Resistance of corals and coralline algae to ocean acidification: physiological control of calcification under natural pH variability

Abstract

Ocean acidification is a threat to the continued accretion of coral reefs, though some undergo daily fluctuations in pH exceeding declines predicted by 2100. We test whether exposure to greater pH variability enhances resistance to ocean acidification for the coral sp. and coralline alga from two sites: one with low pH variability (less than 0.15 units daily; Shell Island) and a site with high pH variability (up to 1.4 pH units daily; Tallon Island). We grew populations of both species for more than 100 days under a combination of differing pH variability (high/low) and means (ambient pH 8.05/ocean acidification pH 7.65). Calcification rates of sp. were unaffected by the examined variables. Calcification rates of were significantly faster in Tallon than in Shell Island individuals, and Tallon Island individuals calcified faster in the high variability pH 8.05 treatment compared with all others. Geochemical proxies for carbonate chemistry within the calcifying fluid (cf) of both species indicated that only mean seawater pH influenced pH pH treatments had no effect on proxies for Ω These limited responses to extreme pH treatments demonstrate that some calcifying taxa may be capable of maintaining constant rates of calcification under ocean acidification by actively modifying Ω.

Environmental and physiochemical controls on coral calcification along a latitudinal temperature gradient in Western Australia

“…Consistent with previous studies, pH cf was generally counter‐regulated with DIC cf (Cornwall et al, ; D'Olivo & McCulloch, ; McCulloch et al, ; Ross et al, ; Schoepf et al, ) thereby maintaining a tightly controlled chemical composition in the calcifying fluid at species‐dependent levels (McCulloch et al, ). Accordingly, changes in coral pH cf upregulation could be a mechanism aimed at maximizing and stabilizing both Ω cf and calcification rates.…”

Investigating marine bio‐calcification mechanisms in a changing ocean with in vivo and high‐resolution ex vivo Raman spectroscopy

“…The measured ν 1 FWHM was 9.5 cm −1 , compared to an expected FWHM of 8.2 cm −1 based on the Mg content (Perrin et al, 2016), leaving a "residual FWHM" of 1.3 cm −1 . Consistent with this result, three previous studies of coralline algae skeletons calculated residual FWHM in the same way and reported values ranging from approximately 0.3 to 1.6 cm −1 Cornwall et al, 2018;McCoy & Kamenos, 2018). The Amphisorus sp.…”

“…Raman spectroscopy has recently been applied to quantify the response of corals, coralline algae, and fish otoliths to simulated ocean acidification (Coll-Lladó, Giebichenstein, Webb, Bridges, & de la serrana, 2018;Comeau et al, 2018;Cornwall et al, 2018;DeCarlo et al, 2017;DeCarlo, Ren et al, 2018;Foster & Clode, 2016;Kamenos et al, 2013;Kamenos, Perna, Gambi, Micheli, & Kroeker, 2016). While these studies have revealed changes in both the mineralogy and disorder of calcified structures under ocean acidification, they have so far conducted Raman spectroscopy analyses of powders or made spot measurements on intact samples.…”

Impacts of Ocean Warming on Coralline Algal Calcification: Meta-Analysis, Knowledge Gaps, and Key Recommendations for Future Research

“…Exposure to differing ranges in temperature could explain some disparity in the responses reviewed here (e.g., Martone et al, 2010). Temperature variability can be extreme on some shallow coralline algal reefs (e.g., 14 • C daily, max 38 • C, excluding marine heatwave data) (Gruber et al, 2017;Cornwall et al, 2018). Therefore, estimating ambient temperatures for many of the collection sites was difficult, and we had to usually rely on a single value provided by authors, without knowing the summer maximum monthly mean or daily variability at collections sites.…”