8.4 Friday, Jan. 4 Effects of Elevated Oceanic CO2 and Temperature on Sperm Motility and Swimming Speed in Northern and Southern Populations of the Sea Urchin Arbacia punctulata CASTRO, D.A.*; PODOLSKY, R.D.; College of Charleston; College of Charleston email@example.com
Increases in atmospheric CO2 are raising CO2 levels in the ocean, driving a decrease in oceanic pH through the process of ocean acidification. Several key biological processes, including calcification and cellular metabolism, are sensitive to small changes in pH. Little is known, however, about how populations evolving under different conditions have responded to variation in CO2 or to the synergistic effects of CO2 and other environmental parameters like temperature. Latitudinal comparisons are a powerful way to address such questions. We examined the swimming performance of sperm cells under different CO2 and temperature conditions for sea urchins (Arbacia punctulata) collected from northern and southern populations in the western Atlantic. Prior work found that increases in CO2 through about 2.5 times current levels, corresponding to 100 years in the future based on climate models, led to significant linear declines in both sperm motility and swimming speed. We exposed sperm from each population to each of the two respective collection temperatures (14 and 24C) under a range of CO2 concentrations (pre-industrial, current, 1.75 times current, and 2.5 times current). We predicted that sperm of northern and southern populations would show differences in the degree of sensitivity to CO2 at a common temperature. Sperm from southern urchins likely show greater sensitivity because a given CO2 change leads to smaller pH changes in southern waters compared to the same CO2 change and associated pH change in northern waters. Our results will be discussed in terms of differences expected in the solubility of CO2, in oceanic upwelling, and in aragonite saturation levels between northern and southern latitudes.