Ocean warming drives decline in coral metabolism while acidification highlights species-specific responses

ABSTRACT

Ocean warming and acidification can have negative implications on coral reefs. This mechanistic study aims to evaluate the proximal causes of the observed negative response of Hawaiian corals to climate change scenarios. Net calcification (G_net), gross photosynthesis, and dark respiration were measured in three species of Hawaiian corals across a range of temperature and acidification regimes using endpoint incubations. Calcification rates showed a curvilinear response with temperature, with the highest calcification rates observed at 26°C. Coral response to ocean acidification (OA) was species dependent and highly variable. OA enhanced calcification rates by 45% in the perforate coral, Montipora capitata, but had no short-term effect on the calcification or photosynthetic rates of imperforate corals, Pocillopora damicornis or Leptastrea purpurea. Further investigations revealed M. capitata to effectively dissipate protons (H⁺) while increasing uptake of bicarbonate (${\mathrm{HCO}}_3^{-}$), therefore maintaining high rates of G_net under acute OA stress. This study demonstrates the first experimental evidence of the ability of a coral species to take advantage of increased dissolved inorganic carbon and overcome an increasing proton gradient in the boundary layer under OA conditions. These observed differences in coral metabolism may underlie the species-specific responses to climate change.

SUBJECT EDITOR:

• Naoko Isomura

KEYWORDS:

• Coral reefs
• climate change
• calcification
• physiology

Acknowledgements

We are grateful for the lab assistance from L. Guirkinger. This work is dedicated to the late Dr. Paul Jokiel and his breakthrough in coral physiology and ecology. This is the Hawai‘i Institute of Marine Biology (HIMB) contribution #1645 and the School of Ocean and Earth Science and Technology (SOEST) contribution #9558. Corals were collected under the Hawaiʻi Institute of Marine Biology Special Activity Permit 2015–2017.

Disclosure Statement

No potential conflict of interest was reported by the authors.

ORCID

Keisha D. Bahr http://orcid.org/0000-0002-8092-833X