Assessing the impacts of ocean acidification on marine biodiversity and species adaptation (High-CO2 Seas)

Ocean acidification (OA) is expected to profoundly alter the diversity and function of marine ecosystems, as well as the services they provide to society. Thus, understanding how future oceans will function in the face of OA represents one of the main challenges and needs for marine science and management. Studies of OA impacts to date have been conducted primarily in the laboratory, thereby preventing assessments of how whole ecosystems comprised of multiple, interacting species will be affected. Naturally acidified systems can provide novel and critical insights into the emergent effects of OA on entire ecosystems, not just single species. Studies using the shallow volcanic CO2 vents near Castello Aragonese on the island of Ischia (Tyrrhenian Sea, Italy), the first CO2vent system studied in the world, have generated key insights on the direct and indirect effects of OA on the surrounding ecosystems. These natural CO2 vents cause local acidification of seawater by as much as 1.5 pH units below the average ocean pH (on total scale pHT) of 8.1-8.2. Corresponding to this pH drop, the diversity and biomass of benthic organisms decrease. Here, we propose to study newly discovered vents along the coast of Ischia across depths of 3 to 48 m. These sites span a variety of different habitats (e.g. Posidonia oceanica meadows, a cave, coralligenous outcrops), which are hotspots of Mediterranean marine biodiversity, but it is unknown how they will be affected by OA. Thus, these new vents place Ischia at the forefront of natural laboratories for OA studies, allowing us to investigate and report how a suite of ecosystem types responds to acidification. The project High-CO2 Seas seeks to integrate three major objectives to advance our understanding of the ecological impacts of OA in newly discovered CO2 vent systems: 1) characterize water chemistry and pH variability, 2) assess the vulnerability of marine benthic biodiversity using a trait-functional approach; and 3) determine the role of acclimation/adaptation in the responses to OA of the coral Astroides calycularis. Moreover, we will use virtual reality technology to increase public understanding and awareness of OA. This project is highly collaborative, international, and multidisciplinary leveraging the skills and expertise of an international team of top leaders of marine scientists. High-CO2 Seas is expected to considerably expand our knowledge on the vulnerability of marine biodiversity and its function to OA. It has a strong link to management and policy at the EU and international levels. Images, videos and results of scientific analyses will provide ample material for outreach products to communicate the anticipated impacts of OA to the public and decision makers.