Toward an assessment of ocean acidification in the Adriatic sea and its impact on the biogeochemistry of marine carbonate system

The increase of CO2 amount in the atmosphere has created great concern: it will in all probability result in changes in temperature, precipitation and/or their seasonal amplitudes with consequences not only on sea level rise but also on chemical equilibrium of the CO2 system in seawater, mainly reducing pH and carbonate ion concentration (Ocean Acidification). The process is now well documented in field data from all around the world. However is not sufficiently witnessed in the Mediterreranean Sea, due to the scarcity of good quality data. On this concern, results for the Adriatic Sea are presented: from experimental measures of pH and total alkalinity, two seasonal pictures of pH and carbonate system parameters have been drawn. In addition, a pH decrease of 0.063 pHT units with related chemistry changes has been inferred in the North Adriatic Dense Water (NAdDW) over the two last decades. These results, although preliminary, merit attention as confirm that N. A. sea has been affected by OA, being sensitive to the climate forcing. Potential impacts of OA are several and should be assessed, as many might even exacerbate hyopoxia/anoxia events, already affecting the area. OA might also affetc the food web, as the carbonate reduction has the potential to alter the distribution and abundance of marine organisms that use calcium carbonate to build their shells or skeletons (corals, plankton) and the organisms that depend on them for survival (fishes, marine mammals).