Coupling Bacterioplankton Populations and Environment to Community Function in Coastal Temperate Waters.

Bacterioplankton play a key role in marine waters facilitating processes important for carbon cycling. However, the influence of specific bacterial populations and environmental conditions on bacterioplankton community performance remains unclear. The aim of the present study was to identify drivers of bacterioplankton community functions, taking into account the variability in community composition and environmental conditions over seasons, in two contrasting coastal systems.

Significant N₂ fixation by heterotrophs, photoheterotrophs and heterocystous cyanobacteria in two temperate estuaries.

Nitrogen (N) fixation is fueling planktonic production in a multitude of aquatic environments. In meso- and poly-haline estuaries, however, the contribution of N by pelagic N₂ fixation is believed to be insignificant due to the high input of N from land and the presumed absence of active N₂-fixing organisms. Here we report N₂ fixation rates, nifH gene composition and nifH gene transcript abundance for key diazotrophic groups over 1 year in two contrasting, temperate, estuarine systems: Roskilde Fjord (RF) and the Great Belt (GB) strait.