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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Hydrography-Driven Variability of Optically Active Constituents of Water in the South Brazilian Bight: Biogeochemical Implications

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Author(s):
Goncalves-Araujo, Rafael [1, 2] ; Roettgers, Ruediger [3] ; Haraguchi, Lumi [4, 5] ; Brandini, Frederico Pereira [1]
Total Authors: 4
Affiliation:
[1] Univ Sao Paulo, Oceanog Inst, Sao Paulo, SP - Brazil
[2] Tech Univ Denmark DTU Aqua, Natl Inst Aquat Resources, Lyngby - Denmark
[3] Helmholtz Zentrum Geesthacht, Inst Coastal Res, Remote Sensing Dept, Ctr Mat & Coastal Res, Geesthacht - Germany
[4] Aarhus Univ, Dept Biosci, Aarhus - Denmark
[5] Finnish Environm Inst SYKE, Marine Res Ctr, Helsinki - Finland
Total Affiliations: 5
Document type: Journal article
Source: FRONTIERS IN MARINE SCIENCE; v. 6, NOV 19 2019.
Web of Science Citations: 0
Abstract

The South Brazilian Bight (SBB) is a hydrographically dynamic environment with strong seasonality that sustains a diverse planktonic community involved in diverse biogeochemical processes. The inherent optical properties (IOPs; e.g., absorption and scattering coefficients) of optically actives constituents of water (OACs; phytoplankton, non-algal particles-NAP, and colored dissolved organic matter-CDOM) have been widely employed to retrieve information on biogeochemical parameters in the water. In this study conducted in the SBB, a cross-shelf transect was performed for biogeochernistry and hydrographic sampling during a summer expedition. Our research aimed to determine the distribution and amount of the OACs based on their spectral signature, in relation to the distribution of water masses in the region. That allows us to get insights into the biogeochemical processes within each water mass and in the boundaries between them. We observed a strong intrusion of South Atlantic Central Water (SACW) over the shelf, mainly driven by the wind action. With that, phytoplankton development was fueled by the input of nutrients, and increased chlorophyll-a (Chl-a) concentrations were observed within the shallowest stations. Colored dissolved organic matter did not follow the distribution of dissolved organic carbon (DOC). Both CDOM and DOC presented high values at the low salinity Coastal Water (CW), as an indication of the continental influence over the shelf. However, CDOM was inversely correlated with salinity and lowest values were observed within Tropical Water (TW), whereas DOC values within TW were as high as within CW, indicating an autochthonous DOM source. Additionally, a deep Chl-a maximum (DCM) was noticed in the boundary between the TW and SACW. Along with the DCM, we observed the production of fresh, non-colored DOM attributed to the microbial community. Finally, our results suggest that CDOM is photodegraded at the surface of CW. This is mainly due to the Ekman transport effect over the region that traps CW at the surface, making it longer exposed to solar radiation. (AU)

FAPESP's process: 17/19907-7 - Biogeochemistry of Dissolved Organic Matter in the SW Atlantic: Characterization, Quantification and Reactivity (DOMAt)
Grantee:Rafael Gonçalves Araujo
Support Opportunities: Scholarships in Brazil - Post-Doctoral