Ocean acidification (OA), the reduction of seawater pH as a result of increasing levels of atmospheric CO2, is an important climate change stressor in the Southern Ocean and Antarctic. We examined the impact of OA on fertilization success in the Antarctic sea urchin Sterechinus neumayeri using pH treatment conditions reflective of the current and near future ‘pH seascape’ for this species: current (Control: pH 8.052, 384.1 µatm pCO2), a High CO2 treatment approximating the 0.2-0.3 unit decrease in pH predicted for 2100 (High CO2: pH 7.830, 666.0 µatm pCO2), and an intermediate Medium CO2 (pH 7.967, 473.4 µatm pCO2). Using a fertilization kinetics approach and mixed effects models we observed significant variation in the OA response between individual male/female pairs (N=7), and a significant population-level increase (70-100%) in tb (time for a complete block to polyspermy) at Medium and High CO2; a mechanism that potentially explains the higher levels of abnormal development seen in OA conditions. However, two pairs showed higher fertilization success with CO2 treatment, and a non-significant effect. Future studies should focus on the mechanisms and levels of inter-individual variability in OA response, so that we can consider the potential for selection and adaptation of organisms to a future ocean.
Sewell M. A., Millar R., Yu P., Kapsenberg L. & Hofmann G., in press. Ocean acidification and fertilization in the Antarctic sea urchin Sterechinus neumayeri: the importance of polyspermy. Environmental Science and Technology. Article (subscription required).
