The role of symbiont diversity in cnidarian bleaching and in re-establishing the cnidarianzooxanthellae symbiosis

Matthew Johnson, Biology



Coral reefs are profoundly important ecosystems in tropical oceans that structure coastal  community trophic networks and biogeochemical cycling. The fragility of coral reef ecosystems  has become increasingly apparent due to rising sea surface temperatures and numerous other  chemical and physical anthropogenic impacts. At its root, the problem is one of a delicate  symbiosis between corals and their zooxanthellae (= algae). This fundamental relationship,  which has driven the explosion of biodiversity for coral reef communities, unravels when one or  both partners undergo severe stress. This proposal will determine the role of symbiont diversity  in cnidarian (= corals, anemones, jellyfish) heat stress responses and in re-establishing their  symbiosis with zooxanthellae after bleaching. I will use a model cnidarian, the anemone Aiptasia  palida, and cultured zooxanthellae (Symbiodinium) with determined levels of heat tolerance, in  order to create specific host-symbiont pairings. Heat stress will be evaluated by measuring the  photosynthetic health of the zooxanthellae and several biochemical indicators of stress. I will  also measure respiration and oxygen production by anemones with different symbionts under  normal and high temperature conditions. The amount of zooxanthellae types within A. palida  polyps will be determined over time by using qPCR. The work proposed herein will help to move  my research in a new direction, by allowing me to study cnidarians and their symbiotic  relationship with zooxanthellae. Data from this project will also be valuable for securing  additional funding from NSF.