Effect of feeding selectivity on the transfer of methylmercury through experimental marine food chains

Abstract

The present study established an experimental marine food chain of three levels (microalgae → zooplankton → fish) to investigate the effect of feeding selectivity on the transfer of methylmercury (MeHg) through the food chain. Total Hg concentrations in Chlorella sp., Nitzschia closterium and Isochrysis galbana exposed to 1 μg L−1 MeHg for three days were 27.91, 32.74 and 40.03 μg g−1 respectively and were significantly different (p < 0.05) between species. Moina mongolica and Artemia sp. primarily selected Chlorella sp. as the sole diet, though the Artemia sp. partly grazed on I. galbana as well. Harpacticus uniremis, however, preferred to graze N. closterium and I. galbana and avoided Chlorella sp. The varying concentration of Hg in the microalgae species as well as the selectivity of zooplankton to the algal diet resulted in varying Hg accumulation in three zooplankton species (M. mongolica < Artemia sp. < H. uniremis with total Hg concentrations of 0.14, 0.66 and 0.82 μg g−1, respectively). Scophthalmus maximus and Paralichthys olivaceus mainly preyed on H. uniremis and partly on M. mongolica, while Fugu rubripes primarily preyed on M. mongolica and secondarily on Artemia sp. Thus, similar reasoning as above could explain the significant difference in Hg accumulation in the fish (S. maximus > P. olivaceus > F. rubripes with total Hg concentrations of 0.0042, 0.0031 and 0.0020 μg g−1, respectively). These investigations suggested feeding selectivity plays a key role in the transfer of MeHg along marine food chains.