The effects of temperature on the growth of and ammonia uptake by marine microalgae

Four species of microalgae were evaluated at different temperatures for their ability to remove ammonia from intensive marine fish/shrimp culture systems. Growth rates were highest on the first of three days of culturing for marine microalgae Nannochloropsis oculata, Isochrysis aff. galbana, Chaetoceros muelleri, and Tetraselmis chui. This rate was used to compare both the growth and the total ammonium nitrogen (TAN) uptake efficiencies of these organisms at different temperatures. Their dry weights (DWs) per cell were 10.3 pg for Nannochloropsis oculata, 40.4 pg for Isochrysis aff. galbana, 39.7 pg for Chaetoceros muelleri, and 369 pg for Tetraselmis chui at 25°C. Temperatures for their respective optimal growth rates were 26, 28, 33, and 25°C. There were no significant differences in growth rates among these four microalgal species at 25°C. Temperatures for maximal biomass production were 30°C for both Nannochloropsis oculata and Isochrysis aff. galbana, 35°C for Chaetoceros muelleri, and 20~30°C for Tetraselmis chui. Temperatures for maximal specific TAN uptake were respectively 25, 25, 20~30, and 25°C. Overall, Tetraselmis chui was the most efficient at TAN uptake among the four species. Our results suggest that T. chui is a good choice for removing ammonia from indoor intensive marine culture systems.