Diazotrophs and N-Fixation Associated With Particles in Coastal Estuarine Waters.

Putative heterotrophic bacteria carrying out N-fixation, so-called non-cyanobacterial diazotrophs (NCDs), are widely distributed in marine waters, but details of how the O-inhibited N-fixation process is promoted in the oxic water column remains ambiguous. Here we carried out two experiments with water from a eutrophic temperate fjord to examine whether low-oxygen microenvironments within particulate organic matter could be loci suitable for N-fixation. First, water enriched with natural particles or sediment showed higher N-fixation rates than bulk water, and nitrogenase genes () revealed that specific diazotrophs were affiliated with the particulate matter.