Can we save the Baltic through reoxygenation of its deep sediments? Can we help nature take care of its excess in nutrients, e.g. phosphorus by re-oxygenating sediments?

The aim of the experiment is to test whether reoxygenation of hypoxic/anoxic sediments and bioturbation by the worm Marenzelleria can increase the trapping of P and favour denitrification in the sediment and thus help counteract eutrophication.

Twelve sediment boxcores were sampled at 100 m depth in Kanholmsfjärden in June during our yearly benthic monitoring cruise with the Askö personal. The boxcores were brought to Askö and placed in a thermoconstant room and maintained at 5-7 C in the dark over the summer in hypoxic conditions.

In August they were transfered to the experimental hall and an experimental system allowing a continuous flow of hypoxic or oxic water was set up. The invading polychaete Marenzelleria will be sampled and added to one of three treatments:
1) oxic water + Marenzelleria,
2) oxic water only,
3) hypoxic water
Nutrients (P, N) fluxes will be measured as well as metal release from sediment.

The project runs in collaboration with two large field projects BOX and WEBAP on the West and East coasts respectively, where large field trials are being conducted in order to re-oxygenate bottom water by artificially pumping surface water down to the sediment surface. The projects are funded by the Swedish EPA and are involving several scientists from GU, SU, IVL and others.

Stockholms universitet, Systemekologiska institutionen

Jonas Gunnarsson, forskare, jonas@ecology.su.se
Caroline Raymond, caroline@ecology.su.se
Ola Svensson, ola@ecology.su.se
Tove Porseryd