Phytoplankton colonization and seasonal succession in new experimental ponds

Abstract

Following the U.S. Environmental Protection Agency’s specifications for pesticide registration tests, 12 experimental ponds were constructed in Blackstone, VA at VPI&SU Southern Piedmont Agricultural Experiment Station. Colonization and succession of the ponds’ phytoplankton communities were investigated during the first year after filling. Taxa richness and densities, biomass as chlorophyll a, and primary productivity (in situ oxygen method) were measured. In addition, water quality data were collected and analyzed. The dominant taxonomic groups were the Cyanophyceae, Chlorophyceae (with Desmidiaceae dominating), Dinobryon (in the Chrysophyceae), Dinophyceae, and Bacillariophyceae. Similar successional patterns in all 12 ponds occurred, however, the community structure between ponds was not similar at any given time. Although the ponds had statistically similar environmental characteristics, they varied in their community structure indicating that, after one year, they were not mature enough for use as replicate test systems. No structural parameter could be measured with reasonable precision using a three replicate pond scheme recommended by the USEPA. Taxa richness could be measured with a precision of approximately 25% over the year; and was ≤11% during the peak growing months. Taxa densities could usually be measured with a precision of <100% during these months. The in situ oxygen method for measuring primary productivity was found to be to insensitive during early colonization. The heterogeneity of the ponds’ phytoplankton communities indicate that mesocosms will need to be managed to produce replicate experimental units.