Ross V. Hyne

Invertebrate biomarkers: links to toxicosis that predict population decline.

The application of biochemical measurements that can be used as individual biomarkers of impaired biological function in invertebrates is reviewed to evaluate whether biochemical biomarkers of aquatic invertebrates can predict changes in natural populations. Biomarkers that measure toxic effects at the molecular level (e.g., the inhibition of brain acetylcholinesterase activity by organophosphorus pesticides) have been shown to provide rapid quantitative predictions of a toxic effect upon individuals in laboratory studies. Such biomarkers should not be used as a replacement for conventional aquatic monitoring techniques, but should be applied as supplementary approaches for demonstrating links between sublethal biochemical and adverse effects in natural populations in field studies. The research challenge for using biomarker measurements in aquatic invertebrates is to predict effects at the population level from effects at the individual level measured upon individuals collected in the field.

Short-term exposure to aqueous endosulfan affects macroinvertebrate assemblages

The toxicity of the organochlorine pesticide endosulfan to macroinvertebrate assemblages was tested using a system of 24 artificial streams. In separate experiments, the effects of 12- and 48-h exposure to aqueous endosulfan were assessed. No-observed-effect concentrations (NOEC) for endosulfan on macroinvertebrate assemblages were 8.69 and 1.00 microg/L for the 12- and 48-h exposure studies, respectively. In both studies, changes were driven by reduced abundances of the mayfly, Jappa kutera. Algal blooms occurred in the 48-h exposure experiment in streams that received the 6.87 or 30.70 microg/L treatments. These effects occurred at concentrations that might occur as a result of episodic events such as accidental overspray or rainstorms. By establishing a causal link between endosulfan and changes to macroinvertebrate assemblages, this study adds further weight to the hypothesis that endosulfan is a major contributor to changes observed in rivers of the cotton-growing region of New South Wales, Australia during the pesticide spray season.

Toxicity of endosulfan to Atalophlebia spp. (Ephemeroptera) in the laboratory, mesocosm, and field

A series of single-species toxicity tests was conducted in the laboratory and in outdoor stream mesocosms. The mayfly nymphs of Atalophlebia spp. (A. av2 and A. av6) were exposed to the organochlorine pesticide endosulfan for either 12- or 48-h periods, with mortality recorded after 96 h. For both exposure periods, the lethal concentration (LC50 and LC 10) values were not significantly different between laboratory and mesocosm single-species tests, suggesting that the absence of natural environmental conditions and biological interactions in laboratory single-species tests did not influence the toxicity of technical endosulfan to Atalophlebia spp. Interpolation of toxicity test data indicates that peak endosulfan concentrations recorded in the rivers during storm events are likely to cause only minimal impact on Atalophlebia spp. populations. This suggests that changes in the abundance of populations observed in the field, if due to total endosulfan alone, are the result of chronic rather than acute exposure.