Controls on boron isotopes in a cold-water coral and the cost of resilience to ocean acidification

Gagnon, Alex; Gothmann, Anne M.; Branson, Oscar; Rae, J. W. B.; Stewart, Joseph

doi:10.1002/essoar.10503664.1

Cited by 9 publications

(19 citation statements)

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“…Further, corals do not directly precipitate calcium carbonate from the seawater, rather they precipitate from the calcifying fluid located between the calicoblastic cell membrane and skeleton (Allemand et al., 2004; Cohen & McConnaughey, 2003). During the calcification process, corals elevate pH of the calcifying fluid to facilitate aragonite precipitation (Gagnon et al., 2021; McCulloch et al., 2017; Sevilgen et al., 2019). Therefore, corals often show their resilience to counter OA by elevating pH of the calcifying fluid called “pH upregulation” (McCulloch et al., 2012).…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, corals often show their resilience to counter OA by elevating pH of the calcifying fluid called “pH upregulation” (McCulloch et al., 2012). The coral δ 11 B together with B/Ca record is often used to infer about the biomineralization processes (Gagnon et al., 2021). In the present study, δ 11 B and B/Ca proxy records do not show any significant correlations (Figure ), unlike it was observed in the controlled laboratory experiment (Gagnon et al., 2021).…”

Section: Discussionmentioning

confidence: 99%

“…The coral δ 11 B together with B/Ca record is often used to infer about the biomineralization processes (Gagnon et al., 2021). In the present study, δ 11 B and B/Ca proxy records do not show any significant correlations (Figure ), unlike it was observed in the controlled laboratory experiment (Gagnon et al., 2021). Therefore, we could not infer about the role of calcification processes in regulating δ 11 B‐pH of the Lakshadweep coral reef environment.…”

Section: Discussionmentioning

confidence: 99%

“…The pH CF is also regulated by temperature (D'Olivo & McCulloch, 2017; D'Olivo et al., 2019; Guo, 2019), seawater alkalinity (Albright et al., 2016), dissolved inorganic carbon (DIC) concentration (Comeau et al., 2017; McCulloch et al., 2017), presence of photosynthetic symbionts (Venn et al., 2011, 2019), and coralline respiration (Allison et al., 2014; W. J. Cai et al., 2016). A recent study based on coral culture showed that the diffusion of boric acid across the cell membranes has a strong influence on biomineralization and hence the pH CF (Gagnon et al., 2021). However, as the pH of the internal calcifying fluid is strongly correlated to external seawater pH, it implies that the δ 11 B coral tracks the changes in seawater δ 11 B Borate following a quantifiable species specific offset (Holcomb et al., 2014; Krief et al., 2010; Trotter et al., 2011).…”

Section: Methodsmentioning

confidence: 99%

“…These corals are highly vulnerable to anthropogenic CO 2 ‐driven climate change (Wall et al., 2016) such as OA (Hoegh‐Guldberg et al., 2007; Orr et al., 2005) and ocean warming (Guillermic et al., 2021; Hughes et al., 2017; Schoepf et al., 2015). Thus, understanding the effect of OA and ocean warming on corals is critical in predicting the future of these ecosystems (Gagnon et al., 2021; McCulloch et al., 2017; Wall et al., 2015, 2019).…”

Section: Introductionmentioning

confidence: 99%

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Surface pH Record (1990–2013) of the Arabian Sea From Boron Isotopes of Lakshadweep Corals—Trend, Variability, and Control

et al. 2021

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Approximately 30% of the anthropogenic CO 2 emission has been absorbed by the oceans (Friedlingstein et al., 2019;Sabine & Tanhua, 2010). The CO 2 invasion to the oceans since the industrial revolution (∼1850) has caused a decrease of ∼0.1 unit in surface ocean pH, a process commonly known as ocean acidification (OA) (Doney et al., 2009). Numerical model simulations for the end of the century at different scenarios of Abstract Atmospheric CO 2 rise in post-industrial era has resulted in decline in surface ocean pH, commonly known as "ocean acidification (OA)," which has become a threat to marine calcifiers. Instrumental records of ocean pH and its reconstruction utilizing boron isotope (δ 11 B) composition of corals demonstrate a long-term OA trend characterized by large spatio-temporal variability in both Pacific and Atlantic oceans. However, no such record exists to elucidate long-term OA trend of the Indian Ocean. We report the first sub-annually resolved pH record from the Arabian Sea based on δ 11 B measurements on Porites coral from Lakshadweep coral reefs. This pH record is characterized by large variability ranging from 7.93 to 8.65 with no long-term discernable trend. The long-term declining trend expected from the ∼50 ppm increase in atmospheric CO 2 during the coral growth interval appears to be obscured by large surface pH variability in the Arabian Sea. Our investigation reveals that physical oceanographic processes for example, upwelling, downwelling and convective mixing modulated by El Niño-Southern Oscillation (ENSO) largely control surface pH variability and masked expected long-term OA trend resulting from anthropogenic CO 2 rise. Combining the model-based predictions of increase in frequency and amplitude of ENSO events in a future warming scenario and the observed ENSO dependency of surface water pH, we predict more frequent and large pH variability ("pH extremes") in this region. Such pH extremes and their occurrences might be critical for the resilience and adaptability of corals and other calcifiers in Arabian Sea and other similar oceanic settings elsewhere.Plain Language Summary Increase in the atmospheric CO 2 concentration since the industrial revolution (∼1850) has resulted in decrease in ocean pH, known as ocean acidification (OA). Only limited number of pH records are avalable to assess the impacts of OA on marine ecosystems. The available pH records from the Pacific and Atlantic oceans, based on both instrumental observations and coral boron isotope records, demonstrate a long-term declining trend with significant internal variability. However, no such records are available from the Indian Ocean. Here, we provide the first seasonally resolved record of Indian Ocean pH for a 23 year period based on boron isotope study of corals collected from the Lakshadweep, Arabian Sea. pH variability in the Arabian Sea is domiantly controlled by ENSO modulated oceanographic processes such as upwelling and mixing. We did not observe any long-term declining trend corresponding to the ∼50 ppm rise...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surface pH Record (1990–2013) of the Arabian Sea From Boron Isotopes of Lakshadweep Corals—Trend, Variability, and Control

et al. 2021

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Environmental records from coral skeletons: A decade of novel insights and innovation

Thompson

2021

WIREs Climate Change

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Hundreds of coral paleoclimate records have been developed over the past several decades, significantly extending the instrumental record and improving our understanding of tropical climate variability and change in otherwise datapoor regions. Coral "proxy" records measure the change in skeletal geochemistry or growth as a function of ocean conditions at the time of calcification.Over the past decade (since 2010), new syntheses have identified coherent patterns of warming and variability that are unique within the paleo record (albeit not yet unprecedented). In turn, ocean warming and acidification have had a detrimental impact on coral growth, with reduced extension and increased stress banding. Methodological advances have constrained uncertainties and improved our understanding of the processes by which climate information is archived in coral skeletons. Models that describe these processes have been developed to facilitate proxy-model comparisons, identify sources of uncertainties, and provide a benchmark upon which forced changes may be detected within a highly variable climate system. Finally, several innovative new proxies have expanded the climate and environmental information that may be obtained from corals, including: seawater pH, aragonite saturation, anthropogenic nitrogen, runoff, and trade winds. Further extending established and novel proxies should remain a priority, along with seawater monitoring and density measurements with which to screen and calibrate these records. As this critical climate archive is increasingly threatened by warming and ocean acidification, the community must work closely together to collect this invaluable climate data in an ecologically and culturally sensitive manner, before it is too late.

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No ion is an island: Multiple ions influence boron incorporation into CaCO3

Henehan

Gebbinck

Wymans

et al. 2022

Geochimica et Cosmochimica Acta

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Controls on boron isotopes in a cold-water coral and the cost of resilience to ocean acidification

Cited by 9 publications

References 0 publications

Surface pH Record (1990–2013) of the Arabian Sea From Boron Isotopes of Lakshadweep Corals—Trend, Variability, and Control

Surface pH Record (1990–2013) of the Arabian Sea From Boron Isotopes of Lakshadweep Corals—Trend, Variability, and Control

Environmental records from coral skeletons: A decade of novel insights and innovation

No ion is an island: Multiple ions influence boron incorporation into CaCO3

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