Tracing carbon sources in small urbanising streams: catchment‐scale stormwater drainage overwhelms the effects of reach‐scale riparian vegetation

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Urban catchment hydrology overwhelms reach scale effects of riparian vegetation on organic matter dynamics

1. Urbanisation severely affects stream hydrology, biotic integrity and water quality, but relatively little is known about effects on organic matter dynamics. Coarse particulate organic matter (CPOM) is a source of energy and nutrients in aquatic systems, and its availability has implications for ecosystem productivity and aquatic communities. In undisturbed environments, allochthonous inputs from riparian zones provide critical energy subsidies, but the extent to which this occurs in urbanised streams is poorly understood. 2. We investigated CPOM inputs, standing stocks, retention rates and retention mechanisms in urban and peri‐urban streams in Melbourne, Australia. Six streams were chosen along a gradient of catchment urbanisation, with the presence of reach scale riparian canopy cover as a second factor. CPOM retention was assessed at baseflow via replicate releases of marked Eucalyptus leaves where the retention distance and mechanism were recorded. CPOM and small wood (>1 cm diameter) storage were measured via cores and direct counts, respectively, while lateral and horizontal CPOM inputs were assessed using riparian litter traps. Stream discharge, velocity, depth and width were also measured. 3. CPOM inputs were not correlated with urbanisation, but were significantly higher in ‘closed’ canopy reaches. Urbanisation and riparian cover altered CPOM retention mechanisms, but not retention distances. Urban streams showed greater retention by rocks; while in less urban streams, retention by small wood was considerably higher. CPOM and small wood storage were significantly lower in more urban streams, but we found only a weak effect of riparian cover. 4. These findings suggest that while riparian vegetation increases CPOM inputs and has modest/weak effects on storage, catchment scale urbanisation decreases organic matter availability. Using an organic matter budget approach, it appears likely that the increased frequency and magnitude of high flows associated with catchment urbanisation exerts an overriding influence on organic matter availability. 5. We conclude that to maintain both organic matter inputs and storage, the restoration and protection of streams in urban or rapidly urbanising environments relies on the management of both riparian vegetation and catchment hydrology.     

Growth, production and bioenergetics of brown trout in upland streams with contrasting riparian vegetation

1. A series of laboratory-based equations on trout growth and bioenergetics developed by J.M. Elliott were applied to data collected for brown trout ( Salmo trutta L.) under field conditions in Co. Mayo, Western Ireland. Fish were collected by electrofishing eight upland streams with contrasting riparian vegetation; grassland, open canopy and closed canopy deciduous.
2. Stream temperatures, one of the main influencing factors on fish growth and energetics, did not differ significantly between riparian types.
3. Observed growth rates were lower than the predicted maximum growth rates and were not influenced by riparian vegetation type. Growth ranged between 0.66% day⁻¹ for 0 + trout to 0.08% day⁻¹ for 2 + trout.
4. Production estimates showed no clear difference between riparian vegetation types over the growing season.
5. Fish densities and biomass tended to be greater in closed canopy streams particularly in summer.
6. Actual ration sizes calculated for trout were similar to the ration required for maintenance metabolism and were only 45–63% of the maximum potential rations. Although there was an ontogenetic increase in ration size with increasing fish age, the proportion of ration available for growth (i.e. the difference between actual and maintenance rations) did not differ between age classes but was greatest in summer. 1+ and 2+ trout show greatest ration available for growth in grassland streams.
7. Trout growth did not differ between riparian vegetation types but did vary seasonally with greatest attainment in summer. Growth was limited in the present study possibly due to combined effects of reduced prey available to fish and low stream temperatures reducing metabolic requirements. In such food limited systems, terrestrial invertebrate energy subsidies could have significant benefits to brown trout growth, production and bioenergetics.     

Effect of drift sampler exposure time and net mesh size on invertebrate drift density in the Njoro River,Kenya

Although invertebrate drift is an important ecological process in lotic ecosystems, very little is known about it in Kenyan rivers. The primary aim of this study was to investigate the effect of driftnet mesh size and exposure duration on drift density in 2017. Drift samples were dominated by Chironomidae, Baetidae, Simuliidae, Caenidae and Culicidae. The 100 µm mesh driftnet had the highest mean invertebrate density, followed by the 250 µm and 500 µm nets. Invertebrate drift densities decreased with increased exposure time. This study demonstrates that sampler mesh size and exposure time should be taken into account when characterising invertebrate drift in streams. Future studies should consider sampling different biotopes and during different seasons.     

Development, maintenance and role of riparian vegetation in the river landscape

1. Riparian structure and function were considered from a longitudinal perspective in order to identify multiscale couplings with adjacent ecosystems and to identify research needs. 2. We characterized functional zones (with respect to vegetation development in association with various biogeochemical processes) within geomorphological settings using a delineation based upon erosional, transitional and depositional properties. 3. Vegetation dynamics within the riparian corridor are clearly influenced substantially by hydrological disturbance regimes. In turn, we suggest that vegetation productivity and diversity may widely influence riverine biogeochemical processes, especially as related to the consequences of changing redox conditions occurring from upstream to downstream. 4. However, surface and groundwater linkages are the predominant controls of landscape connectivity within riparian systems. 5. The importance of riparian zones as sources and sinks of matter and energy was examined in context of structural and functional attributes, such as sequestering or cycling of nutrients in sediments, retention of water in vegetation, and retention, diffusion or dispersal of biota. 6. The consequences of interactions between different communities (e.g. animals and plants, micro-organisms and plants) on biogeochemical processes are notably in need of research, especially with respect to control of landscape features. Multiscale approaches, coupling regional and local factors in all three spatial dimensions, are needed in order to understand more synthetically and to model biogeochemical and community processes within the river-riparian-upland landscape of catchments.     

Disturbances and species distribution of the riparian vegetation of a Rift Valley stream

The Njoro River riparian vegetation species composition, distribution, disturbances and uses are presented and discussed. Montane Juniperus procera-Olea europaea spp. africana and submontane Acacia abyssinica forests were identified as the main riparian vegetation groups. Approximately 55% of the riparian vegetation species are used for herbal medicine, treating more than 330 health problems, and only 11% of the plants are edible. Albizzia gummifera in the Syzygium cordatum-Pittosporum abyssinicum-Hibiscus diversifolius forest is cut selectively for herbal medicine preparations. Disturbances on the riparian vegetation zone are broadly classified as those induced by man, livestock and wildlife. Comprehensive effects of disturbance included loss of vegetation vertical strata, increase/decrease of species diversity, introduction of alien plant species, and reduction of plant sizes and vegetation hectarage. The effects of grazing on the vegetation were severe around livestock watering points. Grazing and browsing by wildlife were the main disturbances of the vegetation near the Njoro River estuary at the Lake Nakuru National Park. Periodic flooding, as a natural disturbance, regulates growth and survival of vegetation at the Lake Nakuru drawdown. Quantification of species diversity and the extent of disturbance by humans and livestock is important for future management of the vegetation and, consequently, the river.     

A model to predict the presence of longfin eels in some New Zealand streams, with particular reference to riparian vegetation and elevation

Two logistic regression models were developed from a database of 27 biotic and physicochemical variables for 99 sites in the Taieri River, New Zealand, to predict the probability of occurrence of longfin eels. Average depth was associated positively with eels while woody debris and oxygen concentration were negatively associated. At a macro-scale probability of eel occurrence declined with increasing elevation and, for a given elevation, was higher in tussock and pasture catchments and lower in pine and native forest settings. Using a separate fish database for the Taieri River this macro-scale model predicted eel presence 95·4% in agreement with observation. A map was generated from the model showing areas of predicted high, moderate and low probabilities of eel occurrence. The model also estimated the minimum total number of eels present in the Taieri River catchment (excluding lakes, and streams below 100 m and above 1000 m) as 20 865 (95% CL: 10 560-36 350).     

Leaf Litter Decomposition of Three Riparian Tree Species and Associated Macroinvertebrates of Eswathu Oya,a Low Order Tropical Stream in Sri Lanka

Leaf decomposition, an important component of the organic matter dynamics in streams, has been widely examined in temperate regions but much less documented in tropical regions. We report here the first study of leaf decomposition in a Sri Lankan stream. The litterbag technique was used. Coarse (8 mm) and fine (100 µm) litterbags, that included or excluded macroinvertebrates respectively, were used to enclose leaves of three dominant riparian tree species: native Ochlandra stridula (bamboo), and the introduced Alstonia macrophylla and Hevea brasiliensis (rubber). A fourth set of litterbags contained a mixture of these three species. Leaf colonization by macroinvertebrates was highest in the early stages of the decomposition process on Hevea leaves but invertebrate densities declined later. The opposite colonization effect was observed on the native Ochlandra leaves: slow colonization with continuing low densities from the beginning to the end of the process. Decomposition of all three species was significantly faster in the coarse than in the fine mesh bags. Alstonia, which has the softest leaf tissue, was most rapidly decomposed while Ochlandra, with its tough structure, was the slowest. Among the invertebrates, insects were the most important leaf colonizing animals, with Diptera, Coleoptera and Trichoptera the most dominant. The invertebrate variety in the mixed bags was higher than in the single‐species leaf bags, where Chironomidae dominated the colonizing assemblages. This study has shown that toughness, indicated by the ‘specific weight of leaf tissue’, and the quality of the leaves was more important in determining breakdown rates than their origin. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Seasonal dynamics of macroinvertebrate assemblages in the benthos and associated with detritus packs in two low-order streams with different riparian vegetation

• 1 The seasonal dynamics of the benthic macroinvertebrate assemblage, and the subset of this assemblage colonising naturally formed detritus accumulations, was investigated in two streams in south‐west Ireland, one draining a conifer plantation (Streamhill West) and the other with deciduous riparian vegetation (Glenfinish). The streams differed in the quantity, quality and diversity of allochthonous detritus and in hydrochemistry, the conifer stream being more acid at high discharge. We expected the macroinvertebrate assemblage colonising detritus to differ in the two streams, due to differences in the diversity and quantity of detrital inputs.
• 2 Benthic density and taxon richness did not differ between the two streams, but the density of shredders was greater in the conifer stream, where there was a greater mass of benthic detritus. There was a significant positive correlation between shredder density and detritus biomass in both streams over the study period.
• 3 Detritus packs in the deciduous stream were colonised by a greater number of macroinvertebrates and taxa than in the conifer stream, but packs in both streams had a similar abundance of shredders. The relative abundance of taxa colonising detritus packs was almost always significantly different to that found in the source pool of the benthos.
• 4 Correspondence analysis illustrated that there were distinct faunal differences between the two streams overall and seasonally within each stream. Differences between the streams were related to species tolerances to acid episodes in the conifer stream. Canonical correspondence analysis demonstrated a distinct seasonal pattern in the detrital composition of the packs and a corresponding seasonal pattern in the structure of the detritus pack macroinvertebrate assemblage.
• 5 Within‐stream seasonal variation both in benthic and detritus pack assemblages and in detrital inputs was of similar magnitude to the between‐stream variation. The conifer stream received less and poorer quality detritus than the deciduous stream, yet it retained more detritus and had more shredders in the benthos. This apparent contradiction may be explained by the influence of hydrochemistry (during spate events) on the shredder assemblage, by differences in riparian vegetation between the two streams, and possibly by the ability of some taxa to exhibit more generalist feeding habits and thus supplement their diets in the absence of high quality detritus.

     

城市化地区河岸带植被特征及其与河岸硬度的关系——以晋江市为例

确立了滨河河道硬度与滨河土地硬度两个指标,用以研究城市化地区河岸带的植物构成、多样性与均匀度、优势植物等特征与河岸硬度的关系。选定晋江市都市区12条主要河流作为研究对象,通过样地调查收集数据,并采用相应指数进行数据处理分析,结果表明:(1)调查河流的河岸带植被物种共计70科143属159种,其中乔木20科30属41种,灌木15科15属20种,草本35科98属98种,草本居主导地位,河流间种类分布不均衡;(2)河岸带植物乔灌草区系均以广义热带性成分居多,其次为世界性成分、温带性成分,无中国特有分布类型,乔木中广义热带成分占绝对主导,直观反映地带性特征,灌木与草本中的温带成分多于乔木中的温带成分,类型趋于多元,种类更丰富;(3)从河岸植被优势植物构成来看,主要优势乔木与灌木基本为本土植物,而主要草本中外来植物入侵严重,对地带性植物景观的指示显然不及乔木与灌木;(4)从河岸植被的人工美学属性来看,灌木优势植物中园林观赏植物的种类数显著多于乔木、草本优势植物,反映出晋江人工审美主导的滨河景观空间主要改变与塑造了灌木层植被景观;(5)从河岸植物的人居需求属性来看,龙眼、杨桃等多见于庭院林、水岸林的水果树种也在河岸植被中频繁出现,反映出人口密集区由于对植物生产用途的重视而对河岸植被产生的影响;(6)滨河土地硬度与河道硬度对河岸带灌木植物的影响最强烈,二者均对河岸带植物多样性造成威胁,且前者具有更大的影响力,而后者直接影响了河岸植物的分布形态,出于生产与审美目的的人为干扰对河岸带植物优势种的影响力随滨河硬度的增加而加强,低滨河硬度有助留存原生植被群落;(7)天然弯曲的河流形态对河流植被特征具有积极影响,有助于保留更多本土植被类型,并能在某种程度上丰富乔灌草的植物种类,但这种缓和作用无法根本扭转河岸硬化对植物多样性的胁迫影响。研究表明,城市化地区河流的岸带植被特征与沿线人为干扰类型和强度密切相关,恢复与塑造河岸生态景观要以乡土植被为主,通过乔木景观塑造地带性景观,并以灌木与草本丰富植被景观。     

河流岸带湿地沉积物重金属分布对植被物种多样性和底栖动物群落特征的影响

河流岸带湿地栖息地完整性对河流水环境、水生态和水文的安全与健康具有重要意义,为探究河流岸带湿地表层沉积物重金属分布特征及其对植被和底栖动物的影响,对滦河干流上中下游河段表层沉积物、植物群落和底栖动物调查分析,采用生物毒性效应系数法和综合潜在生态风险指数法评价沉积物重金属污染特征,采用植被物种多样性指数和底栖动物完整性指数评价滦河植物和底栖动物群落特征,探究岸带湿地沉积物重金属空间分布与植被及底栖动物群落特征之间关系。结果表明,滦河表层沉积物总体呈清洁水平,但不同河段重金属空间分布差异较大,下游重金属生态危害系数和潜在生态风险指数高于上中游。湿地物种调查共识别维管束植物219种,大型无脊椎底栖动物105种,综合评价结果表明下游植物群落物种多样性和底栖动物群落完整性低于上中游。滦河下游岸带湿地沉积物重金属对生物群落具有生物毒性和潜在的生态风险,降低了植被物种多样性和底栖动物群落完整性。大型底栖动物完整性指数能够综合反映底栖动物群落结构特征变化,对河岸带湿地生态健康评价和监测具有重要意义。     

Development of a stable isotope index to assess decadal-scale vegetation change and application to woodlands of the Burdekin catchment, Australia

Forty-four study sites were established in remnant woodland in the Burdekin River catchment in tropical north-east Queensland, Australia, to assess recent (decadal) vegetation change. The aim of this study was further to evaluate whether wide-scale vegetation ‘thickening’ (proliferation of woody plants in formerly more open woodlands) had occurred during the last century, coinciding with significant changes in land management. Soil samples from several depth intervals were size separated into different soil organic carbon (SOC) fractions, which differed from one another by chemical composition and turnover times. Tropical (C₄) grasses dominate in the Burdekin catchment, and thus δ¹³C analyses of SOC fractions with different turnover times can be used to assess whether the relative proportion of trees (C₃) and grasses (C₄) had changed over time. However, a method was required to permit standardized assessment of the δ¹³C data for the individual sites within the 13 Mha catchment, which varied in soil and vegetation characteristics. Thus, an index was developed using data from three detailed study sites and global literature to standardize individual isotopic data from different soil depths and SOC fractions to reflect only the changed proportion of trees (C₃) to grasses (C₄) over decadal timescales. When applied to the 44 individual sites distributed throughout the Burdekin catchment, 64% of the sites were shown to have experienced decadal vegetation thickening, while 29% had remained stable and the remaining 7% had thinned. Thus, the development of this index enabled regional scale assessment and comparison of decadal vegetation patterns without having to rely on prior knowledge of vegetation changes or aerial photography.     

河岸带生态系统植被与土壤对水文变化的响应研究进展

河岸带的植被与土壤是生态系统重要组成部分,对于维持河岸带的生态健康、生态系统服务与可持续性具有至关重要的作用。水文变化是河岸带生态系统的首要干扰因子,系统总结了水文变化对河岸带植被的特征以及植被形态、群落分布、繁殖、生存策略的影响,并阐述了河岸带水文和植被对土壤氮磷迁移转化的影响机制。根系作为土壤与植物地上部分之间物质、能量流动与信号传导的关键纽带,目前对根系的研究还较欠缺,需要加强水文变化对河岸带湿地植物根系形态、结构、功能特征的影响机理研究,以及湿地植物对水文变化的适应机制和耐受阈值方面的探究。在微观方面,应加强水文变化与植被等多因素耦合对土壤氮磷迁移转化过程的机理研究。河流形态和土壤的多样性决定着河岸带水文作用特征的复杂性,今后需注重河岸带个性特征与水文响应的关系研究。河岸带是横向的水陆生态过渡带和河流上下游的纵向生态廊道,亟需综合考虑和模拟流域土壤、植被与水文、人类活动之间的耦合关系,预测未来气候与社会经济情境下的河岸带生态系统演变规律,为河岸带生态系统的生态调节、生物多样性保护与生态恢复等提供理论依据与技术支撑。     

The distribution of Austrocrangonyx new species (Crustacea: Amphipoda) on the eastern New England plateau, Australia, with reference to riparian clearing

The amphipod Austrocrangonyx n.sp. livesin forested streams above 1165m on the easternNew England plateau in NSW. Classification andRegression Tree (CART) analysis and principalcomponent biplots showed low streamtemperatures and high levels of coarseparticulate organic matter (CPOM), among manyenvironmental factors measured, were the mainfactors associated with its distribution andabundance. Riparian clearing, which increaseswater temperature and greatly reduces CPOM, isassociated with local extinction ofAustrocrangonyx. Secondary reafforestation isnot accompanied by return of the amphipod.     

人类活动干扰下区域植被动态变化——以西双版纳为例

云南省西双版纳地区是我国典型热带雨林区,随着社会经济发展,人类活动对区域植被格局与动态产生强烈影响。利用NDVI变化趋势分析、土地利用转移矩阵和基于MODIS数据的干扰指数（MGDI）3种方法,分析了2000-2010年人类活动干扰下研究区植被动态变化,构建了人类活动干扰指数,并利用冗余分析的方法,分析其与植被特征的相关性。结果表明：通过NDVI变化趋势得出,2000-2010年间,研究区植被覆盖度总体较高,植被变化趋势的斜率均大于0,说明植被总体趋于改善;基于土地利用转移矩阵结果表明,植被变化主要发生在常绿阔叶林、常绿针叶林转变为乔木园地、灌木园地、人工园地或居住用地;基于MODIS影像结果得出,西双版纳地区MGDI分布很不均匀,且2000-2010不同土地覆被类型MGDI相差不大。构建的人类活动干扰指数结果显示人类干扰强度由中心向边缘呈递增趋势,呈分散分布,这与人类活动的分布规模和强度相关。通过冗余分析可知,NDVI与人类活动相关性较大,MGDI与人类活动相关性不大。总体上来说,上述3种方法能够从不同侧面反映出人类活动干扰下植被长时间的变化趋势。因此,对于西双版纳地区,局地的人类活动特别是旅游、基础设施建设、农业活动等对热带雨林自然生态系统的干扰不容忽视。     

Water sources of riparian plants during a rainy season in Taihu Lake Basin,China: a stable isotope study

In this study, we investigated water sources of three typical plant species, i.e., Ginkgo biloba (Ginkgo biloba L.), Green soybean (Glycine max (L) Merr.), and Mulberry tree (Morus alba L.) in a rainy season by using a dual stable isotope approach (δ¹⁸O and δ²H). Potential water sources were divided into direct or internal (i.e. soil water at different depths) and indirect or external water sources (i.e. precipitation, river water and groundwater). The results indicated that the surface soil water δ¹⁸O and δ²H is enriched probably due to evaporation. Ginkgo biloba and Green soybean prefer using soil water from the upper soil layer (0–60 cm) and precipitation, and the Mulberry tree mainly used deep soil water (120-150 cm) and groundwater. The different water use strategies of the three plant species are likely to be determined by their different root distribution at the above correspondent soil depths.     

草地植物群落最优分类数的确定——以黄河三角洲为例

植被生态学研究中常需要将样地-物种属性数据划分为多个具有生态意义的集群,在植被分类过程中不仅要在分类方法上做选择,还要确定该植被数据分多少类最合适.有很多指标来确定群落划分中的最优分类数,但都没有得到一致的认可.将黄河三角洲227个样地数据用ward等级聚类法进行了分类.为了找到最优的分类数和判断指标,用不同的判断标准对植被数据分为2到15类时进行分析.主要从3个方面对最优分类数进行判断:1)比较集群内的同质性和集群间的异质性;2)基于集群的物种组成、环境变量的不同,确定集群与环境的相关性;3)基于物种在不同集群内的频度与多度.判断指标主要包括:average silhouette width指数、Goodman and Kruskal's Gamma系数、Dunn指数、集群分布的熵、wb.ratio指数、Calinski and Harabasz 指数、C-index指数、partana指数、biserial指数.用多响应置换过程对集群间物种组成和环境差异显著性进行分析.用指示物种从生态角度对各集群进行判别,并对指示物种的显著性进行了分析.不同判断标准得到的黄河三角洲最优分类数不同,得到的最优分类数包括分为2、5、7、和15类;多方面综合判断,认为在分为7类时最好.群落分类中应该有较优的断点,划分类较少时,集群特征不明确;划分类较多时,集群特征虽然更明确,但可能会导致较多的小集群,且小集群间环境差异不显著.7类较优,能满足物种组成差异、环境差异、群落内和群落间差异、所含信息量多的要求.分为2-6类时应该都是有意义的,只是所代表的群落特征不同.各判断标准中,dunn、silhouette、Calinski和Harabasz指数和指示物种能比较有效的判断最优分类数.不同的分类方法和物种属性数据的得到的结果有待进一步研究.     

Resilience,Restoration, and Riparian Ecosystems: Case Study of a Dryland,Urban River

Resilient systems can absorb disturbance and persist despite variability as long as the capacity of the system to adapt is not exceeded. Riparian plant communities of dryland alluvial rivers are expected to be naturally resilient systems because they persist in the highly variable floodplain. River modification has altered the flow regime on many dryland rivers, in some cases exceeding the adaptive capacity of the riparian vegetation, but these changes may be readily reversible. The Salt River in Phoenix, Arizona has been impounded, dewatered, channelized, but also re‐watered with urban effluent and storm drain runoff. To determine whether riparian vegetation is resilient to these various perturbations, paired comparisons were made in the vegetation and seed bank between a non‐diverted reference reach, a diverted reach, and a re‐watered urban reach. In the diverted reach, composition had shifted to that of a stress tolerant xeroriparian shrubland with low diversity in both the seed bank and extant vegetation. Most surprisingly, few differences were observed in the composition and structure of the vegetation and soil seed banks between the reference reach and the urban reach, particularly in the wet patches, suggesting that hydric riparian plant communities have the capacity to adapt to these modified conditions. These results provide support for a process‐oriented approach to restoration on the Salt River and other urban dryland rivers using patches of persisting vegetation as models for achievable restoration targets.     

人为营养物质输入对汉丰湖不同营养级生物的影响--稳定C、N同位素分析

以长江一级支流小江上游的汉丰湖为研究对象,设置了4个采样点(影响组:A, B;对照组:C, D),应用碳、氮稳定性同位素探讨人类生活污水和农业面源污染对汉丰湖水生生态系统中不同营养级水平生物类群的影响。结果表明:影响组POM(颗粒有机物)和螺类碳、氮稳定性同位素比值范围分别为-25.93‰--24.63‰、4.12‰-9.86‰,-14.28‰--21.60‰、7.97‰-19.99‰;对照组POM(颗粒有机物)和螺类碳、氮稳定性同位素比值范围分别为-25.62‰--22.51‰、0.01‰-6.56‰,-22.96‰--19.21‰、6.75‰-8.89‰;不同组间POM和初级消费者螺类碳同位素比值无明显空间变化(P>0.05), 而氮稳定性同位素比值空间变化显著(P<0.05)。因此,在汉丰湖食物网中,氮稳定性同位素特征更好地反应了营养物质(人为输入)吸收和富集的信息。与固着藻类、鱼类等相比,POM和软体动物螺类更适合作为环境评价的指示物。影响组A、B样点的部分生物类群已经受到了人为营养物质输入的影响,影响强度B样点区域>A样点区域。结果建议加强汉丰湖水环境保护,控制污水排放量及提高污水处理水平,对于保护小江和三峡库区水质具有十分重要的意义。