The Structure of Crustacean Zooplankton Communities in Glaciated Eastern North America

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Abstract
The zooplankton community structure of 696 lakes in Pleistocene glaciated eastern North America indicated to us that glacial influence was the primary determinant of community structure. Using this criterion we successfully discriminated 82% of the lakes between glacial lakes, to which Diaptomus sicilis, Limnocalanus macrurus, Mysis relicta, and Senecella calanoides were restricted, and nonglacial lakes, to which Cyclops scutifer, Eubosmina longispina, Daphnia pulex, D. catawba, and other species were characteristic. A third large group of common species was distributed throughout the study area with no particular relation to glacial lake influence. No clear patterns in community structure with respect to size of zooplankters were discerned. Although some species distributions or abundances were consistent with the well-known predatory and competitive interactions among zooplankters typical of small lakes and ponds, for example, the negative correlation between the predatory Mysis relicta and Eubosmina longispina, most were not. We suggest that this arose partly because the study area is large and heterogeneous and partly because the biological interactions observed in small lakes and ponds may be less intense in the more physically complex environment of large lakes.Key words: zooplankton, community structure, glacial opportunists, multivariate analysis, zoogeography, size-efficiency hypothesis