Tolerances of five benthic invertebrates to hydrogen ions and metals (Cd, Pb, Al)

Abstract

96-hr LC50 static bioassays were carried out to determine if the hydrogen ion content and the levels of cadmium, lead, and aluminum characteristic of lakes in the Muskoka District, Ontario, are lethal to benthic macroinvertebrates in four functional groups. The results show that cadmium is the most toxic of the three metals tested to all four functional groups (filter feeders, scrapers, shredders, predators), but the lethal concentrations of cadmium and lead are at least two orders of magnitude higher than the levels found in Muskoka lakes at pH 5.0; similarity, the highest levels of inorganic monomeric aluminum (325 μg Al L−1) reported in central Ontario lakes is not acutely toxic to any of the five species tested. The most sensitive species tested was the shredder,Hyalella azteca, followed by the scraper,Amnicola limosa. The most tolerant species tested was the predator,Enallagma sp., followed by the filter feeders.Pisidium casertanum andPisidium compressun. Hydrogen ion content has a significant effect, but has no pronounced pattern, on the LC50 values for lead and cadmium in all invertebrates tested. The acute toxicity levels appear to be more representative of the species than of their functional feeding behavior. Populations ofH. azteca andA. limosa from low-alkalinity waters can tolerate lower pH levels than populations from high-alkalinity water.