Please use this identifier to cite or link to this item: https://hdl.handle.net/1959.11/15834
Title: No stimulation of nitrogen fixation by non-filamentous diazotrophs under elevated CO₂ in the South Pacific
Contributor(s): Law, Cliff S (author); Breitbarth, Eike (author); Hoffmann, Linn J (author); McGraw, Christina  (author); Langlois, Rebecca J (author); LaRoche, Julie (author); Marriner, Andrew (author); Safi, Karl A (author)
Publication Date: 2012
DOI: 10.1111/j.1365-2486.2012.02777.x
Handle Link: https://hdl.handle.net/1959.11/15834
Abstract: Nitrogen fixation by diazotrophic cyanobacteria is a critical source of new nitrogen to the oligotrophic surface ocean. Research to date indicates that some diazotroph groups may increase nitrogen fixation under elevated pCO₂. To test this in natural plankton communities, four manipulation experiments were carried out during two voyages in the South Pacific (30-35⁰S). High CO₂ treatments, produced using 750 ppmv CO₂ to adjust pH to 0.2 below ambient, and 'Greenhouse' treatments (0.2 below ambient pH and ambient temperature +3 °C), were compared with Controls in trace metal clean deckboard incubations in triplicate. No significant change was observed in nitrogen fixation in either the High CO₂ or Greenhouse treatments over 5 day incubations. qPCR measurements and optical microscopy determined that the diazotroph community was dominated by Group A unicellular cyanobacteria (UCYN-A), which may account for the difference in response of nitrogen fixation under elevated CO₂ to that reported previously for 'Trichodesmium'. This may reflect physiological differences, in that the greater cell surface area:volume of UCYN-A and its lack of metabolic pathways involved in carbon fixation may confer no benefit under elevated CO₂. However, multiple environmental controls may also be a factor, with the low dissolved iron concentrations in oligotrophic surface waters limiting the response to elevated CO₂. If nitrogen fixation by UCYN-A is not stimulated by elevated pCO₂, then future increases in CO₂ and warming may alter the regional distribution and dominance of different diazotroph groups, with implications for dissolved iron availability and new nitrogen supply in oligotrophic regions.
Publication Type: Journal Article
Source of Publication: Global Change Biology, 18(10), p. 3004-3014
Publisher: Wiley-Blackwell Publishing Ltd
Place of Publication: United Kingdom
ISSN: 1365-2486
1354-1013
Fields of Research (FoR) 2008: 060205 Marine and Estuarine Ecology (incl Marine Ichthyology)
030105 Instrumental Methods (excl Immunological and Bioassay Methods)
Fields of Research (FoR) 2020: 310305 Marine and estuarine ecology (incl. marine ichthyology)
340105 Instrumental methods (excl. immunological and bioassay methods)
Socio-Economic Objective (SEO) 2008: 960307 Effects of Climate Change and Variability on Australia (excl. Social Impacts)
960308 Effects of Climate Change and Variability on New Zealand (excl. Social Impacts)
Socio-Economic Objective (SEO) 2020: 190504 Effects of climate change on Australia (excl. social impacts)
190505 Effects of climate change on New Zealand (excl. social impacts)
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
Appears in Collections:Journal Article

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