MEPS 135:123-135 (1996)  -  doi:10.3354/meps135123

Effects of trace metals on infaunal species composition in polluted intertidal and subtidal marine sediments near a lead smelter, Spencer Gulf, South Australia

Ward TJ, Hutchings PA

The infauna of intertidal and subtidal marine sediments at 18 sites near a large lead-zinc smelter in Spencer Gulf, South Australia, was sampled twice about 6 mo apart. The sampled habitats were bare intertidal mudflats, intertidal seagrass (Zostera sp.) beds, subtidal seagrass (Posidonia spp.) beds, and unvegetated sediments at 5 to 10 m depth. The infauna consisted of 372 identifiable taxa, mainly polychaetes, molluscs and crustaceans. The number of taxa at each site and time showed no simple relationship with the concentrations of trace metals in sediments, habitat type or time of sampling. However, the patterns of distribution, analysed using frequencies of occurrence of taxa derived from multivariate classification and ordination techniques, were related to the sediment concentrations of As, Cu, Mn, Pb, Sb and Zn. The extremely high concentrations of these trace elements (probably mainly Pb and Zn) appeared to affect both the abundances and distribution of many infaunal species. The multivariate techniques could detect which species were affected in the most metal-polluted sites (the intertidal sites). However, in the less-polluted subtidal sites, patterns in species composition were detected but only a few individual species could be unambiguously correlated to the presence of the metals. The polluted intertidal sediments, which had some of the highest metal concentrations ever recorded in marine sediments (Pb up to 5270 ug g-1 and Zn up to 16700 ug g-1), supported 42 taxa. The polychaetes Heteromastus filiformis, Capitella 'capitata' and Glycera americana, and the crustacean Tanais dulongii were very abundant in these sites; they apparently can selectively exploit the metal-contaminated conditions. C. 'capitata' and T. dulongii were found almost exclusively in these sites. In contrast, 15 species of polychaetes, 5 crustaceans and 4 molluscs found elsewhere in the study area, representing 26, 20, and 17% of these intertidal taxa respectively, were not found in the metal-polluted sites. No taxonomic selectivity in the effects of the metals was detected amongst the 3 major groups-polychaetes, molluscs and crustaceans. Future studies may, therefore, be able to sample indicator species from only one of these major groups to determine the spatial extent of ecological effects or to monitor metal effects in this area.

Metals . Infauna . Species composition . Biological effects . Monitoring . Smelter

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