Meeting Abstract

P2.56  Sunday, Jan. 5 15:30  Interactive effects of temperature, pCO₂, and sperm age on fertilization success in northern and southern populations of the sea urchin Arbacia punctulata. BENFIELD, CR*; PODOLSKY, RD; Cornell University; College of Charleston crb235@cornell.edu

Decreases in oceanic pH can have negative consequences for various biological processes. In addition to more extensively studied effects on calcification, reduced pH can also negatively affect reproduction, in part by suppressing the activity of sperm that are held quiescent in testes under low pH conditions. Our lab showed previously that sea urchin sperm swimming and motility are reduced by changes in pH expected under predicted near-future atmospheric pCO₂. However, little is known about population variation in this response, particularly across a latitudinal gradient of temperature and carbonate saturation. We investigated the effects of pCO₂ and temperature on the fertilization success of sea urchins (Arbacia punctulata) collected from northern and southern populations. We assayed fertilization success in a factorial design under different pCO₂s (1x, 2.5x and 4x current atmospheric levels) and temperatures (14°C and 24°C, corresponding to collection temperatures for the two populations). We also varied the amount of time sperm were exposed to these conditions before fertilization to test the hypothesis that sperm longevity could benefit from metabolic suppression at low pH. Animals from the northern population showed higher fertilization success under all conditions. Animals from the southern population showed the expected decline in fertilization as a function of pCO₂; northern animals, however, showed no evidence of a decline. Although sperm age had a negative effect on fertilization success, it showed no interaction with pCO₂. Our results suggest that populations may face different levels of risk in response to near-future ocean acidification, with southern populations being especially vulnerable.