The role of planktonic bacteria in phosphorus cycling in lakes ‐ Sink and link

Abstract

Due to their high P content (~10 times that of the algae), the bacteria in Lake Nesjøvatn were responsible for 80% of the net uptake of this element in summer. Thus, the heterotrophic bacteria acted as a sink and competed for inorganic phosphate with the algae, but the bacteria were unable to achieve physiological P saturation. Heterotrophic flagellates feeding on P‐rich bacteria regenerated two‐thirds of the P released by grazers. Therefore the role of bacteria is not as mineralizers but as net consumers of phosphate, and, because of their high requirement for P, they are a key factor in regulating the P flux in lakes. The main importance of bacteria in regeneration of P is as P‐rich food particles.