Structure and function of zooplankton colonization in twelve new experimental ponds

This study examined the structural and functional development of zooplankton communities in 12 new experimental ponds for one year and tested four predictions derived from the Random Placement Hypothesis (Coleman 1981). Physico-chemistry, zooplankton colonization dynamics, zooplankton community structure and function were analyzed every two weeks from 5 February 1988 to 10 February 1989. Ponds varied in physico-chemistry at points in time but followed similar patterns during the study year.

Ponds were not colonized by zooplankton similarly. Some species occurred in all ponds with about the same timing, but many species exhibited variable timing among ponds or never occurred in more than a few ponds. Colonization curves varied among ponds and through time, and species accrual curves differed in both accrual rates and the numbers of species accrued. Observed colonization curves did not closely match the curve expected according to the Random Placement Hypothesis.

Zooplankton community structure also varied among ponds. Multivariate analyses could not discern similar trends in zooplankton community structure among ponds due to the disparity of species trends among ponds. species data were pooled into taxa (Copepoda, Cladocera, Rotifera, ostracoda and Chaoborus) and analyzed. Rotifers dominated zooplankton communities in densities and biomass, and ponds differed in taxa densities and biomasses.

Zooplankton community function was more similar among ponds than community structure. Multivariate analyses indicated ponds generally followed similar trajectories in zooplankton community function through the year.

Zooplankton did not colonize experimental ponds equally and did not develop similar zooplankton community structure among ponds. Dispersal processes probably limited colonization and development of zooplankton community structure. Zooplankton community function was generally more similar among ponds than community structure, probably due to the functional redundancy of zooplankton species. Implications of these results for experimental pond studies are discussed.