Many of the invertebrate organisms that inhabit reefs form a symbiosis with unicellular algae of the genus Symbiodinium. While the host organisms can be giant clams, anemone’s, soft corals, fire corals and hydroids the best known association is formed with hard or ‘scleractinian’ corals. The symbionts live inside the endodermal layer of their host and provide the majority of daily energy requirements (Muscatine and Porter 1977). As a result corals cannot survive prolonged loss of the symbionts during episodes of stress without impacting their survival. While many factors threaten the persistence of coral reefs, increasing sea surface temperature (SST) disrupting the symbiosis (aka coral bleaching) is regarded as a primary threat and has caused substantial mortality of reef invertebrates over the last two decades (Hoegh-Guldberg 1999; Hughes et al. 2003; Pandolfi et al. 2003).
Symbiodinium has received a lot of research attention in the past decade stimulated by the need to understand coral reef deterioration. On the Great Barrier Reef (GBR) alone at least 25 studies involved Symbiodinium diversity. With the rapid accumulation of information, it is becoming increasingly difficult to assess newly acquired Symbiodinium data in light of previous studies and compare it to established patterns of host-symbiont specificity. Therefore, we developed the SymbioGBR database, which endeavors to compile all currently available sequence and host-association data of Symbiodinium reported for the GBR into a single relational database that is accessible as a web-based application.
SymbioGBR allows users to query Symbiodinium types (ITS1/ITS2) or sequences, and invertebrate host species to explore their reported associations. In addition it includes information of other regions such as 18S, cp23S and the single-copy marker psbAncr, allowing cross-referencing between single-copy and multi-copy markers. The database will be continuously updated and expanded. Finally, as the database is based on the collection details of individual specimens, such host-symbiont associations can be assessed quantitatively and viewed in an environmental (e.g., depth) and geographic context (e.g., latitude).
The genus Symbiodinium consists of nine broad genetic clades, A-I (Pochon and Gates 2010), each of which contain various genetically and ecologically distinct types or sub-clades (van Oppen et al. 2001; Iglesias-Prieto et al. 2004; LaJeunesse et al. 2004a; LaJeunesse et al. 2004b; Warner et al. 2006; Pochon et al. 2007; Sampayo et al. 2007; Frade et al. 2008). While inter-clade differences are substantial genetic distances within Symbiodinium clades are small, sometimes only a few base pairs. Yet these small differences can relate to distinct functional characteristics that influence traits like photosynthetic efficiency, growth and thermal tolerance of the host (Iglesias-Prieto et al. 2004; Little et al. 2004; Berkelmans and van Oppen 2006). The identification of physiological differences in heat stress tolerance and bleaching susceptibility between Symbiodinium types at the subcladal level combined with rising SST’s underline the importance of understanding Symbiodinium diversity and its geographic range.
Symbiodinium types D1, D1-4 (previously known as D1a: see nomenclature section), C1, C8/a and C78 and C15 have been found to be more resistant to heat stress (Rowan 2004; van Oppen et al. 2005; Berkelmans and van Oppen 2006; Jones et al. 2008; Sampayo et al. 2008; Fitt et al. 2009). Having these genetic varieties of Symbiodinium may be beneficial to the host in terms of surviving thermal stress and mass coral bleaching. However, this advantage may also incur physiological trade-offs such as reduced photosynthetic efficiency (Rowan 2004) and growth rates(Little et al. 2004), or an increased susceptibility to pathogenic infections(Littman et al. 2009). It is important to emphasize that clade level designations such as clade C versus D, which are often used to indicate bleaching susceptible versus more temperature tolerant Symbiodinium, should be interpreted with care since not all types within a clade respond equally to stress.
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Symbiodinium Wikipedia Page (http://en.wikipedia.org/wiki/Symbiodinium) Symbiodinium Database of the Santos Lab (http://www.auburn.edu/~santosr/sd2_ged.htm) GeoSymbio (https://sites.google.com/site/geosymbio) Symbiodinium transcriptome sequences Medina Lab (http://medinalab.org/zoox/) Blast Alignment search tool: (http://blast.ncbi.nlm.nih.gov/Blast.cgi)