48. New volcanic CO2 vents along the coast off the Ischia Island (Italy) provide a glimpse of the potential impacts of ocean acidification

Teixidó Núria (1), Enric Ballesteros (2), Kristy Kroeker (3)*, Fiorenza Micheli (4), Maria Cristina Gambi (1)

1 Stazione Zoologica Anton Dohrn, Naples, Italy, 80077, Italy
2 Center for Advanced Studies of Blanes (CEAB-CSIC), Blanes, Spain, 17300, Spain
3 University California of Santa Cruz, Santa Cruz, USA, 95064, USA
4 Stanford University, Pacific Grove, USA, 93950, USA

Ocean acidification (OA), a suite of changes in seawater chemistry associated with increased CO2 concentrations in the atmosphere, is expected to profoundly alter the diversity and function of marine ecosystems. In recent years, studies using a shallow volcanic CO2 vent system near the Castello Aragonese on the island of Ischia (Italy) have generated key insights on the direct and indirect effects of OA on the surrounding ecosystems. These natural CO2 vents locally acidify the seawater by as much as 1.5 pH units below the average ocean pH of 8.1-8.2. Corresponding to this pH drop, the diversity and biomass of marine organisms decrease. Here, we present newly discovered vents along the coast of Ischia across depths of 3-48 m. These sites span a variety of different habitats such as Posidonia oceanica seagrass meadows, gravel and sandy bottoms, semi-dark cave habitats and coralligenous outcrops, the latter dominated by calcifying organisms that are particularly vulnerable to OA. These habitats are hotspots of Mediterranean marine biodiversity, but it is unknown how they will be affected by OA. We are carrying out SCUBA diving surveys to characterize the water chemistry and pH and to quantitatively assess seafloor community among pH zones at each of the vents as well as nearby reference areas with normal pH. This study provides new insights regarding OA’s effects on a range of community types, thereby enabling generality in our predictions of OA’s impacts. These new vents place Ischia at the forefront of natural laboratories for OA studies, as the only locations known to date where CO2 vents span a variety of habitat types, allowing us to investigate and report how a suite of ecosystem types responds to acidification.