title: The Shifts of Diazotrophic Communities in Spring and Summer Associated with CoralGalaxea astreata, Pavona decussata, andPorites lutea.
abstract: The coral holobiont often resides in oligotrophic waters; both coral cells and their symbiotic dinoflagellates possess ammonium assimilation enzymes and potentially benefit from the nitrogen fixation of coral-associated diazotrophs. However, the seasonal dynamics of coral-associated diazotrophs are not well characterized. Here, the seasonal variations of diazotrophic communities associated with three corals,Galaxea astreata, Pavona decussata, andPorites lutea, were studied usingnifHgene amplicon pyrosequencing techniques. Our results revealed a great diversity of coral-associated diazotrophs.nifHsequences related toAlphaproteobacteria, Deltaproteobacteria, andGammaproteobacteriawere ubiquitous and dominant in all corals in two seasons. In contrast with the coralP. decussata, bothG. astreataandP. luteashowed significant seasonal changes in the diazotrophic communities andnifHgene abundance. Variable diazotroph groups accounted for a range from 11 to 49% within individual coral samples. Most of the variable diazotrophic groups fromP. decussatawere species-specific, however, the majority of overlapping variable groups inG. astreataandP. luteashowed the same seasonal variation characteristics.Rhodopseudomonas palustris- andGluconacetobacter diazotrophicus-affiliated sequences were relatively abundant in the summer, whereas anifHsequence related toHalorhodospira halophilawas relatively abundant in springG. astreataandP. lutea. The seasonal variations of all diazotrophic communities were significantly correlated with the seasonal shifts of ammonium and nitrate, suggesting that diazotrophs play an important role in the nitrogen cycle of the coral holobiont.
authors.affiliation: CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of SciencesGuangzhou, China; Tropical Marine Biological Research Station in Hainan, South China Sea Institute of Oceanology, Chinese Academy of SciencesSanya, China; Department of Microbiology and Plant Biology, Institute for Environmental Genomics, University of Oklahoma, NormanOK, USA.
authors.forename: Yanying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences Guangzhou, China.
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Yang
authors.affiliation: CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences Guangzhou, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Ling
authors.affiliation: Department of Microbiology and Plant Biology, Institute for Environmental Genomics, University of Oklahoma, Norman OK, USA.
authors.forename: Joy D
authors.initials: JD
authors.lastname: Van Nostrand
authors.affiliation: Department of Microbiology and Plant Biology, Institute for Environmental Genomics, University of Oklahoma, Norman OK, USA.
authors.forename: Zhou
authors.initials: Z
authors.lastname: Shi
authors.affiliation: Department of Microbiology and Plant Biology, Institute for Environmental Genomics, University of Oklahoma, Norman OK, USA.
authors.forename: Jizhong
authors.initials: J
authors.lastname: Zhou
authors.affiliation: CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of SciencesGuangzhou, China; Tropical Marine Biological Research Station in Hainan, South China Sea Institute of Oceanology, Chinese Academy of SciencesSanya, China.
authors.forename: Junde
authors.initials: J
authors.lastname: Dong
keywords: coral reef; diazotrophs; diversity; nifH; pyrosequencing