Oxidative stress responses in brackish water flea exposed to microcystin-LR and algal bloom waters from Nakdong River, Republic of Korea

Abstract

Microcystis blooms and the impact of their toxins, particularly microcystin (MC), in coastal ecosystems is an emerging threat, but the species-specific effects of MC and the potential for bioconcentration are not fully understood. We exposed the brackish water flea, Diaphanosoma celebensis, to MC-LR, which showed antioxidant responses measured at the molecular to enzyme levels but no acute toxicity. We extended our experimental investigation to measure the released MC and its uptake by D. celebensis exposed to river water. In a short-term exposure (48 h) experiment, D. celebensis exposed to water from an algal bloom (approximately 2 mu g L-1- MC) assimilated more than 50 pg MC per individual. The significant increase of MCs suggests the potential for the species to accumulate MCs. The dose-dependent increase in the antioxidant response observed in the mRNA levels also showed that D. celebensis exposed to diluted algal bloom waters were affected by toxins from cyanobacteria.