Nutrient uplift in a cyclonic eddy increases diversity, primary productivity and iron demand of microbial communities relative to a western boundary current

Doblin, MA; Petrou, K; Sinutok, S; Seymour, JR; Messer, LF; Brown, MV; Norman, L; Everett, JD; McInnes, AS; Ralph, PJ; Thompson, PA; Hassler, CS

Nutrient uplift in a cyclonic eddy increases diversity, primary productivity and iron demand of microbial communities relative to a western boundary current

Doblin, MA

Petrou, K

Sinutok, S Seymour, JR

Messer, LF

Brown, MV Norman, L Everett, JD McInnes, AS

Ralph, PJ

Thompson, PA Hassler, CS

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Publication Type:: Journal Article
Citation:: PeerJ, 2016, 2016 (4)
Issue Date:: 2016-01-01

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Field	Value	Language
dc.contributor.author	Doblin, MA https://orcid.org/0000-0001-8750-3433	en_US
dc.contributor.author	Petrou, K https://orcid.org/0000-0002-2703-0694	en_US
dc.contributor.author	Sinutok, S	en_US
dc.contributor.author	Seymour, JR https://orcid.org/0000-0002-3745-6541	en_US
dc.contributor.author	Messer, LF https://orcid.org/0000-0002-8335-2807	en_US
dc.contributor.author	Brown, MV	en_US
dc.contributor.author	Norman, L	en_US
dc.contributor.author	Everett, JD	en_US
dc.contributor.author	McInnes, AS https://orcid.org/0000-0002-8340-3133	en_US
dc.contributor.author	Ralph, PJ https://orcid.org/0000-0002-3103-7346	en_US
dc.contributor.author	Thompson, PA	en_US
dc.contributor.author	Hassler, CS	en_US
dc.date.available	2016-04-05	en_US
dc.date.issued	2016-01-01	en_US
dc.identifier.citation	PeerJ, 2016, 2016 (4)	en_US
dc.identifier.uri	http://hdl.handle.net/10453/121686
dc.description.abstract	© 2016 Doblin et al. The intensification of western boundary currents in the global ocean will potentially influence meso-scale eddy generation, and redistribute microbes and their associated ecological and biogeochemical functions. To understand eddy-induced changes in microbial community composition as well as how they control growth, we targeted the East Australian Current (EAC) region to sample microbes in a cyclonic (cold-core) eddy (CCE) and the adjacent EAC. Phototrophic and diazotrophic microbes were more diverse (2-10 times greater Shannon index) in the CCE relative to the EAC, and the cell size distribution in the CCE was dominated (67%) by larger micro-plankton (≥ 20μm), as opposed to pico- and nano-sized cells in the EAC. Nutrient addition experiments determined that nitrogen was the principal nutrient limiting growth in the EAC, while iron was a secondary limiting nutrient in the CCE. Among the diazotrophic community, heterotrophic NifH gene sequences dominated in the EAC and were attributable to members of the gamma-, beta-, and delta-proteobacteria, while the CCE contained both phototrophic and heterotrophic diazotrophs, including Trichodesmium, UCYN- A and gamma-proteobacteria. Daily sampling of incubation bottles following nutrient amendment captured a cascade of effects at the cellular, population and community level, indicating taxon-specific differences in the speed of response of microbes to nutrient supply. Nitrogen addition to the CCE community increased picoeukaryote chlorophyll a quotas within 24 h, suggesting that nutrient uplift by eddies causes a 'greening' effect as well as an increase in phytoplankton biomass. After three days in both the EAC and CCE, diatoms increased in abundance with macronutrient (N, P, Si) and iron amendment, whereas haptophytes and phototrophic dinoflagellates declined. Our results indicate that cyclonic eddies increase delivery of nitrogen to the upper ocean to potentially mitigate the negative consequences of increased stratification due to ocean warming, but also increase the biological demand for iron that is necessary to sustain the growth of large-celled phototrophs and potentially support the diversity of diazotrophs over longer time-scales.	en_US
dc.relation	http://purl.org/au-research/grants/arc/DP140101340
dc.relation	http://purl.org/au-research/grants/arc/DP1092892
dc.relation.ispartof	PeerJ	en_US
dc.relation.isbasedon	10.7717/peerj.1973	en_US
dc.title	Nutrient uplift in a cyclonic eddy increases diversity, primary productivity and iron demand of microbial communities relative to a western boundary current	en_US
dc.type	Journal Article
utslib.citation.volume	4	en_US
utslib.citation.volume	2016	en_US
utslib.for	0602 Ecology	en_US
utslib.for	06 Biological Sciences	en_US
utslib.for	11 Medical and Health Sciences	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Life Sciences
pubs.organisational-group	/University of Technology Sydney/Strength - C3 - Climate Change Cluster
pubs.organisational-group	/University of Technology Sydney/Students
utslib.copyright.status	open_access
pubs.issue	4	en_US
pubs.publication-status	Published	en_US
pubs.volume	2016	en_US

Abstract:

© 2016 Doblin et al. The intensification of western boundary currents in the global ocean will potentially influence meso-scale eddy generation, and redistribute microbes and their associated ecological and biogeochemical functions. To understand eddy-induced changes in microbial community composition as well as how they control growth, we targeted the East Australian Current (EAC) region to sample microbes in a cyclonic (cold-core) eddy (CCE) and the adjacent EAC. Phototrophic and diazotrophic microbes were more diverse (2-10 times greater Shannon index) in the CCE relative to the EAC, and the cell size distribution in the CCE was dominated (67%) by larger micro-plankton (≥ 20μm), as opposed to pico- and nano-sized cells in the EAC. Nutrient addition experiments determined that nitrogen was the principal nutrient limiting growth in the EAC, while iron was a secondary limiting nutrient in the CCE. Among the diazotrophic community, heterotrophic NifH gene sequences dominated in the EAC and were attributable to members of the gamma-, beta-, and delta-proteobacteria, while the CCE contained both phototrophic and heterotrophic diazotrophs, including Trichodesmium, UCYN- A and gamma-proteobacteria. Daily sampling of incubation bottles following nutrient amendment captured a cascade of effects at the cellular, population and community level, indicating taxon-specific differences in the speed of response of microbes to nutrient supply. Nitrogen addition to the CCE community increased picoeukaryote chlorophyll a quotas within 24 h, suggesting that nutrient uplift by eddies causes a 'greening' effect as well as an increase in phytoplankton biomass. After three days in both the EAC and CCE, diatoms increased in abundance with macronutrient (N, P, Si) and iron amendment, whereas haptophytes and phototrophic dinoflagellates declined. Our results indicate that cyclonic eddies increase delivery of nitrogen to the upper ocean to potentially mitigate the negative consequences of increased stratification due to ocean warming, but also increase the biological demand for iron that is necessary to sustain the growth of large-celled phototrophs and potentially support the diversity of diazotrophs over longer time-scales.

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http://hdl.handle.net/10453/121686