Contrasting phytoplankton composition and primary productivity in multiple mesoscale eddies along the East Australian coast

Firme, GF; Hughes, DJ; Laiolo, L; Roughan, M; Suthers, IM; Doblin, MA

Contrasting phytoplankton composition and primary productivity in multiple mesoscale eddies along the East Australian coast

Firme, GF Hughes, DJ Laiolo, L Roughan, M Suthers, IM Doblin, MA

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Publisher:: PERGAMON-ELSEVIER SCIENCE LTD
Publication Type:: Journal Article
Citation:: Deep-Sea Research Part I: Oceanographic Research Papers, 2023, 193
Issue Date:: 2023-03-01

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Field	Value	Language
dc.contributor.author	Firme, GF
dc.contributor.author	Hughes, DJ
dc.contributor.author	Laiolo, L
dc.contributor.author	Roughan, M
dc.contributor.author	Suthers, IM
dc.contributor.author	Doblin, MA
dc.date.accessioned	2024-03-15T00:31:25Z
dc.date.available	2024-03-15T00:31:25Z
dc.date.issued	2023-03-01
dc.identifier.citation	Deep-Sea Research Part I: Oceanographic Research Papers, 2023, 193
dc.identifier.issn	0967-0637
dc.identifier.issn	1879-0119
dc.identifier.uri	http://hdl.handle.net/10453/176739
dc.description.abstract	Mesoscale eddies drive variability in phytoplankton functional trait composition and primary productivity (PP) relative to adjacent waters. Offshore waters in southeast Australia are subject to substantial mesoscale eddies that form when the East Australian Current (EAC) travels poleward along the coast, forming distinctive habitats in the upper ocean. Eddies provide an important enrichment mechanism in the nitrogen-limited waters of the Tasman Sea, yet there is limited knowledge of PP within cold- and warm-core eddies in the region and how physico-chemical and biological factors affect phytoplankton communities in this variable environment. We addressed the scarcity of observations by quantifying net PP using 13C isotopic enrichment incubations of surface waters over 10 degrees of latitude, comparing phytoplankton species composition in five different environments: a coastal shelf station, an oceanic cold and warm-core eddy, and a coastal dipole. Cold-core (cyclonic) eddies were significantly more productive than their warm-core (anticyclonic) counterparts (∼35 versus 0 mg C m−3 d−1), with centric diatoms the most prominent phytoplankton group, with a relatively high centric:pennate ratio. The diffuse attenuation coefficient, Kd (PAR), and silicate were the best overall predictors of phytoplankton composition, explaining 88% of variation based on pigment analysis and size fractionation. Variance in net PP did not correlate significantly with physico-chemical parameters frequently used in PP models (temperature, Kd [PAR], Chl a), yet inclusion of size-fractionated Chl a generated substantial improvement in our statistical model (from 36 to 77%). We show that cold-core eddies play a key role in regulating PP in eastern Australian waters and highlight a need for eddy-resolving models to incorporate descriptors of phytoplankton size structure to improve the accuracy of PP forecasts in eddy intensive regions.
dc.language	English
dc.publisher	PERGAMON-ELSEVIER SCIENCE LTD
dc.relation	http://purl.org/au-research/grants/arc/DP140101340
dc.relation	http://purl.org/au-research/grants/arc/DP180100054
dc.relation.ispartof	Deep-Sea Research Part I: Oceanographic Research Papers
dc.relation.isbasedon	10.1016/j.dsr.2022.103952
dc.rights	info:eu-repo/semantics/openAccess
dc.subject	0402 Geochemistry, 0403 Geology, 0405 Oceanography
dc.subject.classification	Oceanography
dc.subject.classification	3708 Oceanography
dc.title	Contrasting phytoplankton composition and primary productivity in multiple mesoscale eddies along the East Australian coast
dc.type	Journal Article
utslib.citation.volume	193
utslib.for	0402 Geochemistry
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
pubs.organisational-group	University of Technology Sydney/Faculty of Science/School of Life Sciences
utslib.copyright.status	open_access	*
dc.date.updated	2024-03-15T00:31:23Z
pubs.publication-status	Published
pubs.volume	193

Abstract:

Mesoscale eddies drive variability in phytoplankton functional trait composition and primary productivity (PP) relative to adjacent waters. Offshore waters in southeast Australia are subject to substantial mesoscale eddies that form when the East Australian Current (EAC) travels poleward along the coast, forming distinctive habitats in the upper ocean. Eddies provide an important enrichment mechanism in the nitrogen-limited waters of the Tasman Sea, yet there is limited knowledge of PP within cold- and warm-core eddies in the region and how physico-chemical and biological factors affect phytoplankton communities in this variable environment. We addressed the scarcity of observations by quantifying net PP using 13C isotopic enrichment incubations of surface waters over 10 degrees of latitude, comparing phytoplankton species composition in five different environments: a coastal shelf station, an oceanic cold and warm-core eddy, and a coastal dipole. Cold-core (cyclonic) eddies were significantly more productive than their warm-core (anticyclonic) counterparts (∼35 versus 0 mg C m−3 d−1), with centric diatoms the most prominent phytoplankton group, with a relatively high centric:pennate ratio. The diffuse attenuation coefficient, Kd (PAR), and silicate were the best overall predictors of phytoplankton composition, explaining 88% of variation based on pigment analysis and size fractionation. Variance in net PP did not correlate significantly with physico-chemical parameters frequently used in PP models (temperature, Kd [PAR], Chl a), yet inclusion of size-fractionated Chl a generated substantial improvement in our statistical model (from 36 to 77%). We show that cold-core eddies play a key role in regulating PP in eastern Australian waters and highlight a need for eddy-resolving models to incorporate descriptors of phytoplankton size structure to improve the accuracy of PP forecasts in eddy intensive regions.

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