Effects of temperature on Zooxanthellae strains in coral species Rhodactis rhodostoma

Abstract

ABSTRACT Effects of temperature on Zooxanthellae strains in coral species Rhodactis rhodostoma. (May 2014)

McKensie Daugherty Department of Biology Texas A&M University

Research Advisor: Dr. Duncan MacKenzie Department of Biology

Coral reefs are among the most diverse and fragile ecosystems in the ocean. Corals living in lighted zones can have a mutualistic symbiosis with algal dinoflagellates known as Zooxanthellae, specifically the genus Symbiodinium. In the event of stress from the environment (e.g. greater water temperature, acidity, or light permeation), coral can expel Zooxanthellae from their tissues in a process called bleaching. Bleaching is reversible, and it is possible for corals to repopulate with Zooxanthellae strains that are genetically distinct from the original symbiont and thus potentially better suited for the stressing environment. To determine whether this process of bleaching and repopulation could be studied in a small volume captive recirculating system, I took tissues samples from the soft coral Rhodactis rhodostoma held in the Great Aggie Reef, a 135 gallon reef display tank in Texas A&M University’s Biology Department, before and after exposure to increased temperature stress. To determine whether Zooxanthellae were expelled, I used a polymerase chain reaction-based technique to detect the presence of the symbiont-specific ITS1 gene in coral tissue. Whereas more rapid temperature increases were fatal to corals, a gradual increase to 32 degrees was successful in inducing a loss of ITS1 gene expression in surviving corals. These results suggest that this recirculating system may be suitable for further study of coral bleaching and repopulation with Zooxanthellae under controlled conditions.