Keywords: Alkalinity, total; Alkalinity, total, standard error; Aragonite saturation state; Aragonite saturation state, standard deviation; Benthos; Bicarbonate ion; Bicarbonate ion, standard error; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Buoyant weighing technique according to Davies (1989); Calcification/Dissolution; Calcification rate of calcium carbonate; Calcite saturation state; Calcite saturation state, standard deviation; Calculated; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard error; Carbonate ion; Carbonate ion, standard error; Carbonate system computation flag; Carbon dioxide; Carbon dioxide, standard error; Chlorophyta; Coast and continental shelf; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Experimental treatment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Halimeda opuntia; Halimeda opuntia, segements lost; Halimeda opuntia, weight, dry; Halimeda opuntia tips; Halimeda taenicola; Halimeda taenicola, segements lost; Halimeda taenicola, weight, dry; Halimeda taenicola tips; Initial slope of rapid light curve; Laboratory experiment; Macroalgae; Maximal electron transport rate, relative; PAM (PhytoPAM, Phyto-ED Walz, PPAA0138); Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Partial pressure of carbon dioxide (water) at sea surface temperature (wet air), standard error; pH; pH, standard error; Photoinhibition; Plantae; Potentiometric open-cell titration; Primary production/Photosynthesis; Ratio; Salinity; Salinity, standard error; see reference(s); Shed rate; Single species; SOMMA autoanalyzer; Species; Temperate; Temperature, water