Development of the Indigenous Chironomid Species as Ecotoxicology Test: Tool for Water Quality Management in Thailand

Abstract

In Thailand, heavy metal contamination of the aquatic ecosystem is of concern because of the effect on water quality and toxicity to aquatic biota. The aim of this study was to develop ecotoxicology test protocols using a standard test organism the midge, Chironomus striatipennis Kieffer for measuring acute and chronic toxicology.. This species is an important indigenous freshwater invertebrate in Thailand. The acute effects of cadmium using cadmium chloride and lead as lead nitrate on midge larvae were investigated by static bioassay under laboratory conditions. The observed mortality data of the acute test for median lethal concentration 48 h LC₅₀ of cadmium chloride on first, second, third and fourth instars of midge larvae were 25.1 (14.6-40.7), 201 (60.1-367), 579 (537-620) and 641 (564-717) mg/L, respectively. The 48 h LC₅₀ of lead on first, second, third and fourth instars of midge larvae were 99.9 (14.7-209), 55.5 (266-897), 1,540 (1,200-1,870) and 3790 (2,890-4,410) mg/L, respectively. The results showed that cadmium chloride and lead nitrate were highly toxic to the first instar larvae followed by second, third, and fourth instar larvae, respectively. Sublethal studies of cadmium and lead on midge showed that both cadmium and lead had effects on the body length of larvae, the development time of larvae, dry weight and the number of female and male adults. The results from this study would be useful for developing a biomonitoring tool for heavy metal contamination assessment in freshwater ecosystem and water quality management in Thailand.