High levels of heterogeneity in diazotroph diversity and activity within a putative hotspot for marine nitrogen fixation

Messer, LF; Mahaffey, C; Robinson, CM; Jeffries, TC; Baker, KG; Isaksson, JB; Ostrowski, M; Doblin, MA; Brown, MV; Seymour, JR

High levels of heterogeneity in diazotroph diversity and activity within a putative hotspot for marine nitrogen fixation

Messer, LF

Mahaffey, C Robinson, CM

Jeffries, TC

Baker, KG

Isaksson, JB Ostrowski, M

Doblin, MA

Brown, MV Seymour, JR

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Publication Type:: Journal Article
Citation:: ISME Journal, 2016, 10 (6), pp. 1499 - 1513
Issue Date:: 2016-06-01

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Field	Value	Language
dc.contributor.author	Messer, LF https://orcid.org/0000-0002-8335-2807	en_US
dc.contributor.author	Mahaffey, C	en_US
dc.contributor.author	Robinson, CM https://orcid.org/0000-0001-8519-5641	en_US
dc.contributor.author	Jeffries, TC https://orcid.org/0000-0001-6479-0353	en_US
dc.contributor.author	Baker, KG https://orcid.org/0000-0003-3008-2513	en_US
dc.contributor.author	Isaksson, JB	en_US
dc.contributor.author	Ostrowski, M https://orcid.org/0000-0002-4357-3023	en_US
dc.contributor.author	Doblin, MA https://orcid.org/0000-0001-8750-3433	en_US
dc.contributor.author	Brown, MV	en_US
dc.contributor.author	Seymour, JR https://orcid.org/0000-0002-3745-6541	en_US
dc.date.available	2015-10-07	en_US
dc.date.issued	2016-06-01	en_US
dc.identifier.citation	ISME Journal, 2016, 10 (6), pp. 1499 - 1513	en_US
dc.identifier.issn	1751-7362	en_US
dc.identifier.uri	http://hdl.handle.net/10453/117730
dc.description.abstract	© 2016 International Society for Microbial Ecology. Australia's tropical waters represent predicted 'hotspots' for nitrogen (N 2) fixation based on empirical and modelled data. However, the identity, activity and ecology of diazotrophs within this region are virtually unknown. By coupling DNA and cDNA sequencing of nitrogenase genes (nifH) with size-fractionated N 2 fixation rate measurements, we elucidated diazotroph dynamics across the shelf region of the Arafura and Timor Seas (ATS) and oceanic Coral Sea during Austral spring and winter. During spring, Trichodesmium dominated ATS assemblages, comprising 60% of nifH DNA sequences, while Candidatus Atelocyanobacterium thalassa (UCYN-A) comprised 42% in the Coral Sea. In contrast, during winter the relative abundance of heterotrophic unicellular diazotrophs (δ-proteobacteria and γ-24774A11) increased in both regions, concomitant with a marked decline in UCYN-A sequences, whereby this clade effectively disappeared in the Coral Sea. Conservative estimates of N 2 fixation rates ranged from <1 to 91 nmol l -1 day -1, and size fractionation indicated that unicellular organisms dominated N 2 fixation during both spring and winter, but average unicellular rates were up to 10-fold higher in winter than in spring. Relative abundances of UCYN-A1 and γ-24774A11 nifH transcripts negatively correlated to silicate and phosphate, suggesting an affinity for oligotrophy. Our results indicate that Australia's tropical waters are indeed hotspots for N 2 fixation and that regional physicochemical characteristics drive differential contributions of cyanobacterial and heterotrophic phylotypes to N 2 fixation.	en_US
dc.relation	http://purl.org/au-research/grants/arc/FT130100218
dc.relation	http://purl.org/au-research/grants/arc/DP1092892
dc.relation	http://purl.org/au-research/grants/arc/DP120102764
dc.relation.ispartof	ISME Journal	en_US
dc.relation.isbasedon	10.1038/ismej.2015.205	en_US
dc.subject.classification	Microbiology	en_US
dc.subject.mesh	Animals	en_US
dc.subject.mesh	Anthozoa	en_US
dc.subject.mesh	Cyanobacteria	en_US
dc.subject.mesh	Deltaproteobacteria	en_US
dc.subject.mesh	Nitrogenase	en_US
dc.subject.mesh	Sequence Analysis, DNA	en_US
dc.subject.mesh	Ecology	en_US
dc.subject.mesh	Seasons	en_US
dc.subject.mesh	Seawater	en_US
dc.subject.mesh	Nitrogen Fixation	en_US
dc.subject.mesh	Australia	en_US
dc.subject.mesh	Oceans and Seas	en_US
dc.subject.mesh	Heterotrophic Processes	en_US
dc.subject.mesh	Trichodesmium	en_US
dc.title	High levels of heterogeneity in diazotroph diversity and activity within a putative hotspot for marine nitrogen fixation	en_US
dc.type	Journal Article
utslib.citation.volume	6	en_US
utslib.citation.volume	10	en_US
utslib.for	0605 Microbiology	en_US
utslib.for	05 Environmental Sciences	en_US
utslib.for	06 Biological Sciences	en_US
utslib.for	10 Technology	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/Strength - C3 - Climate Change Cluster
pubs.organisational-group	/University of Technology Sydney/Students
utslib.copyright.status	closed_access
pubs.issue	6	en_US
pubs.publication-status	Published	en_US
pubs.volume	10	en_US

Abstract:

© 2016 International Society for Microbial Ecology. Australia's tropical waters represent predicted 'hotspots' for nitrogen (N 2) fixation based on empirical and modelled data. However, the identity, activity and ecology of diazotrophs within this region are virtually unknown. By coupling DNA and cDNA sequencing of nitrogenase genes (nifH) with size-fractionated N 2 fixation rate measurements, we elucidated diazotroph dynamics across the shelf region of the Arafura and Timor Seas (ATS) and oceanic Coral Sea during Austral spring and winter. During spring, Trichodesmium dominated ATS assemblages, comprising 60% of nifH DNA sequences, while Candidatus Atelocyanobacterium thalassa (UCYN-A) comprised 42% in the Coral Sea. In contrast, during winter the relative abundance of heterotrophic unicellular diazotrophs (δ-proteobacteria and γ-24774A11) increased in both regions, concomitant with a marked decline in UCYN-A sequences, whereby this clade effectively disappeared in the Coral Sea. Conservative estimates of N 2 fixation rates ranged from <1 to 91 nmol l -1 day -1, and size fractionation indicated that unicellular organisms dominated N 2 fixation during both spring and winter, but average unicellular rates were up to 10-fold higher in winter than in spring. Relative abundances of UCYN-A1 and γ-24774A11 nifH transcripts negatively correlated to silicate and phosphate, suggesting an affinity for oligotrophy. Our results indicate that Australia's tropical waters are indeed hotspots for N 2 fixation and that regional physicochemical characteristics drive differential contributions of cyanobacterial and heterotrophic phylotypes to N 2 fixation.

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http://hdl.handle.net/10453/117730