Dissolved inorganic nitrogen flux in symbiotic and nonsymbiotic medusae1

Abstract

Symbiotic Mastigias from Eil Malk Jellyfish Lake and Palau lagoon take up and retain ammonium during both day and night. Uptake is due to symbiotic dinoflagellates (zooxanthellae). Nitrate is not taken up, and is barely detectable in the environment. Nonsymbiotic Aurelia in the same lake excrete rather than take up ammonium. Mastigias migrates vertically repeatedly at night, periodically visiting the nutrient‐rich chemocline at about 15 m where, together with that taken up at ambient concentrations, the animals may take up enough ammonium to satisfy the total daily nitrogen requirement of their symbiotic algae. These observations are consistent with the hypothesis that repeated vertical migration by Mastigias is a behavioral adaptation in the animal that facilitates nutrient acquisition by its algal symbionts.