The dissolved inorganic nitrogen to phosphorus (DIN:DIP) ratio is decreasing in the Baltic Sea leaving an excess of phosphate in the water column after the northern Baltic spring bloom. This condition is assumed to favour the growth of diazotrophic filamentous cyanobacteria, which are capable of N2-fixation and therefore not dependent on bioavailable nitrogen forms like other phytoplankton. However, filamentous cyanobacteria grow relatively slowly and require higher water temperatures for optimal growth compared to other phytoplankton and typically bloom ~2 months after the termination of the spring bloom.
This project investigates the potential of the post-spring-bloom plankton community in excess phosphate removal before the massive cyanobacterial blooms in later summer months. Understanding the relationship between the excess phosphate and cyanobacteria blooms is important in developing cyanobacteria bloom forecasts and improve the management of the Baltic Sea eutrophication problem.