Introduction to Nitrogen Fixation Biological N2 fixation is an
important part of the marine nitrogen cycle as it provides a
source of new nitrogen that can support biological carbon export
and sequestration. Research in the past decade has focused on
determining the patterns of distribution and abundance of
diazotrophs, defining the environmental features leading to
these patterns and characterizing the factors that constrain
marine N2 fixation overall. The export of organic material from
surface into deeper waters is dependent on the amount of CO2
fixation (primary production) that is based on new nitrogen
inputs (N2 fixation or nitrate diffusion from deep waters).
Alternatively, some primary productivity is based on the
regeneration of organic material to ammonia in surface waters.
PON, particulate organic nitrogen.