Factors influencing acute toxicity estimates of hydrogen sulfide to freshwater invertebrates

Abstract

Abstract Acute bioassay tests of hydrogen sulfide were run on Assellus militaris Hay, Crangonyx richmondensis laurentianus Bousfield. Gammarus pseudolimnacus Bousfield. Bactis vagans McDonough. Ephemera simulans Walker and Hexagenia limbata (Serville). Size and type of test chamber, type of substrate for barrowing forms or those seeking shelter in gravel, oxygen concentration, pH, and season of collection influenced the sensitivity of organisms. Hydrogen sulfide exposure at sublethal levels reduced feeding activity of Gammarus . Data indicate that test conditions should approximate natural habitat conditions as closely as practical. The most acceptable 96-h LC 50 hydrogen sulfide concentrations for the various species are: Assellus 1.07 mg 1 −1 Crangonyx 0.84 mg 1 −1 . Gammarus 0.059 mg 1 −1 . Baetis 0.020 mg 1 −1 . Ephemera 0.316 mg 1 −1 , and Hexagenia , 0.111 mg 1 −1 . Chronic exposure tests now in progress suggest that the no-effect levels are 8–12 per cent of the 96-h LC 50 .