Responses of coral gastrovascular cavity pH during light and dark incubations to reduced seawater pH suggest species-spe
- PDF / 2,234,534 Bytes
- 17 Pages / 595.276 x 790.866 pts Page_size
- 15 Downloads / 138 Views
REPORT
Responses of coral gastrovascular cavity pH during light and dark incubations to reduced seawater pH suggest species-specific responses to the effects of ocean acidification on calcification Colleen B. Bove1,2
•
Robert F. Whitehead2
•
Alina M. Szmant2
Received: 2 May 2019 / Accepted: 18 August 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Coral polyps have a fluid-filled internal compartment, the gastrovascular cavity (GVC). Respiration and photosynthesis cause large daily excursions in GVC oxygen concentration (O2) and pH, but few studies have examined how this correlates with calcification rates. We hypothesized that GVC chemistry can mediate and ameliorate the effects of decreasing seawater pH (pHSW) on coral calcification. Microelectrodes were used to monitor O2 and pH within the GVC of Montastraea cavernosa and Duncanopsammia axifuga (pH only) in both the light and the dark, and three pHSW levels (8.2, 7.9, and 7.6). At pHSW 8.2, GVC O2 ranged from ca. 0 to over 400% saturation in the dark and light, respectively, with transitions from low to high (and vice versa) within minutes of turning the light on or off. For all three pHSW treatments and both species, pHGVC was always significantly above and below pHSW in the light and dark, respectively. For M. cavernosa in the light, pHGVC reached levels of pH 8.4–8.7 with no difference among pHSW treatments tested; in the dark, pHGVC dropped below pHSW and even below pH 7.0 in some trials at pHSW 7.6. For D. axifuga in both the light and the dark, pHGVC decreased linearly as pHSW decreased.
Topic Editor Morgan S.Pratchett
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00338-020-01995-7) contains supplementary material, which is available to authorized users. & Alina M. Szmant [email protected] 1
Environment, Ecology, and Energy Program, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
2
Center for Marine Science, University of North Carolina Wilmington, Wilmington, NC, USA
Calcification rates were measured in the light concurrent with measurements of GVC O2 and pHGVC. For both species, calcification rates were similar at pHSW 8.2 and 7.9 but were significantly lower at pHSW 7.6. Thus, for both species, calcification was protected from seawater acidification by intrinsic coral physiology at pHSW 7.9 but not 7.6. Calcification was not correlated with pHGVC for M. cavernosa but was for D. axifuga. These results highlight the diverse responses of corals to changes in pHSW, their varying abilities to control pHGVC, and consequently their susceptibility to ocean acidification. Keywords Ocean acidification Gastrovascular cavity Gastrovascular chemistry Photosynthesis Coral calcification Seawater pH Coral metabolism
Introduction Since the industrial revolution, the concentration of carbon dioxide (CO2) in the Earth’s atmosphere has drastically increased from less than 300 ppm to now more than 410 ppm (Tans and Keeling 2017). About one-third
Data Loading...
