Effects of CO2-driven acidification on the ostracod Cypridopsis vidua: what are its likely environmental consequences?

Abstract

If anthropogenic CO2 emissions are maintained at the current rate, the pH of freshwater ecosystems will drop by 0.2–0.3 pH units by the year 2100, which will have great effects on aquatic biota. The impact of acidification on the ostracod species Cypridopsis vidua as a model organism has been studied. To provide the best rearing conditions, a preliminary experiment with different food concentrations was performed. Cypridopsis vidua reached higher survival under the established experimental conditions when reared with 1.5 × 106 cells of Scenedesmus obliquus per ostracod. Two CO2-driven acidification experiments were designed: the first, an acute experiment (96 hours) pH 6.0, 6.5, 7.0 and 8.3 showed that at low pH the survival rate decreased by more than 90%. The second was a chronic experiment (21 days) pH 7.3, 7.8 and 8.3 with a sharp decrease (60%) in reproduction rate and effects on phototactic behaviour at low pH. Abbreviations: CCAP: culture collection of algae and protozoa (in the Scottish Association for Marine Science); CR1: chronic test at medium pH (7.78 ± 0.11); CR2: chronic test at low pH (7.30 ± 0.16); GLM: generalized linear model; IPCC: intergovernmental panel on climate change; LT: lethal time; TA: total alkalinity; pCO2: partial pressure of carbon dioxide; PI: phototactic index; R0: treatment in starvation (no food); R1: low food concentration treatment (7.5 × 105 cell per individual); R2: optimal food concentration treatment (1.5 × 106 cell per individual); R3: high food concentration treatment (3.0 × 106 cell per individual); UTM: universal transverse mercator (coordinate system); YSI: yellow spring instruments