The Yellow Sea Warm Current flushes the Bohai Sea microbial community in winter

Abstract

The effect of the Yellow Sea Warm Current (YSWC) on virio- and bacterioplankton communities in the Bohai Sea is unknown. In this study, the composition and dynamic changes of virio- and bacterioplankton at the entrance of the Bohai Sea were measured to determine the influence of the YSWC on those communities and vice versa. In the Bohai Strait, there were east to west gradients of water chemistry and hydrology. The turbulent mixing between the deep north-western ‘warm’ current, which is 9°C, and the cold, nutrient-rich Bohai Sea water at 7–8°C appears to stimulate the abundance of both viruses and heterotrophic bacteria, with numbers at the junction of ‘warm’ and cold water being almost 10-fold greater than in the low-thermohaline areas, and peaking where the temperature is the highest. The average viral and bacterial abundances in the north-eastern area are much higher than in the south-western area. It proved that the YSWC entered the Bohai Sea with poor biomass and exited with rich biomass, which, in turn, enriches the Yellow Sea microbial loop. Our results showed the dramatic effect of temperature rise and increasing eutrophication on microbial abundance and marine microbial communities.