Characterization of phytoplankton productivity and bio-optical variability in a polar marine ecosystem

Kerkar, AU; Tripathy, SC; Hughes, DJ; Sabu, P; Pandi, SR; Sarkar, A; Tiwari, M

Characterization of phytoplankton productivity and bio-optical variability in a polar marine ecosystem

Kerkar, AU Tripathy, SC Hughes, DJ Sabu, P Pandi, SR Sarkar, A Tiwari, M

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Publisher:: PERGAMON-ELSEVIER SCIENCE LTD
Publication Type:: Journal Article
Citation:: Progress in Oceanography, 2021, 195
Issue Date:: 2021-07-01

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Field	Value	Language
dc.contributor.author	Kerkar, AU
dc.contributor.author	Tripathy, SC
dc.contributor.author	Hughes, DJ
dc.contributor.author	Sabu, P
dc.contributor.author	Pandi, SR
dc.contributor.author	Sarkar, A
dc.contributor.author	Tiwari, M
dc.date.accessioned	2022-01-22T23:27:58Z
dc.date.available	2022-01-22T23:27:58Z
dc.date.issued	2021-07-01
dc.identifier.citation	Progress in Oceanography, 2021, 195
dc.identifier.issn	0079-6611
dc.identifier.issn	1873-4472
dc.identifier.uri	http://hdl.handle.net/10453/153444
dc.description.abstract	Knowledge of Southern Ocean carbon cycling is limited by a paucity of phytoplankton primary productivity (PP) and spectral absorption data in this globally-important region. We measured 13C-based PP in the Indian sector of Southern Ocean (ISSO) during austral summer 2017, examining its link with spectral absorption coefficients and phytoplankton size structure derived from an absorption-based global model. Phytoplankton productivity was assessed at both coastal (60°S-69°S) and frontal stations (40°S-60°S), characterized by silicate- replete and -deplete water masses, respectively (indicated by measured nutrient ratios) to capture a range of phytoplankton growth conditions. Bio-optical relationships were used as indicators of phytoplankton community size structure and to assess the extent of cellular pigment packaging - a phenomenon reported previously for phytoplankton in this region. Blue-Red (B/R) ratios of phytoplankton absorption (aph) spectra indicated that microphytoplankton (more prone to “package effects”) were the dominant size class at most sites sampled. Overall, PP was better explained by aph (R2 = 0.85) than total chlorophyll-a (R2 = 0.64) in surface waters. The a*ph (675)-chlorophyll-a relationship explained package effects more effectively in frontal regions (R2 = 0.63) than stations further south (R2 = 0.30). The global absorption-based model captured smaller (pico, nano) phytoplankton size classes but failed to identify larger microphytoplankton, underscoring the need for region-specific algorithm modifications. Our findings improve existing understanding of spatio-temporal trends in PP and bio-optical variability within the Indian Sector of the Southern Ocean (ISSO) – knowledge that is essential to improve capacity to retrieve PP from satellite-based models in this region.
dc.language	English
dc.publisher	PERGAMON-ELSEVIER SCIENCE LTD
dc.relation.ispartof	Progress in Oceanography
dc.relation.isbasedon	10.1016/j.pocean.2021.102573
dc.rights	info:eu-repo/semantics/closedAccess
dc.subject	0403 Geology, 0405 Oceanography
dc.subject.classification	Oceanography
dc.title	Characterization of phytoplankton productivity and bio-optical variability in a polar marine ecosystem
dc.type	Journal Article
utslib.citation.volume	195
utslib.for	0403 Geology
utslib.for	0405 Oceanography
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Strength - C3 - Climate Change Cluster
utslib.copyright.status	closed_access	*
dc.date.updated	2022-01-22T23:27:50Z
pubs.publication-status	Published
pubs.volume	195

Abstract:

Knowledge of Southern Ocean carbon cycling is limited by a paucity of phytoplankton primary productivity (PP) and spectral absorption data in this globally-important region. We measured 13C-based PP in the Indian sector of Southern Ocean (ISSO) during austral summer 2017, examining its link with spectral absorption coefficients and phytoplankton size structure derived from an absorption-based global model. Phytoplankton productivity was assessed at both coastal (60°S-69°S) and frontal stations (40°S-60°S), characterized by silicate- replete and -deplete water masses, respectively (indicated by measured nutrient ratios) to capture a range of phytoplankton growth conditions. Bio-optical relationships were used as indicators of phytoplankton community size structure and to assess the extent of cellular pigment packaging - a phenomenon reported previously for phytoplankton in this region. Blue-Red (B/R) ratios of phytoplankton absorption (aph) spectra indicated that microphytoplankton (more prone to “package effects”) were the dominant size class at most sites sampled. Overall, PP was better explained by aph (R2 = 0.85) than total chlorophyll-a (R2 = 0.64) in surface waters. The a*ph (675)-chlorophyll-a relationship explained package effects more effectively in frontal regions (R2 = 0.63) than stations further south (R2 = 0.30). The global absorption-based model captured smaller (pico, nano) phytoplankton size classes but failed to identify larger microphytoplankton, underscoring the need for region-specific algorithm modifications. Our findings improve existing understanding of spatio-temporal trends in PP and bio-optical variability within the Indian Sector of the Southern Ocean (ISSO) – knowledge that is essential to improve capacity to retrieve PP from satellite-based models in this region.

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http://hdl.handle.net/10453/153444