Marine micronutrient vectors: seabirds, marine mammals and fishes egest high concentrations of bioactive metals in the subantarctic island ecosystem

[摘要] ABSTRACT: We investigated concentrations of bioactive metals (Mn, Fe, Co, Ni, Cu, Zn, As, Cd) in organic matter source pools: suspended particulate organic matter and macroalgae, and macrozooplankton from the vicinity of the Snares Islands, situated adjacent to the Subtropical Frontal Zone south of New Zealand. Further we sampled egested material from 6 coastal fishes, 8 seabirds and 2 pinniped species with rookeries on the islands. Analysis of δ¹⁵N and δ¹³C from basal organic matter sources, zooplankton, fish muscle tissue and egesta of fishes, seabirds and pinnipeds was used to estimate trophic position for each group. We found a food web heavily dependent on pelagic productivity culminating with New Zealand fur seals and Hooker’s sea lions. We compared multivariate concentration profiles of metals in the egesta of 4 trophic level groups from the Snares Islands with 4 similar trophic groups from the Auckland Islands. Results indicated more variation in concentration of bioactive metals in egesta among trophic level groups, than among islands. These results demonstrated that several potentially limiting micronutrients (Mn, Fe, Co, Zn) are bioaccumulated in the egesta of upper trophic levels of subantarctic food webs. The variance in concentration patterns of bioactive metals is more coincident with differences in food web structure than differences in water mass type surrounding the 2 islands. The patterns observed have important implications for understanding the interactions between food web architecture, biological vectors and productivity around the subantarctic islands of the Southern Ocean.

[学科分类] 海洋学与技术

[关键词] Southern Ocean;Iron;Seabird;Fish;Marine mammal;Nutrient vector