The Effect of Ocean Acidification on Feeding Rate of Hydrozoan Jellyfish Mitrochoma cellularia

Abstract

Global ocean acidification caused by an increase in absorbed CO2 is changing oceanic ecology world wide, however little is known on how this change will effect medusozoan Cnidarians (jellyfish). Many studies have predicted that lower pH may be causing an increase in the abundance of jellyfish, however many more have refuted these results. Jellyfish are predators of epipelagic crustaceans and compete with fish for prey. A change in jellyfish population or feeding behavior may affect the entire pelagic ecosystem. This project aims to investigate the relationship between feeding rate of jellyfish Mitrocoma cellularia on crustacean prey Artemia spp., under variable seawater CO2 concentrations: ambient local seawater (about 700ppm), 400 ppm and 950 ppm. Feeding rates of M. cellularia were calculated and compared with those of Aequorea victoria under local seawater conditions and the feeding rate of A. victoria under CO2 treated saltwater conditions was calculated. It was found that M. cellularia had a faster feeding rate than A. victoria in ambient conditions (p=0.042). No significant difference was found among the feeding rates under the three water treatments (p= 0.297) however a slight trend of increasing feeding rate was observed as pH decreased. To understand how Ocean acidification affects medusozoan Cnidarians more refined methods are needed as well as an increase in trials.