The increasing absorption of CO2 and associated decline in seawater pH values is thought to pose direct harm to marine life in the decades and centuries to come by affecting rates of survival, calcification, growth, development and/or reproduction. However, as ever more pertinent evidence accumulates, a much more optimistic viewpoint is emerging.
A controlled lab study led by Mote Marine Laboratory and published June 1 in the peer-reviewed journal PLOS ONE revealed that black band disease was less deadly to mountainous star coral (Orbicella faveolata) as water acidified, or decreased in pH.
Regardless of the actual mechanism responsible for the densely aggregated corals to maintain calcification rates in the face of ocean acidification, the study of Evensen and Edmunds, in their words, offers “a compelling case for differential densities of branching coral colonies (i.e. aggregation types) mediating the sensitivity of coral communities in at least some habitats” and it further supports “recent indications that neighboring organisms, such as conspecific coral colonies in the present example, can create small-scale refugia from the negative effects of ocean acidification” And that is more good news for those concerned about the future health of these important marine ecosystems.
Stony corals may be more resilient to ocean acidification than once thought, according to a Rutgers University study that shows they rely on proteins to help create their rock-hard skeletons.
“The bottom line is that corals will make rock even under adverse conditions,” said Paul G. Falkowski, a distinguished professor who leads the Environmental Biophysics and Molecular Ecology Laboratory at Rutgers University-New Brunswick. “They will probably make rock even as the ocean becomes slightly acidic from the burning of fossil fuels.”
Writing as background for their work, Ventura et al. (2016) say that “non-calcifying photosynthetic anthozoans have emerged as a group that may thrive under high carbon dioxide partial pressure (pCO2) conditions via increased productivity,” yet they add that “the physiological mechanisms underlying this potential success are unclear.”
L’acidification n’est pas une simple réponse statique à l’augmentation de la concentration de CO2 dans l’atmosphère : c’est la résultante de processus biologiques et physico-chimiques qui entraînent une répartition inégale du carbone sur la verticale de l’océan. D’autre part la vie océanique a survécu à des niveaux beaucoup plus élevés de CO2 depuis des millions d’années dans le passé.