Plankton as an indicator of heavy metal pollution in a freshwater reservoir of Madhya Pradesh, India.

Halali Reservoir is an important freshwater body of Madhya Pradesh. The water of the reservoir is used for drinking, irrigation and aquaculture practices. It receives untreated sewage, wastes from small scale industries and agricultural runoff from the catchment area. Various heavy metal (Cd, Cr, Cu, Ni, Pb and Zn) levels were measured in plankton of Halali Reservoir during 2006-2007 by inductively coupled plasma-optical emission spectrometry. Mean concentration ranges for Cd, Cr, Cu, Ni, Pb and Zn were 0.0018-0.0037, 0.0038-0.2257, 0.0013-0.0228, 0.0011-0.0086, 0.0133-0.0494 and 0.0130-0.1168 μg g⁻¹, respectively. Overall, mean Cr concentrations in the plankton were generally the highest of the six metals at four of the five study sites. Metal concentrations at these four sites generally followed the order: Cr > Zn > Pb > Cu > Ni > Cd. Mean concentrations of all metals at a fifth site were consistently lower than at the other sites. The high levels of Cr in the plankton are in agreement with high Cr levels that have been reported in fish from this reservoir, indicating that plankton may serve as a useful indicator of metal pollution in fish.