Heavy metal contents of macrobrachium hainanense fed with waste-grown chlorella pyrenoidosa

A two level aquatic food chain was simulated for the study of the transfer of heavy metals. The food chain involved animal manures and sewage sludges as nutrient sources, a unicellular green alga (Chlorella pyrenoidosa) as the primary producer and a freshwater shrimp (Macrobrachium hainanense) as the primary consumer. The results demonstrated that animal manures yielded algae and shrimps with higher productivity, but lower heavy metal contents, than sewage sludges. Shrimps fed with sludge-grown algae had the smaller increase in body weight (activated sludge: 6–8%; digested sludge: 17–23%) and the higher concentration of heavy metals. Larger increases in body weight (chicken manure: 36–39%, pig manure: 42–45%) and lower concentrations of heavy metals were found in those fed with manure-grown algae. When analysing the heavy metal contents, it was found that both biomagnification and bioelimination existed. Pb, Cu, Zn and Mn were accumulated in Chlorella cells grown in waste materials. Shrimps fed with these algae had high contents of Pb, Cu and Zn in their flesh, as well as exoskeleton, at the end of the culture period and the heavy metals (Pb, Cu and Zn) were found to be significantly correlated (p < 0·01) with those in the algae used as food. However, the moulted exoskeleton of the shrimps during the culture period also had a high level of all the metals which suggests that moulting might play an important rôle in bioelimination of the excessive toxic metals. Copyright © 1985 Published by Elsevier Ltd.