Seasonal mesocosm community experiments: Four successive runs of ca 10 weeks in 12 outdoor mesocosms (ca 1400 L) with flow-through and a orthogonally crossed warming ("ambient" temperature vs warming by 5°C = "OW") and acidification ("ambient" CO2 vs increase by 700 µatm = "OA" and combined warming and acidification = "OWA" ) treatment. The tanks were started with the same community composition (Fucus vesiculosus; mesograzers Idotea spp., Gammarus spp., Littorina littorea; seastar Asteria rubens, filter feeders Balanus improvisus, Mytilus edulis); details in Wahl et al. 2015.Seasonal responses to the various treatments were (a) mean daily relative Fucus length growth of thallus tips (%), (b) relative Mytilus shell length growth (%), (c) mean daily relative growth of Balanus basal plate, (d-f) the relative population size changes of the three mesograzer species expressed as the log of final divided by initial abundances, (g) the relative survival of Asterias (%).