The Gulf of Finland belongs to one of the most loaded and eutrophicated regions of the Baltic Sea, where the occurrence and extension of both the hypoxic conditions and cyanobacterial blooms have increased significantly since the mid-1990s.
After the invasion and establishment of the polychaete Marenzelleria, the ecosystem have gone through drastic changes.
Novel 3D model explores ecosystem changes
In a new study Oleg Savchuk and researchers from Russia explore possible mechanisms of these changes and how Marenzelleria affect the Gulf of Finland ecosystem with its bioirrigation.
By modifying the 3D ecosystem model SPBEM (St. PetersBurg Eutrophication Model), that couples a transport module with a biogeochemical module, they have accounted for bioirrigation by Marenzellaria.
The researchers have then used the model to run different scenarios for the Gulf of Finland ecosystem, studying how the ecosystem would respond to future climate with- and without this invasive species for the time period 2007-2040.
Increasing oxygenation of sediments
In both scenarios increasing oxygenation of sediments were projected, with decreased denitrification and increased phosphorus sediment P retention. Pelagic DIN/DIP increase resulted in decreasing cyanobacterial nitrogen fixation.
Their study demonstrates that on a system level biogeochemical consequences of both implemented climate changes scenario and polychaete activity are equivalent to a weakening of “vicious circle” of the Baltic Sea eutrophication.