Diel Vertical Migration of Zooplankton in Lakes and Oceans by Joop Ringelberg

Author:Joop Ringelberg
Language: eng
Format: epub
Publisher: Springer Netherlands, Dordrecht

Obviously, similarities and differences in migration behaviour exist between the two species.

At least three different processes might be in operation during the first few weeks: (1) non-migrant individuals are weeded from the population by predation; (2) the number of migrating individuals in the population increases; and (3) individuals swim farther down.

1.A population of plankton animals is not genetically homogenous and the traits contributing to migration behaviour are possibly variously distributed over individuals. During the first 2 weeks of the DVM period in 1997, high numbers of a certain allozyme type of D. galeata x hyalina were still present in the epilimnion of Lake Maarsseveen (Ringelberg et al., 2004). They were gradually eaten by the 0+ perch. If no distinction can be made in genotypes and all individuals figure in the calculation of a population mean depth, this depth gradually increases as a result. For Lake Constance, a differentiation in hybrids of different genetic signature was made (Weider and Stich, 1992) some years after the seasonal migration pattern of the two parent species was described (Stich and Lampert, 1981). These hybrids have a more or less intermediate vertical distribution between the parental species and, if omitted from the calculated amplitude of what was considered D. hyalina, the amplitude of this species would become larger. Also, the presented (Stich and Lampert, 1984) increased daytime vertical distribution of D. hyalina over the summer months could have been due to predation mortality of the hybrids predominantly, and not the result of a changed behaviour.

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