At present,the understanding of the dynamics of denitrifiers at different dissolved oxygen(DO)layers under organic carbon consumption within the surface sediments remains inadequate.In this study,high-throughput seque...At present,the understanding of the dynamics of denitrifiers at different dissolved oxygen(DO)layers under organic carbon consumption within the surface sediments remains inadequate.In this study,high-throughput sequencing and quantitative PCR targeting nirS gene were used to analyze the denitrifier abundance dynamics,community composition,and structure for aerobic(DO 0.5-6.9 mg/L),hypoxic-anoxic(DO 0-0.5 mg/L),and anoxic(DO 0 mg/L)layers in surface sediments under organic carbon consumption.Based on the analysis of nirS gene abundance,the values of denitrifying bacteria decreased with organic carbon consumption at different DO layers.When the bacterial species abundance at the genus level were compared between the high-carbon and low-carbon sediments,there was significant increase in 6 out of 36,7 out of 36 and 6 out of 36 genera respectively for the aerobic,hypoxic-anoxic and anoxic layers.On the other hand,14 out of 36,9 out of 36 and 15 out of 36 genera showed significant decrease in bacterial species abundance respectively for the aerobic,hypoxic-anoxic and anoxic layers.Additionally,14 out of 36,20 out of 36,and 15 out of 36 genera had no change in bacterial species abundance respectively for the aerobic,hypoxic-anoxic,and anoxic layers.This indicates that the carbon utilization ability of different denitrifiers on each DO layers was generally different from each other.Diversity of denitrifying bacteria also presented significant differences in different DO layers between the high-and low-carbon content sediment layers.Moreover,under the high-carbon and low-carbon content,the abundance of nirS gene showed a high peak within the hypoxic-anoxic regions,suggesting that this region might be the main distribution area for the denitrifying bacteria within the surface sediments.Furthermore,community of unique denitrifiers occurred in different DO layers and the adaptive changes of the denitrifier community followed the organic carbon consumption.展开更多
There is an urgent need to develop efficient evaluation tools that use easily measured variables to make rapid and timely eutrophication assessments, which are important for marine health management, and to implement ...There is an urgent need to develop efficient evaluation tools that use easily measured variables to make rapid and timely eutrophication assessments, which are important for marine health management, and to implement eutrophication monitoring programs. In this study, an approach for rapidly assessing the eutrophication status of coastal waters with three easily measured parameters(turbidity, chlorophyll a and dissolved oxygen) was developed by the grid search(GS) optimized support vector machine(SVM), with trophic index TRIX classification results as the reference. With the optimized penalty parameter C =64 and the kernel parameter γ =1, the classification accuracy rates reached 89.3% for the training data, 88.3% for the cross-validation, and 88.5% for the validation dataset. Because the developed approach only used three easy-to-measure variables, its application could facilitate the rapid assessment of the eutrophication status of coastal waters, resulting in potential cost savings in marine monitoring programs and assisting in the provision of timely advice for marine management.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.31800112,31800390,31870450,31670465)。
文摘At present,the understanding of the dynamics of denitrifiers at different dissolved oxygen(DO)layers under organic carbon consumption within the surface sediments remains inadequate.In this study,high-throughput sequencing and quantitative PCR targeting nirS gene were used to analyze the denitrifier abundance dynamics,community composition,and structure for aerobic(DO 0.5-6.9 mg/L),hypoxic-anoxic(DO 0-0.5 mg/L),and anoxic(DO 0 mg/L)layers in surface sediments under organic carbon consumption.Based on the analysis of nirS gene abundance,the values of denitrifying bacteria decreased with organic carbon consumption at different DO layers.When the bacterial species abundance at the genus level were compared between the high-carbon and low-carbon sediments,there was significant increase in 6 out of 36,7 out of 36 and 6 out of 36 genera respectively for the aerobic,hypoxic-anoxic and anoxic layers.On the other hand,14 out of 36,9 out of 36 and 15 out of 36 genera showed significant decrease in bacterial species abundance respectively for the aerobic,hypoxic-anoxic and anoxic layers.Additionally,14 out of 36,20 out of 36,and 15 out of 36 genera had no change in bacterial species abundance respectively for the aerobic,hypoxic-anoxic,and anoxic layers.This indicates that the carbon utilization ability of different denitrifiers on each DO layers was generally different from each other.Diversity of denitrifying bacteria also presented significant differences in different DO layers between the high-and low-carbon content sediment layers.Moreover,under the high-carbon and low-carbon content,the abundance of nirS gene showed a high peak within the hypoxic-anoxic regions,suggesting that this region might be the main distribution area for the denitrifying bacteria within the surface sediments.Furthermore,community of unique denitrifiers occurred in different DO layers and the adaptive changes of the denitrifier community followed the organic carbon consumption.
基金Supported by the National Key Research and Development Program(No.2016YFC1402101)the National Natural Science Foundation of China(No.41376106)the Natural Science Foundation of Shandong Province(No.ZR2013DM017)
文摘There is an urgent need to develop efficient evaluation tools that use easily measured variables to make rapid and timely eutrophication assessments, which are important for marine health management, and to implement eutrophication monitoring programs. In this study, an approach for rapidly assessing the eutrophication status of coastal waters with three easily measured parameters(turbidity, chlorophyll a and dissolved oxygen) was developed by the grid search(GS) optimized support vector machine(SVM), with trophic index TRIX classification results as the reference. With the optimized penalty parameter C =64 and the kernel parameter γ =1, the classification accuracy rates reached 89.3% for the training data, 88.3% for the cross-validation, and 88.5% for the validation dataset. Because the developed approach only used three easy-to-measure variables, its application could facilitate the rapid assessment of the eutrophication status of coastal waters, resulting in potential cost savings in marine monitoring programs and assisting in the provision of timely advice for marine management.
