Springer Online Journal Archives 1860-2000
Abstract Horizontal distributions of zooplankton were investigated in two kettle lakes in southern Ontario. In Tory Lake a set of random samples at 1 m depth showed that Skistodiaptomus oregonensis and copepod nauplii were overdispersed (patchy). In Lake St. George a 20 point grid sampled at each of 0.5, 2, 4, and 6 m showed that Polyarthra spp., Keratella cochlearis, Asplanchna spp., Daphnia galeata mendotae, Bosmina longirostris, Eubosmina coregoni and copepod nauplii were all patchy in terms of both vertical and horizontal distributions. Contour diagrams showed that the patches tended to be comprised of unique groups of species. This was confirmed by principal components analysis which showed that Polyarthra spp. and K. cochlearis occurred together, that D. g. mendotae was found in a unispecies patch and that B. longirostris and E. coregoni were together. None of the zooplankton patches correlated with chlorophyll a measurements. A literature review suggests that there are four basic types of patches occurring in lakes and that there are at least 16 identifiable forces which might cause these distributions. The patch types are: I) large scale (〉 1 km diameter), II) small scale, caused by wind-induced water movement, III) Langmuir circulation aggregations and IV) swarms, potentially caused by biotic factors.
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