共查询到16条相似文献，搜索用时 156 毫秒
1.
武汉东湖底栖藻类在不同基质上生长的比较 总被引：4，自引：2，他引：2
测定了富营养化武汉东湖中的底栖藻类在不同人工基质上建群发展为成熟群落的生物量(Chl.a),定性分析了人工和天然基质上成熟硅藻群落的种类组成和结构特征.通过比较建群期间底栖藻类在花岗岩、玻璃、塑料(PVC)和木板4种不同人工基质上的生物量变化,发现底栖藻类在PVC上的生物量峰值(Chl.a,71.0μg/cm2)明显高于其它人工基质,说明PVC是最适合底柄藻类生长的人工基质.分析发现人工基质花岗岩上底柄硅藻群落的种类组成、主要优势种类、群落的相似性指数、多样性指数都和天然基质上的硅藻群落是高度相似的,显示该人工基质能够代表天然基质上的藻类群落,表明花岗岩应该是以底栖藻类作指示生物监测和评价水质的理想人工基质. 相似文献
2.
着生藻类一般生长位置相对稳定,其群落分布主要受环境因素的影响,同时,着生藻类还是重要的水环境指示生物.本研究对鄱阳湖丰水期5个典型湖区(主航道、西部湿地、南矶湿地、撮箕湖和东南湖汊)着生藻类的群落结构特征进行调查,包括生物量、优势种及生物多样性,分析影响着生藻类群落区域分布的环境因子,以期为鄱阳湖水环境保护和水资源合理利用提供基础资料.结果表明:鄱阳湖着生藻类群落以硅藻、绿藻和蓝藻为主;鄱阳湖着生藻类总生物量有着明显的区域差异:主航道区域的生物量相对最高,平均为419 mg/m^2;其次是东南湖汊,平均为322 mg/m^2;南矶湿地和西部湿地分别为172和52 mg/m^2;而撮箕湖的总生物量相对最低,为9 mg/m^2.主航道的着生藻类优势种群为绿藻和硅藻,西部湿地、南矶湿地、撮箕湖和东南湖汊4个区域的优势种群为硅藻.冗余分析结果显示鄱阳湖丰水期着生藻类群落分布与总磷、电导率、pH值、总氮、硝态氮和悬浮物等理化因子关系较为密切.鄱阳湖主航道与长江连通,水体流速高;西部湿地、南矶湿地、撮箕湖和东南湖汊为季节性连通湖泊,丰水季节与主湖区水体连为一体,枯水季节独立蓄水.5个湖区的区域差异是导致其着生藻类群落结构差异的重要原因之一.着生藻类的多样性指数分析表明鄱阳湖水体处于中度污染状态. 相似文献
3.
许多证据表明缓慢的水动力条件是水华暴发的重要诱因,尽管以临界流速和水体置换为基础的流量管理实践在水华控制中已见成效,但受限于水动力对藻类生长小生境的干扰机制尚不明晰,长期的流量管理实践效果并不理想.在长期野外观测、围隔实验和室内模拟等一系列研究的基础上,以现有水动力对藻类影响机制的讨论为依据,从细胞学角度提出了水动力对藻类生长影响的3种不同的概念机制,即低强度的水力扰动导致藻细胞外扩散层厚度变薄,有利于周边水体向藻细胞输送营养物质,促进藻类生长;中等强度的水力扰动导致藻类营养盐吸收及光合作用能力受损,抑制藻类生长;高强度的水流剪切导致藻细胞壁破损.基于该机制认为流量管理中临界流速应分别从水体置换和细胞学两方面考虑.研究结果可为流量管理中控制藻类水华暴发和维持水体水质的策略提供重要的理论支持. 相似文献
4.
水动力条件对水体富营养化的影响 总被引：6，自引：3，他引：3
水动力条件是影响水体富营养化状态和进程的主要自然因素.研究水动力条件对水体富营养化的影响对于水体富营养化模拟、预测和控制具有十分重要的意义.水动力条件能直接作用于水华藻类细胞,影响其生长繁殖与种间竞争,同时改变水体环境及营养盐的状况.其中,流速不仅对藻类的生长聚集与分布具有十分明显的影响,同时还能影响水体营养物质与优势藻的种类;流量则主要通过单位时间内水量的变化影响水体富营养化的发生与消亡;水体扰动直接作用于水体中藻类细胞与藻团,加强藻类的聚集,同时影响营养物质的混合与运移,从而使水体富营养化得以发生并持续.本文综述了流速、流量和水体扰动等水动力因子对水体富营养化的影响研究,并对其未来的研究方向进行展望,最后指出:不同水动力条件对营养盐存在形态、藻类生长及水体富营养化状态的影响机理和水动力条件对水体富营养化影响的滞后性规律与临界值研究有待进一步加强. 相似文献
5.
流速对浮游藻类生长和种群变化影响的模拟试验 总被引：3，自引：2，他引：1
采集夏季崇明岛中心湖原水,在环形有机玻璃水槽开展了不同流速对浮游藻类生长和种群变化影响的研究.相对于静止水槽,实验前期不同的流速条件均对浮游藻类的生长产生了一定的抑制作用,实验后期浮游藻类叶绿素a含量均稳定在一定水平,且流动水槽中叶绿素a含量略大于静止水槽,这可能与静止围隔中出现大量枝角类浮游动物有关,而流动条件则抑制了浮游动物的生长,减轻了对浮游藻类的捕食压力.水体流动导致了浮游藻类种群的变化,蓝藻的迅速消失、绿藻和硅藻形成生长优势是主要特征,表明持续的流动条件是导致浮游植物种属减少和群落结构变化的直接原因.该研究可为调水引流在河道、湖泊和水库中的富营养化控制和水华防治提供基础依据. 相似文献
6.
夏季短期调水对太湖贡湖湾湖区水质及藻类的影响 总被引：1，自引：0，他引：1
贡湖湾作为"引江济太"工程长江来水进入太湖的第一站,湖湾水体生态环境的变化是对调水工程净水效果的最好响应,因此本文针对贡湖湾一次夏季短期调水展开调查研究,分别取2013年7月24日(调水前)和2013年8月18日(短期调水后)两次监测水样的水体理化指标和浮游藻类群落数据进行了对比分析,并对浮游藻类群落与环境因子做了相关性分析.结果表明:受来水影响,短期调水后监测区水体的p H略有下降,溶解氧、浊度、硝态氮、总氮、总磷以及高锰酸盐指数等水体理化指标浓度均较调水前有所升高;其中受调水影响最为显著的区域为望虞河的入湖口区、湾心区.两次监测调水前后湖区水体优势藻种属未发生变化,仍以微囊藻为主,但蓝藻种属比例有所下降,绿藻和硅藻等种属比例则有所上升.望虞河入湖口区和贡湖湾湾心区的Shannon-Wiener多样性指数和Pielou均匀度指数受调水的影响升高.同时,浮游藻类群落结构与受水水体理化参数的冗余分析结果表明,此次监测的短期调水后,太湖贡湖湾监测湖区水体p H、溶解氧、硝态氮、总氮、总磷、高锰酸盐指数等环境因子与浮游藻类的群落分布呈显著相关,是影响受水水体中藻类群落的主要环境因子. 相似文献
7.
8.
三峡水库水环境与水生态研究的进展与展望 总被引：4，自引：0，他引：4
伴随着举世瞩目的三峡工程全面竣工,三峡水库于2010年正式进入年水位落差达30 m的正常运行阶段.水库湖沼学可为环境友好型大坝建设和水库可持续管理提供科学依据.本文在三峡成库8 a以来生态系统长期监测与研究的基础上,对三峡水库水环境现状进行了归纳和总结,分析了水环境动态的时空异质性、水库纵向分区与群落组成、垂向分布及藻类水华的成因和动态,并对三峡水库藻类水华预警与生态-水文调控机制展开了论述.最后,本文尝试给出以下两方面的展望:1)大型水库湖沼学观测研究应有长期的策略;2)近期研究应重点关注水华暴发水动力学机制的量化和水华预警模型及生态水力调度平台的耦合. 相似文献
9.
本文于2008-2009年按照季节调查了西藏地区尼洋河着生藻类群落的组成、丰度和多样性,并运用多元统计方法定量分析了着生藻类的空间和季节变化特征及其与主要环境因子之间的关系.结果显示,尼洋河着生藻类共计6门30科49属,其中硅藻为优势着生藻类.着生藻类的Shannon-Wiener多样性指数在尼洋河中游最高,在中上游河段和中下游河段呈下降趋势,符合中间高度膨胀(mid-altitude bulge)假说.着生藻类的总丰度、物种丰富度以及Shannon-Wiener多样性指数在尼洋河沿程不存在显著差异,总丰度在各个季节之间不存在显著差异,但物种丰富度在秋季和冬季存在显著差异,夏、秋季着生藻类的Shannon-Wiener多样性指数显著高于冬、春季.主成分分析(PCA)表明,随着海拔的升高,着生藻类的物种丰富度和总丰度呈递减趋势;典范对应分析(CCA)表明,尼洋河部分硅藻与理化因子相关联,如:双壁藻(Diploneis)的丰度与总磷相关联,窗纹藻(Epithemia)的丰度与铵态氮相关联,双菱藻属(Surirella)的丰度与pH值相关联;部分绿藻与理化因子相关联,如:小球藻属(Chlorella)、栅藻属(Scenedesmus)、溪菜属(Prasiola)的丰度与水温相关联,小椿藻(Characium)的丰度与硬度相关联,转板藻(Mougeotia)的丰度与表层溶氧、矿化度相关联,新月藻属(Closterium)的丰度与碱度相关联;分类回归树(CART)模型预测了尼洋河着生藻类时空分布与主要环境因子之间的定量关系,即低海拔水域的着生藻类总丰度较高海拔高,高矿化度水域的着生藻类总丰度较低矿化度的高,不能用影响尼洋河着生藻类种类和数量的环境因子来解释着生藻类的Shannon-Wiener多样性指数.这些关键环境因子对尼洋河水域着生藻类的时空变化有着重要的指示作用,建议加强对着生藻类及这些环境因子的关注,保障尼洋河水域生态环境的可持续发展. 相似文献
10.
雷诺数对藻类垂向分布特性的影响 总被引：1，自引：1，他引：0
为研究紊流水体中藻类的垂向分布特性,依据三峡水库次级河流回水段的水动力状况,自行设计了水流实验装置,选取次级河流回水区水华高发时段的气候状况和营养盐水平为实验条件,研究了雷诺数对蓝藻、绿藻和硅藻垂向分布的影响以及雷诺数对不同水深处藻类的悬浮和聚集行为的作用.研究结果表明:在水温为20℃、光照强度为5000 lx的富营养水体中,当断面平均流速在0～0.005 m/s、雷诺数在0～1750时,蓝藻主要悬浮聚集在0.2～0.8 m的表层水体中;而当断面平均流速在0.1～0.5 m/s、雷诺数在35000～175000时,硅藻主要悬浮聚集在0.2～0.8 m的表层水体中;与蓝藻和硅藻相比,绿藻适宜的雷诺数范围更宽,当断面平均流速在0～0.05 m/s、雷诺数在0～17500时,绝大部分的绿藻都能悬浮聚集在0.2～0.8 m的表层水体中. 相似文献
11.
Rooted aquatic macrophytes affect abiotic conditions in low-gradient rivers by altering channel hydraulics, consuming biologically available nutrients, controlling sediment transport and deposition, and shading the water surface. Due to seasonal macrophyte growth and senescence, the magnitude of these effects may vary temporally. Seasonal changes in aquatic macrophyte biomass, channel roughness and flow velocity, were quantified and trends were related to spatiotemporal patterns in water temperature in a low-gradient, spring-fed river downstream from high-volume, constant-temperature groundwater springs. Between spring and summer, a nearly threefold increase in macrophyte biomass was positively correlated with channel roughness and inversely related to flow velocity. On average, flow velocity declined by 34% during the study period, and channel roughness increased 63% (from 0.064 to 0.104). During the spring and fall period, the location of a minimum water temperature variability “node” migrated upstream more than 4 km, whereas daily maximum water temperature cooled by 2–3°C. Water temperature modelling shows that the longitudinal extent of cold-water habitat was shortened due to increased channel roughness independent of seasonal surface water diversions. These results suggest that macrophyte growth mediates spatiotemporal patterns of water temperature, constraining available cold-water habitat while simultaneously improving its quality. Understanding complex spatial and temporal dynamics between macrophyte growth and water temperature is critical to developing regulatory standards reflective of naturally occurring variability and has important implications for the management and conservation of cold-water biota. 相似文献
12.
In this study an incompressible smoothed particle hydrodynamics (ISPH) approach coupled with the sediment erosion model is developed to investigate the sediment bed scour and grain movement under the dam break flows. Two-phase formulations are used in the ISPH numerical algorithms to examine the free surface and bed evolution profiles, in which the entrained sediments are treated as a different fluid component as compared with the water. The sediment bed erosion model is based on the concept of pick-up flow velocity and the sediment is initiated when the local flow velocity exceeds a critical value. The proposed model is used to reproduce the sediment erosion and follow-on entrainment process under an instantaneous dam break flow and the results are compared with those from the weakly compressible moving particle semi-implicit (WCMPS) method as well as the experimental data. It has been demonstrated that the two-phase ISPH model performed well with the experimental data. The study shows that the ISPH modelling approach can accurately predict the dynamic sediment scouring process without the need to use empirical sediment transport formulas. 相似文献
13.
Bed scour by debris flows: experimental investigation of effects of debris‐flow composition 
下载免费PDF全文
下载免费PDF全文 Debris flows can grow greatly in size by entrainment of bed material, enhancing their runout and hazardous impact. Here, we experimentally investigate the effects of debris‐flow composition on the amount and spatial patterns of bed scour and erosion downstream of a fixed to erodible bed transition. The experimental debris flows were observed to entrain bed particles both grain by grain and en masse, and the majority of entrainment was observed to occur during passage of the flow front. The spatial bed scour patterns are highly variable, but large‐scale patterns are largely similar over 22.5–35° channel slopes for debris flows of similar composition. Scour depth is generally largest slightly downstream of the fixed to erodible bed transition, except for clay‐rich debris flows, which cause a relatively uniform scour pattern. The spatial variability in the scour depth decreases with increasing water, gravel (= grain size) and clay fraction. Basal scour depth increases with channel slope, flow velocity, flow depth, discharge and shear stress in our experiments, whereas there is no correlation with grain collisional stress. The strongest correlation is between basal scour and shear stress and discharge. There are substantial differences in the scour caused by different types of debris flows. In general, mean and maximum scour depths become larger with increasing water fraction and grain size, and decrease with increasing clay content. However, the erodibility of coarse‐grained experimental debris flows (gravel fraction = 0.64) is similar on a wide range of channel slopes, flow depths, flow velocities, discharges and shear stresses. This probably relates to the relatively large influence of grain‐collisional stress to the total bed stress in these flows (30–50%). The relative effect of grain‐collisional stress is low in the other experimental debris flows (<5%), causing erosion to be largely controlled by basal shear stress. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
14.
Hydro‐morphodynamic evolution in a 90° movable bed discordant confluence with low discharge ratio 下载免费PDF全文
下载免费PDF全文 Sebastián Guillén‐Ludeña Mário J. Franca António H. Cardoso Anton J. Schleiss 《地球表面变化过程与地形》2015,40(14):1927-1938
Confluences with low discharge and momentum ratios, where narrow steep tributaries with high sediment load join a wide low‐gradient main channel that provides the main discharge, are often observed in high mountain regions such as in the upper‐Rhone river catchment in Switzerland. Few existing studies have examined the hydro‐morphodynamics of this type of river confluence while considering sediment discharge in both confluent channels. This paper presents the evolution of the bed morphology and hydrodynamics as observed in an experimental facility with a movable bed. For that purpose, one experiment was carried out in a laboratory confluence with low discharge and momentum ratios, where constant sediment rates were supplied to both flumes. During the experiment, bed topography and water surface elevations were systematically recorded. When the bed topography reached a steady state (so‐called equilibrium) and the outgoing sediment rate approximated the incoming rate, flow velocity was measured at 12 different points distributed throughout the confluence, and the grain size distribution of the bed surface was analyzed. Typical morphodynamic features of discordant confluences such as a bank‐attached bar and a flow deflection zone are identified in this study. Nevertheless, the presence of a marked scour hole in the discordant confluence and distinct flow regimes for the tributary and main channel, differ from results obtained in previous studies. Strong acceleration of the flow along the outer bank of the main channel is responsible for the scour hole. This erosion is facilitated by the sediment discharge into the confluence from the main channel which inhibits bed armoring in this region. The supercritical flow regime observed in the tributary is the hydrodynamic response to the imposed sediment rate in the tributary. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
15.
16.
Francesc Ordines Gabriel JordàAntoni Quetglas Mar FlexasJoan Moranta Enric Massutí 《Continental Shelf Research》2011,31(17):1835-1844
Linking the abiotic and biotic traits of ecosystems is a critical step towards understanding their structure and functioning. Here we attempt to determine the connections between the hydrodynamics, benthic landscape and the associated fish communities on the coastal continental shelf off the Balearic Islands (western Mediterranean). Specifically we investigate the role the hydrodynamics play in shaping the benthic landscape, and whether the hydrodynamics affect the composition and structure of demersal fish communities. A realistic numerical model was used to establish the hydrodynamic characteristics of the area. The study area showed high hydrodynamic variability on a medium spatial scale (tens of km) in terms of mean water velocity (ū). Principal component analysis was used to determine the main gradients of macro-epibenthic variability. Redundancy analysis (RDA) was used to model the effect of the hydrodynamics on macro-epibenthic species. RDA was also used to model the effect of the hydrodynamics and macro-epibenthos on the abundance of the associated fish fauna, and on its biomass at a community level using biomass spectra classes. The results showed that the hydrodynamics had a significant influence on the distribution of both macro-epibenthic species and the associated fish species. The latter was also influenced by the macro-epibenthos. Fish size appeared to be a key attribute for the distribution of species across gradients of ū and macro-epibenthic change. Our findings can be applied in ecosystem-based fisheries management, as they show that it is necessary to take into account both the biotic and abiotic traits of the habitats when the habitat use and requirements of the associated species are defined. 相似文献