Colimitation of the unicellular photosynthetic diazotroph <i>Crocosphaera watsonii</i> by phosphorus, light, and carbon dioxide

Garcia, Nathan S.; Fu, Fei-Xue; Hutchins, David A.

doi:10.4319/lo.2013.58.4.1501

Cited by 32 publications

(35 citation statements)

References 43 publications

(79 reference statements)

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“…N 2 fixation rates were significantly reduced in the ocean acidification treatment compared to the ambient scenario in the light. Other studies reported an increase of N 2 fixation activity under elevated CO 2 conditions for planktonic cyanobacteria due to increased photosynthetic carbon fixation by overcoming CO 2 limitation (Hutchins et al 2007, Garcia et al 2013. This may be the case for planktonic autotrophic diazotrophs, but CO 2 limitation is unlikely to occur in the S. hystrix holobiont due to respiration by the coral host.…”

Section: Discussionmentioning

confidence: 95%

Ocean acidification rapidly reduces dinitrogen fixation associated with the hermatypic coral Seriatopora hystrix

Rädecker¹,

Meyer²,

Bednarz³

et al. 2014

Mar. Ecol. Prog. Ser.

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Since productivity and growth of coral-associated dinoflagellate algae is nitrogen (N)-limited, dinitrogen (N 2 ) fixation by coral-associated microbes is likely crucial for maintaining the coral−dinoflagellate symbiosis. It is thus essential to understand the effects future climate change will have on N 2 fixation by the coral holobiont. This laboratory study is the first to investigate short-term effects of ocean acidification on N 2 fixation activity associated with the tropical, hermatypic coral Seriatopora hystrix using the acetylene reduction assay in combination with calcification measurements. Findings reveal that simulated ocean acidification ( pCO 2 1080 µatm) caused a rapid and significant decrease (53%) in N 2 fixation rates associated with S. hystrix compared to the present day scenario ( pCO 2 486 µatm). In addition, N 2 fixation associated with the coral holobiont showed a positive exponential relationship with its calcification rates. This suggests that even small declines in calcification rates of hermatypic corals under high CO 2 conditions may result in decreased N 2 fixation activity, since these 2 processes may compete for energy in the coral holobiont. Ultimately, an intensified N limitation in combination with a decline in skeletal growth may trigger a negative feedback loop on coral productivity exacerbating the negative long-term effects of ocean acidification.

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Section: Discussionmentioning

confidence: 95%

Ocean acidification rapidly reduces dinitrogen fixation associated with the hermatypic coral Seriatopora hystrix

Rädecker¹,

Meyer²,

Bednarz³

et al. 2014

Mar. Ecol. Prog. Ser.

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“…Cultures were acclimated to low-P conditions as described by Garcia et al (2013). Briefly, after establishment of steady-state growth at each P concentration, cultures were then successively transferred to the neighboring lower P treatment until a new steady-state growth rate was achieved before sampling and further transfers.…”

Section: Methodsmentioning

confidence: 99%

“…Thus, these measurements in the lowest P treatments in experiments with Trichodesmium and Crocosphaera were considered to represent values where the growth rate approached zero. We calculated growth rates as described previously (Garcia et al, 2013) using volumespecific estimates of cell number or total filament length. Hyperbolic functions of the form f (x) ¼ ax/(b þ x) were fit to the data in Figure 1 using an iterative method (Garcia et al, 2013) with Sigma Plot 10 software, where a ¼ m max , b ¼ Km and C min is the minimum concentration of P needed to support growth.…”

Section: Methodsmentioning

confidence: 99%

“…We calculated growth rates as described previously (Garcia et al, 2013) using volumespecific estimates of cell number or total filament length. Hyperbolic functions of the form f (x) ¼ ax/(b þ x) were fit to the data in Figure 1 using an iterative method (Garcia et al, 2013) with Sigma Plot 10 software, where a ¼ m max , b ¼ Km and C min is the minimum concentration of P needed to support growth. Diameters of B12 cells (C. watsonii) were measured microscopically from each treatment (except the 0.6 mM P treatment) with an ocular micrometer.…”

Section: Methodsmentioning

confidence: 99%

“…Diameters of B12 cells (C. watsonii) were measured microscopically from each treatment (except the 0.6 mM P treatment) with an ocular micrometer. We measured N 2 fixation and particulate C, N and P at the end of a 3-day growth period following the final dilution, as previously described (Garcia et al, 2013). We used growth rates (d À 1 ) and P-quota (fmol per cell) measurements to estimate cell-specific P-uptake rates.…”

Section: Methodsmentioning

confidence: 99%

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Iron deficiency increases growth and nitrogen-fixation rates of phosphorus-deficient marine cyanobacteria

Garcia

Sedwick

et al. 2014

The ISME Journal

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Marine dinitrogen (N 2 )-fixing cyanobacteria have large impacts on global biogeochemistry as they fix carbon dioxide (CO 2 ) and fertilize oligotrophic ocean waters with new nitrogen. Iron (Fe) and phosphorus (P) are the two most important limiting nutrients for marine biological N 2 fixation, and their availabilities vary between major ocean basins and regions. A long-standing question concerns the ability of two globally dominant N 2 -fixing cyanobacteria, unicellular Crocosphaera and filamentous Trichodesmium, to maintain relatively high N 2 -fixation rates in these regimes where both Fe and P are typically scarce. We show that under P-deficient conditions, cultures of these two cyanobacteria are able to grow and fix N 2 faster when Fe deficient than when Fe replete. In addition, growth affinities relative to P increase while minimum concentrations of P that support growth decrease at low Fe concentrations. In Crocosphaera, this effect is accompanied by a reduction in cell sizes and elemental quotas. Relatively high growth rates of these two biogeochemically critical cyanobacteria in low-P, low-Fe environments such as those that characterize much of the oligotrophic ocean challenge the common assumption that low Fe levels can have only negative effects on marine primary producers. The closely interdependent influence of Fe and P on N 2 -fixing cyanobacteria suggests that even subtle shifts in their supply ratio in the past, present and future oceans could have large consequences for global carbon and nitrogen cycles.

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Environmental controls on the biogeography of diazotrophy and Trichodesmium in the Atlantic Ocean

Snow

Schlösser

Woodward

et al. 2015

Global Biogeochemical Cycles

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The cyanobacterium Trichodesmium is responsible for a significant proportion of the annual "new" nitrogen introduced into the global ocean. Despite being arguably the best studied marine diazotroph, the factors controlling the distribution and growth of Trichodesmium remain a subject of debate, with sea surface temperature, the partial pressure of CO 2 , and nutrients including iron (Fe) and phosphorus (P), all suggested to be important. Synthesizing data from seven cruises collectively spanning large temporal and spatial scales across the Atlantic Ocean, including two previously unreported studies crossing the largely undersampled South Atlantic gyre, we assessed the relationship between proposed environmental drivers and both community N 2 fixation rates and the distribution of Trichodesmium. Simple linear regression analysis would suggest no relationship between any of the sampled environmental variables and N 2 fixation rates. However, considering the concentrations of iron and phosphorus together within a simplified resource-ratio framework, illustrated using an idealized numerical model, indicates the combined effects these nutrients have on Trichodesmium and broader diazotroph biogeography, alongside the reciprocal maintenance of different biogeographic provinces of the (sub)tropical Atlantic in states of Fe or P oligotrophy by diazotrophy. The qualitative principles of the resource-ratio framework are argued to be consistent with both the previously described North-South Atlantic contrast in Trichodesmium abundance and the presence and consequence of a substantial non-Trichodesmium diazotrophic community in the western South Atlantic subtropical gyre. A comprehensive, observation-based explanation of the interactions between Trichodesmium and the wider diazotrophic community with iron and phosphorus in the Atlantic Ocean is thus revealed.

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Colimitation of the unicellular photosynthetic diazotroph Crocosphaera watsonii by phosphorus, light, and carbon dioxide

Cited by 32 publications

References 43 publications

Ocean acidification rapidly reduces dinitrogen fixation associated with the hermatypic coral Seriatopora hystrix

Ocean acidification rapidly reduces dinitrogen fixation associated with the hermatypic coral Seriatopora hystrix

Iron deficiency increases growth and nitrogen-fixation rates of phosphorus-deficient marine cyanobacteria

Environmental controls on the biogeography of diazotrophy and Trichodesmium in the Atlantic Ocean

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