Completion of the experiment to assess the impacts of global change on a cold water coral species as part of the European research project iAtlantic

The iAtlantic European research project, an international and multidisciplinary initiative to combine the efforts of different institutions with the participation of the expert Andrea Gori from the Faculty of Biology and the IRBio of the University of Barcelona, has as main goal to provide adequate scientific advice to achieve the sustainable management of marine resources, as well as better monitoring of the processes that take place in the Atlantic Ocean and the state of its ecosystems.

Multiple stressors experiment

The multiple stressor experiment to assess the impacts of global change on the cold water coral (CWC) Dendrophyllia cornigera has ended with very good results. Thanks to the close collaboration between the IEO-CSIC, the University of Barcelona and the Aquarium Finisterrae, it has been successfully achieved the maintenance of the corals during ten months under experimental conditions in the Aquarium Finisterrae. Twenty four experimental tanks contained the coral fragments, where they have been exposed to different environmental conditions to evaluate the single and multiple effects of warming, acidification and deoxygenation in its ecophysiological response.

Designing and setting up the aquarium for these treatments has not been an easy task as it took over a year to implement and ensure stable conditions of temperature, pH and dissolved oxygen concentration in all tanks.

Meanwhile, 144 coral nubbins (the experimental unit consisting of a fragment of the colony with at least one polyp) were prepared and kept in a rearing aquarium until the start of the experiment. In April 2022, acclimation of the nubbins to the different environmental scenarios began, and the parameters (i.e., temperature, pH, and dissolved oxygen) were gradually changed over several weeks. Throughout the experimental time, growth, respiration, excretion and tissue changes of D. cornigera nubbins were measured periodically.

During the last weeks of February 2023, the last ecophysiological measurements (i.e. growth, respiration and excretion) were performed. After the experiment was completed, the corals were snap-frozen in liquid nitrogen under sterile conditions, kept in a -80⁰C freezer, and shipped on dry ice to GEOMAR (Kiel, Germany) for further analysis to be performed in collaboration with coral expert Marlene Wall. Currently, its DNA and RNA are being extracted with the aim of characterizing the composition of the microbiome. The work at GEOMAR is being supported by the COST MAF-World Action (CA20102) thanks to a short-term Scientific Mission granted to Cristina Gutiérrez-Zárate, from the IEO-CSIC and PhD student at the University of Barcelona.

The results of this experiment will help to better understand the potential impact and interactions between these stressors on the performance of D. cornigera. It will also contribute to a better understanding of CWC's vulnerability and resilience to global change.