Why Fix N2 in High N Supply Regions?

Angela Landolfi1, Wolfgang Koeve1 and Andreas Oschlies2, (1)GEOMAR Helmholtz Centre for Ocean Research Kiel, Marine Biogeochemical Modeling, Kiel, Germany, (2)GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Abstract:
Growing slowly, marine N2 fixers are expected to be competitive where nitrogen (N) supply falls short relative to that of phosphorus (P) with respect to the cellular N:P ratio (R) of non-fixing phytoplankton. Why do N2 fixers persist in the
the oligotrophic North Atlantic where the ratio of nutrients supplied to the surface is elevated in N relative to the average R (16:1)? Combining resource competition theory and a global coupled ecosystem-circulation model we find a novel mechanism that can expand the ecological niche of N2 fixers also to regions where the nutrient supply is high in N relative to R, offering a new perspective on the environmental controls of marine N2-fixers.