UCB Moorea Class: Biology and Geomorphology of Tropical Islands

Anthropogenic increases in atmospheric CO₂ compound the rates of long-term changes in the abiotic conditions of the Earth’s oceans. Because many physiological processes, including calcification rate, depend on these physical factors, there is mounting concern over how changes in temperature (T) and the CaCO₃ saturation of seawater will affect marine organisms.  These effects may be particularly relevant during development— many organisms produce protective calcified structures critical for pelagic dispersal and larval survivability.  I investigated how unmitigated increases in oceanic pCO₂ and temperature consistent with climate change predictions affect the embryonic development rate, hatching success, and veliger morphology of the opisthobranch gastropod,Stylocheilus striatus. Embryos were reared in four seawater treatments: 1) control (pH=8.02, T=27°C), 2) high-temperature (pH=8.02, T=31°C), 3) acidified(pH=7.67, T=27°C), 4) acidified high-temperature (pH=7.67, T=31°C). Development times increased under reduced pH conditions, but substantially decreased under high-temperature and acidifiedhigh-temperature treatments, with significant interaction between temperature and pH. The percentage of embryos that hatched into veligers significantly decreased in all three treatments (<70%reductionsin acidified high-temperature conditions).Larval shell size decreased in all three treatments— effects of acidification and temperature were synergistic, causing greater decreases in shell size with significant interaction in acidified high-temperature treatments. Additionally, there were observable deformities in the shell morphology of hatchlings incubated in decreased pH treatments— these deformities were exacerbated by temperature increases. Thus, my results indicate that oceanic conditions congruent with climate change predictions ca. 2100 suppress successful development in encapsulating gastropod embryos, potentially reducing their viability as pelagic larvae.