Seawater carbonate chemistry and variation in community development, supplement to: Kroeker, Kristy J; Micheli, Fiorenza; Gambi, Maria Cristina (2012): Ocean acidification causes ecosystem shifts via altered competitive interactions. Nature Climate Change, 3(2), 156-159

• Main Authors: Kroeker, Kristy J, Micheli, Fiorenza, Gambi, Maria Cristina
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2013
• Subjects: Benthos; CO2 vent; Coast and continental shelf; Community composition and diversity; Entire community; Field observation; Growth/Morphology; Mediterranean Sea; Rocky-shore community; Temperate; Type; Figure; Time in weeks; Treatment; Coverage; Coverage, standard error; Species richness; Species richness, standard error; Category; Group; Proportion; Proportion, standard error; Site; Growth rate; Salinity; Salinity, standard deviation; Alkalinity, total; Alkalinity, total, standard deviation; Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Temperature, water; Temperature, water, standard deviation; pH; pH, standard deviation; Partial pressure of carbon dioxide water at sea surface temperature wet air; Carbon dioxide, partial pressure, standard deviation; Aragonite saturation state; Aragonite saturation state, standard deviation; Calcite saturation state; Calcite saturation state, standard deviation; Carbonate system computation flag; Carbon dioxide; Fugacity of carbon dioxide water at sea surface temperature wet air; Bicarbonate ion; Carbonate ion; Calculated using seacarb after Nisumaa et al. 2010; Ocean Acidification International Coordination Centre OA-ICC; Ocean acidification
• Online Access: https://dx.doi.org/10.1594/pangaea.881077; https://doi.pangaea.de/10.1594/PANGAEA.881077

Ocean acidification represents a pervasive environmental change that is predicted to affect a wide range of species, yet our understanding of the emergent ecosystem impacts is very limited. Many studies report detrimental effects of acidification on single species in lab studies, especially those with calcareous shells or skeletons. Observational studies using naturally acidified ecosystems have shown profound shifts away from such calcareous species, and there has been an assumption that direct impacts of acidification on sensitive species drive most ecosystem responses. We tested an alternative hypothesis that species interactions attenuate or amplify the direct effects of acidification on individual species. Here, we show that altered competitive dynamics between calcareous species and fleshy seaweeds drive significant ecosystem shifts in acidified conditions. Although calcareous species recruited and grew at similar rates in ambient and low pH conditions during early successional stages, they were rapidly overgrown by fleshy seaweeds later in succession in low pH conditions. The altered competitive dynamics between calcareous species and fleshy seaweeds is probably the combined result of decreased growth rates of calcareous species, increased growth rates of fleshy seaweeds, and/or altered grazing rates. Phase shifts towards ecosystems dominated by fleshy seaweed are common in many marine ecosystems, and our results suggest that changes in the competitive balance between these groups represent a key leverage point through which the physiological responses of individual species to acidification could indirectly lead to profound ecosystem changes in an acidified ocean. : In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2016) 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 2017-09-28.