HOLLAND, L. P.*; COATES, K. A. ; TRAPIDO-ROSENTHAL, H; University of Toronto; University of Toronto; Bermuda Biological Station for Research: Molecular Diversity of Gorgonian Symbionts (Symbiodinium spp) in Bermuda

The ubiquitous marine endosymbiont Symbiodinium has been separated into clades showing high levels of internal genetic variation. Most research on cnidarian-algal symbioses has focused on variation between clades within scleractinian corals of the Caribbean, whereas this study considers symbiont diversity of soft corals (order Alcyonacea) of Bermuda. Bermudian reefs have among the lowest diversity of cnidarians, and thus gorgonians, of any well-studied reef system. However, the question of whether there is a correspondingly lower diversity in the cnidarian symbiont community has not been fully explored. Prior research has revealed that of the known symbiont clades, type B, a “generalist” adapted to varying light intensity, may predominate in Bermuda. Symbionts within six gorgonian species (Pseudoplexaura porosa, Gorgonia ventalina, Pseudoterogorgia americana, Plexaura homomalla, Eunicea tourneforti and Briareum polyanthes) have been analysed from five different sites on the Bermuda platform spanning the upper half of their depth range. Standard RFLP methods were used to determine clade-level identity; subsequently partial DNA sequences of the nuclear 18S and 24S ribosomal subunit genes and their internal transcribed spacer (ITS) regions were evaluated to determine specific level identities and genetic similarity within the clades. Phylogenetic relationships between all symbionts were analysed using standard likelihood and parsimony methods and comparisons made to phylogenies of their gorgonian hosts. Finally, comparisons were made to Caribbean symbionts of conspecific hosts to identify symbiont gene flow levels from the Gulf Stream.