Meeting Abstract
Uptake of anthropogenic carbon dioxide (CO2) by the ocean has led to a 30% drop in the average pH of surface waters since the start of the Industrial Revolution. This process, known as ocean acidification (OA), results from the reaction of CO2 with water to form carbonic acid. OA is of major ecological concern because it can interfere with pH-sensitive biological processes, including fertilization. Recent research in our lab suggested that predicted near-future (50-100 y) levels of atmospheric CO2 will negatively affect gamete function (e.g., sperm speed, motility, and fertilization success) in the free-spawning sea urchin Arbacia punctulata. However, a recent review noted that OA tends to more weakly affect fertilization success in studies that mixed sperm and eggs from more than one mating pair as compared with single pair spawnings. To test the hypothesis that group spawning reduces the negative effects of OA, we measured fertilization success under current and 2.5x-current CO2 conditions using single-and multiple-male crosses. Surprisingly, we did not find a significant effect of CO2 on fertilization and the multiple-male crosses did not show greater resistance to the effects of increased CO2. However, the multiple-male crosses showed significantly lower fertilization than the average fertilization of single-male crosses involving the same males. These results suggest an interaction among sperm from different males that could reduce fertilization success for females that spawn in larger aggregations, which could have important implications for differences in optimal aggregation strategies for males and females.
