Sampling was carried out between 28th and 31st July 2011 in the Panarea Island area along a 9-station transect. One extra station located north of the vent field was sampled as a reference (i.e., no ventinfluenced). At each station, temperature, salinity, oxygen, and pH vertical profiles were registered using a CTD SBE9 Seabird. Seawater was collected with 10 L Niskin bottles for determining pH, the concentrations of chlorophyll a, macronutrients, dissolved inorganic carbon, particulate organic carbon, and nitrogen concentrations, as well as prokaryotic abundance, the rates of heterotrophic carbon production and extracellular enzymatic activities, and to depict the prokaryotic community structure by 16S rRNA gene amplicon sequencing (at seven stations).

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2022) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2023-12-13.Abundance of prokaryotes (heterotrophs and phototrophs), nanoplankton (heterotrophs and phototrophs), microphytoplanktonic and microzooplanktonic abundance divided into major taxonomic groups. Detailed floristic and faunistic lists on request. Measure of degradation processes by exoenzymatic prokaryotic activities (beta-glucosidase, phosphatase and lipase).