The Symbiotic Relationship Between Zooxanthellae (Symbiodinium) and Upside Down Jellyfish (Cassiopea sp.) Under Different Light Conditions

Jose Deniz and Julia Donaton

Coral reef bleaching is an issue that affects corals globally. Jamaica is not an exception to this. Discovery Bay Marine Lab illustrates a rich biodiversity that allows us to study the characteristics and behavior of such an ecological ecosystem. The lagoon adjacent to the bay is a perfect area to study corals and upside down jellyfish. These species belong to the same phylum of Cnidaria. In fact, both upside down jellyfish and corals have a mutualistic relationship with the symbiotic algae, Symbiodinium, also referred to as zooxanthellae. These are dinoflagellate chlorophyll cells that live in a symbiotic relation with the upside down jellyfish, providing it with nutrients. In order to determinate whether or not upside down jellyfish under extreme condition of darkness present the same characteristic of coral bleaching: expelling the zooxanthellae, four upside down jellyfish were caught for further investigation. Two of those jellyfish were kept in regular light conditions and the other two were kept in absolute darkness. Tissue was removed from all four jellyfish in increments of 24hrs, everyday for seven days. The tissue was dissolved in ethanol and salt water to extract the zooxanthellae, which were then counted and photographed. The data supported our hypothesis, showing overall that jellyfish in the dark had a lower density of zooxantellae present in the tissue than those kept in normal light conditions.

Jose counting zooxanthellae.