Effect of ocean acidification on cyanobacteria in the subtropical North Atlantic

Lomas, Michael W.; Hopkinson, Brian M.; Losh, Jenna L.; Ryan, D.E.; Shi, Dalin; Xu, Yan; Morel, François M. M.

doi:10.3354/ame01576

Cited by 68 publications

(59 citation statements)

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“…In this situation, an increase in CO 2 and bicarbonate concentration can result in a substantial energetic savings for the cells. Such savings probably explain the beneficial effects of high pCO 2 on N 2 and C fixation observed in P-and Fe-replete incubations of Trichodesmium thiebautii colonies collected from the field (19).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

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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Section: Discussionmentioning

confidence: 99%

“…Stimulation of N 2 fixation and growth at elevated pCO 2 has been observed in both laboratory and field studies (11)(12)(13)(14)(15)(16)(17)(18)(19). The beneficial effect of high pCO 2 has been attributed largely to the down-regulation of the CCM, which saves energetic resources for other cellular processes, such as N 2 fixation (14, 15).…”

mentioning

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

View full text Add to dashboard Cite

show abstract

“…Moreover, cell lines kept in culture may not even have retained the physiological characteristics of the original clones (Joint et al, 2011). Natural community perturbation experiments have the potential to provide a greater environmental relevance through investigation of the entire (microbial) ecosystem structure and function in an environment better approximating natural conditions (Tortell et al, 2002;Delille et al, 2005;Engel et al, 2005;Hare et al, 2007;Feng et al, 2009;Hopkinson et al, 2010;Lomas et al, 2012;Losh et al, 2012). However, interpreting the results of such field experiments can be complicated by the multiple biogeochemical feedbacks and food web interactions, which characterise responses to perturbation in any complex natural community Krause et al, 2012;Brussaard et al, 2013).…”

Section: S Richier Et Al: Phytoplankton Responses and Associated Camentioning

confidence: 99%

Phytoplankton responses and associated carbon cycling during shipboard carbonate chemistry manipulation experiments conducted around Northwest European shelf seas

et al. 2014

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Abstract. The ongoing oceanic uptake of anthropogenic carbon dioxide (CO 2 ) is significantly altering the carbonate chemistry of seawater, a phenomenon referred to as ocean acidification. Experimental manipulations have been increasingly used to gauge how continued ocean acidification will potentially impact marine ecosystems and their associated biogeochemical cycles in the future; however, results amongst studies, particularly when performed on natural communities, are highly variable, which may reflect community/environment-specific responses or inconsistencies in experimental approach. To investigate the potential for identification of more generic responses and greater experimentally reproducibility, we devised and implemented a series (n = 8) of short-term (2-4 days) multi-level (≥ 4 conditions) carbonate chemistry/nutrient manipulation experiments on a range of natural microbial communities sampled in Northwest European shelf seas. Carbonate chemistry manipulations and resulting biological responses were found to be highly reproducible within individual experiments and to a lesser extent between geographically separated experiments. Statistically robust reproducible physiological responses of phytoplankton to increasing pCO 2 , characterised by a suppression of net growth for small-sized cells (< 10 µm), were observed in the majority of the experiments, irrespective of natural or manipulated nutrient status. Remaining between-experiment variability was potentially linked to initial community structure and/or other site-specific environmental factors. Analysis of carbon cycling within the experiments revealed the expected increased sensitivity of carbonate chemistry to biological processes at higher pCO 2 and hence lower buffer capacity. The results thus emphasise how biogeochemical feedbacks may be altered in the future ocean.

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“…The main consequences of this increase which will affect planktonic organisms are (a) seawater acidification, (b) increase of seawater temperature, (c) water column stratification, (d) expansion of OMZs, and (e) desertification of terrestrial systems and associated increase of desert dust inputs to the ocean (Boyd and Doney, 2002;Jickells, 2005;Stramma et al, 2008b). While seawater acidification can either enhance photosynthetic activity in some species, or be harmful for others (Malakoff, 2012), seawater warming and stratification will likely enhance the proliferation of diazotrophic cyanobacteria such as Trichodesmium (Lomas et al, 2012), although their response to increased pCO 2 levels may depend on a variety of environmental factors . Indeed, culture experiments have revealed that the length of Trichodesmium filaments and their N 2 fixation rates increase when exposed to increasing levels of CO 2 (Levitan et al, 2007).…”

Section: What Is There Left To Be Known?mentioning

confidence: 99%

Five decades of N2 fixation research in the North Atlantic Ocean

Benavides

Voß

2015

Front. Mar. Sci.

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Dinitrogen (N 2 ) fixation (the reduction of atmospheric N 2 to ammonium by specialized prokaryotic microbes), represents an important input of fixed nitrogen and contributes significantly to primary productivity in the oceans. Marine N 2 fixation was discovered in the North Atlantic Ocean (NA) in the 1960s. Ever since, the NA has been subject to numerous studies that have looked into the diversity and abundance of N 2 -fixing microbes (diazotrophs), the spatial and temporal variability of N 2 fixation rates, and the range of physical and chemical variables that control them. The NA provides 10-25% of the globally fixed N 2 , ranking as the third basin with the largest N 2 fixation inputs in the world's oceans. This basin suffers a chronic depletion in phosphorus availability, more aeolian dust deposition than any other basin in the world's oceans, and significant nutrient inputs from important rivers like the Amazon and the Congo. These characteristics make it unique in comparison with other oceanic basins. After five decades of intensive research, here we present a comprehensive review of our current understanding of diazotrophic activity in the NA from both a geochemical and biological perspective. We discuss the advantages and disadvantages of current methods, future perspectives, and questions which remain to be answered.

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Effect of ocean acidification on cyanobacteria in the subtropical North Atlantic

Cited by 68 publications

References 50 publications

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

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

Phytoplankton responses and associated carbon cycling during shipboard carbonate chemistry manipulation experiments conducted around Northwest European shelf seas

Five decades of N2 fixation research in the North Atlantic Ocean

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