Archives par mot-clé : Acidification


by Kate Wheeling, April 19, 2018 in PacificStandard

Coral reefs are facing no shortage of threats including ocean acidification, overfishing, plastic pollution, and rising temperatures. Sea surface temperatures have been climbing on average for over a century, and ocean heat waves—which can trigger coral bleaching events—are becoming more common and severe. Scientists have long worried that as coral-killing spikes in temperature become more frequent, corals won’t have enough time to recover between bleaching events and will ultimately go extinct. But a new paper, published today in PLoS Genetics, suggests that corals might be able to adapt to another century of warming.

The Resilience of a Coralline Red Algae to Ocean Acidification

by  Donald et al. 2017, in CO2Science from Géochim.Cosmochim.Acta

The influence of pHsw on both pHcf and the calcification rate of Neogoniolithon is plotted in Figure 1 below. As indicated there, this coralline algal species is able to elevate its pHcf so as to increase its rate of calcification under moderate levels of ocean acidification (pHsw of 7.91 and 8.05), which increase the authors say is “most likely due to CO2-fertilization of [algal] photosynthesis” that is limited in Neogoniolithon at these lower pCO2 conditions. (….)

Indirect Positive Effects of Ocean Acidification Can Overpower Sometimes Observed Direct Negative Effects

by S.D. Connell et al., 2017 in Current Biology (in CO2 Science)

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.

Densely Aggregated Corals Maintain Calcification Under Ocean Acidification Conditions

by N.R. Evensen and P.J. Edmunds, 2017, J. Exp. Biology

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 more resistant to climate change than thought

by Rutgers University, June1, 2017 in SienceDaily

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.”

See also here

L’acidification des océans : causes anthropiques versus variabililité naturelle

Usbek, 13 avril 2017

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.