scholarly journals Measuring coral calcification under ocean acidification: methodological considerations for the 45Ca-uptake and total alkalinity anomaly technique

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3749 ◽  
Author(s):  
Stephanie Cohen ◽  
Thomas Krueger ◽  
Maoz Fine
Keyword(s):  
Ocean Acidification ◽  
Calcium Influx ◽  
Total Alkalinity ◽  
Prolonged Incubation ◽  
Coral Calcification ◽  
Closed Systems ◽  
Seawater Carbonate Chemistry ◽  
The Difference ◽  
Methodological Considerations ◽  
Skeletal Calcium

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.

scholarly journals Coral calcifying fluid pH is modulated by seawater carbonate chemistry not solely seawater pH

2017 ◽  
Vol 284 (1847) ◽  
pp. 20161669 ◽  
Author(s):  
S. Comeau ◽  
E. Tambutté ◽  
R. C. Carpenter ◽  
P. J. Edmunds ◽  
N. R. Evensen ◽  
...  
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Reef Coral ◽  
Total Alkalinity ◽  
Published Data ◽  
Carbonate Chemistry ◽  
Stylophora Pistillata ◽  
Coral Calcification ◽  
Seawater Ph ◽  
Constant Ph ◽  
Seawater Carbonate Chemistry

Reef coral calcification depends on regulation of pH in the internal calcifying fluid (CF) in which the coral skeleton forms. However, little is known about calcifying fluid pH (pH CF ) regulation, despite its importance in determining the response of corals to ocean acidification. Here, we investigate pH CF in the coral Stylophora pistillata in seawater maintained at constant pH with manipulated carbonate chemistry to alter dissolved inorganic carbon (DIC) concentration, and therefore total alkalinity (A T ). We also investigate the intracellular pH of calcifying cells, photosynthesis, respiration and calcification rates under the same conditions. Our results show that despite constant pH in the surrounding seawater, pH CF is sensitive to shifts in carbonate chemistry associated with changes in [DIC] and [A T ], revealing that seawater pH is not the sole driver of pH CF . Notably, when we synthesize our results with published data, we identify linear relationships of pH CF with the seawater [DIC]/[H + ] ratio, [A T ]/ [H + ] ratio and [ ]. Our findings contribute new insights into the mechanisms determining the sensitivity of coral calcification to changes in seawater carbonate chemistry, which are needed for predicting effects of environmental change on coral reefs and for robust interpretations of isotopic palaeoenvironmental records in coral skeletons.

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

2012 ◽  
Vol 9 (7) ◽  
pp. 8241-8272 ◽  
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).

scholarly journals Long-term trend of CO<sub>2</sub> and ocean acidification in the surface water of the Ulleung Basin, the East/Japan Sea inferred from the underway observational data

2014 ◽  
Vol 11 (9) ◽  
pp. 2443-2454 ◽  
Author(s):  
J.-Y. Kim ◽  
D.-J. Kang ◽  
T. Lee ◽  
K.-R. Kim
Keyword(s):  
Surface Water ◽  
Ocean Acidification ◽  
Thermal Effect ◽  
Japan Sea ◽  
Ulleung Basin ◽  
Total Alkalinity ◽  
Marginal Seas ◽  
Relative Contribution ◽  
Decadal Trend ◽  
The Difference

Abstract. Anthropogenic carbon is responsible for both global warming and ocean acidification. Efforts are underway to understand the role of ocean in a high CO2 world on a global context. However, marginal seas received little attention despite their significant contribution to biogeochemical cycles. Here we report the CO2 increase and ocean acidification in the surface waters of the Ulleung Basin (UB) of the East/Japan Sea, and possible causes are discussed. Fourteen observations of surface fCO2 were made in the period from 1995 to 2009. The contribution of temperature variation to the seasonality of fCO2 was almost equivalent to the non-thermal effect in the UB. However, the difference of relative contribution with the season makes two seasonal peaks of fCO2 in the surface water of the UB. Non-thermal effect contributed to the surface fCO2 drawdown in summer, whereas the surface fCO2 elevation in winter. The decadal trend of fCO2 increment was estimated by harmonic analysis. The estimated rates of increase of fCO2 were 1.8 ± 0.4 μatm yr−1 for the atmosphere and 2.7 ± 1.1 μatm yr−1 for the surface water. The ocean acidification trend, calculated from total alkalinity and fCO2, was estimated to be −0.03 ± 0.02 pH units decade−1. These rates seem to be higher than observations at most other ocean time-series sites during the same period of time. Sustained observations are required to understand more accurate trend in this area.

scholarly journals Feedbacks and responses of coral calcification on the Bermuda reef system to seasonal changes in biological processes and ocean acidification

2010 ◽  
Vol 7 (8) ◽  
pp. 2509-2530 ◽  
Author(s):  
N. R. Bates ◽  
A. Amat ◽  
A. J. Andersson
Keyword(s):  
Coral Reef ◽  
Ocean Acidification ◽  
High Latitude ◽  
Carbonate Chemistry ◽  
Coral Calcification ◽  
Reef System ◽  
Seawater Carbonate Chemistry ◽  
Potential Impact ◽  
Reef Ecosystem

Abstract. Despite the potential impact of ocean acidification on ecosystems such as coral reefs, surprisingly, there is very limited field data on the relationships between calcification and seawater carbonate chemistry. In this study, contemporaneous in situ datasets of seawater carbonate chemistry and calcification rates from the high-latitude coral reef of Bermuda over annual timescales provide a framework for investigating the present and future potential impact of rising carbon dioxide (CO2) levels and ocean acidification on coral reef ecosystems in their natural environment. A strong correlation was found between the in situ rates of calcification for the major framework building coral species Diploria labyrinthiformis and the seasonal variability of [CO32-] and aragonite saturation state Ωaragonite, rather than other environmental factors such as light and temperature. These field observations provide sufficient data to hypothesize that there is a seasonal "Carbonate Chemistry Coral Reef Ecosystem Feedback" (CREF hypothesis) between the primary components of the reef ecosystem (i.e., scleractinian hard corals and macroalgae) and seawater carbonate chemistry. In early summer, strong net autotrophy from benthic components of the reef system enhance [CO32-] and Ωaragonite conditions, and rates of coral calcification due to the photosynthetic uptake of CO2. In late summer, rates of coral calcification are suppressed by release of CO2 from reef metabolism during a period of strong net heterotrophy. It is likely that this seasonal CREF mechanism is present in other tropical reefs although attenuated compared to high-latitude reefs such as Bermuda. Due to lower annual mean surface seawater [CO32-] and Ωaragonite in Bermuda compared to tropical regions, we anticipate that Bermuda corals will experience seasonal periods of zero net calcification within the next decade at [CO32-] and Ωaragonite thresholds of ~184 μmoles kg−1 and 2.65. However, net autotrophy of the reef during winter and spring (as part of the CREF hypothesis) may delay the onset of zero NEC or decalcification going forward by enhancing [CO32-] and Ωaragonite. The Bermuda coral reef is one of the first responders to the negative impacts of ocean acidification, and we estimate that calcification rates for D. labyrinthiformis have declined by >50% compared to pre-industrial times.

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

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.

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

2013 ◽  
Vol 10 (5) ◽  
pp. 8283-8311 ◽  
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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