Novel estuarine bacterioplankton in rRNA operon libraries from the Chesapeake Bay

Abstract

Compared to open oceans and freshwater systems, less is known about the phylogenetic diversity in temperate estuaries. In the present study, 6 rRNA operon libraries constructed along the salinity gradient in the Chesapeake Bay in 2 different seasons were analyzed and sequenced. Phylo- genetic analyses showed that Chesapeake Bay bacterioplankton represented a mixture of typical marine and freshwater clades, but several groups that had not been previously retrieved from either system were also found in the bay. Unique or novel SAR11 (Pelagibacter ubique), Roseobacter, SAR86 and Actinobacteria subclades present in the bay suggested that these microorganisms might be adapted to large temperate estuaries with long residence times, such as the Chesapeake Bay. These results represent the first comprehensive study of phylogenetic diversity in estuaries with long residence times.