9530057 Coffroth Symbioses between cnidarians and dinoflagellates in the genus Symbiodinium are widespread in the marine environment. Their importance to reef-building corals and reef nutrient cycles is well documented, but surprisingly little is known about the ontogency of the symbiosis and the demographics of zooxanthellae populations within their hosts. An understanding of these processes is essential to understanding the symbiosis. Physiologic adaptations to conditions such as temperature and light may in fact be mediated by the demographics of the algal symbionts. The objective of this researech is to determine the ontogeny of the symbiosis in a gorgonian coral that produces azooxanthellate planulae larvae. Dr. Coffroth will examine initial zooxanthellate infection in planulae larvae and characterized the population structure of the zooxanthellae in established symbioses in adult colonies. These data will determine whether the observed host-algal association are the result of selection (mediated by the host or alga), stochastic process or simply suitability of the host "habitat" to the alga. Understanding the population dynamics of zooxanthellae communities has important ramifications for studying the symbiosis and how the symbiosis responds to environmental changes. It is now recognized that zooxanthellae are a diverse group. If this diversity is widespread among single host colonies or if the association is in a state of continual flux, then changes in functional and physiologic traits may reflect changes in the algal community structure. In this case it will be critical to examine each component of the symbiosis and consider the population dynamics and ecological responses of both the coral and the algae to understand and preserve reef ecosystems. The first step, however, is to quantify this diversity a nd address how this diversity is established.
