On the way to cyanobacterial blooms: impact of the herbicide metribuzin on the competition between a green alga (Scenedesmus) and a cyanobacterium (Microcystis).
The hypothesis that exposure to a common and widely applied photosynthesis-inhibiting herbicide, metribuzin, would alter the outcome of the competitive battle between susceptible green algae (Scenedesmus obliquus) and tolerant cyanobacteria (Microcystis aeruginosa) was tested. In a long-term (17 d) experiment, Scenedesmus and Microcystis populations as well as mixtures that started with different inoculum composition (i.e. 3:1, 1:1 and 1:3 Scenedesmus:Microcystis) were grown in the absence or presence of metribuzin (100 microg l-1). In the absence of metribuzin, Scenedesmus was competitively superior and out-competed Microcystis regardless the initial composition of the mixed communities. However, this competitive outcome was reversed completely in the presence of metribuzin, where despite growth inhibition Microcystis became dominant. Hence, photosynthesis-inhibiting herbicides may not only affect algal community structure, but also provide cyanobacteria founder populations a window for dominance and thus play an important role in promoting cyanobacteria blooms.
Department of Environmental Sciences, Aquatic Ecology and Water Quality Management Group, Wageningen University, P.O. Box 8080, 6700 DD Wageningen, The Netherlands. miquel.lurling@wur.nl
Miquel
M
Lürling
Ivo
I
Roessink
D004351:Drug Resistance; D006540:Herbicides / Q000633:toxicity*; D046931:Microcystis / Q000187:drug effects* / Q000254:growth & development; D010788:Photosynthesis / Q000187:drug effects; D044444:Scenedesmus / Q000187:drug effects* / Q000254:growth & development; D014227:Triazines / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D006540:Herbicides; D014227:Triazines; D014874:Water Pollutants, Chemical; C009235:metribuzin