Abstract
Ocean acidification (OA) is a major threat to marine ecosystems, particularly coral reefs which are heavily reliant on calcareous species. OA decreases seawater pH and calcium carbonate saturation state (Ω), and increases the concentration of dissolved inorganic carbon (DIC). Intense scientific effort has attempted to determine the mechanisms via which ocean acidification (OA) influences calcification, led by early hypotheses that calcium carbonate saturation state (Ω) is the main driver. We grew corals and coralline algae for 8–21 weeks, under treatments where the seawater parameters Ω, pH, and DIC were manipulated to examine their differential effects on calcification rates and calcifying fluid chemistry (Ωcf, pHcf, and DICcf). Here, using long duration experiments, we provide geochemical evidence that differing physiological controls on carbonate chemistry at the site of calcification, rather than seawater Ω, are the main determinants of calcification. We found that changes in seawater pH and DIC rather than Ω had the greatest effects on calcification and calcifying fluid chemistry, though the effects of seawater carbonate chemistry were limited. Our results demonstrate the capacity of organisms from taxa with vastly different calcification mechanisms to regulate their internal chemistry under extreme chemical conditions. These findings provide an explanation for the resistance of some species to OA, while also demonstrating how changes in seawater DIC and pH under OA influence calcification of key coral reef taxa.
Original language | English (US) |
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Pages (from-to) | 4857-4868 |
Number of pages | 12 |
Journal | Global change biology |
Volume | 24 |
Issue number | 10 |
DOIs | |
State | Published - Oct 2018 |
Bibliographical note
Funding Information:B Moore, A‐M Comeau‐Nisumaa, and V Schoepf provided vital laboratory support. MTM was supported by an ARC Laureate Fellowship (LF120100049), S. C. was supported by an ARC DECRA (DE160100668). The authors acknowledge the facilities, and the scientific and technical assistance of the Australian Microscopy & Microanalysis Research Facility at the Centre for Microscopy, Characterisation & Analysis, The University of Western Australia, a facility funded by the University, State and Commonwealth Governments.
Publisher Copyright:
© 2018 John Wiley & Sons Ltd
Keywords
- calcifying fluid
- calcium
- coral
- coralline alga
- dissolved inorganic carbon
- pH
- physiology
ASJC Scopus subject areas
- Global and Planetary Change
- Environmental Chemistry
- Ecology
- General Environmental Science