Water striders (Heteroptera, Gerridae) as bioindicators of heavy metal pollution

Heavy metal contents of water striders collected near a steel factory and from control sites were analyzed by AAS. The average concentrations µg/g of dry weight found near the factory vs. the control areas were: Al 76, 65; Fe 840, 330; Mn 49, 37; Zn 310, 280; Cu 44, 42; Cd 1.6, 6.5, respectively. In most cases Ni and Pb concentrations were below the determination limit in both sites. There were significant differences between sites in the concentrations of iron and cadmium. Fifth instar larvae had higher iron content than adults, but sexes did not differ in heavy metal content. There were also significant differences between different water strider species as accumulators of zinc, aluminium and cadmium. It is concluded that water striders seem suitable as bioindicators of heavy metals.