The Effect of Ocean Acidification on Feeding Rate of Hydromedusa Aequorea Victoria

Abstract

Global ocean acidification may be causing an increase in abundance of medusoid hydrozoans. Many medusoid hydrozoans are predators of epipelagic crustaceans and ecological competitors of fish for epipelagic prey. A change in this predator-prey dynamic may affect the entire epipelagic ecosystem. Ocean acidification exerts a physiological stress on planktonic crustaceans, which possess calcareous exoskeleton. It is therefore hypothesized that ocean acidification increases the feeding rate of medusoid hydrozoan on crustacean prey. This project aims to investigate the relationship between feeding rates of hydromedusa Aequorea Victoria on crustacean prey Artemia sp., under variable seawater CO2 concentrations: 450ppm CO2 and 950ppm CO2 . Each individual of A. Victoria was given 50 individual Artemia sp. and let feed for 1h under ambient temperature. Clearance rate was then calculated from the raw count of prey remaining after 1h. There is no statistically significant difference between the clearance rates of A. Victoria among the two treatment conditions and ambient seawater (n=5~9, p>0.05). However, median of clearance rate under 950ppm CO2 treatment condition was higher than that under 450ppm CO2 treatment condition, suggesting a possible general trend.