TY - JOUR
T1 - Controls on the fate of dissolved organic carbon under contrasting upwelling conditions
AU - Bif, Mariana B.
AU - Hansell, Dennis A.
AU - Popendorf, Kimberly J.
N1 - Funding Information:
MB has a Ph.D. Fellowship supported by Cnpq (Conselho Nacional de Desenvolvimento Científico e Tecnológico), Process No. 205233/2014-7. DH was supported by NSF award OCE-1436748. We thank 27°N NOAA cruise Chief Scientist Ryan Smith for the opportunity to join the cruise and collect water samples for the experiments, Research Associate Lillian Custals for support in DOC and DON analyses, and Dr. Larry Brand for use of his incubation facilities at RSMAS
PY - 2018/12/5
Y1 - 2018/12/5
N2 - To understand controls on the production and remineralization of recalcitrant dissolved organic carbon (DOC) produced in association with positive net community production (NCP), we simulated upwelling systems of different intensities by combining and incubating whole seawater collected from different depths in the Florida Strait (27°N, ~79°W). The natural microbial communities in the treatments grew under controlled light and temperature for 15 days (i.e., the autotrophic phase); they were subsequently incubated for 35 days in the dark heterotrophic phase. We analyzed the phytoplankton composition and pigment fluorescence intensity during the light phase, and dissolved organic and inorganic variables during both phases. Initial high or low availability of inorganic nutrients controlled phytoplankton growth and the magnitude of NCP. In the strong upwelling treatment with higher initial inorganic nutrients, 25% of NCP accumulated as DOC after 15 days, however, this material was in turn fully remineralized during the dark phase. In contrast, low nutrients in the weak upwelling treatment limited the magnitude of NCP and accumulated DOC, which represented 11% of NCP. Surprisingly, most of this fraction resisted microbial remineralization in the dark phase, suggesting that upwellings of different intensities affect the quality of dissolved organic matter produced, thereby affecting the timing and location of its remineralization and, hence, its prospects for export to the deep ocean.
AB - To understand controls on the production and remineralization of recalcitrant dissolved organic carbon (DOC) produced in association with positive net community production (NCP), we simulated upwelling systems of different intensities by combining and incubating whole seawater collected from different depths in the Florida Strait (27°N, ~79°W). The natural microbial communities in the treatments grew under controlled light and temperature for 15 days (i.e., the autotrophic phase); they were subsequently incubated for 35 days in the dark heterotrophic phase. We analyzed the phytoplankton composition and pigment fluorescence intensity during the light phase, and dissolved organic and inorganic variables during both phases. Initial high or low availability of inorganic nutrients controlled phytoplankton growth and the magnitude of NCP. In the strong upwelling treatment with higher initial inorganic nutrients, 25% of NCP accumulated as DOC after 15 days, however, this material was in turn fully remineralized during the dark phase. In contrast, low nutrients in the weak upwelling treatment limited the magnitude of NCP and accumulated DOC, which represented 11% of NCP. Surprisingly, most of this fraction resisted microbial remineralization in the dark phase, suggesting that upwellings of different intensities affect the quality of dissolved organic matter produced, thereby affecting the timing and location of its remineralization and, hence, its prospects for export to the deep ocean.
KW - Carbon cycle
KW - Dissolved organic carbon
KW - Dissolved organic matter
KW - Net community production
KW - Remineralization
KW - Upwelling
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U2 - 10.3389/fmars.2018.00463
DO - 10.3389/fmars.2018.00463
M3 - Article
AN - SCOPUS:85058933787
VL - 5
JO - Frontiers in Marine Science
JF - Frontiers in Marine Science
SN - 2296-7745
IS - DEC
M1 - 463
ER -