Interactive effects of chemical contamination and elevated temperature on phytoplankton abundance and community composition

REU Fellow: Kaitlyn O. Parker, University of Mary Washington

Mentor: Dr. Risa A. Cohen

Chemical contamination has damaging effects on aquatic ecosystems. Surfactants, such as alkyl polyglucoside (APG), in cleaning products enter surface water in runoff and wastewater, decreasing phytoplankton food availability for grazers. Furthermore, environmental conditions such as elevated temperature may enhance phytoplankton susceptibility to APG. Not all phytoplankton species provide sufficient nutrition to grazers, therefore, APG-induced dominance by unpalatable or toxic species could affect food availability to zooplankton. To determine whether temperature influences algal community responses to APG, phytoplankton communities (Navicula sp., Microcystis sp., and Scenedesmus sp.) were exposed to different temperatures (20, 25, 30, 35, or 40°C) and APG concentrations (0, 2.5, or 10 mg L-1) in incubators. After one week, cell density generally decreased with increasing APG concentration for all three species. Responses to temperature were species-specific; highest densities of Navicula sp. and Scenedesmus sp. typically occurred between 25-35°C. Microcystis sp. densities were low across all treatments, though it was the only species to tolerate 40°C. Surprisingly, Scenedesmus sp. was most abundant and comprised >90% of the community at 35°C with 10 mg L-1 APG. Thus, temperature alters phytoplankton community responses to APG, potentially shifting dominance toward unpalatable species and reduced food web support for higher trophic levels.