EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Carbonate System and Acidification of the Adriatic Sea

Valentina Turk1, Nina Bednarsek2, Jadran Faganeli1, Blaženka Gasparovic3, Michele Giani4, Roberta Guerra5, Nives Kovac1, Alenka Malej1, Bor Krajnc6, Donata Melaku Canu4, and Nives Ogrinc6
Valentina Turk et al.
  • 1National Institute of Biology, Marine Biology Station Piran, Slovenia (
  • 2Southern California Coastal Water Research Project, Costa Mesa, CA 92626, USA (
  • 3Ruđer Bošković Institute, Division of Marine and Environmental Research, Zagreb, Croatia (
  • 4Istituto Nazionale di Oceanografia e di Geofisica Applicata-OGS, Trieste, Italy (
  • 5University of Bologna, Centro Interdipartimentale di Ricerca per le Scienze Ambientali, Ravenna, Italy (
  • 6Jožef Stefan Institute, Dept. Environmental Sciences, Ljubljana, Slovenia (

Although the marginal seas represent only 7% of the total ocean area, the CO2 fluxes are intensive and important for the carbon budget, exposing to an intense process of anthropogenic ocean acidification (OA). A decline in pH, especially in the estuarine waters, results also from the eutrophication-induced acidification. The Adriatic Sea is currently a CO2 sink with an annual flux of approximately -1.2 to -3 mol C m-2 yr-1 which is twice as low compared to the net sink rates in the NW Mediterranean (-4 to -5 mol C m-2 yr-1). Based on the comparison of two winter cruises carried out in in the 25-year interval between 1983 and 2008, acidification rate of 0.003 pHT units yr−1 was estimated in the northern Adriatic which is similar to the Mediterranean open waters (with recent estimations of −0.0028 ± 0.0003 units pHT yr−1) and the surface coastal waters (-0.003 ± 0.001 and -0.0044 ± 0.00006 pHT units yr−1). The computed Revelle factor for the Adriatic Sea, with the value of about 10, indicates that the buffer capacity is rather high and that the waters should not be particularly exposed to acidification. Total alkalinity (TA) in the Adriatic (2.6-2.7 mM) is in the upper range of TA measured in the Mediterranean Sea because riverine inputs transport carbonates dissolved from the Alpine dolomites and karstic watersheds. The Adriatic Sea is the second sub-basin (319 Gmol yr-1), following the Aegean Sea (which receives the TA contribution from the Black Sea), that contribute to the riverine TA discharges into the Mediterranean Sea. About 60% of the TA inflow into the Adriatic Sea is attributed to the Po river discharge with TA of ~3 mM and TA decreases with increasing salinity. Saturation state indicates that the waters of the Adriatic are supersaturated with respect to calcite (ΩCa) and aragonite (ΩAr) throughout the year. However, saturation states are considerably lower in the bottom water layers, due to the prevalence of benthic remineralization processes in the stratification period. The seasonal changes of the chemical and environmental conditions and relatively small size of the Adriatic Sea area the microbial community composition, function (growth, enzymatic activity) and carbon and nitrogen biogeochemical cycles. Significant effects on calcifying organisms and phytoplankton are expected while the effects of possible OA on microbially-driven processes are not known yet.

How to cite: Turk, V., Bednarsek, N., Faganeli, J., Gasparovic, B., Giani, M., Guerra, R., Kovac, N., Malej, A., Krajnc, B., Melaku Canu, D., and Ogrinc, N.: Carbonate System and Acidification of the Adriatic Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10977,, 2020

This abstract will not be presented.