Herbicide effects on planktonic systems of different complexity

Abstract

Bioassays of different complexity were compared with respect to their capability to predict the environmental impact of the herbicide atrazine in aquatic systems. Acute toxicity tests with Daphnia did not yield meaningful results. Sublethal tests with Daphnia (feeding inhibition, reduction of growth and reproduction) were more sensitive, but effective concentrations of atrazine were still rather high (2 mg/L). A relatively complicated 'artificial food chain' system that incorporated direct and indirect effects on Daphnia yielded significant reduction of daphnid population growth at 0.1 mg/L. Enclosure experiments with natural communities were by far the most sensitive tools. Community responses could be measured at concentrations as low as 1 g/L and 0.1 #g atrazine/L. At the lowest concentration, however, communities recovered after three weeks. We conclude that in complex systems indirect effects can be more important than direct effects, so that, contrary to the conditions in simple tests, non-target organisms may be the better indicators of herbicide stress to natural communities.

Occurrence of Sediment-Bound Pyrethroids in Danish Streams and their Impact on Ecosystem Function

“…Our results also clearly indicate that not only does the particle-bound pyrethroids affect the individual but they also influence the interactions between members of different levels of the food web. It is even possible that the pesticides will have a cascading effect through the ecosystem as described for herbicides in lakes by Lampert, Fleckner, Pott, Schober, and Storkel (1989). In this way the effects of pesticides at the individual level might have even stronger impact on the functioning of the entire stream ecosystem.…”

Effect of Organic Four Solvents on Natural Phytoplankton Assemblages: Consequences for Ecotoxicological Experiments on Herbicides

“…The natural composition of algal community, with interspcific interactions, increases the complexity of the system studied. It is possible that this complexity increases the sensitivity of our phytoplankton system to a stress like DMSO solvent (Lampert et al 1989). These results confirm the potential effect of solvents on natural assemblages of phytoplankton and the necessity to perform preliminary experiments with DMSO when the use of organic solvent in ecotoxicological phytoplankton experiments is required.…”

Effects of Microcystis aeruginosa on interference competition between Daphnia pulex and Keratella cochlearis

“…In addition, others found sublethal effects in Daphnia species which, although not investigated, have the potential to affect interactions with rotifers vulnerable to interference competition . The herbicide atrazine decreased adult body size in Daphnia pulex (Schober & Lampert, 1977) and depressed feeding rates in D. pulicaria (Lampert et al, 1989) while the insecticide lindane decreased filtering rates in D. pulex (Gliwicz & Sieniawska, 1986) . Toxicity studies concerned only with lethal effects or relative susceptibilities ignore the aspect of species' interactions within complex ecosystems (Winner & Farrell, 1976) .…”