Ecological Processes And Diversity Of Virioplankton In The Typical Estuary Of China

Viruses are the most abundant biological entities in the marine environments and play important roles in controlling the diversity of microbial community,material cycle and energy flow in the marine ecosystem.Estuary is a special ecosystem where is an important hinge of nutrient inputs with the freshwater inputting the sea.It is complicated because of the influence by anthropogenic activities,the mixture of fresh water and seawater.However,researches of viral dynamics and diversity are limited in estuaries.We systematically investigated viral production and decay in typical estuaries of China and investigated the diversity of T4-like myoviruses in East China Sea,trying to understand viral dynamics and diversity in estuaries.The main outcomes include:1.We systematically investigated viral abundance,production and decay with low-salt water and medium-salt water in the Yangtze River estuary,the Qiantang River estuary,the Pearl River estuary and Yellow River estuary.The results showed that viral abundance range from 7.14 ± 0.31 × 105 to 2.45 ± 0.03 x 107particles mL-1,viral abundance was significantly correlated to prokaryotic abundance,and it was greatly influenced by temperature,presenting obvious seasonal change that viral abundance in the summer was significantly higher than that in the winter.The average viral production was 2.36±1.73×106 mL-1 h-1 in the summer and 1.15 ± 0.86×106 mL-1 h-1 in the winter.Viral production in summer was higher than that in the winter.Viral production varies in different estuaries because of the nutritional status and geographical factors,and it was the highest in the Yangtze River estuary and lowest in the Pearl River estuary.In the summer,viral production of low-salt water was lower than that of medium-salt water in the Pearl River estuary,the Qiantang River estuary and the Yellow River estuary,but higher in the winter.However,this situation opposited in the Yangtze River estuary.The average viral decay rates were 1.26 ±0.75%h-1 in the summer and 0.74 ±0.29%h-1 in the winter.Viral decay rate was significantly higher in the summer,meanwhile viral decay rate was higher in the medium-salt water than that in low-salt water,but had no regularity in the winter.It showed that different factors influence viral production and decay rates in different season.Pearson correlation analysis identified positive correlation between viral production and viral abundance,prokaryotic abundance and pH.However,viral decay rate had no correlation with abiotic factors.2.The major capsid protein gene,g23,was used to investigate the diversity of T4-like myoviruses community structure through high throughput sequencing method in East China Sea.The results showed that there was a high diversity of T4-like myoviruses community in East China Sea.The diversity of T4-like myoviruses at the surface layer was higher than that at the bottom of the corresponding station in the study area,one or two OTUs(groups)had predominant advantages at all stations,with more obvious patterns at the bottom.The vast majority of OTUs just appeared in individual station,but only a few of OTUs in all stations.Phylogenetic analysis found that the Marine groups were the main groups,and Marine Group IV was the most abundant,almost as the dominant group at all stations.Marine Group I,Marine Group III,Marine Group IV,Marine Group V and Exo T-evens appeared at all stations,Paddy Group only appeared at the surface.T4-like myoviruses community was strongly influenced by different water masses,Changjiang dilute water had brought more freshwater communities,Marine Group ? abounds in dilute water area,and less in other areas,so we speculated that this group is more suitable for freshwater or low salinity environments.