VanLandeghem, M.M., Farooqi, M., Southard, G., Patiño, R. 2015. Associations between water physicochemistry and Prymnesium parvum presence, abundance, and toxicity in west Texas reservoirs. Journal of the American Water Resources Association 51: 471-486.
Toxic blooms of golden alga (Prymnesium parvum) have caused substantial ecological and economic harm in freshwater and marine systems throughout the world. In North America, golden alga has invaded freshwater systems including large reservoirs; management of water quality is one proposed option for golden alga control in these systems. We therefore tested the hypothesis that physicochemical characteristics of water influence golden alga presence, abundance, and toxicity in the Upper Colorado River basin (UCR) in west Texas. The UCR contains reservoirs that have experienced repeated blooms and other reservoirs where golden alga is present but has not been toxic. We quantified golden alga abundance (hemocytometer counts), ichthyotoxicity (bioassay), and water quality (surface grab samples) in three impacted reservoirs from the Colorado River or its tributaries; two reference reservoirs from the Concho River; and three sites at the confluence of the Colorado and Concho rivers. Sampling occurred monthly from January 2010 to July 2011. Impacted sites were characterized by higher specific conductance, hardness, and fluoride than reference and confluence sites. Within impacted reservoirs, golden alga abundance and ichthyotoxicity were associated with water temperature. Blooms peaked at ~10°C and generally did not occur above 20°C. Overall, these findings suggest that management of land and water use to reduce hardness or salinity could produce unfavorable conditions for golden alga.