Wetlands Australia Journal, Vol 21, No 2 (2004)

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Accumulation of metals by the seagrass, Z. Capricorni in Lake Illawarra

Christine Howley, R. John Morrison, Ron J. West


The concentrations of arsenic, cadmium, copper, lead, manganese, nickel and zinc in Zostera capricorni leaves and rhizomes were analyzed in order to document the accumulation of metals in Lake Illawarra seagrass tissues and to evaluate the potential role of Z. capricorni in the cycling of metals within the lake. Metal concentrations in seagrass tissues were compared with porewater metal concentrations and previously documented sediment concentrations to determine if the seagrass tissues reflect ambient metal concentrations. Zostera leaves and/or rhizomes reflected ambient concentrations of arsenic, cadmium, copper, manganese and zinc. Lead and nickel were not accumulated to high concentrations in most tissue samples from Lake Illawarra, although differences in ambient lead concentrations were reflected in some groups of leaf samples. Metal concentrations in seagrass tissues collected near to the Port Kembla industrial complex, and adjacent to the former Tallawarra power station, were significantly higher than concentrations in seagrass samples collected from the lake entrance. The majority of metals was accumulated to higher concentrations in leaves than in rhizomes; however, arsenic concentrations were highest in rhizomes. Z. capricorni in Lake Illawarra is likely to play a significant role in the cycling of copper, manganese, and possibly lead, via uptake from sediments, acropetal transferrance to leaves, and the release of metals from leaves into the water column or into the detrital food chain via leaf litter.

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