Comparison of Phytoplankton and Autotrophic Picoplankton Populations Over a 24-Hour Period From a Pond\u27s Surface and Subsurface Waters

Phytoplankton abundance and composition relationships within the surface layer changed over short time periods (4-6 hours) in comparison with more constant associations at 2 cm below the surface. Both strata had a diverse algal flora (\u3e50 taxa), but no distinct neuston assemblage characterized the surface layer algal composition over the 24-hour study. The similarity between the two strata indicated the floral composition of the surface layer came from the water column algae below the surface. Chlorophytes, diatoms, cyanobacteria, and cryptophytes represented the most abundant algal categories for both strata with a total mean phytoplankton abundance of 3,566 cells ml-1 at the surface and 40,532 cells ml-1 at 2 cm over the 24 hours. The autotrophic picoplankton had generally similar levels of abundance over time. Their mean abundance for the 24 hours was 469 and 599 X 103 cells ml-1 at the surface and 2 cm respectively