Abstract:

Microcystin release in freshwaters is a major public health and ecological threat, affecting survival and trophic interactions across food web components. Although bioaccumulation has been suggested to represent an important pathway for microcystin uptake and trophic transfer across different food web compartments, it is rarely known how microcystin exposure may affect survival and accumulation among lower trophic levels under environmentally realistic scenario. Therefore, in this study, survival and microcystin accumulations in the UK native amphipod species, Gammarus pulex were monitored during a 96-hour static acute toxicity experiment. Animals were exposed to a range of environmentally relevant microcystin concentrations (0.01–10μg/L) across two treatment types, purified MC-LR and crude extract of microcystin-producing Microcystis aeruginosa. Survival of G. pulex individuals across the two treatments showed no evidence of significant difference from the control. Microcystin concentrations observed in G. pulex exposed to the purified MC-LR and crude extract ranged from (12.8 – 27.5) ng/g of MC-LR and (5.6-12.8) ng/g of MC-LR respectively. Microcystin concentrations measured in animals showed strong positive correlations with toxin concentrations in the experimental media across the two treatments, suggesting G. pulex can bioaccumulate microcystins, therefore may represent a potential vector for microcystin exposure to higher food web consumers. These results highlight the fact that exposure of benthic food web components to environmental microcystin concentrations may constitute an important route of toxin transfer within freshwater food webs.