When the results of field studies contradict the results of laboratory trials, it is always important to try and understand why. Some aquatic insects, particularly mayflies and stoneflies, are suspected of being highly sensitive to metals due to field survey results, but results of in-lab toxicity testing have instead shown them to be quite tolerant. A group of researchers attempted to reconcile the difference by performing community-level microcosm experiments, measuring the effects of Cu and Zn, alone and together, on stream insect communities. The EC50 values they observed (the concentration at which the abundance of aquatic insects were reduced by 50%) using this method were several orders of magnitude lower than published values from single species tests. Despite using theoretically similar toxicity levels, they also observed that Cu alone was significantly more toxic than the combination of Cu and Zn. The researchers hypothesize that “the short duration of laboratory toxicity tests and the failure to evaluate effects of metals on sensitive early life stages are the primary factors responsible for unrealistically high LC50 values in the literature.” Article: Responses of Aquatic Insects to Cu and Zn in Stream Microcosms: Understanding Differences Between Single Species Tests and Field Responses. Environmental Science & Technology (2013) DOI: 10.1021/es401255h bit.ly/11m0pia #toxicitytesting #environmental #science #aquatictoxicology
Posted on: Mon, 24 Jun 2013 07:16:05 +0000