Although lakes dominated by macrophytes are conducive to ecological balance, this balance is easily disrupted by excessive nutrients flowing into the lake. However, knowledge of whether excessive nutrients lead to different microbial environmental vulnerabilities in the lake sediment between macrophyte-dominated areas and macrophyte-free areas is a prerequisite for the implementation of targeted protection measures. In this study, we investigated bacterial communities in sediments using high-throughput sequencing of 16S rRNA genes. Our results showed that the sources of total nitrogen (TN) and organic matter (OM) were related to the macrophytes. The structure, drivers, and interspecific associations of bacterial community, which were more susceptible to increased changes in TN and OM, differed significantly between macrophyte-dominated areas and macrophyte-free areas. More precisely, the lake edge, where was occupied by macrophytes, had a higher proportion of deterministic phylogenetic turnover (88.89%) than other sites, as well as a wider ecological niche and a tighter network structure. Further, as the difference in TN increased, the main assembly processes in surface sediments changed from stochastic to deterministic. However, the majority of phyla from the lake edge showed a greater correlation with excessive nutrients, and the selection of the community by excessive nutrients was more obvious at the edge of the lake. In addition, our results demonstrated that the stability of the bacterial community in macrophyte-free areas is greater than in macrophyte-dominated areas, while an excessively high deterministic process ratio and nutrient (TN and OM) concentration significantly reduced bacterial community stability at macrophyte-dominated areas. Taken together, these results provide a better understanding of the effects of excessive nutrients derived from macrophytes on bacterial community patterns, and highlight the importance of avoiding the accumulation of TN and OM in macrophyte-dominated areas to enhance the sustainability of the ecosystem after restoration of lakes with macrophytes.

水产养殖生态系统由于其高氮负荷而成为氧化亚氮(N2O)的潜在释放源,为探究其排放特征,选择福建省九龙江河口养虾塘为研究对象,采用悬浮箱-气相色谱仪法测定其水-气界面N2O排放通量变化,并结合气象要素和水环境因子分析其主要影响因素.结果表明:九龙江河口养殖塘水-气界面N2O排放通量的变化范围和均值分别为0.10～0.64μmol·m-2·h-1和(0.26±0.07)μmol·m-2·h-1,均表现为向大气释放N2O的源.N2O排放通量随养殖期推迟呈现持续增加,且在白天不同时刻存在显著变化.相关分析表明,N2O排放通量与养殖水体的温度、溶解性有机碳、NO-2-N和NO-3-N浓度呈显著正相关,与盐度呈显著负相关.多元回归分析表明,水体盐度和NO-2-N浓度是影响养虾塘N2O排放的主要因素.

Aquaculture ponds are important anthropogenic sources of nitrous oxide (N2O). Direct N2O emissions arising from feed application to ponds have been widely investigated, but indirect emissions from N2O production from residual feeds in pond water are much less understood and characterized to refine the IPCC emission factor. In this study, we determined the concentrations and spatiotemporal variations of dissolved N2O and NO3-N in situ in three aquaculture ponds at the MM River Estuary in southeastern China during the culture period over two years, and calculated the indirect N2O emission factor (EF5) for aquaculture ponds using the N2O-N/NO3-N mass ratio methodology. Our results indicated that the EF5 values in the ponds over the culture period ranged between 0.0007 and 0.0543, with a clear seasonal pattern which closely followed that of the DOC:NO3N ratio. We also observed significant spatial variations in EF5 among the three ponds, which could be attributed to the difference in feed conversion rate. In addition, we assessed the EF5 values from aquaculture ponds in five regions of the Chinese coastline across the latitudinal gradient from the tropical to the temperate zones. The average EF5 value from aquaculture ponds across the five coastal regions was 0.0093 +/- 0.0024, which was approximately 3.7 times of the IPCC default value for rivers and estuaries (0.0025). Moreover, the EF5 values demonstrated considerable spatial variations across these coastal regions with a coefficient of variation of 59%, which were largely related to the difference in water salinity. Our findings filled a key knowledge gap about the indirect N2O emission factor from aquaculture ponds, and provided field evidence for the refinement of EF5 value currently adopted by IPCC in the national greenhouse gas inventory. (C) 2021 Elsevier Ltd. All rights reserved.

Water quality deterioration can adversely affect the long-term sustainability of aquaculture industry. Understanding the processes of nutrient regeneration and uptake is important for improving water quality and the overall ecosystem health of aquaculture system. In spite of the importance of dissolved nutrients (DOC, DIC, N-NOx-, N-NH4+, and P-PO43-) in governing water quality and ecosystem functioning, the spatiotemporal variations in the production and uptake of dissolved nutrients in aquaculture ponds is still poorly understood. In this study, the nutrient production and uptake rates in the overlying water were quantified among different shrimp growth stages in the aquaculture ponds in the Min River Estuary (MRE) and Jiulong River Estuary (JRE), southeast China. Significant differences in the nutrient production and uptake rates in the overlying water were observed among the three growth stages and two estuaries. The temporal variations of DOC and DIC production rates in both estuarine ponds closely followed the seasonal cycle of temperature, while the difference in DOC and DIC production rates between the two estuaries was likely caused by differences in water salinity. The changes in the production and uptake rates of dissolved inorganic nitrogen (N-NOx- and N-NH4+) and P-PO43- in the water column over time were partly related to the interactions between thermal conditions and phytoplankton biomass (e.g., chlorophyll a concentrations) in the ponds. Our results demonstrate the complex dynamics and environmental risk of dissolved nutrients in subtropical shrimp ponds, and call for a more effective management of nutrient-laden wastewater in safeguarding the long-term sustainability of aquaculture production.

氧化亚氮(N2O)是一种重要的痕量温室气体,对全球气温升高和酸雨形成起着重要作用,并对臭氧层造成严重损害.水产养殖是N2O的潜在释放源,该研究以中国东南沿海的闽江河口湿地围垦养虾塘为研究对象,采用过程抑制法,通过室内培养试验区分N2O不同产生过程及其对沉积物N2O总产生速率的贡献,在此基础上分析沉积物理化性质对N2O产生的影响.结果表明:养虾塘沉积物N2O总产生速率在养殖初期、中期和末期的均值分别为1.80、5.95和8.70 nmol/(kg·h),其中硝化作用、反硝化作用、硝化细菌反硝化作用和非生物作用的贡献率均值分别为?162.04％、327.52％、?239.45％和90.27％,从而得出结论:反硝化作用和非生物作用是产生沉积物N2O的主要来源,硝化作用和硝化细菌反硝化作用则对沉积物N2O的产生有所削弱;养虾塘沉积物N2O总产生速率在高温低盐条件下最大,在低温高盐条件下出现最小值,总体呈现随着温度升高而增加,随着盐度升高而降低的趋势;相关分析表明N2O总产生速率与总碳(total carbon,TC)、土壤有机碳(soil organic carbon,SOC)、NH4+-N含量和C:N比均呈显著正相关关系,而在其不同产生过程中仅有非生物过程受到TC、SOC含量的显著影响.

Diffusion model methods are frequently applied in monitoring water-atmosphere methane (CH4) fluxes. To explore the variation character and influence factors of CH4 transfer velocity (kx) and diffusive fluxes across the water-atmosphere interface from aquaculture shrimp ponds, this study chooses six different model methods for estimating kxand CH4 diffusive fluxes in the Min River estuary (MRE) and Jiulong River estuary (JRE) on the southeast coast of China. For each estuary, water samples were collected using a hydrophore sampler from three shrimp ponds in June, August, and October 2015, respectively. Meanwhile, meteorological parameter (air temperature, wind speed and atmospheric pressure) and water-quality indicators (water temperature, pH, dissolved oxygen and salinity) were measured in situ using a portable instrument. A headspace equilibration technique was used for the measurement of dissolved CH4 concentration. The mean kxat MRE and JRE ponds during the study period ranged between1.60±0.75 and 6.29±1.30 cm/h, and 0.89±0.19 and 6.07± 0.61 cm/h, respectively. The mean CH4 diffusive fluxes in the MRE and JRE ponds over the study period ranged between 9.19±2.67 and 30.64±6.28 μmol/ (m2·h), and 3.18±0.48 and 21.03±2.13μmol/ (m2·h), respectively. The results showed that kxand CH4 diffusive fluxes across the water-atmosphere interface from the estuaries of shrimp ponds greatly varied in spatial and seasonal dynamics. The CH4 diffusive fluxes were significantly higher from the shrimp ponds in the Min River estuary than in the Jiulong River estuary (P＜0.05). Average seasonal kx (or CH4 diffusive fluxes) in MRE and JRE shows an increasing trend over time. The wind speed, water dissolved CH4 concentration and salinity are important factors that drive the changes in CH4 diffusive fluxes emission. There are differences in CH4 transfer velocity across the water-atmosphere interface from aquaculture shrimp ponds between the different model methods, indicating that the CH4 diffusive fluxes from the model-based estimation has a certain degree of uncertainty.

研究了超高效液相色谱(UPLC)法同时测定湿地土壤中柠檬酸、草酸、苹果酸、酒石酸和丁二酸等5种有机酸的方法,并测定了武昌湖、巢湖和鄱阳湖湿地土壤样品中的有机酸组成含量,为揭示有机酸在土壤-植物-根际环境中的转运、分配和分泌提供理论依据.结果 表明:利用UPLC法可以快速地分离5种有机酸,比HPLC分离时间缩短1倍左右;各有机酸的加标回收率为99.17％～103.55％,相对标准偏差为0.48％ ～ 1.92％,检测限为0.05～0.18 mg /kg,该方法线性关系优良(R2＞0.997);除了鄱阳湖湿地土壤样品的酒石酸未能检测出,其他湿地土壤样品中的5种有机酸都能检测出;不同湿地土壤样品的优势有机酸种类不同,武昌湖湿地土壤中的柠檬酸和苹果酸对有机酸总量贡献较大,巢湖湿地土壤中的柠檬酸对有机酸总量的贡献最大,鄱阳湖湿地土壤中丁二酸占有机酸总量的比例小于10％;湿地土壤有机酸含量多集中在土壤深度为30～ 50 cm处,这与该区域植物根系分布及微生物活性较高有关.

Aquaculture ponds which is rich in nutrients due to a large amount of organic matter supply from daily input of feeds, is an important sources of atmospheric nitrous oxide (N2O). In this study, dissolved N2O concentration and saturation in surface water were determined using static headspace⁃gas chromatography method in the shrimp ponds in the Min River estuary of Fujian Province. N2O diffusive fluxes across the water \ air interface in shrimp ponds were also estimated by the two⁃layer model of diffusive gas exchange. Meanwhile, the meteorological parameters and water environmental indicators were measured. The average concentration and saturation of dissolved N2 O among different culture stages were 17. 96 nmol·L-1 and 198. 03%, respectively. Significant differences in mean N2O concentration were recorded among the three shrimp culture stages and the highest values was detected in the middle period of culture. The N2 O concentration and saturation in the shrimp ponds were positively correlated with temperature, NH4 ⁃N and chlorophyll a (p<0.05), while being negatively correlated to air pressure, wind speed and water pH ( p<0.05) . The averaged N2 O diffusive fluxes calculated by LM86, W92 and RC01 models from aquaculture ponds were 20.80, 183.75 and 298.52 nmol·m-2 ·h-1, respectively. N2O diffusive fluxes across the the water \air interface in the shrimp ponds greatly varied among different culture stages, which showing a remarkable increasing tendency over time. The wind speed and dissolved N2O are important factors controlling the changed in N2O diffusive fluxes. Furthermore, the N2O diffusive fluxes were 环 境 科 学 学 报 7 期 金宝石等:闽江河口养殖塘水体溶存氧化亚氮浓度及扩散通量研究 closely related to the gas transfer velocity. There are differences in N2O transfer velocity across water \ air interface in the shrimp ponds among the three models. Our results suggest that RC01 model is the more suitable method to estimate the N2O transfer velocity and diffusive fluxes in shrimp ponds in the Min River estuary than the LM86 and W92 model. These results provided scientific reference for the inventory compilation of N2O emission from coastal aquaculture ponds and the protection of coastal water environment.

为研究不同浓度低分子量有机酸与提取的土壤重金属含量之间的关系,本文以采自安徽省安庆市某铜矿区及其周围的土壤为例,通过浸提法,研究了不同浓度苹果酸、甲酸对采样点土壤中重金属Cu、Mn、Zn、Pb提取能力的影响并进行模型拟合.结果表明:不同浓度苹果酸和甲酸对采样点土壤中重金属的提取量不同,两种有机酸对低pH、高重金属含量采样点及其周围土壤中的重金属提取量较大,两种低分子量有机酸对S6采样点的重金属Mn的提取量最大,分别为322.5 mg·kg-1和193.58 mg·kg-1,提取率达70.02％和42.03％,Zn、Pb次之,Cu最低;随着苹果酸、甲酸浓度的升高,土壤中重金属Cu、Mn、Zn、Pb的提取量增加,苹果酸对土壤中重金属的提取能力大于甲酸;拟合模型对于两种低分子量有机酸与其提取的土壤中部分重金属含量之间的关系,具有较好的拟合性,其决定系数R2在0.8293～0.9990之间,都具有显著性(p＜0.05),该模型可以定量表征低分子量有机酸对土壤重金属的提取能力,此研究结果为土壤中重金属的固定化和增强植物修复受重金属污染的土壤提供了理论支持.

安庆沿江湿地作为长江中下游现存相对完好的内陆淡水湖泊湿地,受到了国内外自然保护组织和专家学者的广泛关注.根据安庆沿江湿地生态环境的实际情况,从信息系统管理开发和软件工程的角度出发,设计了基于GIS的湿地信息系统开发思路,并利用组件式GIS软件SuperMap Objects为开发平台,以VS.NET 2008为开发环境,具体编程实现了湿地信息系统的查询和空间分析功能.该系统基本上满足了湿地管理部门进行安庆沿江湿地资源环境的监测分析和决策需求.

本科地理科学类专业在我国高等教育中具有举足轻重的地位,对基础教育师资队伍建设和科研创新型人才培养起着重要作用.通过对安徽省高校地理科学类专业设置和2017年各专业招生状况进行统计分析发现:地理科学类专业布点和本科招生数量明显增加,但生源质量有待提高;各专业招收比例不均衡,师范类的地理科学专业招生最多;高中地理和大学地理科学类专业的学科性质差异使得文理兼收成为高校招生的主要模式;高校教育改革势在必行,应用型和实践型人才培养成为主要趋势.

Aquaculture ponds play an important role in the global carbon cycle.In order to understand the dynamics of carbon in the shrimp ponds,dissolved carbon (dissolved organic carbon [DOC] and dissolved inorganic carbon [DIC]) concentrations in the pond water column,and the exchange fluxes of dissolved carbon across the sediment-water interface,were investigated in the Min River estuary (MRE) and Jiulong River estuary (JRE) on the southeast coast of China.Water and sediment samples were collected using a hydrophore and sediment sampler from three shrimp ponds in June,August,and October 2015,respectively.Meanwhile,water-quality indicators (water temperature,pH,dissolved oxygen,and salinity) were measured in situ using a portable instrument.The dissolved carbon concentration in water was analyzed using a SHIMADZU TOC-VCPH-VCPH/CPN analyzer.Sediment oxygen and nutrient exchange (SONE) incubation techniques were used to measure the rates of dissolved carbon fluxes.The results showed that dissolved carbon concentrations in the pond water,and fluxes across the sediment-water interface from the estuaries of shrimp ponds greatly varied in spatial and seasonal dynamics.Mean dissolved carbon concentrations and fluxes were significantly higher from the shrimp ponds in the Min River estuary than in the Jiulong River estuary (P＜0.05).Average seasonal dissolved carbon concentrations (or fluxes) in the Min River estuary and Jiulong River estuary followed the order:August＞October＞June and October＞August＞June,respectively.The variations in dissolved carbon concentrations in the water were significantly positively correlated with the dissolved carbon fluxes across the sediment-water interface,indicating that the process of dissolved carbon release in the sediment affects the dynamic variation of dissolved carbon concentrations in the water column.Overall,the dynamic variation of dissolved carbon concentrations and fluxes in the shrimp ponds could be due to the synthetic action of abiotic factors (e.g.,temperature and salinity),the foraging and metabolic activity of shrimp,and feed supply.Our study highlights the need to consider the spatio-temporal difference of carbonic biogeochemical cycles to better understand the dynamic of carbon cycling from the aquaculture ecosystems in the estuaries.

While aquaculture pond is a dominant land use/cover type and a distinct aquatic ecosystem in the coastal zones of China and southeast Asia, their contributions to the fluxes of greenhouse gases (GHGs) have only been poorly quantified. Fluxes of CO2 and CH4 in the shrimp ponds with different salinities were simultaneously measured in situ using the floating chamber technique in two different subtropical estuaries, namely, the Min River Estuary (MRE) and Jiulong River Estuary (JRE). The average CO2 and CH4 fluxes in the shrimp ponds over the observation periods varied from −2.09 to 3.37mmol CO2 m−2h−1 and from 0.28 to 16.28mmol CH4 m−2h−1, respectively, with higher fluxes being detected during the middle stage of aquaculture. The temporal variation of CO2 and CH4 fluxes in both estuaries ponds closely followed the seasonal cycle of temperature. Higher CH4 emissions were observed in MRE ponds than in JRE ponds because of the lower water salinity and N-NO3− concentrations as well as a greater supply of carbon substrates. Our findings suggested that shrimp ponds were CH4 emission “hotspots” in the subtropical estuaries of China. Based on a new global warming potential model, we conservatively estimated an anuual GHG emission rate of approximately 63.68Tg CO2-eq during the culture period from aquaculture ponds across the subtropical estuaries of China. Our results demonstrate the importance of aquaculture ponds as a major GHG source and a contributor to climate warming in the subtropical estuarine regions of China, and call for effective regulation of GHG emissions from these ponds for climate mitigation in future.

Eutrophication is increasingly challengiug the sustainability and healthy development of aquaculture.The effects of variations in nutrient dynamics remain unclear,including porewater nutrient concentrations and nutrient fluxes at the sediment-water interface (SWI),from aquaculture ponds globally,and particularly in China.In this study,temporal variation of the concentrations of nitrogen and phosphorus in porewater and their fluxes across the interface of sediment-waterwas investigated in the Jiulong River estuary,a subtropic estuary on the southeast coast of China.Overlying water,intact sediments,and sediment porewater were collected using sediment samplers from three shrimp ponds in June,August,and October 2015.Overlying water and sediment porewater nutrient analyses were performed using an automatic continuous flow analyzer.SONE (sediment oxygen and nutrient exchanges) incubation techniques were used to measure rates of nutrient fluxes (NO-2-N,NO-3-N,NH+4-N,and PO3-4-P).NO-2-N,NO-3-N,NH+4-N,and PO3-4-P concentrations in porewater ranged from 0.01 to 0.06,0.06 to 0.22,10.31 to 14.13,and 0.05 to 0.35 mg/L,respectively,with mean values of 0.04,0.15,11.83,and 0.17 mg/L.Higher NO-2-N and NO-3-N concentrations in porewater occurred during June and higher NH+4-N and PO3-4-P concentrations occurred during August.The NO-2-N,NO-3-N,NH+4-N,and PO3-4-P fluxes across the interface of sediment-water ranged from-2.96 to 7.60,-1.00 to 3.15,-0.79 to 4.95,and 19.23 to 91.73 mg m-2 h-1,respectively.The fluxes of nitrogen and phosphorus nutrients across the interface of sedimentwater showed significant temporal variation,with higher nutrient release fluxes during June and lower fluxes during October.The mean fluxes of NO2-N,NO3N,and PO34--P from the sediment to overlying water were (1.87±1.15),(1.58±0.52),and (1.22±0.62) mg m-2 h-1,respectively,indicating that the shrimp pond sediment acted as a nitrogen and phosphorus release source.Dissolved inorganic nitrogen (DIN) release dominated by excess NH+4-N,and the NH+4-N flux from sediment was (46.18±13.82) mg m-2 h-1.Pearson's correlation analysis showed that the temporal variation of nitrogen and phosphorus fluxes were significantly positively correlated with sediment temperature (P ＜ 0.05),but significantly negatively correlated with shrimp biomass (P ＜ 0.05).The results suggest that the temporal variation of nutrients fluxes across the sediment-water interface in shrimp ponds was controlled by the nutrient concentration gradient,sediment temperature,and the foraging and metabolic activity of shrimp.This study highlighted that the relatively high DIN (NO-2-N and NH+4-N) release from sediment during the initial and middle stages of aquaculture could be a potential pollution source in shrimp ponds,which might increase the risk of shrimp mortality.

To clarify the effect of invasive alien plants on ecosystem functions, soil total carbon (TC), total carbon (TN), and total phosphorus (TP) contents were studied in the exotic invasive plant Spartina alterniflora marsh with different durations and the native species Cyperus malaccensis marsh in the Minjiang River estuary. The results showed that there were different variations of TC, TN and TP at 0-50 cm soil layer in the C. malaccensis marsh invaded by S. alterniflora, but the changes of TC and TN were similar and the change of the TP lagged behind them. Soil C/N increased continually with the increase of TC. Soil TP was a key factor affecting soil C/P and N/P during the S. alterniflora invasion, and the change of C/P and N/P followed a similar trend. The changes of TC, TN and TP were influenced by abiotic factors such as soil salinity, bulk density, soil water content and clay composition. C, N and P stoichiometric ratios were influenced mainly by soil salinity and grain composition. C/N and C/P were the good indicators for soil carbon enrichment ability in S. alterniflora marsh. S. alterniflora invasion induced the change of biomass and marsh habitats. Soil carbon, nitrogen, phosphorus contents, and their ecological stoichiometric ratios changed significantly in the C. malaccensis marsh invaded by S. alterniflora and showed diffe-rent change characteristics with different invasion duration.

The invasion of Spartina alterniflora has a significant influence on soil biogeochemistry cycling in coastal wetlands. However, the roles of the S. alterniflora invasion chronosequence in regulating soil dissimilatory NO3 − reduction processes (denitrification (DNF), anaerobic ammonium oxidation (ANA) and dissimilatory nitrate reduction to ammonium (DNRA)) remains unclear. The objective of this study was therefore to reveal the effects of S. alterniflora invasion on the soil NO3 − reduction processes and associated gene abundance.

Temporal variation of the contents of dissolved inorganic nitrogen,phosphate and chlorophyll a at different depth and the possible nutrient limitation to the phytoplankton growth were investigated in the Jiulong River estuary,southeastern China.Water samples were collected using a hydrophore from three shrimp (Penaeus vannamei) ponds in June 18,August 20,and October 10,2015.Meanwhile,water quality indicators (water temperature,pH,dissolved oxygen and salinity) also were measured in situ using portable instruments.Water nutrients analyses were preformed using an automatic continuous flow analyzer.The chlorophyll a samples were extracted with 90％ ethanol and measured using an ultraviolet and visible spectrophotometer.During the study period,the contents of dissolved inorganic nitrogen,phosphate and chlorophyll a from shrimp ponds ranged from 0.67 to 1.25 mg/L,0.019 to 0.148 mg/L,and 24.71 to 110.23 μg/L,respectively,with mean values of (0.94±0.04) mg/L,(0.068 ±0.003) mg/L and (69.45 ±4.88) μg/L.Water nutrients and chlorophyll a varied significantly during aquaculture stages and followed the order:August (middle stage),October (late stage) and June (initial stage).However,no significant difference of water nutrients and chlorophyll a concentrations among the sampling depth was recorded.Temporal variations of dissolved nutrients contents were influenced by the interactions of water quality indicators,bait feeding,and the foraging and metabolic activity of shrimp,while those of chlorophyll a contents were primarily affected by water nutrient contents,water quality indicators (temperature,salinity,and pH) and shrimp biomass.

The wetland landscape pattern and its dynamic change are the focus of wetland ecology and landscape ecology.There were lots of studies about the wetland landscape changes of long time series through the different periods,with little thinking of the seasonal changes of wetland landscape.In fact,the seasonal changes were also very obvious because of the water level and vegetation seasonal growth,especially in shallow lakes.In this paper,we took lake Caizi as an example,selected SPOT-5 images in April,August and December of the near year,interpreted lake wetland landscape based on RS/GIS,analyzed wetland landscape structure of the different seasons and their transformation each other according to statistics,and discussed the wetland landscape pattern index of the different seasons from the two levels of the landscape and the type by Fragstats software.The results showed that lake wetland landscape was mainly composed of water and the structure of wetland landscape had obvious seasonal variation by the level of the lake and the vegetation growth status.The seasonal changes of wetland landscape were implemented the reversible transfer among different types.With the structure of wetland landscape change,the landscape pattern indexes of landscape and types level had seasonal fluctuation.The study could provide the scientific basis for selecting remote sensing images which can be used in long time change of wetland landscape pattern in shallow lake.