Increased nutrient retention and cyanobacterial blooms in a future coastal zone

Abstract

Climate change and coastal management directly affect the magnitude of nutrient loads and the functioning of the coastal zones. In this novel approach, a coastal-zone-model was used to study future retention capacity of nitrogen and phosphorus loads and changes in cyanobacterial blooms in an archipelago in a eutrophied coastal sea. By conducting projections under the combined impact of changing climate and nutrient loads we demonstrate that i) future filter efficiency of the archipelago increases compared to present day regardless of the nutrient load projection, ii) the cyanobacteria biomass increased 5-fold in a worst-case nutrient load projection and iii) resulting in an increased spread of bottom anoxia and hypoxia. However, the phytoplankton biomass and hypoxia/anoxia will remain stable if the planned mitigation is successfully implemented. This study highlights the importance of nutrient load management and the need to understand more about the complex interactions taking place in the coastal systems.