Abstract
AbstractCyprinids (Margariscus margarita, Phoxinus spp., Pimephales promelas) have resumed reproduction in a boreal headwater lake (Lake 302S, Experimental Lakes Area, northwestern Ontario) that is recovering from experimental acidification. Concomitant changes to the littoral food web suggested that these omnivorous minnows suppressed the development of green algal mats, termed metaphyton. We tested this hypothesis by conducting an experiment using minnow enclosures, minnow exclosures, and open control plots in the shallow littoral zone of Lake 302S. Minnows significantly suppressed zooplankton biomass, and altered community composition by disproportionally reducing large daphnids and chydorids. Epiphytic chironomids were also significantly less abundant in the presence of minnows. Minnows had a significant time-dependent, negative effect on benthic invertebrate biomass and community composition because chironomids and anisopterans were suppressed during the second half of the 6-wk experiment. However, m...
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