Diversity and Activity of Diazotrophs in Great Barrier Reef Surface Waters
Discrepancies between bioavailable nitrogen (N) concentrations and phytoplankton growth rates in the oligotrophic waters of the Great Barrier Reef (GBR) suggest that undetermined N sources must play a significant role in supporting primary productivity. One such source could be biological dinitrogen...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2017-06-01
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| Series: | Frontiers in Microbiology |
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| Online Access: | http://journal.frontiersin.org/article/10.3389/fmicb.2017.00967/full |
| _version_ | 1828764812783386624 |
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| author | Lauren F. Messer Lauren F. Messer Mark V. Brown Miles J. Furnas Richard L. Carney A. D. McKinnon Justin R. Seymour |
| author_facet | Lauren F. Messer Lauren F. Messer Mark V. Brown Miles J. Furnas Richard L. Carney A. D. McKinnon Justin R. Seymour |
| author_sort | Lauren F. Messer |
| collection | DOAJ |
| description | Discrepancies between bioavailable nitrogen (N) concentrations and phytoplankton growth rates in the oligotrophic waters of the Great Barrier Reef (GBR) suggest that undetermined N sources must play a significant role in supporting primary productivity. One such source could be biological dinitrogen (N2) fixation through the activity of “diazotrophic” bacterioplankton. Here, we investigated N2 fixation and diazotroph community composition over 10° S of latitude within GBR surface waters. Qualitative N2 fixation rates were found to be variable across the GBR but were relatively high in coastal, inner and outer GBR waters, reaching 68 nmol L-1 d-1. Diazotroph assemblages, identified by amplicon sequencing of the nifH gene, were dominated by the cyanobacterium Trichodesmium erythraeum, γ-proteobacteria from the Gamma A clade, and δ-proteobacterial phylotypes related to sulfate-reducing genera. However, diazotroph communities exhibited significant spatial heterogeneity, correlated with shifts in dissolved inorganic nutrient concentrations. Specifically, heterotrophic diazotrophs generally increased in relative abundance with increasing concentrations of phosphate and N, while Trichodesmium was proportionally more abundant when concentrations of these nutrients were low. This study provides the first in-depth characterization of diazotroph community composition and N2 fixation dynamics within the oligotrophic, N-limited surface waters of the GBR. Our observations highlight the need to re-evaluate N cycling dynamics within oligotrophic coral reef systems, to include diverse N2 fixing assemblages as a potentially significant source of dissolved N within the water column. |
| first_indexed | 2024-12-11T06:38:45Z |
| format | Article |
| id | doaj.art-8973de854b604be69f45c71e4fec8df0 |
| institution | Directory Open Access Journal |
| issn | 1664-302X |
| language | English |
| last_indexed | 2024-12-11T06:38:45Z |
| publishDate | 2017-06-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Microbiology |
| spelling | doaj.art-8973de854b604be69f45c71e4fec8df02022-12-22T01:17:18ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2017-06-01810.3389/fmicb.2017.00967253228Diversity and Activity of Diazotrophs in Great Barrier Reef Surface WatersLauren F. Messer0Lauren F. Messer1Mark V. Brown2Miles J. Furnas3Richard L. Carney4A. D. McKinnon5Justin R. Seymour6Climate Change Cluster, School of Life Sciences, University of Technology Sydney, SydneyNSW, AustraliaSchool of Biotechnology and Biomolecular Sciences, University of New South Wales, SydneyNSW, AustraliaSchool of Biotechnology and Biomolecular Sciences, University of New South Wales, SydneyNSW, AustraliaAustralian Institute of Marine Science, TownsvilleQLD, AustraliaClimate Change Cluster, School of Life Sciences, University of Technology Sydney, SydneyNSW, AustraliaAustralian Institute of Marine Science, TownsvilleQLD, AustraliaClimate Change Cluster, School of Life Sciences, University of Technology Sydney, SydneyNSW, AustraliaDiscrepancies between bioavailable nitrogen (N) concentrations and phytoplankton growth rates in the oligotrophic waters of the Great Barrier Reef (GBR) suggest that undetermined N sources must play a significant role in supporting primary productivity. One such source could be biological dinitrogen (N2) fixation through the activity of “diazotrophic” bacterioplankton. Here, we investigated N2 fixation and diazotroph community composition over 10° S of latitude within GBR surface waters. Qualitative N2 fixation rates were found to be variable across the GBR but were relatively high in coastal, inner and outer GBR waters, reaching 68 nmol L-1 d-1. Diazotroph assemblages, identified by amplicon sequencing of the nifH gene, were dominated by the cyanobacterium Trichodesmium erythraeum, γ-proteobacteria from the Gamma A clade, and δ-proteobacterial phylotypes related to sulfate-reducing genera. However, diazotroph communities exhibited significant spatial heterogeneity, correlated with shifts in dissolved inorganic nutrient concentrations. Specifically, heterotrophic diazotrophs generally increased in relative abundance with increasing concentrations of phosphate and N, while Trichodesmium was proportionally more abundant when concentrations of these nutrients were low. This study provides the first in-depth characterization of diazotroph community composition and N2 fixation dynamics within the oligotrophic, N-limited surface waters of the GBR. Our observations highlight the need to re-evaluate N cycling dynamics within oligotrophic coral reef systems, to include diverse N2 fixing assemblages as a potentially significant source of dissolved N within the water column.http://journal.frontiersin.org/article/10.3389/fmicb.2017.00967/fullN2 fixationGreat Barrier ReefdiazotrophsdiversitynifH amplicon sequencing |
| spellingShingle | Lauren F. Messer Lauren F. Messer Mark V. Brown Miles J. Furnas Richard L. Carney A. D. McKinnon Justin R. Seymour Diversity and Activity of Diazotrophs in Great Barrier Reef Surface Waters Frontiers in Microbiology N2 fixation Great Barrier Reef diazotrophs diversity nifH amplicon sequencing |
| title | Diversity and Activity of Diazotrophs in Great Barrier Reef Surface Waters |
| title_full | Diversity and Activity of Diazotrophs in Great Barrier Reef Surface Waters |
| title_fullStr | Diversity and Activity of Diazotrophs in Great Barrier Reef Surface Waters |
| title_full_unstemmed | Diversity and Activity of Diazotrophs in Great Barrier Reef Surface Waters |
| title_short | Diversity and Activity of Diazotrophs in Great Barrier Reef Surface Waters |
| title_sort | diversity and activity of diazotrophs in great barrier reef surface waters |
| topic | N2 fixation Great Barrier Reef diazotrophs diversity nifH amplicon sequencing |
| url | http://journal.frontiersin.org/article/10.3389/fmicb.2017.00967/full |
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