Biogeography Of Benthic Intertidal Microbes Along The Coasts Of China And Fungi In The Bohai Sea And The North Yellow Sea

Intertidal zone represents a typical coastal habitats in coastal ecosystems,with high biodiversity and biomass,and dramatic environmental variations.Although tidal zonation is known for macrofauna in intertidal zones,little is known about of the distributional patterns of microbial inhabitants(bacteri,archaea and micro-eukaryotes)in intertidal sediments,among seasons and among regions,let alone the patterns at a large spatial scale.It is konwn that fungal community in neritic oceans shows a strong seasonality.However,little is known about the seasonal and regional distribution of benthic fungi.In this study,using 16 S and 18 S r DNA high throughput sequencing and quantitative PCR,the bacteria,archaea and micro-eukaryotes in the surface sediments of 14 typical intertidal zones along the coasts of China were investigated.The benthic fungi,often thought to be of little seasonality,were also studied during two seasonal cruises at the Bohai Sea and the North Yellow Sea.The main results are as follows:Alpha diversities(Chao1 and PD)of bacteria are significantly higher in the south than those in the north and in the central regions.However,no distinct variations were observed among three tidal zones.Spearman's correlation analysis showed a latitudinal trend of alpha diversity.A considerable proportion(about 53.5%)of reads was affiliated with Proteobacteria,of which Gammaproteobacteria accounted for 24.8%,while Deltaproteobacteria,Alphaproteobacteria and Epsilonproteobacteria 15.6%,9.4% and 0.8% respectively.There were Chloroflexi(8.4%),Bacteroidetes(7.5%),Firmicutes(7.5%),Actinobacteria(6.9%),Acidobacteria(4.6%),Planctomycetes(3.5%),Gemmatimonadetes(2.2%)and Verrucomicrobia(1.3%).Bacterial community structure were significantly different between seasons and among threes regions,however not among three tidal zones.The proportion of Gammaproteobacteria and Alphaproteobacteria was much higher in the north,conversely,the proportion of Betaproteobacteria was much higher in the south.The 16 S r DNA copy numbers decrease form the south to the north in both seasons.Correlation analysis showed that TOC,TON grain size,N nutrient and metal concentrations could be the main factors affecting the abundance of most bacteria taxa.Both geographic distance and latitude significantly shape the benthic bacterial community.Alpha diversity of archaea showed great seasonality,and was significantly higher in the south than those in the other two regions.However,no distinct variation observed among three tidal zones.The richness of benthic archaea showed a latitudinal pattern.Grain size,metal content,TON,NH4+,temperature and TOC significantly shaped the richness.In term of the proportion of the reads,DHVEG-6 of Euryarchaeotaand dominated(90.7%)followed by MHVG(4.0%)and MCG of Thaumarchaeota(3.5%).The archaea community structure was significantly different among three regions and between two seasons.There was no significant variation in beta diversity among three tidal zones except when only the summer samples were considered.Most taxa with high proportion and abundance showed no significant variation between summer and winter,indicating the rare groups were the main reason causing seasonality of archaea community.Most groups showed no variation among tidal zones.Unlike the result based on the proportion of the reads,the abundance of most taxa showed no regional variation.Within the high abundance taxa,the abundance of Thaumarchaeota was significantly higher in the south than in the other two regions.Similarly,most groups showed no variation among tidal zones.Both geographic distance and latitude significantly shape the succession of benthic archaea community,and the effect of geographic distance was greater than latitude and environment factors.The alpha diversity of micro-eukaryotes showed a distinct seasonality,and was significantly higher in the central than the other two regions,and the subtidal zone had the highest aong three tidal zones.The species diversity of benthic micro-eukaryotes increased with the latitude.TOC was the most important factor affecting the richness.Overall,most reads were affiliated with Bacillariophyta(35.1%),followed by Dinophyceae(13.1%),Chlorophyta(12.2%),Cercozoa(11%)and Fungi(8.1%).The microeukaryotic community structure was significantly different among three regions and between two seasons and the regional variation was greater than seasonality.There was no significant variation in beta diversity among three tidal zones.Although the variations among tidal zones were not significant,many groups showed a decreasing trend or an increasing trend along the tidal zones.Most microeukaryotic groups adapted to the sediment environment with fine grain size,high content of TOC,TON and matels.Geographic distance was the most important factor shaping the succession of benthic microeukaryotic community.Benthic fungal diversities in Bohai Sea and North Yellow Sea were investigated using pyrosequencing of 18 S r DNA.Overall,Chytridiomycota dominated,followed by Basidiomycota,Ascomycota and Cryptomycota,in terms of alpha diversities and relative abundance.The beta diversity of benthic fungi showed a significant seasonality but no regional differences,accounted for by contrasting relative abundances of Chytridiomycota and Basidiomycota.Significantly seasonal changes in Chytridiomycota and Basidiomycota assemblage structure were also observed,but not for Ascomycota and Cryptomycota.Environmental filtering was more important than water depth and geographic distance in shaping the distribution of benthic fungi in the neritic oceans.The overall fungal beta diversity co-varied with concentration of chlorophylla,p H,and salinity,distance from land,and water depth.The assemblage structure of benthic Chytridiomycota,Basidiomycota,Ascomycota and Cryptomycota co-varied with different sets of environmental parameters,suggesting their niche differentiations in the coastal sediments.