青森県・屏風山湖沼群における動物プランクトンの群集構造

概要

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Composition and abundance were studied for zooplankton communities in 26 small lakes and irrigation ponds in the ByobusanLakes, Aomori Prefecture, northern Honshu, Japan. Total number of zoplankton taxa recorded varied from 7 to 35 amongthe lakes, and more densely vegetated lakes tended to harbor more number of taxa with rich cladcocerans. In a sand dune lake,L. Hiyamizu-numa, the zooplankton communities were richer in vegetated sites than in open water sites. Thus it is suggestedthat diversity of zooplankton communities depends on aquatic vegetation. Total density of zooplankton was significantlycorrelated with chlorophyll a concentration in the lake water. In many of the lakes, rotifers, especially Keratella cochlearisand Polyarthra spp. dominated in the open waters and densities of these two taxa were reversely correlated to each other,suggesting some competition between them. Comparing with past records, it is suggested that decrease of aquatic vegetationand increase of predation pressures by planktonivorous fish have changed from crustacean-dominated to rotifer-dominatedzooplankton communities at least in some lakes.
2009-03-30