Molecular characterization of the spatial diversity and novel lineages of mycoplankton in Hawaiian coastal waters.

Microbial community diversity and composition have critical biogeochemical roles in the functioning of marine ecosystems. Large populations of planktonic fungi exist in coastal ocean waters, yet their diversity and role in carbon and nutrient cycling remain largely unknown. Lack of information on critical functional microbial groups limits our understanding of their ecological roles in coastal oceans and hence our understanding of its functioning in the ocean's carbon and nutrient cycles. To address this gap, this study applied the molecular approach denaturing gradient gel electrophoresis (DGGE) coupled with clone library construction to investigate mycoplankton communities in Hawaiian coastal waters. Mycoplankton communities displayed distinct lateral and vertical variations in diversity and composition. Compared with the open ocean, surface (<100 m) near-shore waters had the greatest diversity and species richness of mycoplankton, whereas no differences were found among stations at depths below 150 m. Vertical diversity profiles in the coastal waters suggested that diversity and species richness were positively correlated to phytoplankton biomass in the coastal waters, but not in offshore waters. A total of 46 species were identified and belonging to two phyla Basidiomycota and Ascomycota, with the basidiomycetes as the dominant group (n=42). The majority (n=27) of the basidiomycetes are novel phylotypes showing less than 98% identity in the 18S rRNA gene with any sequence in GenBank. This study provides insight into mycoplankton ecology and is the first molecular analysis of planktonic fungi in the oceans.