Interspecific differences in coralline algae calcification and internal pH regulation response to ocean acidification

Coralline algae are foundational species that act as important reef builders in many marine ecosystems. Coralline algae primarily produce high-Mg calcite, a more soluble calcium carbonate polymorph which renders these organisms more susceptible to ocean acidification (OA). In the study we evaluate the interspecific impact that OA has on the calcification and δ11B, a proxy for the internal pH of their calcification space (pHcf), of different species of coralline algae. We examine four species from two distinct morphological groups: geniculate (Corallina spp. and Corallina berteroi) and non-geniculate coralline algae (Phymatolithopsis repanda and Pneophyllum spp.). We exposed specimens to four pH treatments that represented ambient seawater pH (8.03) and three end-of-century seawater pH scenarios (7.93, 7.83, and 7.63) following IPCC relative concentration pathways. We found that OA resulted in a decrease in calcification for all species. Additionally, all species maintained an internal pHcf well above seawater pH, consistent with previous studies. Three species maintained a constant pHcf across all pH treatments, indicating a marked resilience to ocean acidification. This study provides insight into the ability of different geniculate and non-geniculate coralline algae species to potentially regulate the internal pH of their calcification space (pHcf) to buffer against the impacts of OA.

Presentation Preference: Oral

Primary Presenter: Blanca Alvarez Caraveo, University of California, Los Angeles (alvarezblanca@g.ucla.edu)

Authors:

Blanca Alvarez Caraveo, University of California, Los Angeles  (alvarezblanca@g.ucla.edu)

Erik Krieger, King Abdullah University of Science and Technology (KAUST)  (erik.krieger@kaust.edu.sa)

Maxence Guillermic, University of California, Los Angeles  (maxence.guillermic@gmail.com)

Robert Eagle, University of California, Los Angeles  (robeagle@g.ucla.edu)

Christopher Cornwall, Victoria University of Wellington  (christopher.cornwall@vuw.ac.nz)