Remote assessment of the fate of phytoplankton in the Southern Ocean sea-ice zone

Abstract In the Southern Ocean, large-scale phytoplankton blooms occur in open water and the sea-ice zone (SIZ). These blooms have a range of fates including physical advection, downward carbon export, or grazing. Here, we determine the magnitude, timing and spatial trends of the biogeochemical (exp...

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Bibliographic Details
Published in:Nature Communications
Main Authors: Moreau, Sébastien, Boyd, Philip W., Strutton, Peter G.
Format: Article in Journal/Newspaper
Language:English
Published: Springer Science and Business Media LLC 2020
Subjects:
General Physics and Astronomy
General Biochemistry, Genetics and Molecular Biology
General Chemistry
Southern Ocean
Sea ice
Online Access:http://dx.doi.org/10.1038/s41467-020-16931-0
http://www.nature.com/articles/s41467-020-16931-0.pdf
http://www.nature.com/articles/s41467-020-16931-0
Description
Summary:Abstract In the Southern Ocean, large-scale phytoplankton blooms occur in open water and the sea-ice zone (SIZ). These blooms have a range of fates including physical advection, downward carbon export, or grazing. Here, we determine the magnitude, timing and spatial trends of the biogeochemical (export) and ecological (foodwebs) fates of phytoplankton, based on seven BGC-Argo floats spanning three years across the SIZ. We calculate loss terms using the production of chlorophyll—based on nitrate depletion—compared with measured chlorophyll. Export losses are estimated using conspicuous chlorophyll pulses at depth. By subtracting export losses, we calculate grazing-mediated losses. Herbivory accounts for ~90% of the annually-averaged losses (169 mg C m −2 d −1 ), and phytodetritus POC export comprises ~10%. Furthermore, export and grazing losses each exhibit distinctive seasonality captured by all floats spanning 60°S to 69°S. These similar trends reveal widespread patterns in phytoplankton fate throughout the Southern Ocean SIZ.

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