The influence of nitrogen and phosphorus on algal growth and quality in outdoor mass algal cultures

An adequate supply of nitrogen and phosphorus is imperative to ensure high production rates in mass microalgal cultures. High yield coefficients, low crude protein contents and low productivities were measured at low supplies of these nutrients. The highest production rates were measured at N and P concentrations exceeding 25 and 2 mg litre−1 respectively, at which supply the highest crude protein contents were measured. Although the carbohydrate content followed, under certain N supply conditions, an inverse relationship with the crude protein content, it was generally not affected by changes in N and P concentrations. Scenedesmus-Chlorella types had higher crude protein contents than Monoraphidium, but the latter displayed the highest productivity. A nitrogen supply ratio of NO3N:NH3N = 3:1, gave the highest production rates. Nitrogen losses of up to 69% of the supply concentrations were measured under certain conditions.