Effects of temperature and nutrients on changes in genetic diversity of bacterioplankton communities as revealed by 454 pyrosequencing in a semi-closed bay, South Korea

Abstract

Bacterioplankton play critical roles in controlling nutrients and dissolved inorganic nitrogen, as well as facilitating interactions among other biota in marine ecosystems, and can also serve as indicators of the health of the marine environment. Bacterioplankton communities in the surface seawater of a semi-closed bay (Jangmok Bay, South Korea) were analysed using a 16S rDNA multiplex 454 pyrosequencing approach. The following conclusions were drawn: 1) Diversity and operational taxonomic units (OTUs) are highest in cold water seasons and lowest in warm water ones. 2) During cold water seasons, alpha-proteobacteria respond rapidly to pulses of the concentration of inorganic nutrients. 3) During warm water seasons, gamma-proteobacteria are the most active type of bacterioplankton present in the prevailing conditions, which include high dissolved organic carbon,rainfall, chemical oxygen demand and primary production, but low nutrient concentration. 4) Cyanobacteria, a minor group constituting 4.58% of the total bacterioplankton, are more abundant at low temperatures. 5) The Cytophagia-Flavobacteria group is more abundant in nutrient-rich conditions, including high concentrations of dissolved organic carbon and inorganic nutrients the abundance of this group also demonstrated a delayed decline following summer phytoplankton blooms. The pronounced seasonal oscillations in phosphorus concentration and temperature exert nment. Bacterioplankton communities in the surface seawater of a semi-closed bay (Jangmok Bay, South Korea) were analysed using a 16S rDNA multiplex 454 pyrosequencing approach. The following conclusions were drawn: 1) Diversity and operational taxonomic units (OTUs) are highest in cold water seasons and lowest in warm water ones. 2) During cold water seasons, alpha-proteobacteria respond rapidly to pulses of the concentration of inorganic nutrients. 3) During warm water seasons, gamma-proteobacteria are the most active type of bacterioplankton present in the prevailing conditions, which include high dissolved organic carbon,rainfall, chemical oxygen demand and primary production, but low nutrient concentration. 4) Cyanobacteria, a minor group constituting 4.58% of the total bacterioplankton, are more abundant at low temperatures. 5) The Cytophagia-Flavobacteria group is more abundant in nutrient-rich conditions, including high concentrations of dissolved organic carbon and inorganic nutrients the abundance of this group also demonstrated a delayed decline following summer phytoplankton blooms. The pronounced seasonal oscillations in phosphorus concentration and temperature exert