Macroalgal response to a warmer ocean with higher CO2 concentration

Primary production and respiration rates were studied for six seaweed species (Cystoseira abies-marina,Lobophora variegata, Pterocladiella capillacea, Canistrocarpus cervicornis, Padina pavonica and Corallina caespitosa)from Subtropical North-East Atlantic, to estimate the combined effects of different pH and temperature levels.Macroalgal samples were cultured at temperature and pH combinations ranging from current levels to thosepredicted for the next century (19, 21, 23, 25 °C, pH: 8.1, 7.7 and 7.4). Decreased pH had a positive effect onshort-term production of the studied species. Raised temperatures had a more varied and species dependenteffect on short term primary production. Thermophilic algae increased their production at higher temperatures,while temperate species were more productive at lower or present temperature conditions. Temperature alsoaffected algal respiration rates, which were higher at low temperature levels. The results suggest that biomassand productivity of the more tropical species in coastal ecosystems would be enhanced by future ocean con-ditions.