In sediment samples from the Great Chagos Bank (Three Brothers) and Salomon the concentration levels of the selected PAHs were just above their quantification limits, which were in the 10 to 300 picogram per gram lipid range. Of all PAHs selected, phenanthrene, fluoranthene, and pyrene were present in the highest concentrations. Particularly in biota from the Salomon islands all of the selected PAHs could be quantified or at least identified (limit of detection varied from 1.0 ng g-1 lipid for indeno[1,2,3-c,d]pyrene to 25 ng g-1 lipid for phenanthrene). Heavy metals: In surface sediments the concentrations of copper, zinc, cadmium, lead, chromium and nickel were exceptionally low. In biota, the biologically non-essential metals Pb and Cr were very low. Ni was detected in substantial levels only in bivalves and seastars from the Salomon atoll. Cd concentrations in macrobenthic invertebrates were comparable with the enhanced levels generally found in fauna from open ocean areas (5 to 32 ?g g-1 dry weight). Cd concentrations in bird livers and birds eggs were very low, if detectable at all. The concentrations of the biologically essential elements Cu and Zn, were very high in hermit crab and clam. On the basis of the data presented here the marine environments of the Chagos Archipelago as a whole is a pristine environment. The atolls belong to the most non-impacted areas with respect to anthropogenic organic contaminants and toxic metals. Enhanced cadmium levels are possibly correlated with enhanced dissolved cadmium levels in deep ocean water, being closely related with the phoshate distribution. The impact of early exploitation of some of the islands (Salomon atoll) possibly can still be traced in elevated p,p'-DDE and nickel levels in benthic macroinvertebrates.
Everaarts J , Booij K , Fischer C , Mass Y , Nieuwenhuize J .
birds,crabs,Asteroidea(starfish),clams, contaminants, polychlorinated biphenyls, organochlorine pesticides, polyaromatic hydrocarbons, heavy metals, surface sedimen, benthic invertebrates, coral, fish