Meeting Abstract

P1.34  Thursday, Jan. 3  Zooxanthellar symbionts of the Clionaidae: A case study involving the Cliona varians species complex. RAMSBY, Blake*; WEST, Brittany; POPPELL, Ericka; HILL, April; HILL, Malcolm; University of Richmond; University of Richmond; University of Richmond; University of Richmond; University of Richmond mhill2@richmond.edu

Among the Porifera, zooxanthellae are primarily restricted to a single family (Clionaidae), which includes major bioeroders on tropical reefs. Zooxanthellae have been found to benefit their host sponges by elevating growth rates through photosynthetic activities but we know very little about the types of zooxanthellae harbored by these sponges. We examined the types of zooxanthellae found in different morphotypes of Cliona varians in the Florida Keys. Data on the types of zooxanthellae found in each morphs will be presented and related to the substantial habitat differences that exist among the C. varians morphs. We found significant differences in zooxanthellar densities and chlorophyll a concentrations among morphs, which may provide insights into dynamic aspects of the host:symbiont association. To look for evidence of species-level differences, we examined spicule characteristics and compared RFLPs in mtDNA. Finally, we measured photochemical efficiencies for each morphotype and found that the photosynthetic efficiencies of C. varians morphotypes differed in important ways. The shallow water branching morph of C. varians had the highest maximum photochemical yield (Fv/Fm) followed by C. varians forma incrustans, and C. varians forma rigida. Cliona caribbea had the lowest Fv/Fm values. These data will be related to the type of zooxanthellae harbored by the sponge and the environmental conditions experienced by partners involved in the association.