Nitrogen Pollution In The Surface Sediments And Communities Of Bacteriophankton Response To Nitrogen Pollution Among Different Intertidal Zones

There is prominent nitrogen pollution in the intertidal sedments of China.However,the studies about sources identification,pollution assessment and repairation were not complete.In this study,among 11 intertidal zones,we used muti-biogeochemical parameters to analyze nitrogen sources and contents in sediments.At the same time,taking direct and indirect ways to evaluate the status of nitrogen pollution in sediments.Due to the ability of nitrogen degradation,making Shandong Peninsula as typical study areas,investigating the differences of bacterioplankton community from different nitrogen pollution conditions.The main work and results are as follows:（1）Two fieldtrips were arranged in 2014 and 2015,following the dry season（September to December,2014）and wet season（June to August,2015）,respectively.Eleven sites were chosen for sampling,they distributed in the Daliao Estuary,Jianhe Estuary,Yellow River Estuary,Dagu Estuary,Subei Shoal,Yangtze River Estuary,Hangzhou Bay,Minjiang Estuary,Jiulong Estuary,Pearl River Estuary and Dongzhai Bay.At each site,surface sediments,pore-water and overlying seawater samples were collected for chemical analysis.In dry season,TDN concentrations in overlying seawater samples were between 20.1¹23.7 μmol/L.The highest and lowest values appeared in Daliao Estuary and Subei Shoal,respectively.In wet season,TDN concentrations were between 61.8³35.3 μmol/L.The highest and lowest values appeared in Jiulong Estuary and Subei Shoal,respectively.In dry season,TDN concentrations in pore-water samples were between 30.1¹77.8 μmol/L.The highest and lowest values appeared in Pearl River and Yangtze River Estuary,respectively.In wet season,TDN concentrations were between 90.7³57.9 μmol/L.The highest and lowest values appeared in Jianhe Estuary and Dongzhai Bay,respectively.In dry season,TN contents in sediments were between 168.9⁹00.9 μg/g.The highest and lowest values appeared in Jiulong Estuary and Yellow River Estuary,respectively.In wet season,TN contents were between 177.6¹125 μg/g.The highest and lowest values appeared in Jianhe Estuary and Yellow River Estuary,respectively（2）In dry season,δ¹⁵N varied from 4.3‰ to 8.0‰.The highest and lowest values appeared in Jianhe Estuary and Dongzhai Bay,respectively.In wet season,δ¹⁵N values from 3.1‰⁷.2‰.The highest and lowest values appeared in Jianhe Estuary and Yellow River Estuary,respectively.δ¹⁵N values in Yellow River Estuary,Subei Shoal,and Dongzhai Bay were almost in range of marine nitrate.However,δ¹⁵N values in other sites were exceed 5‰.δ¹⁵N values in Daliao Estuary,Jianhe Estuary,and Dagu Estuary were significantly higher than those in other sites,these suggested exogenous nitrogen input did exit in the intertidal zones.C/N ratios varied from 7.7¹4.7 in dry season and 8.2¹4.6 in wet season.C/N ratios in almost all of sites were between 10¹5,which suggested organic matters in sediments were a mixture of marine and terrestrial organic matters.It’s remarkable that C/N ratios in Yangtze River Estuary,Minjiang Estuary,Jiulong Estuary,and Pearl River Estuary were relative high（>12）.However,C/N ratios in Yellow River Estuary and Subei Shoal were significantly low and close to the marine range（5⁸）.In order to comprehensively understand nitrogen sources,we analyzed δ¹⁵N and C/N ratios combined with the nutrients data,geographical position and human acivities in different sampling sites.The results showed fertilizers,aquaculture,wastewater discharge and river transportation were main nitrogen sources in the intertidal sediments.（3）We evaluate the conditions of nitrogen pollution in seawater,porewater and sediments.Compared to non-estuarine areas,nitrogen pollution were more heavily in estuaries.Nitrogen pollution in estuaries with little runoff were more heavily than that in the estuaries with large runoff.Rainfall and river transportation may transport lots of nitrogen contaminants to the intertidal zones during the wet season.（4）In order to know the response of bacterioplankton community to nitrogen pollution,bacterioplankton samples from different intertidal zones were collected in July,2014.The sampling sites were distributed in rocky,sandy and muddy flat of Yantai,wetlands inhabited by Suaeda and Sparina in the Yellow River Estuary,wetlands with seagrass in Swan Lake,respectively.Constructing 16 S rDNA clone libraries to study the community structure and diversity of bacterioplankton.Non-metric multidimensional scaling（NMDS）and analysis of similarity（ANOSIM）were conducted to know the differences of community structure.The contents and diversity of nitrogen has a great influence in bacteriophankton communities,vegetation coverage can also affect bacteriophankton communities by absorbing nitrogen and releasing various types of organic matters.Remarkably,due to the sewage discharge and eutrophication in seawater,Alteromonas become the dominant bacteria in the rocky areas,which was important to finding functional bacteria for nitrogen removal.