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 per iod of seven months from winter to summer. Under simulated field conditions , dilution bioassays were applied to assess limitation by N, P and trace nu trients. Growth kinetics of individual phytoplankton taxa in response to se veral levels of enrichment with N or P were analyzed. In every season studi ed, growth rates of algal laxa were often nutrient limited, with N-limitati on and colimitation being especially common. Cyclotella was the dominant ta xon in both lakes on an annual average, reaching its highest biomass in win ter. During succession from winter to summer, there was a partial replaceme nt of Cyclotella by cyanobacteria. Estimates of the Monod growth parameters were obtained for 21 taxa under N-limitation, and for 11 taxa under P-limi tation. Cyclotella spp. should compete well for N in that its growth affini ty was the highest of all the algal taxa we could study.