Research

Research
Coffroth
Dynamics of Cnidarian-algal symbioses
Coral reef genomics
Reef Connectivity
Undergrad Opportunities
Graduate Student and Post-doc Opportunities

Dynamics of Cnidarian-algal symbioses

One of the main focuses of my lab is understanding variation among Symbiodinium populations in both newly-settled (primary) polyps and in adult hosts, and characterizing the variation within a single host colony, within a host genotype and across the host population. We have studied the development and dynamics of symbioses between Symbiodinium and octocoral hosts. In particular, we have shown that at initial infection, multiple taxa of algae establish a symbiosis. However, over time there is a sorting that results in the domination of a single taxon of Symbiodinium in the adult host (Coffroth et al. 2001). These data confirm models of specificity in cnidarians which propose that a broad group of dinoflagellates initially enter the host after which a sorting of algal genotypes occurs, leading to the specificity observed in the adult host. Additionally we have demonstrated that that adult corals retain the ability to acquire new symbionts from the environment (Lewis and Coffroth 2004). This finding is significant as uptake of exogenous symbionts provides a mechanism for resilience in the symbiosis by which the symbiosis may respond to changes in the environment.

Most cnidarian-microalgae symbioses exhibit some degree of specificity in host-symbiont pairing, but the level of specificity and the mechanisms by which it is achieved are not clear. By defining the population structure of Symbiodinium within an individual host and among the host population and detailing the early stages of this symbiosis, we are identifying the level of host specificity of Symbiodinium symbiotic within a number of Caribbean octocorals and the dynamics of these symbioses. A key component of this research has been using, and when necessary developing, molecular markers with differing levels of resolution in order to fully characterize Symbiodinium diversity. For example, using both restriction fragment length polymorphism (RFLP) analysis of small subunit ribosomal genes (SSU rDNA) and length variation in Domain V of the large subunit (23S) of chloroplast rDNA (cp-genotyping), we have shown that the vast majority of Caribbean octocorals at all depths host Clade B Symbiodinium (Goulet 1999, Coffroth et al. 2001, Santos et al. 2001, Goulet & Coffroth, 2004) and in particular the cp-23S rDNA genotype designated B184 (Santos et al 2003) This is in contrast to the majority of Caribbean hard corals which harbor a range of Symbiodinium types. We have also found sequence variation in the flanking regions surrounding microsatellites in a series of Symbiodinium clade B symbionts and have identified seven distinct sequence variants, unequivocally demonstrating the existence of fine-scale selectivity between Caribbean octocorals and these algae (Santos et al. 2004).

Coral reef genomics

In a related project, I am working with colleagues at the University of California – Merced and the University of North Carolina at Wilmington to conduct a genome-wide assessment of gene expression in the Montastraea faveolata-Symbiodinium symbiosis as symbiosis genes are turned on and off. The project is funded through the NSF Biocomplexity Program. Using a genome expression profiling approach, our objectives are to: (a) use expression microarray profiling of Expressed Sequence Tags (ESTs) to identify the genes and cellular pathways involved in regulation, maintenance and disruption of host-zooxanthellae symbiosis, (b) understand how changes in environmental conditions (i.e. light, temperature) can affect these genes, (c) generate bacterial artificial chromosome (BAC) libraries and sequence BAC clones containing symbiosis genes in order to better understand cis-regulation and genomic structure in both host and symbiont genomes, and (d) provide these data on a real-time basis to other researchers and the public through several outreach programs. This research is the first attempt to look at an important mutualistic relationship using a genome wide analysis of gene expression. Gaining a better understanding of host-symbiont relationships in coral reef ecosystems will have implications for atmospheric and ocean sciences, conservation biology and the study and diagnosis of microbial diseases in corals.

Reef Connectivity

Another area of active research in my lab concerns the degree of connectedness of marine populations. Along with my former graduate student Tonya Shearer, we have examined connectedness of the Caribbean corals Montastraea cavernosa and Porites astreoides over a variety of spatial scales with multiple grants from NOAA National Undersea Research Program. My continued effort in this area is through my participation in the Connectivity Working group in the Targeted Research for Sustainable Management of Coral Reefs. The Program is funded through the World Bank and the Global Environmental Facility (GEF). Using molecular techniques, we are examining the level of local dispersal and source of coral recruits to the reefs in Mesoamerica (to be extended to the IndoPacific) in order to assess reef interdependence or connectivity. We are using population genetic structure to infer present (or recent) gene flow patterns in the scleractinian corals, Acropora palmata and Montastraea faveolata. These data are essential for designing and managing marine protected areas and to predict the ability of reefs to recover from perturbations such as hurricanes and massive coral bleaching. The focus of the GEF and our working group is to address the relevant scientific questions and through training programs build a capacity within developing nations to address these questions. As part of the program I am recruiting students and researchers from MesoAmerica to my lab in Buffalo to train them in the appropriate molecular techniques.