Fate and toxicity of acephate (Orthene) added to a coastal B. C. stream

Acephate was added to a small, coastal B. C. stream to yield a concentration of 1100-1200 ppb for a 5-h period. It was rapidly taken up by fish, sediments, insect nymphs and larvae. No fish or insect mortality was noted although the more toxic methamidophos was found in both groups of animals. Acephate and methamidophos residues in animals and sediments declined to trace or non-detectable levels in 24 h and to these levels in water by 96 h. The impact of acephate on the stream and its fauna was limited and localized.