Publication Date:
2022-05-25
Description:
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2013
Description:
Nitrogen and trace metal biogeochemical effects on phytoplankton productivity were
compared through whole water bottle incubations and proteomic evaluation of in situ
harvested particulate matter from two distinct oceanographic regions: the Equatorial
Pacific Upwelling and the South Pacific Gyre. Phytoplankton growth in both regions was
stimulated by nitrogen additions with equivalent response from nitrate and urea. In the
gyre, trace metal additions did not yield a chlorophyll response, however nickel
treatments showed evidence of nickel-limited nitrogen fixation. In contrast, cell growth at
the upwelling site was primarily iron-limited and iron plus urea or nitrate additions
further enhanced the chlorophyll response, indicative of secondary nitrogen limitation.
Nitrogen stress proteins and urea transporters from cyanobacteria in these field sites
showed similar trends, with both increasing in waters containing lower dissolved
inorganic nitrogen. Together with bottle incubations, the abundant urea transporters and
nitrogen stress proteins indicate the importance of urea in these field sites. Representative
cyanobacteria cultures (Synechococcus strain WH8020, and Prochlorococcus strain
MED4) were evaluated to constrain urea uptake rates and explore the potential for
compound specific uptake rates. Together, results from this study indicate that urea may
represent an under-recognized component of the marine microbial nitrogen cycle.
Description:
Funding of our lab by The Gordon and Betty Moore Foundation, the
Center for Microbial Oceanography: Research and Education (C-MORE), “Metzyme”
(KM1128) by NSF Division of Ocean Sciences (OCE-1031271) and “BiG RAPA”
(MV1015) by NSF (DBI-0424599).
Keywords:
Primary productivity
;
Nitrogen cycle
;
Melville (Ship) Cruise MV1015
;
Kilo Moana (Ship) Cruise KM1128
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
