Peer Review #3 of "Measuring coral calcification under ocean acidification: methodological considerations for the 45Ca-uptake and total alkalinity anomaly technique (v0.1)"

As the oceans become less alkaline due to rising CO2 levels, deleterious consequences are expected for calcifying corals. Predicting how coral calcification will be affected by on-going ocean acidification (OA) requires an accurate assessment of CaCO3 deposition and an understanding of the relative importance that decreasing calcification and/or increasing dissolution play for the overall calcification budget of individual corals. Here, we assessed the compatibility of the 45Ca-uptake and total alkalinity (TA) anomaly techniques as measures of gross and net calcification (GC, NC), respectively, to determine coral calcification at pHT 8.1 and 7.5. Considering the differing buffering capacity of seawater at both pH values, we were also interested in how strongly coral calcification alters the seawater carbonate chemistry under prolonged incubation in sealed chambers, potentially interfering with physiological functioning. Our data indicate that NC estimates by TA are erroneously ∼5% and ∼21% higher than GC estimates from 45Ca for ambient and reduced pH, respectively. Considering also previous data, we show that the consistent discrepancy between both techniques across studies is not constant, but largely depends on the absolute value of CaCO3 deposition. Deriving rates of coral dissolution from the difference between NC and GC was not possible and we advocate a more direct approach for the future by simultaneously measuring skeletal calcium influx and efflux. Substantial changes in carbonate system parameters for incubation times beyond two hours in our experiment demonstrate the necessity to test and optimize experimental incubation setups when measuring coral calcification in closed systems, especially under OA conditions.

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Measuring gross and net calcification of a reef coral under ocean acidification conditions: methodological considerations

Biogeosciences Discussions ◽

10.5194/bgd-9-8241-2012 ◽

2012 ◽

Vol 9 (7) ◽

pp. 8241-8272 ◽

Cited By ~ 11

Author(s):

S. Cohen ◽

M. Fine

Keyword(s):

Ocean Acidification ◽

Reef Coral ◽

Total Alkalinity ◽

Carbonate Chemistry ◽

Stylophora Pistillata ◽

Realistic Assessment ◽

Ph Conditions ◽

Low Sensitivity ◽

Methodological Considerations ◽

Projected Changes

Abstract. Ongoing ocean acidification (OA) is rapidly altering carbonate chemistry in the oceans. The projected changes will likely have deleterious consequences for coral reefs by negatively affecting their growth. Nonetheless, diverse responses of reef-building corals calcification to OA hinder our ability to decipher reef susceptibility to elevated pCO2. Some of the inconsistencies between studies originate in measuring net calcification (NC), which does not always consider the proportions of the "real" (gross) calcification (GC) and gross dissolution in the observed response. Here we show that microcolonies of Stylophora pistillata (entirely covered by tissue), incubated under normal (8.2) and reduced (7.6) pH conditions for 16 months, survived and added new skeletal CaCO3, despite low (1.25) Ωarg conditions. Moreover, corals maintained their NC and GC rates under reduced (7.6) pH conditions and displayed positive NC rates at the low-end (7.3) pH treatment while bare coral skeleton underwent marked dissolution. Our findings suggest that S. pistillata may fall into the "low sensitivity" group with respect to OA and that their overlying tissue may be a key determinant in setting their tolerance to reduced pH by limiting dissolution and allowing them to calcify. This study is the first to measure GC and NC rates for a tropical scleractinian corals under OA conditions. We provide a detailed, realistic assessment of the problematic nature of previously accepted methods for measuring calcification (total alkalinity and 45Ca).

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Thermal stress reduces pocilloporid coral resilience to ocean acidification by impairing control over calcifying fluid chemistry

Science Advances ◽

10.1126/sciadv.aba9958 ◽

2021 ◽

Vol 7 (2) ◽

pp. eaba9958

Author(s):

Maxence Guillermic ◽

Louise P. Cameron ◽

Ilian De Corte ◽

Sambuddha Misra ◽

Jelle Bijma ◽

...

Keyword(s):

Thermal Stress ◽

Ocean Acidification ◽

Pocillopora Damicornis ◽

Carbonate Chemistry ◽

Negative Interaction ◽

Saturation State ◽

Stylophora Pistillata ◽

Coral Calcification ◽

Influence Of Temperature On ◽

Different Time Scales

The combination of thermal stress and ocean acidification (OA) can more negatively affect coral calcification than an individual stressors, but the mechanism behind this interaction is unknown. We used two independent methods (microelectrode and boron geochemistry) to measure calcifying fluid pH (pHcf) and carbonate chemistry of the corals Pocillopora damicornis and Stylophora pistillata grown under various temperature and pCO2 conditions. Although these approaches demonstrate that they record pHcf over different time scales, they reveal that both species can cope with OA under optimal temperatures (28°C) by elevating pHcf and aragonite saturation state (Ωcf) in support of calcification. At 31°C, neither species elevated these parameters as they did at 28°C and, likewise, could not maintain substantially positive calcification rates under any pH treatment. These results reveal a previously uncharacterized influence of temperature on coral pHcf regulation—the apparent mechanism behind the negative interaction between thermal stress and OA on coral calcification.

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Peer Review #1 of "Contrasting effects of ocean acidification on tropical fleshy and calcareous algae (v0.1)"

10.7287/peerj.411v0.1/reviews/1 ◽

2014 ◽

Keyword(s):

Ocean Acidification ◽

Peer Review ◽

Calcareous Algae

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Ocean acidification from 1997 to 2011 in the subarctic western North Pacific Ocean

Biogeosciences Discussions ◽

10.5194/bgd-10-8283-2013 ◽

2013 ◽

Vol 10 (5) ◽

pp. 8283-8311 ◽

Cited By ~ 1

Author(s):

M. Wakita ◽

S. Watanabe ◽

M. Honda ◽

A. Nagano ◽

K. Kimoto ◽

...

Keyword(s):

Ocean Acidification ◽

Mixed Layer ◽

North Pacific ◽

Dissolved Inorganic Carbon ◽

North Pacific Ocean ◽

Total Alkalinity ◽

Co2 Uptake ◽

The North ◽

Western Subarctic Gyre ◽

Calcite Saturation

Abstract. Rising atmospheric CO2 contents have led to greater CO2 uptake by the oceans, lowering both pH due to increasing hydrogen ions and CaCO3 saturation states due to declining carbonate ion (CO32−). Here, we used previously compiled data sets and new data collected in 2010 and 2011 to investigate ocean acidification of the North Pacific western subarctic gyre. In winter, the western subarctic gyre is a source of CO2 to the atmosphere because of convective mixing of deep waters rich in dissolved inorganic carbon (DIC). We calculated pH in winter mixed layer from DIC and total alkalinity (TA), and found that it decreased at the rate of −0.001 ± 0.0004 yr−1 from 1997 to 2011. This decrease rate is slower than that expected under condition of seawater/atmosphere equilibration, and it is also slower than the rate in the subtropical regions (−0.002 yr−1). The slow rate is caused by a reduction of CO2 emission in winter due to an increase in TA. Below the mixed layer, the calcite saturation horizon (~185 m depth) shoaled at the rate of 2.9 ± 0.9 m yr−1 as the result of the declining CO32− concentration (−0.03 ± 0.01 μmol k−1yr−1). Between 200 m and 300 m depth, pH decline during the study period (−0.0051 ± 0.0010 yr−1) was larger than ever reported in the open North Pacific. This enhanced acidification rate below the calcite saturation horizon reflected not only the uptake of anthropogenic CO2 but also the increase in the decomposition of organic matter evaluated from the increase in AOU, which suggests that the dissolution of CaCO3 particles increased.

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Ocean alkalinity enhancement as a tool to mitigate ocean acidification and facilitate CO2 uptake from the atmosphere

10.5194/egusphere-egu21-2264 ◽

2021 ◽

Author(s):

Jakob Rønning ◽

Carolin Löscher

Keyword(s):

Ocean Acidification ◽

Total Alkalinity ◽

Small Scale ◽

Marine Biodiversity ◽

Steady Increase ◽

Co2 Uptake ◽

Seawater Ph ◽

Mineral Additions ◽

Primary Producer ◽

Negative Emission Technologies

Anthropogenic global warming over the last century has led to a steady increase of CO2 in the atmosphere. One of the consequences of increasing CO2 concentrations is ocean acidification, a phenomenon problematic to marine biodiversity and biogeochemistry. The ocean reservoir takes up 25% of CO2 from the atmosphere both chemically and biologically. This potential can be made use of to promote CO2 uptake from the atmosphere while mitigating ocean acidification and protecting biodiversity using negative emission technologies associated with the ocean. We have investigated the potential of various alkaline minerals to stabilize seawater pH overtime on a small scale. Those alkaline minerals were predicted to be appropriate for ocean alkalinity enhancement and can offer a toolset to mitigate CO2 from the atmosphere. Specifically, we have examined how chalk, calcite, dolomite, limestone, and olivine affects seawater pH and total alkalinity (TA) on timescales of several months. Thereby, we could identify two promising minerals, dolomite and olivine, and develop a strategy for mineral additions to buffer the seawater pH. Importantly, the often proposed had an unexpected opposite impact and massively lowered the seawater pH over a timescale of 100 days. The identified advantageous minerals will inform our experiments on primary producer cultures and natural consortia.

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Reviews and Syntheses: Responses of coccolithophores to ocean acidification: a meta-analysis

Biogeosciences ◽

10.5194/bg-12-1671-2015 ◽

2015 ◽

Vol 12 (6) ◽

pp. 1671-1682 ◽

Cited By ~ 80

Author(s):

J. Meyer ◽

U. Riebesell

Keyword(s):

Ocean Acidification ◽

Dissolved Inorganic Carbon ◽

Meta Analysis ◽

Physiological Responses ◽

Total Alkalinity ◽

Adaptive Responses ◽

Negative Effects ◽

Ecological Fitness ◽

Negative Effect ◽

Gephyrocapsa Oceanica

Abstract. Concerning their sensitivity to ocean acidification, coccolithophores, a group of calcifying single-celled phytoplankton, are one of the best-studied groups of marine organisms. However, in spite of the large number of studies investigating coccolithophore physiological responses to ocean acidification, uncertainties still remain due to variable and partly contradictory results. In the present study we have used all existing data in a meta-analysis to estimate the effect size of future pCO2 changes on the rates of calcification and photosynthesis and the ratio of particulate inorganic to organic carbon (PIC / POC) in different coccolithophore species. Our results indicate that ocean acidification has a negative effect on calcification and the cellular PIC / POC ratio in the two most abundant coccolithophore species: Emiliania huxleyi and Gephyrocapsa oceanica. In contrast, the more heavily calcified species Coccolithus braarudii did not show a distinct response when exposed to elevated pCO2/reduced pH. Photosynthesis in Gephyrocapsa oceanica was positively affected by high CO2, while no effect was observed for the other coccolithophore species. There was no indication that the method of carbonate chemistry manipulation was responsible for the inconsistent results regarding observed responses in calcification and the PIC / POC ratio. The perturbation method, however, appears to affect photosynthesis, as responses varied significantly between total alkalinity (TA) and dissolved inorganic carbon (DIC) manipulations. These results emphasize that coccolithophore species respond differently to ocean acidification, both in terms of calcification and photosynthesis. Where negative effects occur, they become evident at CO2 levels in the range projected for this century in the case of unabated CO2 emissions. As the data sets used in this meta-analysis do not account for adaptive responses, ecological fitness and ecosystem interactions, the question remains as to how these physiological responses play out in the natural environment.

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