Seasonal Variability in Diazotroph Abundance and Gene Expression at a Coastal N₂ Fixation Hotspot (Outer Banks, NC)

Presenter and Co-Authors

Katherine Crider, Old Dominion UniversityFollow
Corday Selden, Old Dominion University
Kimberly Powell, Old Dominion University
P. Dreux Chappell, Old Dominion University

College

College of Sciences

Department

Ocean/Earth/Atmos Sciences

Program

Oceanography

Publication Date

4-2021

DOI

10.25883/rhas-yp76

Abstract

Marine microbial dinitrogen (N₂) fixation, the conversion of gaseous N₂ to bioavailable species, is the primary source of new oceanic nitrogen (N). N is present in nucleic acids, amino acids, and proteins, and is essential to all life. Long considered to be a primarily oligotrophic ocean process, significant N₂ fixation rates have recently been observed in coastal environments, including along the Cape Hatteras front. To see if elevated N₂ fixation was a persistent feature in this region, N₂ fixation rates and N₂ fixer (diazotroph) abundance and gene expression were investigated through roughly monthly sampling at a field station (Jennette’s Pier) in the Outer Banks, NC, from June 2019 to August 2020, as well as a day-long cruise around the pier in August of 2019. In addition to rate and molecular samples, chlorophyll, and particulate N samples were collected and salinity/temperature profiles were measured. Using quantitative polymerase chain reaction techniques, we investigated the abundance and gene expression of diazotrophic (N₂ fixing) cyanobacteria possibly responsible for these high coastal rates, and compared these results to N₂ fixation rates measured using a variant of the ¹⁵N₂ tracer assay. Diazotroph species investigated include Trichodesmium spp. and 5 endosymbiont cyanobacteria. Preliminary results suggest evidence of Gulf Stream intrusions within 300m from the shore, and a seasonal variability pattern of nitrogen fixation rates. This study provides useful measurements of coastal N inputs in the context of the global ocean N cycle and budget, and explores chemical and physical factors that affect these processes.

Disciplines

Biogeochemistry | Marine Biology | Oceanography

Files

Recommended Citation

Crider, Katherine; Selden, Corday; Powell, Kimberly; and Chappell, P. Dreux, "Seasonal Variability in Diazotroph Abundance and Gene Expression at a Coastal N₂ Fixation Hotspot (Outer Banks, NC)" (2021). College of Sciences Posters. 10.
https://digitalcommons.odu.edu/gradposters2021_sciences/10