Heterotrophic bacterial mediation of ammonium and dissolved free amino acid fluxes in the Mississippi River plume

Measurements of NH₄ regeneration after manipulating bacterial abundances suggest that heterotrophic bacteria contributed a variable proportion (7 to 50%) of total N-regeneration in summer and that dissolved free amino acids could be a major substrate for ammonium regeneration. Depth profiles, spatial distributions, and seasonal differences in ammonium regeneration rates imply that the fastest regeneration rates occur spatially and temporally where primary production is the greatest. -from Authors