Effects of Temperature and Food Availability on Growth and Development of Pisaster ochraceus Larvae

Climate change is expected to increase temperatures and shift the algal regime and biomass in the Salish Sea. Previous studies suggest that growth and survival of echinoderm larvae are dependent on temperature and access to food. However, no study we know of has tested the combined effects of these factors on larvae of the sea star Pisaster ochraceus. We tested the effects of sustained low and high temperatures and feeding regimes on Pisaster ochraceus bipinnariae and brachiolariae larvae. Thirty-three and 40 days after fertilization, we measured larval length and width, and survival. In line with expectations, size and development of larvae was heavily affected by the level of food available to them. High water temperatures of 18 °C had a small negative effect on length and width of larvae, much less than the effect of feeding. While sample size was low for survival, our study suggests that 18°C temperatures may have increased survival of Pisaster ochraceus larvae, while feeding treatment had no effect. These results suggest that Pisaster larvae are resilient to direct effects of sustained ocean warming, but may be heavily affected by secondary ecological effects like shifting algal ecology