Genetic diversity of free-living Symbiodinium in surface water and sediment of Hawai‘i and Florida
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Marine dinoflagellates in the genus Symbiodinium are primarily known for their symbiotic associations with invertebrates and protists, although they are also found free-living in nanoplankton and microphytobenthic communities. Free-living Symbiodinium are necessary for hosts that must acquire their symbionts anew each generation and for the possible reestablishment of endosymbiosis in bleached adults. The diversity and ecology of free-living Symbiodinium are not well studied by comparison with their endosymbiotic counterparts, and as a result, our understanding of the linkages between free-living and endosymbiotic Symbiodinium is poor. Here, we begin to address this knowledge gap by describing the genetic diversity of Symbiodinium in the surface water and reef sediments of Hawai‘i and Florida using Symbiodinium-specific primers for the hypervariable region of the chloroplast 23S domain V (cp23S-HVR). In total, 29 Symbiodinium sequence types were detected, 16 of which were novel. The majority of Symbiodinium sequence types in free-living environments belonged to clades A and B, but smaller numbers of sequence types belonging to clades C, D, and G were also detected. The majority of sequences recovered from Hawai‘i belonged to clades A and C and those from Florida to clade B. Such distribution patterns are consistent with the endosymbiotic diversity previously reported for these two regions. The ancestral sequence types in each clade were typically recovered from surface water and sediments both in Hawai‘i and Florida and have been previously reported as endosymbionts of a range of invertebrates, suggesting that these types have the capacity to exploit a range of very different habitats. More derived sequence types in clades A, B, C, and G were not recovered here, suggesting they are potentially restricted to endosymbiotic environments.
KeywordsSymbiodinium Dinoflagellate Chloroplast ribosomal 23S Hypervariable region of DomainV (cp23S-HVR)
This research was supported in part by the National Oceanic and Atmospheric Administration, Project #R/CR-16, which is sponsored by the University of Hawai‘i Sea Grant College Program (NA05OAR4171048 to M.T.), a National Science Foundation Award (OCE-0752604 to R.D.G.), the Swiss National Science Foundation (PBGEA-115118 to X.P.), the School of Ocean and Earth Science and Technology at the University of Hawai‘i and the Edwin Pauley Foundation. Nathaniel Olson, Renee Shutt, and Monika Frazier provided assistance and were supported by Research Experience for Undergraduate internship program (NSF #0453630; PI D.K. Price) and the University of Hawai‘i Experimental Program to Stimulate Competitive Research (NSF EPS0554657). We thank Michiko Ojimi, Vivian Cumbo, Paula Ayotte, Mark Manuel, Nakoa Goo, Nancy Chaney, and Kevin Kaluna for field support. Florida Keys National Marine Sanctuary permitted our collections (permit number FKNMS-2008-049). This is Hawai‘i Sea Grant publication JC-08-32, Hawai‘i Institute of Marine Biology publication contribution #1437, and School of Ocean and Earth Science and Technology contribution #8116.
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