Nitrogen fixation by diazotrophic cyanobacteria in the Baltic Sea and transfer of the newly fixed nitrogen to picoplankton organisms

摘要: Nitrogen fixation ( 15 N 2 -tracer method) by filamentous cyanobacteria and the flux of newly fixed nitrogen into picoplanktonic organisms were investigated during three cruises in central Baltic Sea July August 1995 1996. The diazotrophic consisted mainly Aphanizomenon Nodularia picoplankton fraction Synechococcus, a coccoid nondiazotrophic cyanobacterium. average -fixation rate measured two studies (3.9 nmol l -1 h 2.4 1996), was about 13 times higher than (0.3 ). During studies, 5-10% total found fraction, but none August. study shows that early stage cyanobacterial bloom new is provided for pelagic foodweb through release recently diazotrophs, whereas late input occurs lysing decaying cells. Considerable temporal local variations this indicate broader time location are needed to assess contribution budget Sea.