As the ocean warms, thermal tolerance of developmental stages may be a key driver of changes in the geographical distributions and abundance of marine invertebrates. Additional stressors such as ocean acidification may influence developmental thermal windows and are therefore important considerations for predicting distributions of species under climate change scenarios. The effects of reduced seawater pH on the thermal windows of fertilisation, embryology and larval morphology were examined using five echinoderm species; two polar (Sterechinus neumayeri and Odontaster validus), two temperate (Fellaster zelandiae and Patiriella regularis) and one tropical (Arachnoides placenta). Responses were examined across 12 to 13 temperatures ranging from -1.1°–5.7°C (S. neumayeri), -0.5°–10.7°C (O. validus), 5.8°–27°C (F. zelandiae), 6.0°–27.1°C (P. regularis) and 13.9°–34.8°C (A. placenta) under present day and near future (2100+) ocean acidification conditions (-0.3 pH units) and for 3 important early developmental stages 1) fertilisation, 2) embryo (pre hatching) and 3) larval development. Thermal windows for fertilisation were broad and were not influenced by a pH decrease. Embryological development was less thermotolerant. For O. validus, P. regularis and A. placenta, low pH reduced normal development, albeit with no effect on thermal windows. Larval development in all five species was affected by both temperature and pH, however thermal tolerance was not reduced by pH. Results of this study suggest that in terms of fertilisation and development, temperature will remain as the most important factor influencing species’ latitudinal distributions as the ocean continues to warm and decrease in pH, and that there is little evidence of a synergistic effect of temperature and ocean acidification on the thermal control of species ranges.
Karelitz S. E., Uthicke S., Foo S. A., Barker M. F., Byrne M., Pecorino D. & Lamare M. D., in press. Ocean acidification has little effect on developmental thermal windows of echinoderms from Antarctica to the tropics. Global Change Biology. Article (subscription required).
