10.10.2013: "Nitrogen cycling in the Baltic Sea – leaps and gaps in knowledge"

11:00h, Hörsaal GEOMAR West, Düsternbrooker Weg 20

 
Abstract
Twenty years ago we knew everything that was to know about nitrogen cycling in the Baltic Sea: Denitrification taking place in open sea muddy sediments was the only process removing nitrogen from the water ecosystem. Those sediments did not harbour any DNRA process, because they were not excessively burdened with organic loading. The end product of denitrification was at least 95% N2, with N2O not playing any significant role. Coastal areas acted as transport routes for nitrogen, and no denitrification took place in sandy sediments, because there was not enough organic carbon for the denitrifiers to make a living. The same went for the water column – no denitrification could be expected in such a dilute environment, with the exception of large deteriorating cyanobacterial blooms in which denitrification hot spots could form.
Since then the picture has changed dramatically: The discovery of anammox in the Baltic Sea, the better understanding of the dynamics of DNRA, the measurements of autotrophic denitrification taking place in the water column but not in cyanobacterial aggregates and the realization that the coastal rim is highly active have all challenged our earlier view of the nitrogen cycling. In my talk I will discuss the recent progress in Baltic nitrogen cycling studies. I will also try to point out the current knowledge gaps and tell what my group is planning to do in future to fill in those gaps.