Effects of a pulsed treatment with the herbicide Afalon (active ingredient linuron) on macrophyte-dominated mesocosms. II. Structural responses

• Published in: Environmental toxicology and chemistry Vol. 18; no. 12; pp. 2866 - 2874
• Main Authors: Van Geest, Gerben J., Zwaardemaker, Nathalie G., Van Wijngaarden, René P.A., Cuppen, Jan G.M.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Periodicals, Inc 01-12-1999; SETAC
• Subjects: Animal, plant and microbial ecology; Applied ecology; aquatic ecosystems; aquatische ecosystemen; biocenose; biocoenosis; Biological and medical sciences; ditches; Ecosystem structure; ecosystemen; ecosystems; Ecotoxicology, biological effects of pollution; environmental impact; Fresh water environment; Freshwater; Fundamental and applied biological sciences. Psychology; Hydrologie; Hydrology; Invertebrata; Linuron; Mesocosms; milieueffect; nederland; Netherlands; pesticiden; pesticides; Risk assessment; Scenedesmus acutus; sloten; structure; structuur; Haloragidaceae; Periphyton; Risk; Chlorophyceae; Myriophyllum spicatum; Aquatic environment; Dicotyledones; Ecosystem; Angiospermae; Ureas; Phytoplankton; Aquatic plant; Structure; Thallophyta; Evaluation; Algae; Spraying; Pesticides; Scenedesmus; Experimental study; Herbicide; Chlorophyta; Aquatic weed; Spermatophyta; Zooplankton
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1002/etc.5620181230

Outdoor mesocosms (experimental drainage ditches) were treated repeatedly with linuron at nominal concentrations of 0, 0.5, 5, 15, and 50 micrograms/L. After each of three treatments (with 4-week intervals), the systems were kept static for 1 week. Subsequently, they were flushed with nonpolluted surface water with a residence time of 5 d until the next treatment. Species composition and abundance of macrophytes, periphyton, phytoplankton, zooplankton, and macroinvertebrates were examined at prefixed time intervals. During the treatment periods, significant decreases in oxygen concentration and pH were observed, whereas the systems recovered during the flushing periods. The effects of the pulsed treatments on the structural endpoints (biota) were rarely significant and consistently were difficult to interpret. We conclude that under these experimental conditions, pulsed treatment with linuron causes only minor and negligible effects on the abundance of organisms in mesocosms, even when maximum permissible concentrations are exceeded by about 80 times. Risk assessment based on the more sensitive physiologic and functional endpoints suggested that the safety factor of 0.1 times the acute EC50 of the most sensitive standard alga (Scenedesmus acutus), as adopted in the Uniform Principles of the European Union, is sufficient to protect the community of the mesocosms in an exposure regime that was realistic for Dutch drainage ditches, using a photosynthesis inhibitor as the benchmark compound.