Seasonal and interannual variability in primary productivity and dinitrogen fixation along the northeastern U.S. continental margin

Margaret Mulholland, Old Dominion University, mmulholl@odu.edu (Presenter)
Peter Bernhardt, Old Dominion University, pbernhar@odu.edu
Cory Staryk, Old Dominion University, cstar001@odu.edu
Antonio Mannino, NASA GSFC, antonio.mannino@nasa.gov

Primary productivity varies seasonally and interannually due to variations in top down and bottom up controls. We measured primary production and dinitrogen (N2) fixation during cruise transects spanning all four seasons along the northeastern North American Coast between Cape Hatteras and Georges Bank. In addition to higher rates of primary productivity than what had been observed during the MARMAP study 25 years ago, we found substantial rates of N2 fixation over the study area including on Georges Bank, where N2 fixation had not been previously documented. N and P concentrations were usually measurable throughout the study period suggesting that these elements were not limiting for phytoplankton growth. During the summer sampling transect, N2 fixation rates were highest and qPCR results suggest that nifH gene copies from unicellular cyanobacteria in group (UCYN-A) were the dominant diazotrophic group present throughout most of the study area including Georges Banks.

Presentation Type:  Poster

Session:  Other   (Mon 4:00 PM)

Associated Project(s): 

• Mannino, Antonio: The Impacts of Climate Variability on Primary Productivity and Carbon Distributions in the Middle Atlantic Bight and Gulf of Maine ...details

Poster Location ID: 106