Remediation of a Eutrophic Bay in the Baltic Sea

Eutrophicationof coastal ecosystems is a global problem that often results in bottom wateroxygen deficiency and in turn promotes sediment phosphorus (P) release (A). In order to increase sediment P retention, we injected dissolved aluminum into the anoxic sediment of a eutrophicsemienclosed bayin the Baltic Sea, thereby inhibiting P recycling and further eutrophication(B). The P concentration in the bayremained at half, as did phytoplankton biomass (C), compared to pretreatment conditions and compared to the reference bay. Four years after treatment the water column transparency was increased, allowing submerged vegetation to penetrate deeper, and the habitat suitable for fish and benthic fauna had expanded (D). The lowered P concentration in the baydecreased the P export to the surrounding archipelago. This is the first full-scale marine remediation project using a geo-engineering method that demonstrates a quick recovery. For successful remediation in coastal areas, permanent binding of mobile P ...