Evidence of rapid transfer and bioaccumulation of Microcystin‐ LR poses potential risk to freshwater prawn Macrobrachium rosenbergii (de Man)

Abstract

Microcystins accumulate in aquatic organisms and can be transferred to higher trophic levels, eventually affecting vector animals and consumers. We examined three levels of an aquatic food chain (Microcystis aeruginosa, Daphnia magna and Macrobrachium rosenbergii) to identify the transfer efficiency and risk of microcystin on prawns. Samples were analysed using ultra performance liquid chromatography-mass spectrometry (MS)/MS and microcystin-LR (MC-LR) distributions in prawn tissues were studied. The results showed that prawns accumulate MC-LR both directly from M. aeruginosa and indirectly through D. magna which was pre-exposed to M. aeruginosa. MC-LR was detected in the gills, digestive tracts and hepatopancreas of the prawns 2 h after exposure. MC-LR accumulated in prawns to 0.49 ± 0.04 μg g−1 dry weight in hepatopancreas within 24 h, while it was not detected in muscle samples, and rarely appeared in blood samples in such a short period. Although MC-LR was not detected in muscle, the head including hepatopancreas of the prawns accumulated troublesome amounts of MC-LR. These results demonstrate that microcystis blooms in prawn farming potentially pose a risk to human consumers, although prawns may be exposed to the bloom for a very short time, hence regular monitoring of blue green algae population is recommended.