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Proc Biol Sci. 2017 Jan 25;284(1847). pii: 20161669. doi: 10.1098/rspb.2016.1669.

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

Author information

1
Department of Biology, California State University, 18111 Nordhoff Street, Northridge, CA 91330-8303, USA steeve.comeau@uwa.edu.au.
2
School of Earth and Environment and ARC Centre of Excellence for Coral Reef Studies, The University of Western Australia, Crawley, Western Australia 6009, Australia.
3
Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine 1er, MC98000, Monaco.
4
Laboratoire International Associé 647 «BIOSENSIB», Centre Scientifique de Monaco-Centre National de la Recherche Scientifique, 8 Quai Antoine 1er, MC98000, Monaco.
5
Department of Biology, California State University, 18111 Nordhoff Street, Northridge, CA 91330-8303, USA.
6
Marine Spatial Ecology Lab, ARC Centre of Excellence for Coral Reef Studies and School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia.
7
Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine 1er, MC98000, Monaco avenn@centrescientifique.mc.

Abstract

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 (pHCF) regulation, despite its importance in determining the response of corals to ocean acidification. Here, we investigate pHCF 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 (AT). 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, pHCF is sensitive to shifts in carbonate chemistry associated with changes in [DIC] and [AT], revealing that seawater pH is not the sole driver of pHCF Notably, when we synthesize our results with published data, we identify linear relationships of pHCF with the seawater [DIC]/[H+] ratio, [AT]/ [H+] ratio and [[Formula: see text]]. 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.

KEYWORDS:

calcification; dissolved inorganic carbon; ocean acidification; protons; total alkalinity

PMID:
28100813
PMCID:
PMC5310029
DOI:
10.1098/rspb.2016.1669
[Indexed for MEDLINE]
Free PMC Article

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