1998-2001年长江口近海鱼类群聚结构及其与环境因子的关系

根据1998-2001年长江口近海4个航次鱼类拖网调查数据,运用群落生态学分类和排序方法,分析了长江口近海鱼类群聚结构特征及其与环境因子的关系。筛选后的64个站次的48种长江口近海鱼类分属10目28科,鲈形目种类最多,灯笼鱼目,鲈形目和鲱形目鱼类丰度共占总丰度的 99.81% 。龙头鱼、七星底灯鱼和黄鲫为秋季优势种,银鲳和皮氏叫姑鱼为春季优势种。相同季节年度间的鱼类群聚差异不显著,春季(5月)和秋季(11月)鱼类群聚有明显的季节分化。CCA分析显示：1998-2001年长江口近海鱼类群聚的主要影响因素是水深、底层温度、底层溶解氧、表层总磷和pH值。     

三峡库区试验性蓄水期间浮游生物群落特点研究

蓄水改变了三峡水库的水文情势,使得浮游生物密度及群落结构出现明显改变,在不同蓄水阶段呈现不同的特点。根据2009年三峡水库试验性蓄水期间分季节实地监测结果,分析了浮游动植物在不同季节、不同蓄水位以干流与支流河口的分布变化情况。结果表明：就季节变化而言,秋季浮游植物种类最多、夏季次之、冬春较少;浮游生物密度整体不高,且时空分布不均,为春夏秋冬依次递减,支流河口密度高于干流;与蓄水前相比,蓄水后浮游生物密度显著增加,但与135 m及156 m蓄水位相比,试验性蓄水期间有下降趋势。库区营养盐水平较高,对浮游生物的生长不形成限制,浮游生物分布的时空显著差异是由流量、流速及浊度造成的。     

白洋淀浮游生物群落结构的季节变化及其与环境因子的关系

浮游生物是水生态系统的重要组成部分,由于其对水环境状况的敏感性常被用来作为水环境优劣的指示生物。为研究白洋淀浮游生物群落特征及其与环境因子的关系,于2018年春季(5月)、夏季(8月)和秋季(10月)分别对白洋淀淀区5个采样点的浮游生物及环境因子进行调查分析,并采用Pearson相关性分析法分析白洋淀浮游生物群落结构变化和主要环境因子的相互关系。结果表明:根据TP、NH_3-N、COD_(Mn)、TN等水质参数浓度值进行水体质量评价,白洋淀水体夏季为Ⅴ类水,春季和秋季为Ⅳ类水。白洋淀研究区域共检出浮游植物6门74种,浮游动物3门22种。白洋淀浮游生物的群落结构季节间变化显著,两类浮游生物夏季丰度均达到最大值。浮游植物春、夏季以蓝藻门和绿藻门占绝对优势,秋季则出现硅藻门、裸藻门、甲藻门和隐藻门等优势类群。浮游动物在各个季节均以轮虫为优势类群。根据浮游生物群落特征指数进行水质类别分析,白洋淀在不同季节大部分指数显示为中污染。浮游生物多样性指数反映的水质污染状况与理化因子水质评价结果与季节变化趋势相对一致。浮游植物多样性指数与TP、COD_(Mn)和DO的相关性较大,浮游动物多样性指数与COD_(Mn)、NH_3-N和TN相关性较大。     

三峡水库蓄水前后库区干流浮游藻类变化分析

为了研究三峡水库蓄水前后库区干流水体中浮游藻类的变化情况,结合库区地形和城市分布情况,设立了监测断面。利用1999~2008年的监测资料,对三峡库区藻类变化情况及影响因素进行了分析。结果表明：蓄水后,库区TP、高锰酸盐指数等含量总体稳定,水体悬浮物含量下降,藻类光合作用条件改善,使库区干流藻细胞密度总体增加,且呈库尾至库首逐步上升的趋势。藻密度峰值出现季节由蓄水前的冬季转变为蓄水后的春季;但蓄水前后,库区干流浮游藻类种群结构组成基本一致,均是硅藻、绿藻、蓝藻占主体,蓄水后群落结构总体仍表现为河流型生态群落结构特点,只是库首段水体喜静水性的藻类在蓄水后检出频度有所上升。     

小浪底水库调水调沙对下游河道浮游生物的影响

浮游生物是河流主要生物类群之一,也是鱼类主要饵料,对水环境要素的变化具有较高的响应能力。基于2018年黄河小浪底水库调水调沙前后采样结果,研究黄河小浪底调水调沙对下游河流系统浮游生物群落的动态影响。在2018年调水调沙前和调水调沙期分别进行采样,在小浪底大坝以下的黄河干流河道设置10个采样断面,采集了浮游生物定量样品,同时测量了样点水质理化参数。结果表明:调水调沙过程对浮游生物具有明显影响,调水调沙开始后,浮游植物生物量下降而多样性增长,浮游动物生物量上升而多样性下降。调水调沙对浮游植物的影响最远达到艾山与泺口之间,总长540 km,黄河下游夏季浮游生物的生物多样性总体较低,优势度较高,表明生境趋于单一化。     

长江口表层沉积物中生源硅的时空分布与影响因素

为了解长江口及其邻近海域表层沉积物中生源硅(BSi)的时空变化特征及其与影响因素的关系,依据2014年长江口冬季(2月)、春季(5月)、夏季(8月)和秋季(11月)综合调查数据,测定分析了沉积物中BSi、有机质和粒度等指标。结果表明：长江口及其邻近海域表层沉积物BSi浓度范围是0.045%～0.650%,均值为0.327%;BSi浓度存在显著的时空变化差异：秋季含量最高,夏季和冬季次之,春季最低;不同季节BSi空间分布也存在显著差异,春、夏季呈“北高、南低”的变化趋势,秋、冬季则表现为“南高、北低”的分布特征。Pearson相关性分析结果显示,影响BSi时空分布的因素存在季节差异：春季,BSi与Chl.a之间存在显著正相关,反映了该季主要是底栖硅藻等初级生产者对沉积物中BSi的贡献较大;夏季,BSi除受初级生产的贡献外,还与沉积物中有机碳、氮(TOC、TN)的优先分解而被积累保存相关;秋季,TOC和TN含量及沉积物粒径是影响BSi的重要因素;冬季BSi分布影响因素较为复杂,与沉积物理化性质呈极显著相关性。研究结果揭示,富含有机碳的细颗粒物质富集及底栖硅藻的初级生产是长江口生源硅积累的主...     

白洋淀浮游生物群落动态变化与生物量模拟研究

为探究白洋淀浮游生物群落结构动态特征及其关键影响因子，基于2017年秋，2018年春、夏3个季节的水环境因子与浮游生物野外采样调查结果，采用冗余分析(ＲDA)、广义可加模型(GAMs)等方法探究了白洋淀不同季节的浮游生物群落动态变化，建立了浮游植物生物量与环境因子的非线性关系并进行了率定验证。结果表明:与1992年白洋淀干淀后重新蓄水时相比，浮游植物与浮游动物物种数分别下降了59%与37%，优势群落从绿藻门转化为蓝藻门。根据ＲDA排序结果可知，温度、透明度是影响浮游生物丰度的关键环境因子。运用GAMs构建了环境因子与浮游植物生物量的定量模型，最优模型结构为Biomass-phy～s(T)+s(TN)+s(Cond)+s(Biomass-zoo)+s(Biomass-pro)+te(Biomass-pro_TN)+te(Biomass-pro_Cond)+te(Biomass-pro_Biomass-zoo)。将2019年6月采样数据进行模型验证，计算模拟效果良好，实现了对浮游植物生物量的定量模拟，能够为白洋淀生态恢复与保护提供决策支持。     

岩滩水电站建设对水生生物的影响

根据岩滩水电站河段近30年水生生物自然资源长序列数据,分析水电站建设对水生生物自然资源的影响,研究红水河流域渔业自然资源枯竭的原因。结果表明:岩滩水电站蓄水11年,库区浮游植物种类减少2.7%,单位体积生物质量为蓄水前的4.4倍;浮游动物种类增加97.9%,单位体积生物质量为蓄水前的16.1倍;底栖动物种类减少70.6%,单位面积生物质量为蓄水前的5倍;水生维管束植物种类增加80%;鱼类种类减少40%。岩滩水电站建设前后水域生态环境发生重大变化,水生生物种类组成及生物量结构差异显著,鱼类及底栖动物种类的生物多样性损害严重。     

怀柔水库与潮白河向阳闸鱼类群落特征及影响因子研究

怀柔水库是北京市重要的水源地和调蓄地,向阳闸是潮白河流域上的关键节点,了解其鱼类多样性的现状及变化对于水生态保护尤为重要.根据2020年鱼类调查数据,采用SPSS统计学方法相关性分析,研究怀柔水库和潮白河向阳闸鱼类群落多样性现状及其与环境因子的响应关系.结果 表明:在怀柔水库调查到鱼类分属8目17科41种,潮白河向阳闸采集到的鱼类5目6科21种,均以小体型、生活于水体中上层、杂食性和淡水定居土著鱼类占主导,怀柔水库补给潮白河可能会提升其鱼类多样性.怀柔水库鱼类多样性特征值较高,鱼类群落复杂度较高,群落结构相对稳定,主要与鱼类群落丰富、生境多样化等因素有关.本次调查数据显示,影响鱼类群落分布的环境因子中,硝酸盐氮、高锰酸盐指数与鱼类群落分布和多样性特征有一定关联性.本研究对评估怀柔水库向下游补水的生态风险和对鱼类多样性潜在影响具有一定参考作用.     

澜沧江真核浮游生物的空间格局及其多样性

目前关于澜沧江浮游生物的研究多局限于浮游植物,缺乏从整个真核生物群落的角度进行探讨的研究。为填补相关方面的研究空白,于2020年10月在澜沧江近2 000 km的区域布设了36个样点进行样品采集,基于18S rRNA宏条形码技术探究了真核浮游生物群落的空间分布差异及其对环境因子的响应。测序共得到1 269个OTU,涵盖了45门284属,测序深度足够反映物种多样性。NMDS和ANOSIM分析显示澜沧江真核浮游生物群落依据地理空间分布可划分为3个分组：上游的自然河道段、中游的乌弄龙电站和功果桥电站之间区域、下游的功果桥电站以下区域。根据多样性及群落组成数据发现：属于自然河道段的上游群落组成最为均匀,金藻门和硅藻门广泛分布于该区域;属于水库段的中游和下游多样性类似且均低于上游,隐藻门广泛分布于该区域。影响澜沧江真核浮游生物群落结构变化的环境因子主要为水温和碱度。上、中、下游的环境驱动因子有所不同,电导率是影响上游真核浮游生物群落结构的关键环境因子,水温是影响中游的关键环境因子,而下游则主要受总磷的影响。     

Effect of the Three Gorges Reservoir on vertical distribution of suspended sediment concentration and estimation accuracy of depth-average concentration in downstream reaches

The sediment regime in the middle Yangtze River has been significantly changed from quasi-equilibrium to nonequilibrium since the impoundment of the Three Georges Reservoir (TGR). To understand the effects of the TGR on vertical distribution of suspended sediment concentration (SSC) and estimation accuracy of mean concentration, vertical sediment concentration and flow velocity data at the Shashi and Jianli hydrological stations in the reach before and after the impoundment were collected. Comparisons and analysis of vertical profiles of SSC before and after the TGR impoundment show that after the impoundment of the TGR, due to the coarsening of sediment particle size, the reduction in sediment load, and the significant decrease in sediment saturation, the vertical distribution of SSC in the downstream reaches became more uneven under medium and low water flows, which was reflected in the vertical gradient and the fluctuation degree of SSC significantly increased. In addition, the depth-average sediment concentrations were calculated by the selected-point method and the mean values calculated by the “multi-point method” were regarded as the “true mean” to evaluate the accuracy of the mean value calculated by the “few-point method.” It was found that the relative errors for the selected-point method were mainly positive before impoundment but mainly negative after impoundment. Additionally, the correction factors of one-point, two-point, and three-point methods and the position of the near-bed substituted point for the five-point method were given to reduce the error when the point measurements were used to calculate the depth-average sediment concentration in the downstream reaches.     

Distribution of Botia superciliaris (Günther, 1892) ichthyoplankton in the upper mainstem of the Yangtze River preimpoundment and postimpoundment of the upstream dam cascade

Dam cascades have been a major threat to fishes of the upper Yangtze River. The remaining lotic river segment of the upper mainstem between the Xiangjiaba Dam (XJD) and the Three Gorges Reservoir (TGR) may serve as a critical refuge for endemic fishes. We investigated distribution of ichthyoplankton Botia superciliaris, an endemic species, at three sections preimpoundment and postimpoundment of the XJD, that is, Yibin (close to the XJD), Zhuyang (in the middle of the segment), and Mudong (in the tail of the TGR). Preimpoundment of the XJD, larvae occurred in all three sections, and their abundance tended to be highest at Yibin and lowest at Mudong. Postimpoundment, larval abundance dramatically decreased in all three sections. In particular, no larvae were found at Yibin, and larval abundance tended to be higher at Zhuyang than at Mudong. Eggs were collected from all three sections, and those from Zhuyang accounted for over 90% of the total. Initiation of egg occurrence at Yibin was approximately 1 month later than at Zhuyang and Mudong. Water temperature was lower, and water transparency was higher at Yibin than at Zhuyang and Mudong postimpoundment. We suggest that the decrease in abundance and delayed presence of ichthyoplankton at Yibin postimpoundment of the XJD reflected the impact of upstream dam discharge and that the lower abundance of ichthyoplankton at Mudong compared with Zhuyang both preimpoundment and postimpoundment of the XJD reflected the influence of inundation by the TGR. We recommend that the river sections around Zhuyang become high‐priority conservation areas     

三峡库区草堂河库湾水动力特征

针对三峡库区蓄水后普遍存在的干流水体倒灌支流库湾的现象,为探究干支流水交换过程中的水动力特征,通过逐月(2012年9月至2013年7月)实地观测获取三峡库区中部典型支流草堂河库湾水动力参数及水体温度、浊度等数据,分析了水库运行各期干流与库湾的水交换情况及其对库区水环境的影响。结果表明:由于温度差异、干流惯性作用以及支流特殊地形等因素的影响,草堂河河口存在明显的双向水流结构,水库运行各期干支流交界面进出水体分布差异显著;特殊的河流走向使得全年多数月份草堂河与干流有效交换量高于其他典型支流;干流水体全年均能倒灌至库湾尾部,水库高水位运行期进出水体在河口呈上下分层结构且连续性较好,低水位运行期则以左右环流为主且连续性较差。     

长江洪水期三峡工程对长江口水动力特性及污水稀释扩散影响的数值模拟研究

运用ECOMSED建立了长江口的水动力模型。潮位和流速的验证结果表明模型能够较好地反应长江口的水动力特性,可以应用于长江口的实际计算。对2010年7月长江发生的大洪水对长江口的水动力特性的影响进行了模拟。模型计算结果表明,由于三峡工程的蓄水作用,使得长江口附近的流速发生明显的减小,对污水的稀释扩散和水环境也会产生一定的影响。上海三个排污口分别排出稀释度为1000的污水时,由于三峡工程的蓄水,上游来水量相应减少,不利于上海排出污水的稀释扩散。     

三峡电站日调度驱动的支流振荡对支流水温垂向结构的影响

三峡电站日调度驱动的重力波对其支流动力过程造成显著影响,其中的高频水流波动会显著影响支流库湾的物质、能量等垂向扩散和输运过程,进而影响水华暴发等环境问题。基于三峡水库香溪河支流2021年蓄水期末的水动力及水温垂向结构监测数据,分析了三峡电站日调度驱动的支流库湾高频振荡对水温结构的影响。研究发现,三峡出库流量日波动驱动支流水位也呈日波动和高频波动特征,其中水位日波动振幅约0.3~0.5 m,高频水位波幅约0.04 m。库湾底层水温高频波动比中上层更加明显,与香溪河库湾水深从河口向上游逐渐变浅有关系。支流近底水温波动功率谱分析显示,香溪河湍流耗散速率(6.5×10^-7 W/kg)明显高出一般水库的近底耗散率,表明水库调度驱动的水体高频波动导致较强的湍流发育和耗散。     

Phenology and species diversity in a Lake Huron ichthyoplankton community: Ecological implications of invasive species dominance

Ichthyoplankton communities are dynamic and vary spatiotemporally based on factors such as wind, water currents, and phenology. Nonetheless, ichthyoplankton are an indicator of spawning success in fish populations and examining their community diversity and composition can serve to provide information on ecosystem integrity. Although some ichthyoplankton species may be transient, understanding their distribution in space and time provides information on species composition, abundance, and habitat use during critical early life stages. We sampled the spring-summer ichthyoplankton community during 2008 and 2009 in northern Lake Huron to determine species succession, abundance, and species diversity along physical and environmental gradients. Seasonal succession of species was similar during both years, indicating well-defined patterns in spawning by northern Lake Huron fish populations. Invasive alewife, rainbow smelt, and round goby were the dominant species during both years, with native stickleback species also abundant. Shannon Entropy (H′) increased with increasing water temperature until late summer when H′ declined. H′ decreased with increasing bottom depth and distance to tributary mouth indicating the important ecological role of these habitat features during early life stages. Although ichthyoplankton diversity was comparable to or higher than that reported for other areas of the Great Lakes, the prominence of invasive species in our study is reflective of the disturbed state of the Lake Huron fish community, despite large reductions in invasive planktivorous fish since 2004. Continued monitoring of ichthyoplankton communities will be important for measuring the impacts of species invasions or other ecosystem stressors on fish community structure in the Great Lakes.     

三峡建库前后长江中游河道输沙率变化分析

三峡建库后,水库下游河道含沙水流长期处于严重次饱和状态,输沙由相对平衡状态转变为不平衡状态,输沙强度较自然条件下发生显著变化。根据三峡水库蓄水运用前后(1992—2017年)长江中游主要水文站断面、床沙与水文资料,从输沙率变化、床沙粒径变化、平滩流量等角度研究长江中游河道复式断面输沙强度问题,得出以下结论:三峡水库蓄水运用后,进入下游河道的泥沙大幅度较少,长江中游沿程水文站同流量级输沙率明显减少;床沙粒径沿程出现不同程度的粗化,其中荆江河段粗化最为明显,螺山至武汉河段略有粗化;螺山站和汉口站在自然条件下平滩流量附近输沙强度出现峰值,对应的水流挟沙能力为极大值。     

三峡库区典型支流氢氧同位素时空分布特征研究

定量分析三峡水库支流库湾中水体组成,研究支流库湾水循环过程,有助于分析支流库湾的环境问题。对三峡水库内的草堂河及其毗邻干流进行了连续1 a的观测,分析了水体中氢氧同位素特征,阐述了在干支流相互作用下,三峡水库支流库湾的水团来源及其组成,探讨了三峡水库蓄水后支流库湾水循环的变化。研究表明:长江干流和支流库湾中δD/δ~(18)O与区域降水线十分接近,表明其水团主要来源为大气降水;同时长江和支流库湾中的氘盈余与建库前有明显不同,说明三峡水库蓄水之后长江干流和支流库湾水体组分发生了一定改变;支流库湾中水体混合比存在明显的时空变化,长江干流水团占的比例为76. 9%~99%。     

Assessing Water Quality of Three Gorges Reservoir, China, Over a Five-Year Period From 2006 to 2011

Understanding temporal variability in water quality in the Three Gorges Reservoir (TGR) is crucial for evaluating environmental effects of damming and protecting China’s largest freshwater resource. This study examined water quality changes in the main channel of the Yangtze River after dam completion as well as its relationship with water level fluctuation (WLF), controlled by annual impoundment operations and conditioned by flooding. Finally, the mass balance budget and integrative water quality indexing (WQI) methods were applied to elucidate the status of overall water quality since dam completion. Results showed that TGR outlet water (Yichang) exhibited higher pH and COD_Mn values and lower concentrations of dissolved oxygen (DO) and ammonia nitrogen (NH₃-N) than inlet water (Zhutuo). Temporal variations in water quality parameters displayed similar trends for the outlet and inlet. Water quality parameters all showed negative correlations to water level, revealing the different effects of damming on water quality. It was estimated that reservoir impoundment led to a DO depletion of 1495.5 (±1482.0)?×?10³ tons/yr and a COD_Mn increase of 564.0 (±405.0)?×?10³ tons/yr, likely deriving from various internal pollutant loads from the WLF zone and tributary watersheds. According to WQI, TGR water quality remained at healthy levels. However, WQI linear regression showed that water quality at the outlet significantly decreased over time, indicating that the construction of the Three Gorges Dam generally caused water quality deterioration. Further investigation is required to determine the spatial distribution of point and non-point pollution sources and to identify major factors that influence TGR water quality.