Toxicities of Adda Produced During Microcystin Anoxic/Anaerobic Degradation to Caenorhabditis elegans

Recent studies have shown that micocystins(MCs)can be degraded by indigenous bacteria from lake sediments under anoxic/ anaerobic conditions. Unlike aerobic MCs degradation, in which MCs are completely decomposed, anoxic/anaerobic degradation can produce and accumulate one product Adda. Up to now, however, little is known about the toxicities of this product. To assess the safety of anoxic/ anaerobic degradation of MCs, the toxicities of Adda were investigated using Caenorhabditis elegans(C. elegans)as the animal model. Our results showed that exposure to low dose Adda(not more than 0.05 μmol·L-1)had no negative effect on C. elegans. Exposure to Adda of 0.1 μmol·L-1 could lead to significant defects of head and body locomotion, whereas no negative effect was observed for other functions at the same dosage, suggesting that locomotion ability of C. elegans was more susceptible to Adda than other tested functions. All tested functions except for the rate of vulva abnormality of C. elegans were significantly negatively affected when exposed to Adda of 0.5 μmol·L-1. These re- sults suggest that Adda is far less toxic than MCLR and biodegradation under anoxic/anaerobic conditions can detoxify MCs efficiently. How- ever, the high concentration of Adda may still pose new risks to ecosystem if it accumulates in natural environment during MCs anoxic/anaer- obic degradation.