Using volcanic CO2 vents to assess coral reefs ability to acclimatize and adapt to ocean acidification and warming – PNG-Vents

(This abstract include the main point of the ERC project SELECTION; the abstract of the new ERC project I intend to present in 2018 is not ready and will change according to results obtained in the present ANR proposal. I therefore included here the main changes and pilot experiments I need to perform to improve the ERC proposal)
Although projected ocean acidification (OA) has been recognized as one of the main threat for oceanic life, after more than 15 y of intense research we are not still able to make reliable predictions. Recent studies have also revealed inconsistencies with previous early researches. The problem is that much of the research done until now has been hampered by using both “wrong” set-up and time scales. Indeed, most conclusions stem from short-term laboratory experiments of individual organisms. Laboratory experiments are not ecologically realistic since, for instance, they remove the effects of natural supply of nutrition, and environmental fluctuations. Consequently, modern projections ignore organisms’ capacity for phenotypic buffering and their propensity for adaptation.
I proposed to the ERC CoG (project SELECTION) to assess acclimatization and/or adaptation to OA using species living at the volcanic CO2 vents, which have been chronically exposed to OA conditions during their entire life, contrasting responses with species living at normal conditions. Such vents have been continuously active for centuries, and hence provide a unique opportunity to investigate long-term acclimatization to OA. The originality and the ambition of my project stem on the utilization of an in situ experimental approach combined to the use of physiological and molecular techniques.
The project were not granted by the ERC but the Reviewer’ comments and results from the on-going ANR project CARIOCA clearly suggested the directions to improve the proposal.
In the framework of CARIOCA, we performed with success a reciprocal transplanting experiment at one CO2 vents in PNG (Normanby Island) and we also visited a new vents site (Ambitle Island). Our preliminary results and observations were partially in discrepancy with previous data showing that only massive corals were able to resist to OA, and they have the potential to radically change our knowledge on the effect of OA on coral reefs. If the dramatic shift from branching to massive corals reported from the Normanby vents (Fabricius et al. 2011) was a consequence of OA, we should find similar species-response also in other vents. We intend to expand our observations on the coral response to OA to other CO2 vents and other coral species.
As noticed by Reviewers, CO2 vents are not perfect analogues of future conditions and some limitations exists. For instance, it is difficult to establish if corals living at vents have spent multiple generations there, or whether their original planulae migrate into the vents site from adjacent unexposed reefs and settled there. For that, a multiple generation selection need to be performed before transplantation. Corals will be collected and allowed to reproduce in aquaria under controlled conditions. Once the 2nd generation of planulae will be settled on artificial supports and grown enough, they will be transplanted using a reciprocal transplant experiment. A first pilot experiment and a fine protocol for coral reproduction will be performed during PNG-Vents.
Another limitation is that in general CO2 vents are cold, i.e., lack of changes in other global change stressors, such as warming. For that, we will use the acid and hot emissions we found in Ambitle Island to develop a first pilot system which canalize the hot fluid from the vents near the transplanted corals. Its feasibility and readability will be tested during PNG-Vents in Ambitle.
Results will generate breakthrough knowledge enabling robust, trait-based projections of keystone species to future global change.