A seasonal study of the significance of N2 fixation by Trichodesmium spp. at the Bermuda Atlantic Time-series Study (BATS) site

Orcutt, Karen M.; Lipschultz, Fredric; Gundersen, K.; Arimoto, R.; Michaels, Anthony F.; Knap, Anthony H.; Gallon, John

doi:10.1016/s0967-0645(00)00157-0

Cited by 205 publications

(217 citation statements)

References 79 publications

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“…This range encompassed C:N ratio measurements of natural (5.6-7.3; Carpenter et al, 2004 and 6.6;see Orcutt et al, 2001) and cultivated (6.27s.d. 0.7; Mulholland and Capone, We recognize the apparent non-Redfield-stoichiometric relationship between carbon fixation and N 2 fixation (13-437 mol C mol À1 N) in Trichodesmium as demonstrated in field (Orcutt et al, 2001) and laboratory (Mulholland and Capone, 2001) studies. These fixation ratios were highly variable and substantially larger than molar C:N mass ratios reported throughout the literature (4.7-8.6).…”

Section: Carbon Content a Volumetric Carbon Content Formentioning

confidence: 73%

“…This follows the model assumption of Fennel et al (2002), and is supported by evidence of obligate diazotrophy in Trichodesmium (Wada and Hattori, 1991), as well as evidence for negligible uptake of combined forms of nitrogen based on in situ measurements in the North Atlantic (4.07s.d. 7.7% of total N 2 fixed; Orcutt et al 2001).…”

Section: Carbon Content a Volumetric Carbon Content Formentioning

confidence: 99%

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Modeled contributions of three types of diazotrophs to nitrogen fixation at Station ALOHA

et al. 2007

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A diagnostic model based on biomass and growth was used to assess the relative contributions of filamentous nonheterocystous Trichodesmium and unicellular cyanobacteria, termed Groups A and B, to nitrogen fixation at the North Pacific Station ALOHA over a 2-year period. Average (and 95% confidence interval, CI) annual rates of modeled monthly values for Trichodesmium, Group B and Group A were 92 (52), 14 (4) and 12 (8) mmol N per m 2 per year, respectively. The fractional contribution to modeled instantaneous nitrogen fixation by each diazotroph fluctuated on interannual, seasonal and shorter time scales. Trichodesmium fixed substantially more nitrogen in year 1 (162) than year 2 (12). Group B fixed almost two times more nitrogen in year 1 (17) than year 2 (9). In contrast, Group A fixed two times more nitrogen in year 2 (16) than year 1 (8). When including uncertainties in our estimates using the bootstrap approach, the range of unicellular nitrogen fixation extended from 10% to 68% of the total annual rate of nitrogen fixation for all three diazotrophs. Furthermore, on a seasonal basis, the model demonstrated that unicellular diazotrophs fixed the majority (51%-97%) of nitrogen during winter and spring, whereas Trichodesmium dominated nitrogen fixation during summer and autumn (60%-96%). Sensitivity of the modeled rates to some parameters suggests that this unique attempt to quantify relative rates of nitrogen fixation by different diazotrophs may need to be reevaluated as additional information on cell size, variability in biomass and C:N, and growth characteristics of the different cyanobacterial diazotrophs become available.

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Section: Carbon Content a Volumetric Carbon Content Formentioning

confidence: 73%

Section: Carbon Content a Volumetric Carbon Content Formentioning

confidence: 99%

Modeled contributions of three types of diazotrophs to nitrogen fixation at Station ALOHA

et al. 2007

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“…C and N 2 Fixation and H 2 Evolution. Rates of NaH 13 CO 3 uptake and 15 N 2 incorporation by exponentially growing cells were determined over a 4-h period (between 5 and 9 h after onset of the light) (51,52). In the 2-h short-term experiments, to distinguish the effect of pCO 2 from that of pH on N 2 fixation and H 2 evolution, the acetylene-reduction assay was used to determine the N 2 -fixation rate (53), and H 2 production was measured with a Peak Performer gas chromatograph (Peak Laboratories, LLC).…”

Section: Methodsmentioning

confidence: 99%

Ocean acidification slows nitrogen fixation and growth in the dominant diazotroph Trichodesmium under low-iron conditions

Shi

Kranz

Kim

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

113

104

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Dissolution of anthropogenic CO 2 increases the partial pressure of CO 2 (pCO 2 ) and decreases the pH of seawater. The rate of Fe uptake by the dominant N 2 -fixing cyanobacterium Trichodesmium declines as pH decreases in metal-buffered medium. The slower Fe-uptake rate at low pH results from changes in Fe chemistry and not from a physiological response of the organism. Contrary to previous observations in nutrient-replete media, increasing pCO 2 /decreasing pH causes a decrease in the rates of N 2 fixation and growth in Trichodesmium under low-Fe conditions. This result was obtained even though the bioavailability of Fe was maintained at a constant level by increasing the total Fe concentration at low pH. Short-term experiments in which pCO 2 and pH were varied independently showed that the decrease in N 2 fixation is caused by decreasing pH rather than by increasing pCO 2 and corresponds to a lower efficiency of the nitrogenase enzyme. To compensate partially for the loss of N 2 fixation efficiency at low pH, Trichodesmium synthesizes additional nitrogenase. This increase comes partly at the cost of down-regulation of Fe-containing photosynthetic proteins. Our results show that although increasing pCO 2 often is beneficial to photosynthetic marine organisms, the concurrent decreasing pH can affect primary producers negatively. Such negative effects can occur both through chemical mechanisms, such as the bioavailability of key nutrients like Fe, and through biological mechanisms, as shown by the decrease in N 2 fixation in Fe-limited Trichodesmium.climate change | cyanobacteria | iron limitation A bout one-third of the anthropogenic CO 2 released into the atmosphere dissolves into the surface ocean, increasing the partial pressure of CO 2 , pCO 2 , and lowering the pH. This ocean acidification has been shown to have various consequences for marine phytoplankton (1-5). Organisms that invest a large amount of energy in the operation of a carbon-concentrating mechanism (CCM) are expected to be particularly sensitive to changes in pCO 2 . This is the case for marine cyanobacteria, which must elevate the CO 2 concentration at the site of carbon fixation as a result of the poor affinity for CO 2 of their carboxylating enzyme, ribulose bisphosphate carboxylase oxygenase (RubisCO) (6). Of particular interest is the effect of ocean acidification on the N 2 -fixing filamentous cyanobacterium Trichodesmium, which is responsible for a major fraction of all marine N 2 fixation and thus plays a prominent role in the biogeochemical cycling of C and N (7). This bloom-forming diazotroph thrives throughout the oligotrophic tropical and subtropical oceans where P and/or Fe often limit its growth and N 2 fixation (8-10).In the past few years, the effects of ocean acidification on Trichodesmium have been studied extensively in combination with those of other environmental variables, such as temperature, light intensity, and phosphorus limitation. Stimulation of N 2 fixation and growth at elevated pCO 2 has been observed in both la...

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“…The low nutrient and low chlorophyll North Atlantic Ocean is thought to be one of the most iron-rich oceans owing to eolian inputs (Jickells et al, 2005) and has diverse communities of diazotrophs (Orcutt et al, 2001;Langlois et al, 2008). Actively N 2 -fixing Trichodesmium requires more Fe relative to non-diazotrophic phytoplankton (Berman-Frank et al, 2001), however in the Atlantic its growth was suggested to be either P (Sanudo-Wilhelmy et al, 2001;Hynes et al, 2009) or Fe (Lenes et al, 2001) limited.…”

Section: Introductionmentioning

confidence: 99%

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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A seasonal study of the significance of N2 fixation by Trichodesmium spp. at the Bermuda Atlantic Time-series Study (BATS) site

Cited by 205 publications

References 79 publications

Modeled contributions of three types of diazotrophs to nitrogen fixation at Station ALOHA

Modeled contributions of three types of diazotrophs to nitrogen fixation at Station ALOHA

Ocean acidification slows nitrogen fixation and growth in the dominant diazotroph Trichodesmium under low-iron conditions

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

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