Coupling effects of hydrological characteristics and nutrient load in sediments on the trophic state of reservoirs

Currently,lakes and artificial reservoirs are increasingly threatened by eutrophication,which is the result of the combined action of many natural and anthropogenic factors.In the past,the effect of nutrient load on the trophic state of water bodies has attracted much attention,while few studies have addressed the effect of hydrological characteristics.Therefore,to reveal the coupling effects of hydrological characteristics and nutrient load in sediments on the trophic state of water bodies,this study collected relevant data from 36 lakes and reservoirs across China.Pearson correlation analysis showed that trophic level index was positively and significantly correlated with nutrient load in sediments and hydraulic retention time,while it was negatively correlated with mean depth and hydraulic load.The principal component analysis showed that the nutrient load was the first major component that influenced the trophic state of water bodies,followed by the mean depth and hydraulic retention time.Eutrophication was prone to occur in water bodies with mean depth less than 7 m and hydraulic retention time greater than 14 d,and the trophic level index regression equation with hydrological characteristics and nutrient load in sediments was derived by multiple regression analysis.This study revealed that the trophic state of water bodies influenced by both nutrient load and hydrological characteristics.It provides a new idea to reduce the occurrence of eutrophication in reservoirs by using the artificial hydrological regulation capacity of reservoirs.

Physico-Chemical Features of the Kpassa Reservoir, Northern Benin, with Emphasis on Its Trophic State: A Preliminary Study

This work presents recent data on the physico-chemical properties and the trophic status of Kpassa reservoir at eighteen locations from August 2014 to February 2015. Seventeen physico-chemical parameters were measured and data obtained were statistically analyzed. The descriptive statistics showed their variations (minima-maxima) as follows: pH (4.65 - 7.30), temperature (25.1°C - 29.9°C), dissolved oxygen (1 - 5.79 mg/L), oxydability (0.32 - 10.88 mg O2/L), electrical conductivity (55 - 77 μS/cm𕒵), TDS (76 - 94 mg/L), turbidity (15.70 - 274.40 NTU), transparency (0.24 - 1.55 m), suspended matter (3 - 92 mg/L), total phosphorus (0.25 - 1.90 mg/L), orthophosphate (0.08 - 0.61 mg/L), nitrate (undetected 5.50 mg/L), nitrite (undetected 0.79 mg/L), ammonia (undetected 0.36 mg/L), chlorophyll a (7.20 - 2334.6 μg/L), silica (4.34 - 15.67 mg/L) and N/P ratio (0.08 - 42.62). These parameters were mainly influenced by agricultural activities and climatic conditions. The restriction or the removal of the use of chemical fertilizers in agricultural activities in Kpassa reservoir basin was recommended. The highest values of Pearson and Spearman correlations were observed across TDS and conductivity (0.967;0.951), turbidity and oxydability (0.924;0.665), turbidity and chlorophyll a (0.884;0.663), turbidity and suspended matter (0.982;0.793), suspended matter and transparency (𕒴.781;𕒴.819), suspended matter and nitrate (𕒴.813;𕒴.839), suspended matter and oxydability (0.919;0.602) and suspended matter and chlorophyll a (0.879;0.656). Carlson’s trophic state index (TSI) values varied between 36 and 66 showing that Kpassa reservoir was eutrophic in August and mesotrophic to oligotrophic during the other months of the sampling period. ANOVA and Kruskal-Wallis test indicated that there were no significant differences between sampling stations.

Evaluation of the trophic state in Vilun lagoon

In this paper we present the evaluation of trophic state of lagoon aquatic ecosystems connected to the Adriatic Sea. Vilun lagoon is one of these lagoons in Albania. It is one of the most important ecosystems in the country. For trophic state evaluation, spectrophotometry methods of absorption, as well as turbidimetry ones are applied. This ecosystem is monitored for a year from April to October. The evaluation of trophic state is based on these four indicators: the containment of chlorophyll a in phytoplankton;the distribution of photosynthetic pigments;water turbidity and phosphorus containment in water. The monitoring process is performed in different areas of the lagoon, in order to be able to make a more characteristic evaluation of trophic state. All selected areas of Vilun lagoon show a reasonable level of trophic state, which is characterized such as being mezotrophic. Changes related to trophic level are observed during the monitoring period, in each and all the selected areas. Furthermore, changes in the distribu-tion of chlorophylls and their relative content between selected areas are observed.

Trophic states and nutrient storage of reservoirs in Chongqing

The trophic states of 35 reservoirs were investigated in the region of Chongqing,Southwest China.The results showed that the concentrations of nutrients and chlorophyll a were high and organic pollution and transparence(SD) were low in the water body.The concentrations of total nitrogen(TN) range from 0.52 mg/L to 5.94 mg/L and those of total phosphorus(TP) range from 0.002 mg/L to 0.598 mg/L.Chemical oxygen demand(COD) ranges from 0.75 mg/L to 9.3 mg/L and SD ranges from 0.48 m to 3.2 m.There was a significant positive correlation between COD and chlorophyll a,but a significant negative correlation between SD and chlorophyll a.In terms of the integrated nutrition state index,the eutrophication states of the reservoirs were assessed.Of the investigated reservoirs,about 22 reached the grade of eutrophication.Only one reservoir was in the state of oligotropher,the rest were in the state of mestropher.Integrated nutrition state indices range from 25.4 to 74.5.The storage capacity of nutrients in the reservoirs was calculated.The stored TN,TP and COD were about 4731,206 and 10259 t,respectively.The main pollution sources are industrial and domestic wastes.With the development of aquaculture,the contamination level increases gradually.

Study on the Applicability of Landsat-8 Images as a Tool for Monitoring the Trophic State of Lake Guiers (Senegal)

In this study, an algorithm to transform LANDSAT 8 images of Lake Guiers into chlorophyll-a concentration maps was developed. The objective was to see the feasibility of this method as a mapping tool for monitoring the trophic state of the Lake. The available data are 15 in-situ measurements of the CHL-a content of Lake Guiers’ water using a Micro FLU device and images of the lake acquired in 2013 and 2016 by the LANSAT 8 OLI sensor. A series of correlation tests (simple linear functions, multi-variables, or containing two- order terms) were performed between the spectral sensor signal of June 19, 2016 LANSAT 8 image (“corrected” and converted into reflectance) and the CHL-a content of Lake waters measured on the same day of the satellite record. This was, to find the best regression equation that can be inferred to develop an algorithm to transform LANDSAT 8 image into CHL-a concentration maps. The best equation obtained by correlating the ground truths and the reflectance ratios of the visible and near infrared bands (B2, B3, B4 and B5), is as follows: where B2 = Blue band, B3 = Green band, B4 = Red band, B5 = NIR band. The obtained R2 is 0.703 (e.g., a correlation coefficientof 0.84), revealed that the measured concentrations are well reproduced by the regression model. Applying this model to the 2013 and 2016 image data revealed the monthly variations of the lake CHL-a contents and their seasonal evolution and interannual variations. The obtained results are quite consistent with those from similar studies and provide valuable information regarding Lake Guiers’ vulnerability to algal development. The calculation and analysis of the variability of the CHL-a contents over the study period made it possible to evaluate the trophic state of the Lake, which shows a general tendency for eutrophication process, leading to a progressive degradation of the quality of the water resource.

Plankton- Based Assessment of the Trophic State of Three Tropical Lakes

In developing countries, lakes being important sources of water supply and fishing are vulnerable to anthropogenic impact, yet knowledge of their trophic state in relation to changes in species composition, and environmental variables, are limited. This study is aimed at assessing the trophic status of lakes by monthly sampling of three lakes located along the floodplain of Cross River, Nigeria between January 2008 and December 2009. Samples were analyzed for water quality parameters, zooplankton and phytoplankton composition and distribution. Results were subjected to community structure analysis using trophic state index, species richness and diversity indexes. Essential primary productivity nutrients, nitrates, sulphates and phosphates were highest in Ejagham Lake, and lowest in Ikot Okpora Lake. Dominant phytoplankton species Oscillatoria lacustria (Cyanophyceae), Cyclotella operculata (Bacilliarophyceae) and zooplankton Keratella tropica, Keratella quadrata, Filinia longiseta, Branchionus anguillaris and Trichocerca pusilla (rotifers) all typical of eutrophic communities were recorded in high densities in Ejagham Lake in both dry and wet seasons while Cladocerans, Bosmina longirostris and Moina micrura and copepods considered indicators of oligotrophy and mesotrophy were recorded in large numbers in Ikot Okpora and Obubra Lakes respectively. Higher values of species richness, Evenness and Shannon-Wiener diversity index for both phytoplankton and zooplankton, were recorded in Ejagham Lake during the dry season than wet. Also values of the Trophic state index were generally highest at the Ejagham Lake in the savanna region of the floodplain and lowest at Ikot Okpora in the forest region of the floodplain. Forest region is therefore a limiting factor in the productivity of lakes in the tropics.

Land Use Changes Do Not Rapidly Change the Trophic State of a Deep Lake. Amvrakia Lake, Greece

The study of physicochemical and biological parameters can assess the trend of a lake’s trophic state. A trophic state index (TSI) was used to assess eutrophication of LakeAmvrakia. Total phosphorus and chlorophyll concentrations that recorded were generally at the same level with those recorded in previous years, a fact which indicates that lake’s trophic state did not change. But in the past ten years, agricultural uses have been modified by almost 25% of the catchment area, because of the major reduction of tobacco cultivation. One year of monthly monitoring, in nine sampling stations can report this result. Even if the catchment is small and the agricultural areas are the 47% of the basin, the water quality of the lake did not change. The trophic state is stable probably because the lake is deep monomictic, and seasonally anoxic. For this reason internal phosphorus contribution is very important in the deep hypolimnion.

Numerical modeling of nutrient transport to assess the agricultural impact on the trophic state of reservoirs

A trophic state increase relates to surface water bodies nutrient enrichment,due to the chemical products used such as fertilizers in agriculture and residues from cattle raising activities.This research consists of nutrient transport numerical modeling to analyze the Betancíreservoir trophic state in Colombia;Water samples were collected to analyze total nitrogen,total phosphorus,ammonia,nitrates,nitrites,phosphates,chlorophyll-a,dissolved oxygen,BOD,COD,suspended solids,and water trans-parency.The water quality model MOHID Studio was implemented and after its calibration,scenarios of increase and decrease of nutrients and inflows to the reservoir through its main tributaries were simulated to reproduce the agricultural activity changes in the basin and the effects that would have on the reservoir's trophic state dynamics;Therefore,the Carlson Trophic Status Index was calculated for each case.The results show that variations in total nitrogen concentration and increased inflows present short-term consequences on the reservoir's trophic state.Increasing the incoming total nitrogen con-centrations by 100%causes the reservoir to change from a light eutrophic to a hypereutrophic state.The results of this research provide a starting tool to water resources integrated management in reservoirs.

子流域景观格局对丹江口水库营养状态的影响分析

探究子流域景观格局与水体富营养化空间异质性间的关系对水源地保护具有重要意义。本文通过遥感影像和半解析方法揭示2013-2023年丹江口水库营养状态的时空变化格局,并利用SHAP机器学习解释方法,量化分析土地利用组成和景观格局指数与水体营养状态间的关系。结果表明:①丹江口水库营养状态指数呈现明显的空间异质性,以中营养为主,富营养化区域主要分布在岸线库湾区及支流附近。泄洪期水体营养状态相对优于蓄水期。②子流域的土地利用和景观格局存在明显的空间差异,在汉江上游和库区南部支流地区斑块密度(PD)、景观形状指数(LSI)和香农多样性指数(SHDI)呈低值聚集,而最大斑块指数(LPI)和蔓延度指数(CONTAG)呈现高值聚集。③土地利用组成和景观格局指数在不同时期对富营养化的影响程度不同,景观格局指数在全年、蓄水期和泄洪期的贡献度分别达到49.31%、50.99%和57.41%。其中斑块密度、林地、草地和不透水面在各时期均具有较高的影响贡献度,而蔓延度指数和香农多样性指数在蓄水期和泄洪期分别具有较高的影响。研究显示,保持子流域自然地表优势景观,降低耕地和不透水面的破碎度有助于改善水库富营养问题。

融合多源信息的大型湖泊营养状态遥感评估

湖泊营养状态直接反映了水环境质量,但在复杂环境因素影响下,全面且准确评估大型湖泊的营养状态是一项挑战。为应对这一难题,综合运用卫星遥感数据和现场实测数据等多源信息,并采用光谱曲线和四分位距原则(IQR)清洗数据异常值,以反演湖泊营养状态表征指标:叶绿素a浓度(Chl-a)和营养状态指数(TSI)。通过统计分析选取关键环境因子,包括pH、温度(T)、平均风速(AWS)和含沙量(SC),基于反向传输神经网络(BP-NN)和麻雀搜索算法(SSA)构建营养状态反演模型SSA-BP-NN。结果表明:基于BP-NN模型的Chl-a和TSI反演精度分别为0.843和0.834,而经SSA算法优化后,二者反演精度提高至0.918和0.936。以洪泽湖为例,运用该模型阐明了大型湖泊营养状态的时空分布特性,即西、北部湖区高于东部湖区。此外,栅格点数据分析表明Chl-a和TSI具有较强的相关性,且TSI的变化范围更稳定。水华因其高度瞬态性而复杂,TSI作为综合性指标可反映水体富营养化的基本情况,为水华风险预警提供背景参考。本研究表明,通过引入与湖泊营养状态相关性较强的环境因子,可以显著提升遥感反演模型评估精度,为大型湖泊生态系统健康状况评估和风险预警提供参考。

巢湖湖区水质状态对浮游植物多样性时空格局的影响

为明晰巢湖湖区水质状态对浮游植物多样性的影响,2020年1月、4月、7月和9月分别测定浮游植物多样性以及水体理化指标。结果表明:巢湖浮游植物多样性存在明显的时空差异,春季浮游植物的Shannon-weiner Index最高(1.45),秋季(0.27)显著低于其他季节(P<0.05);巢湖西湖心的Shannon-weiner Index(0.41)显著低于新河入湖区(2.25)(P=0.03)。Pearson相关性分析结果表明,富营养指数的变化与浮游植物的Shannon-weiner多样性指数不相关(P>0.05),水质等级的下降对浮游植物的Shannon-weiner多样性指数具有显著的负面影响(P=0.001)。季节性的光温变化、湖泊周边土地利用类型所导致的水质差异,以及水体稀释效应是影响浮游植物多样性时空格局的主导因素。

气候变化对湖泊生态系统的影响研究——基于长期环境监测

气候变化是湖泊生态系统的重要影响因子,长期环境监测能够揭示气候变化与湖泊生态系统健康的关联性。以米易县晃桥水库为例,结合长期环境监测,运用卡尔森营养状态指数评估湖泊的营养状况,并分析气候变化对湖泊生态系统的影响。研究表明,气候变化会导致湖泊水温上升,进而影响湖泊中生物的生存环境及其多样性,并威胁湖泊水质和生态平衡。

典型湖库叶绿素a含量测定及富营养化分析

水体富营养化是由自然因素和人为因素的共同作用造成的,其影响水体中营养盐的含量,导致淡水湖泊中氮、磷、钾等元素含量逐渐升高,从而使藻类植物过度增殖。叶绿素a含量是评价水体富营养化状态的重要指标之一。对我国典型大型湖库丹江口水库6个点位的地表水水体中叶绿素a含量进行了提取测定。利用综合营养状态指数法计算丹江口水库营养状态指数。结果表明,6个点位的地表水中叶绿素a浓度范围在1.17~4.31μg/L之间,综合营养状态指数在32.6~38.1之间,湖库营养状态等级总体上处于中营养状态,有进一步富营养化的风险。

Assessment of the Trophic Status by Monitoring of Reservoir’s Water Quality

Continuous long-term monitoring of aquatic systems is important for understanding their complete evolution in order to monitor changes in the trophic status and water quality. The continuous monitoring during a period of 20 years, by sampling once a month at two locations, the water quality of reservoir “Grliste”, which is used for the water supplying town Zajecar (Eastern Serbia), is observed and developmental stages in the life of the reservoir were determinated. It should be noted that the obtained results were used also in the purpose of finding a cause of cyanobacteria bloom, as a consequence of algal production. Limiting factors of algal production usually were nitrogen and phosphorus, however, in this study, obtained results of subtraction between trophic state index, calculated through total chlorophyll a (TSIChl-a) and trophic state index, calculated through total phosphorus (TSITP), indicated that limiting factor of algal production was light. On the basis of the concentrations of dissolved oxygen (DO), total phosphorus (TP) and chlorophyll a (Chl-a) in the surface and in the bottom, it was concluded that the reservoir passed through four development phases during the examined period. Results of long-term monitoring showed that in the first years after the formation of the reservoir, the highest trophicity was detected (hypereutrophic status), but later the reservoir mostly maintained eutrophic status.

Trophic Status of Shallow Lakes of La Pampa (Argentina) and Its Relation with the Land Use in the Basin and Nutrient Internal Load

Phosphorus and nitrogen are essential nutrients for living organisms. Their concentration in the water of an aquatic ecosystem is one of the factors responsible for the trophic status of the lake and is related to the soils of the region and to the human activities carried out in their basins. These nutrients are also found in the bottom sediments, where they can either be retained or re-enter the water column. Since the information about the concentrations of nutrients in the water of some lakes of La Pampa (Argentina) is fragmentary, the aim of this study is to describe the trophic status of some shallow lakes of the semiarid center of Argentina and analyze its relation with the human activities in their basins, the concentrations of nutrients and organic matter and particle size distribution of sediments. To this end, we studied ten shallow lakes subjected to different anthropogenic influences (agriculture, agriculture and livestock and impacted by cities). All were hypertrophic and the concentrations of total phosphorus and total nitrogen were among the highest reported globally. Since some lakes had no fish, cladoceran grazing (top-down effect) led them have reduced concentrations of phytoplankton chlorophyll-a and high water transparency. This relativizes the use of these parameters to determine the trophic status. The sediments of seven of the studied lakes were predominated by fine sands, whereas three were predominated by silts. Nutrient and organic matter content were high, with higher concentrations in lakes with prevalence of fine particles. The reduced adsorption capacity of sediments, the resuspension by wind, the anthropogenic input and the accumulation favored by the arheic character of the basins would explain the high concentrations of nutrients in the water of these Pampean environments.

长江中下游浅水湖泊底栖动物评价指数筛选及其应用研究

以长江中下游13个浅水湖泊周年季节性湖沼学调查所获得的水质生物评价数据为基础,通过指数与环境因子的相关分析,指数值的分布范围分析,以及判别能力分析对其进行筛选,确定了Shannon-Wiener指数、Margalef指数、BI指数3个对水质判别较为敏感的底栖动物生物指数,并采用分位数法确定其水质评价分级标准。应用此3种评价指数对长江中下游13个湖泊进行水质判别,3个指数评价的结果基本吻合,且生物学评价结果和化学评价结果较为接近,属中度污染以上的湖泊,其营养状态均达到了富营养化水平。该评价指数及其评价标准适用于评价长江中下游地区浅水型湖泊的水质状况。

长江中游黄盖湖富营养化趋势分析及原因诊断

为评估黄盖湖富营养状况和变化趋势并诊断主要成因,以2015~2021年环境监测站点水质数据和2021年秋季的4次全湖加密监测数据为基础,采用综合营养状态指数(TLI(Σ))评价了黄盖湖富营养化程度及变化趋势,使用污染指数法评价了黄盖湖表层沉积物污染程度,基于沉积物与水体间氮磷的相关关系和入湖河流水质状况,初步推断了黄盖湖富营养化的主要原因。结果表明,20152021年黄盖湖TLI(Σ)依次为44.14、45.91、42.39、49.79、49.01、49.62和52.77,呈逐年升高的趋势,由中营养状态转变为轻度富营养状态,夏、秋季富营养化程度高于冬、春季;TLI(SD)、TLI(TN)和TLI(TP)贡献率分别为28%、18%和16%,营养盐浓度增加和透明度降低是黄盖湖水体富营养化的主要驱动因子。沉积物TP和TN平均含量分别为791和2691 mg/kg,为重度污染,有较高的释放风险。表层沉积物与表层水体之间TN相关性较弱,TP相关性较强,但受风速、水深等因素影响较大,湖面风速较高时浅水区域表层沉积物中P更容易释放至上覆水。入湖河流的外源输入以及风浪作用下沉积物再悬浮导致的营养盐浓度升高、透明度下降是近几年黄盖湖水体富营养化的主要驱动因子,建议通过河口湿地修复、水生植被修复等措施减缓黄盖湖水体富营养化趋势。

城市小型景观水体水环境质量评价

城市小型景观水体因其水体特征、水文条件及污染来源与大型天然水体存在较大差异,面临的水体富营养化问题及水华风险更为突出。文章以典型城市小型景观水体——张家港市马家泾为研究对象,运用综合营养状态指数法和营养状态指数法进行水体富营养化评价及水环境因子相关性研究,探讨水质变化规律及富营养化程度,分析叶绿素a与各水环境因子的相关性,识别富营养化和水华风险发生的关键因子。结果显示:水体中总氮、总磷等营养物质含量随季节性变化明显,呈现夏季含量最高,南区、北区水体均存在富营养化现象,其中,南区为重度富营养化,北区为中度富营养化,总氮、总磷对水体富营养化贡献程度最高,并与叶绿素a含量具有正相关性,是导致马家泾水体富营养化的主要营养物质。

基于围隔实验研究鳙在亚热带贫-中营养水库的下行效应

为了解鳙在低营养水体中的下行效应,于秋冬季节在流溪河水库开展了原位围隔实验。该实验在水库原水中进行,并根据鳙的生物量(0 g·m^(–3)和3 g·m^(–3))设置了对照组和有鱼组。研究结果显示:总氮(TN)、总磷(TP)、氮磷质量比(TN:TP)和叶绿素(Chl a)在加入鳙后均未发生显著变化。所有围隔中浮游动物群落均是以小个体种类为主,缺少大型枝角类。鳙的存在促进了轮虫和剑水蚤丰度的增加,但降低了枝角类和哲水蚤的丰度,并导致枝角类、桡足类及浮游动物的生物量显著下降。有鱼围隔中甲壳类的平均体长(352—396μm)显著低于对照组(547—592μm)。添加鳙使浮游植物优势门类绿藻与大型浮游植物(最大轴直径≥30μm)的生物量显著升高,但对优势门类硅藻、金藻和甲藻、小型浮游植物(最大轴直径<30μm)以及浮游植物的生物量无显著影响。这些结果显示,鳙对浮游动物群落产生了强烈的下行效应,对浮游植物群落则未产生明显的级联效应。我们的结果表明,在缺少大型牧食性枝角类的低营养水体中,鳙在低温季节对水质的影响可能相对有限。