Algal growth in warm temperate reservoirs: Nutrient-dependent kinetics of individual taxa and seasonal patterns of dominance

Samples of lake water were collected from two warm temperate reservoirs in northern Texas (USA), Cedar Creek Lake, and Eagle Mountain Lake, over a period of seven months from winter to summer. Under simulated field conditions, dilution bioassays were applied to assess limitation by N, P and trace nutrients. Growth kinetics of individual phytoplankton taxa in response to several levels of enrichment with N or P were analyzed. In every season studied, growth rates of algal taxa were often nutrient limited, with N-limitation and colimitation being especially common. Cyclotella was the dominant taxon in both lakes on an annual average, reaching its highest biomass in winter. During succession from winter to summer, there was a partial replacement of Cyclotella by cyanobacteria. Estimates of the Monod growth parameters were obtained for 21 taxa under N-limitation, and for 11 taxa under P-limitation. Cyclotella spp. should compete well for N in that its growth affinity was the highest of all the algal taxa we could study.