Biomonitoring of Trace Metal Pollution Using Fishes From the Cochin Backwaters

Abstract

Trace metal concentrations (Fe, Co, Ni, Cu, Zn, Cd, and Pb) in the muscle, gill and liver of the fishes Mugil cephalus, Etroplus suratensis, Sillago sihama, and Arius arius collected from the Cochin backwaters during monsoon, post-monsoon and pre-monsoon periods were studied. The seasonal average ranges of these metal concentrations in the muscle, gill and liver of fishes were respectively as follows: Fe (546.51 to 956.05 μg/g, 602.87 to 1028.05 μg/g and 706.72 to 1114.58 μg/g); Co (12.50 to 28.05 μg/g, 21.43 to 35.73 μg/g and 30.90 to 52.23 μg/g); Ni (4.45 to 6.63 μg/g, 6.73 to 14.83 μg/g and 11.59 to 39.18 μg/g); Cu (5.12 to 6.16 μg/g, 17.79 to 30.53 μg/g and 33.19 to 44.70 μg/g); Zn (48.97 to 144.50 μg/g, 89.02 to 246.79 μg/g and 200.82 to 403.40 μg/g); Cd (1.17 to 2.35 μg/g, 2.01 to 3.50 μg/g and 3.49 to 4.37 μg/g); and Pb (1.01 to 1.95 μg/g, 1.32 to 2.07 μg/g and 2.11 to 3.03 μg/g). The elevated accumulation of metals in the fishes was well above the natural background levels during all the seasons and could be attributed to the favorable absorption and bioavailability of metals arising from the environmental compartments that are chronically exposed to industrial effluents under the prevailing physicochemical conditions. Regardless of the season, metal bioaccumulation was higher in liver than in gill or muscle. The high metal concentrations in these tissues are most likely related to the high influx of metals as a result of pollution from the industries located on the banks of the Periyar River and the consequent increased bioavailability of metals to the fish there. High metal bioaccumulation and its variability in the muscle, gill, and liver of fish provide evidence of exposure to contamination events in estuarine ecosystems. Additionally, these results suggest the importance of fish as biomonitors of trace metal pollution and their usefulness in forensic investigations for tracing and tracking pollution sources.