The Responses of phytoplankton and bacterial communities along the salinity gradients in the Seomjin River estuary

Abstract

To assess changes in abiotic and biotic factors between flood and ebb tides we investigated the seasonal phytoplankton and bacterial dynamics and environmental conditions along a salinity gradient at 14 stations in the Seomjin River estuary(SRE), Korea. We performed bioassays to identify the effect of additional nutrients (+N, +P, and +NP) on phytoplankton growth and performed high-resolution 16S rRNA tag pyrosequencing to obtain snapshots of the bacterial diversity and community structure along the salinity gradients. Nitrate+nitrite and silicate loading increased as a result of freshwater input, and that phosphates loading may primarily have involved leaching from bottom sediments of the shallow inner bay.Inaddition, we suggested that sufficient N and Si are supplied by river discharges to favor suitable habitat conditions for diatoms, and are a main bottom-up factor affecting phytoplankton blooms during all seasons.(SRE), Korea. We performed bioassays to identify the effect of additional nutrients (+N, +P, and +NP) on phytoplankton growth and performed high-resolution 16S rRNA tag pyrosequencing to obtain snapshots of the bacterial diversity and community structure along the salinity gradients. Nitrate+nitrite and silicate loading increased as a result of freshwater input, and that phosphates loading may primarily have involved leaching from bottom sediments of the shallow inner bay.Inaddition, we suggested that sufficient N and Si are supplied by river discharges to favor suitable habitat conditions for diatoms, and are a main bottom-up factor affecting phytoplankton blooms during all seasons.