MEPS 402:123-136 (2010)  -  DOI: https://doi.org/10.3354/meps08457

ABSTRACT: Heavy metals are anthropogenically introduced into estuaries and cause lethal and sublethal effects on estuarine organisms. Copper (Cu), lead (Pb) and zinc (Zn) are primary sediment contaminants of concern in Auckland, New Zealand. Their concentrations in estuarine sediments tend to correlate with one another spatially across the region, and concentrations of Cu and Zn are predicted to increase over time. A field experiment was done in Orewa estuary, Auckland, to assess the potential effects of Cu, Pb and Zn, individually and in a mixture, on estuarine communities. Surface sediments were replaced with defaunated sediment discs spiked with either Cu (110 µg g^–1), Pb (85 µg g^–1) or Zn (500 µg g^–1), or a mixture of these 3 metals. Infaunal recolonisation was examined after 10 and 20 d. The control, having non-spiked sediments, and the Pb treatment had significantly higher average infaunal abundances and species richness than the Cu, Zn or mixed treatments. The structure of infaunal assemblages in the control and the Pb treatment differed significantly from those in the Cu or Zn treatments, which had lower abundances of polychaetes and the bivalve Macomona liliana. Differential sensitivities of different taxa to the 3 different metals resulted in greater overall impacts on community structure for the mixed treatment than for the treatments spiked with individual metals alone. This experiment clearly showed adverse effects of Cu and Zn on estuarine infauna in the field, indicating that potential increases in metal concentrations in New Zealand’s estuaries through time should be treated as a serious environmental concern.

KEY WORDS:Heavy metal · Manipulative experiment · Infauna · Community structure · Estuary · New Zealand