Unicellular Cyanobacterial Distributions Broaden the Oceanic N
            <sub>2</sub>
            Fixation Domain

Moisander, Pia H.; Beinart, Roxanne A.; Hewson, Ian; White, Angelicque E.; Johnson, Kenneth S.; Carlson, Craig A.; Montoya, Joseph P.; Zehr, Jonathan P.

doi:10.1126/science.1185468

Cited by 411 publications

(539 citation statements)

References 26 publications

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“…Temperatures at stations 8 and 13 were B2-4 1C lower than at the other stations, thus surface water temperatures decreased toward higher latitudes. Parallel to this trend, density surfaces gradually shoaled along the North-South transect from stations 4 to 10 ( Figure 1b, Moisander et al, 2010).…”

Section: Resultsmentioning

confidence: 94%

“…UCYN-A abundance was very low in station 17 and 21 waters (Moisander et al, 2010) and, based on spot tests using the bioassays, was undetectable in most or all treatments. At the westernmost stations 8 and 13, UCYN-A abundances increased when either iron or organic carbon was added (Figure 4).…”

Section: Resultsmentioning

confidence: 99%

“…Physicochemical variables in the study area were measured as described in Moisander et al, 2010. Samples for iron (Fe) measurements were collected by a MITESS ATE/VANE sampler (Bell et al, 2002).…”

Section: Nutrient Limitation In the South Pacific Ocean Ph Moisander mentioning

confidence: 99%

“…The quantitative PCR (qPCR) methods followed previously published protocols (Moisander et al, 2010). DNA extracts were diluted 1:10 (vol:vol) to amplification reactions.…”

Section: Nutrient Limitation In the South Pacific Ocean Ph Moisander mentioning

confidence: 99%

“…An upwelling area in the eastern equatorial South Pacific is characterized by abundant nitrate and low chlorophyll a (Chl a) in the surface waters (hence termed HNLC), and here iron has been found to limit phytoplankton photosynthetic efficiency and growth (Behrenfeld et al, 1996;Coale et al, 1996), while measurements across the oligotrophic South Pacific gyre reported low abundances of diazotrophs and variability in factors limiting phytoplankton, diazotrophs and bacterioplankton Moutin et al, 2008;Van Wambeke et al, 2008). In the western equatorial and southern South Pacific open ocean, both unicellular and filamentous diazotrophs have been recently detected at high abundances, and linked with high N 2 fixation rates in the size fraction corresponding with the unicellular groups (Campbell et al, 2005;Bonnet et al, 2009;Hewson et al, 2009;Moisander et al, 2010). Unicellular diazotrophs were also reported at high abundances from coastal lagoons in Australia and New Caledonia Biegala and Raimbault, 2008).…”

Section: Introductionmentioning

confidence: 99%

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Analogous nutrient limitations in unicellular diazotrophs and Prochlorococcus in the South Pacific Ocean

et al. 2011

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Growth limitation of phytoplankton and unicellular nitrogen (N2) fixers (diazotrophs) were investigated in the oligotrophic Western South Pacific Ocean. Based on change in abundances of nifH or 23S rRNA gene copies during nutrient-enrichment experiments, the factors limiting net growth of the unicellular diazotrophs UCYN-A (Group A), Crocosphaera watsonii, γ-Proteobacterium 24774A11, and the non-diazotrophic picocyanobacterium Prochlorococcus, varied within the region. At the westernmost stations, numbers were enhanced by organic carbon added as simple sugars, a combination of iron and an organic chelator, or iron added with phosphate. At stations nearest the equator, the nutrient-limiting growth was not apparent. Maximum net growth rates for UCYN-A, C. watsonii and γ-24774A11 were 0.19, 0.61 and 0.52 d−1, respectively, which are the first known empirical growth rates reported for the uncultivated UCYN-A and the γ-24774A11. The addition of N enhanced total phytoplankton biomass up to 5-fold, and the non-N2-fixing Synechococcus was among the groups that responded favorably to N addition. Nitrogen was the major nutrient-limiting phytoplankton biomass in the Western South Pacific Ocean, while availability of organic carbon or iron and organic chelator appear to limit abundances of unicellular diazotrophs. Lack of phytoplankton response to nutrient additions in the Pacific warm pool waters suggests diazotroph growth in this area is controlled by different factors than in the higher latitudes, which may partially explain previously observed variability in community composition in the region.

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Nutrient Limitation In the South Pacific Ocean Ph Moisander mentioning

confidence: 99%

“…The quantitative PCR (qPCR) methods followed previously published protocols (Moisander et al, 2010). DNA extracts were diluted 1:10 (vol:vol) to amplification reactions.…”

Section: Nutrient Limitation In the South Pacific Ocean Ph Moisander mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analogous nutrient limitations in unicellular diazotrophs and Prochlorococcus in the South Pacific Ocean

et al. 2011

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Experimental assessment of diazotroph responses to elevated seawater pCO₂ in the North Pacific Subtropical Gyre

Böttjer

Karl

Letelier

et al. 2014

Global Biogeochemical Cycles

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We examined short-term (24-72 h) responses of naturally occurring marine N 2 fixing microorganisms (termed diazotrophs) to abrupt increases in the partial pressure of carbon dioxide (pCO 2 ) in seawater during nine incubation experiments conducted between May 2010 and September 2012 at Station ALOHA (A Long-term Oligotrophic Habitat Assessment) (22°45′N, 158°W) in the North Pacific Subtropical Gyre (NPSG). Rates of N 2 fixation, nitrogenase (nifH) gene abundances and transcripts of six major groups of cyanobacterial diazotrophs (including both unicellular and filamentous phylotypes), and rates of primary productivity (as measured by 14 C-bicarbonate assimilation into plankton biomass) were determined under contemporary (~390 ppm) and elevated pCO 2 conditions (~1100 ppm). Quantitative polymerase chain reaction (QPCR) amplification of planktonic nifH genes revealed that unicellular cyanobacteria phylotypes dominated gene abundances during these experiments. In the majority of experiments (seven out of nine), elevated pCO 2 did not significantly influence rates of dinitrogen (N 2 ) fixation or primary productivity (two-way analysis of variance (ANOVA), P > 0.05). During two experiments, rates of N 2 fixation and primary productivity were significantly lower (by 79 to 82% and 52 to 72%, respectively) in the elevated pCO 2 treatments relative to the ambient controls (two-way ANOVA, P < 0.05). QPCR amplification of nifH genes and gene transcripts revealed that diazotroph abundances and nifH gene expression were largely unchanged by the perturbation of the seawater pCO 2 . Our results suggest that naturally occurring N 2 fixing plankton assemblages in the NPSG are relatively resilient to large, short-term increases in pCO 2 .

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Western Pacific atmospheric nutrient deposition fluxes, their impact on surface ocean productivity

Martino

Hamilton

Baker

et al. 2014

Global Biogeochemical Cycles

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The atmospheric deposition of both macronutrients and micronutrients plays an important role in driving primary productivity, particularly in the low-latitude ocean. We report aerosol major ion measurements for five ship-based sampling campaigns in the western Pacific from~25°N to 20°S and compare the results with those from Atlantic meridional transects (~50°N to 50°S) with aerosols collected and analyzed in the same laboratory, allowing full incomparability. We discuss sources of the main nutrient species (nitrogen (N), phosphorus (P), and iron (Fe)) in the aerosols and their stoichiometry. Striking north-south gradients are evident over both basins with the Northern Hemisphere more impacted by terrestrial dust sources and anthropogenic emissions and the North Atlantic apparently more impacted than the North Pacific. We estimate the atmospheric supply rates of these nutrients and the potential impact of the atmospheric deposition on the tropical western Pacific. Our results suggest that the atmospheric deposition is P deficient relative to the needs of the resident phytoplankton. These findings suggest that atmospheric supply of N, Fe, and P increases primary productivity utilizing some of the residual excess phosphorus (P*) in the surface waters to compensate for aerosol P deficiency. Regional primary productivity is further enhanced via the stimulation of nitrogen fixation fuelled by the residual atmospheric iron and P*. Our stoichiometric calculations reveal that a P* of 0.1 μmol L À1 can offset the P deficiency in atmospheric supply for many months. This study suggests that atmospheric deposition may sustain~10% of primary production in both the western tropical Pacific.

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Unicellular Cyanobacterial Distributions Broaden the Oceanic N ₂ Fixation Domain

Cited by 411 publications

References 26 publications

Analogous nutrient limitations in unicellular diazotrophs and Prochlorococcus in the South Pacific Ocean

Analogous nutrient limitations in unicellular diazotrophs and Prochlorococcus in the South Pacific Ocean

Experimental assessment of diazotroph responses to elevated seawater pCO₂ in the North Pacific Subtropical Gyre

Western Pacific atmospheric nutrient deposition fluxes, their impact on surface ocean productivity

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Unicellular Cyanobacterial Distributions Broaden the Oceanic N 2 Fixation Domain

Cited by 411 publications

References 26 publications

Analogous nutrient limitations in unicellular diazotrophs and Prochlorococcus in the South Pacific Ocean

Analogous nutrient limitations in unicellular diazotrophs and Prochlorococcus in the South Pacific Ocean

Experimental assessment of diazotroph responses to elevated seawater pCO2 in the North Pacific Subtropical Gyre

Western Pacific atmospheric nutrient deposition fluxes, their impact on surface ocean productivity

Contact Info

Product

Resources

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Unicellular Cyanobacterial Distributions Broaden the Oceanic N ₂ Fixation Domain

Experimental assessment of diazotroph responses to elevated seawater pCO₂ in the North Pacific Subtropical Gyre