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Bollmohr S, Schulz R: SEASONAL CHANGES OF MACROINVERTEBRATE COMMUNITIES IN A WESTERN CAPE RIVER, SOUTH AFRICA, RECEIVING NONPOINT-SOURCE INSECTICIDE POLLUTION. Environ Toxicol Chem. 2008 Nov 12:1.
A field study was conducted at three different sites along the Lourens River, South Africa to assess aquatic macroinvertebrate abundances and community structures in relation to seasonal changes in rainfall and particle associated organophosphate (OP) insecticide contamination. Redundancy analysis confirmed OP insecticide contamination as the only significant variable determining the communities. Principal response curves indicated that the invertebrate community dynamic at the highest contaminated site LR3 (51.5 +/- 27.0 microg/kg total OP in suspended particles) differed significantly from the less contaminated site LR2 (10.4 +/- 5.8 microg/kg total OP in suspended particles) during the dry season (October to December; pesticide application period), while there was no difference during the wet season (July to September). Ephemeroptera abundances increased significantly (p=0.0021) at the control site LR1 from wet to dry season, while abundances significantly decreased (p=0.0011) at site LR3. Two-by-two factorial analysis of variance resulted in a significant interaction of site and season for the three most abundant mayfly taxa Baetis sp., Demoreptus sp. and Castanophlebia sp. confirming a potential OP effect. Apart from the OP contamination only flow velocities showed significant differences between wet and dry season at some sites. In conclusion, this study suggests that particle-associated OPs (azinphos-methyl and chlorpyrifos) affected community structure in the Lourens River at levels > 30 mug/kg total OP, while levels <10 mug/kg total OP did not yield any significant effects. |
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