EFFECTS OF COPPER ON THE FAUNAS OF MARINE SOFT-SEDIMENTS - AN EXPERIMENTAL FIELD-STUDY

Although laboratory experimental studies have shown that copper is tox ic to marine organisms at concentrations found in contaminated sedimen ts, there is little unequivocal evidence of undesirable ecological eff ects in the field, other than at extreme concentrations. We describe a study in Botany Bay, New South Wales, Australia, in which the concent rations of copper in marine sediments were experimentally enhanced. Ch anges in the abundance and taxonomic composition of the fauna of coppe r-treated sediments relative to those of two control treatments were m onitored over a period of six months. Univariate (ANOVA) and multivari ate (non-metric multidimensional scaling, MDS) analyses of the changes in the fauna showed that increased concentrations of copper (140 to 1 200 mu g g(-1) compared with background concentrations of 29 to 40 mu g g(-1)) had an impact on the fauna. The nature of the response varied among taxa. For example, in some taxa, numbers of individuals decreas ed through time relative to controls, whereas the abundance of another taxon remained fairly constant through time in the copper treatment w hile numbers of control individuals increased. Differences in the chan ges of the faunas through time among the control and copper treatments were not always consistent among replicate experimental units 5 m apa rt, nor were they consistent between replicate experimental sites 100 m apart. The magnitudes of the changes in the faunas caused by the cop per treatment are considered in the context of the magnitude of previo usly measured ''natural'' temporal variation.