Surfacant Contamination Alters Freshwater Phytoplankton Community Composition

Pollution from cleaning and personal care products enter freshwater systems and have the potential to alter phytoplankton abundance and diversity. Alkyl polyglucoside (APG), a widely used foaming agent in detergents, decreases phytoplankton abundance, but whether sensitivity to APG is affected by taxonomic identity and/or the presence of competitors is unclear. Establishing taxon-specific responses to APG is important, because taxa differ in nutritional quality and palatability for zooplankton grazers. Chapter one describes comparisons between how individual phytoplankton communities respond to the same range of APG concentrations to test hypotheses that: 1) chemical concentration determines how individual taxa respond to APG; 2) individual taxon responses to APG concentration are affected by the presence of competitors. Microcosms were inoculated with either individual phytoplankton species or communities with known cell densities and exposed to one of five APG treatments: 0 (control), 0.01, 0.5, 2, or 10 mg L-1. Cell density and chlorophyll-a concentration responses were used to determine APG effects on phytoplankton. Results indicated that in the lab, changes in community composition were due to losses of Microcystis aeruginosa, while in the field changes were mostly due to losses of Navicula sp. However, natural communities are comprised of many more phytoplankton species than constructed communities, and grazers and other trophic levels are present. Chapter two describes a comparison of two experiments, one experiment where ambient phytoplankton communities were exposed to APG with zooplankton grazers, and one experiment without zooplankton grazers. The hypothesis was that APG influences phytoplankton community composition more in the presence of zooplankton grazers. Results indicate that there was no observed effect of APG without grazers, but with grazers APG influenced community composition and Chlorella sp. abundance. The presence of zooplankton resulted in reduced abundance of palatable taxa considered to be high quality food for grazers