Nutrient Transformations in Mass Cultures of Marine Algae

Two mass cultures of marine algae were maintained for 24 continuous weeks on mixtures of secondarily treated wastewater and seawater. Nitrogen removal and algal growth were related to both nitrogen loading in the form of variations in the waste-seawater mixture and changes in the dilution rate. Nitrogen assimilation was limited to about 4 mg/l. High nitrogen removals were associated with a combination of algal assimilation and ammonia evolution at the high pond pH values attained. Algal concentrations represented as both particulate carbon (PC) and particulate nitrogen (PN) decreased linearly with increases in the dilution rate. Maximum algal yields of 6 g PC m² day¹ occurred at a dilution rate of 0.75 day¹.