The effect of CO<sub>2</sub> on the photosynthetic physiology of phytoplankton in the Gulf of Alaska

Hopkinson, Brian M.; Xu, Yan; Shi, Dalin; McGinn, Patrick J.; Morel, François M. M.

doi:10.4319/lo.2010.55.5.2011

Cited by 67 publications

(66 citation statements)

References 49 publications

(60 reference statements)

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“…Interestingly, in laboratory-based proteomic analyses with cultures of the coastal diatom T. pseudonana, RubisCO was similarly more highly expressed under Fe limitation, while PEPC protein levels were higher under Fe-replete conditions (Nunn et al, 2013). Consistent with our hypothesis, Hopkinson et al (2010) attributed increases in biomass following CO 2 -enrichment of an Fe-limited phytoplankton community in the HNLC Northeast Pacific Ocean to downregulation of the CCM in order to conserve iron and photosynthetically-produced energy. Laboratory-based RubisCO kinetic work with cultured diatom isolates is needed to confirm whether diatoms from HNLC regions minimize their photosynthetic demand for Fe by synthesizing more RubisCO enzymes rather than allocating scarce energy resources into the CCM.…”

Section: Carbon-related Gene Expression Responses As a Function Of Fesupporting

confidence: 73%

Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

Cohen¹,

Ellis²,

Lampe³

et al. 2017

Front. Mar. Sci.

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Section: Carbon-related Gene Expression Responses As a Function Of Fesupporting

confidence: 73%

Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

Cohen¹,

Ellis²,

Lampe³

et al. 2017

Front. Mar. Sci.

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“…Tolerance of CO 2 levels up to ∼ 1000 µatm has often been observed in natural phytoplankton communities in regions exposed to fluctuating CO 2 levels. In these communities, increasing CO 2 often had no effect on primary productivity (Tortell et al, 2000;Tortell and Morel, 2002;Tortell et al, 2008b;Hopkinson et al, 2010;Tanaka et al, 2013;Sommer et al, 2015;Young et al, 2015;Spilling et al, 2016) or growth (Tortell et al, 2008b;Schulz et al, 2013), although an increase in primary production has been observed in some instances (Riebesell, 2004;Tortell et al, 2008b;Egge et al, 2009;Tortell et al, 2010;Hoppe et al, 2013;Holding et al, 2015). These differing responses may be due to differences in community composition, nutrient supply, or ecological adaptations of the phytoplankton community in the region studied.…”

Section: Ocean Acidification Effects On Phytoplankton Productivitymentioning

confidence: 76%

“…5). Acclimation to increased CO 2 has been reported in a number of studies, resulting in shifts in carbon and energy utilisation (Sobrino et al, 2008;Hopkinson et al, 2010;Hennon et al, 2014;Trimborn et al, 2014;Zheng et al, 2015). Numerous photophysiological investigations on individual phytoplankton species also report species-specific tolerances to increased CO 2 (Gao et al, 2012a;Gao and Campbell, 2014;Trimborn et al, 2013Trimborn et al, , 2014, and a general trend toward smaller-celled communities with increased CO 2 has been reported in ocean acidification studies globally .…”

Section: Ocean Acidification Effects On Phytoplankton Productivitymentioning

confidence: 95%

“…Numerous mesocosm studies have now been performed to assess the effect of ocean acidification on natural marine microbial communities around the world (e.g. Kim et al, 2006;Hopkinson et al, 2010;Riebesell et al, 2013;Paul et al, 2015;Bach et al, 2016;Bunse et al, 2016). Studies in the Arctic reported increases in phytoplankton primary productivity, growth, and organic matter concentration at CO 2 levels ≥ 800 µatm under nutrient-replete conditions (Bellerby et al, 2008;Egge et al, 2009;Engel et al, 2013;Schulz et al, 2013), whilst the bacterial community was unaffected (Grossart et al, 2006;Allgaier et al, 2008;Paulino et al, 2008;Baragi et al, 2015).…”

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confidence: 99%

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Ocean acidification of a coastal Antarctic marine microbial community reveals a critical threshold for CO<sub>2</sub> tolerance in phytoplankton productivity

et al. 2018

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Abstract. High-latitude oceans are anticipated to be some of the first regions affected by ocean acidification. Despite this, the effect of ocean acidification on natural communities of Antarctic marine microbes is still not well understood. In this study we exposed an early spring, coastal marine microbial community in Prydz Bay to CO 2 levels ranging from ambient (343 µatm) to 1641 µatm in six 650 L minicosms. Productivity assays were performed to identify whether a CO 2 threshold existed that led to a change in primary productivity, bacterial productivity, and the accumulation of chlorophyll a (Chl a) and particulate organic matter (POM) in the minicosms. In addition, photophysiological measurements were performed to identify possible mechanisms driving changes in the phytoplankton community. A critical threshold for tolerance to ocean acidification was identified in the phytoplankton community between 953 and 1140 µatm. CO 2 levels ≥ 1140 µatm negatively affected photosynthetic performance and Chl a-normalised primary productivity (csGPP14 C ), causing significant reductions in gross primary production (GPP14 C ), Chl a accumulation, nutrient uptake, and POM production. However, there was no effect of CO 2 on C : N ratios. Over time, the phytoplankton community acclimated to high CO 2 conditions, showing a down-regulation of carbon concentrating mechanisms (CCMs) and likely adjusting other intracellular processes. Bacterial abundance initially increased in CO 2 treatments ≥ 953 µatm (days 3-5), yet gross bacterial production (GBP14 C ) remained unchanged and cell-specific bacterial productivity (csBP14 C ) was reduced. Towards the end of the experiment, GBP14 C and csBP14 C markedly increased across all treatments regardless of CO 2 availability. This coincided with increased organic matter availability (POC and PON) combined with improved efficiency of carbon uptake. Changes in phytoplankton community production could have negative effects on the Antarctic food web and the biological pump, resulting in negative feedbacks on anthropogenic CO 2 uptake. Increases in bacterial abundance under high CO 2 conditions may also increase the efficiency of the microbial loop, resulting in increased organic matter remineralisation and further declines in carbon sequestration.

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“…This ocean acidification has been shown to have various consequences for marine phytoplankton (1)(2)(3)(4)(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 .…”

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.

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105

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 effect of CO₂ on the photosynthetic physiology of phytoplankton in the Gulf of Alaska

Cited by 67 publications

References 49 publications

Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

Ocean acidification of a coastal Antarctic marine microbial community reveals a critical threshold for CO<sub>2</sub> tolerance in phytoplankton productivity

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

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The effect of CO2 on the photosynthetic physiology of phytoplankton in the Gulf of Alaska

Cited by 67 publications

References 49 publications

Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

Ocean acidification of a coastal Antarctic marine microbial community reveals a critical threshold for CO&lt;sub&gt;2&lt;/sub&gt; tolerance in phytoplankton productivity

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

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The effect of CO₂ on the photosynthetic physiology of phytoplankton in the Gulf of Alaska

Ocean acidification of a coastal Antarctic marine microbial community reveals a critical threshold for CO<sub>2</sub> tolerance in phytoplankton productivity