Benthic Community Structure and Invertebrate Drift in a Pacific Island Stream,Kosrae, Micronesia1

Tropical Pacific island streams have poorly understood communities that deserve scientific attention. We examined benthic macroinvertebrates and fishes of the Inem River on Kosrae, Federated States of Micronesia. Larval chironomids, lepidopterans, odonates, and freshwater shrimps dominated the benthos and drift. Diel periodicity in drift was not evident. Nine fishes, two shrimps, and one snail species were identified. Kosrae's stream fauna appears even more depauperate than other Pacific high islands, possible due to its extreme isolation.     

Temporal changes in benthic macroinvertebrates and their interactions with fish predators after restoration in the Cheonggyecheon,a downtown stream in Seoul,Korea

The Cheonggyecheon (Cheonggye stream), a downtown stream in Seoul, Korea, was restored by the historic Cheonggyecheon Restoration Project (2003–2005), and its discharge and other environmental conditions are artificially regulated throughout the year. The aim of this study was to assess temporal changes in benthic macroinvertebrates and their interactions with fish predators in the Cheonggyecheon. Sampling was conducted twice a year (spring and autumn) at three sections of the stream from 2006 to 2010 using a Surber sampler (50 × 50 cm) for benthic macroinvertebrates and a cast net (mesh size, 10 × 10 mm) and a kick net (mesh size, 5 × 5 mm) for fishes. Analyses of annual precipitation and most water quality parameters showed no significant differences across the study period (P > 0.05). The species richness and density of benthic macroinvertebrates and fishes varied across the sampling period. Analyses of functional feeding groups and trophic guilds showed distinct trends, such as an increase in the number of insectivorous fish in the absence of invertebrate predators. Correlation and regression analyses for five major groups of benthic macroinvertebrates and fishes demonstrated that the density of certain groups of benthic macroinvertebrates (e.g. Tubificidae, Erpobdellidae, Baetidae, and Chironomidae) and insectivorous fishes (e.g. Gobioninae, Leuciscinae, Danioninae, and Gobiidae) were negatively correlated. In conclusion, in an artificially regulated stream like the restored Cheonggyecheon, where physical environments are nearly unchanged, fish predation can be a major factor controlling benthic macroinvertebrate communities.     

Structural complexity of woody debris patches influences fish and macroinvertebrate species richness in a temperate floodplain-river system

A field experiment was conducted to examine the influence of variable density (complexity) of small patches of woody debris on the abundance and taxonomic richness of macroinvertebrates and fishes in the Brazos River, a meandering lowland river in east-central Texas. Woody debris patches contained bundles of either 8 or 16 sticks of two sizes, and reference plots contained no woody debris. The experiment was conducted in the littoral zone in the river channel and a nearby oxbow lake. Organisms were collected from each patch after 14 days. Abundance and taxonomic assemblage structure of macroinvertebrates in both the river channel and oxbow were significantly and positively influenced by complexity of woody debris. For fish in the oxbow, abundance and species richness were greater in woody debris than sites lacking structure, but the opposite trend was observed for fish in the river channel. This difference could be associated with isolation from source habitats and low colonization of the constructed woody debris patches in the river by fishes with affinities for complex habitats. Small lotic-adapted minnows were captured from reference habitats in the channel, but these species were rare in woody debris patches. This was in contrast to aquatic insects in the river channel, such as caddisfly and midge larvae, that efficiently colonized the small isolated patches of woody debris. In a lotic environment, woody debris provides vertical surfaces that intercept drifting insect larvae and provides protection from the water current. We speculate that greater abundance of macroinvertebrates in woody debris patches in both habitats results from the combined influence of high food resource availability and refuge from predation provided by structurally complex habitats. Handling editor: R. Bailey     

Restoration of rapids habitat in a Great Lakes connecting channel,the St. Marys River,Michigan

Aquatic habitat has been extensively altered throughout the Laurentian Great Lakes to increase navigation connectivity. In particular, the St. Marys River, a Great Lakes connecting channel, lost >50% of its historic rapids habitat over the past century. In 2016, the natural flow was restored to the Little Rapids area of the St. Marys River. The goal of our study was to evaluate physical and ecological responses to the restoration of the Little Rapids area. Extensive habitat and biological data were collected prior to restoration (2013 and 2014), and after restoration (2017 and 2018). Measured parameters included total suspended solids, current velocity, benthic macroinvertebrates, and larval, juvenile, and adult fishes. Total suspended solids stayed low (<4 mg/L) following restoration, with the exception of a single construction‐related event. Pre‐restoration data indicated that all measured velocities were below the target flow rate of 0.24 m/s, whereas 70% of the measured habitat was above the target flow post‐restoration. Abundance and richness of benthic macroinvertebrates were reduced following restoration (>90% reduction). We observed a 45% increase in richness of larval fish 2 years after restoration and a 131% increase in catch per unit effort. For adult fishes, the proportion of individuals with a preference for fast‐moving waters increased from 1.5 to 45% in the restored area, and from 7 to 15% upstream of the restored area; a similar response was observed for lithophilic spawners. The physical and biological conditions of the Little Rapids improved and resembled conditions typical of rapids habitat extent in other areas of the river and other systems.     

太浦河大型底栖动物群落组成及时空分布特征

太浦河连接东太湖和黄浦江,是东太湖向下游行洪的主河道,也是黄浦江上游重要的引水水源。分别于2017年10月、12月和2018年3月、6月在太浦河沿程设置的5个站点开展了大型底栖动物季节频次的取样调研,分析了太浦河大型底栖动物群落的结构特征及其主要影响因子。调查期间共采集到大型底栖动物25种,隶属于3门6纲14科,其中以河蚬（Corbicula fluminea）为代表的双壳类和以铜锈环棱螺（Bellamya aeruginosa）为代表的腹足类处优势地位。太浦河大型底栖动物群落的密度、生物量及多样性特征在不同站点间均存在显著差异（P<0.05）;而在不同季节间均不存在显著差异（P>0.05）。聚类排序分析表明,太浦河大型底栖动物群落在空间上的差异较季节间的变化更为明显。太浦河大型底栖动物群落的物种组成特征与太浦河、东太湖的水文连通格局密切相关;而沿程不同程度人为干扰下的水体营养水平以及底质类型与生境异质性等生境条件对太浦河大型底栖动物群落的分布特征具有重要影响,其综合作用机理有待进一步研究。     

硫铁矿酸性矿山废水对大型底栖动物群落结构的影响

2006年11月和2007年1月通过金属和生物指标的量化监测,就酸性矿山废水对大型底栖动物群落结构的影响及高岚河污染现状进行研究。典型对应分析表明：酸性废水对高岚河上游大型底栖动物群落结构影响最大。对高岚河大型底栖动物群落结构和功能摄食类群进行分析,研究硫铁矿酸性矿山废水对河流大型底栖动物群落的影响,结果表明：高岚河自矿源起约16km河段,大型底栖动物群落结构已经遭到严重破坏;多足摇蚊Polypedilum tritum和真凯氏摇蚊Eukiefferiellab rehmi对酸和金属均具有较强的耐受力;捕食者和刮食者对矿山酸性废水带来的污染反应最为敏感。逐步回归分析表明：大型底栖动物生物多样性受Al、Ca、Cd、Fe、Mg、Mn等金属影响最大;密度受Ca、Cr和Mg的影响最大。     

The Detroit River: effects of contaminants and human activities on aquatic plants and animals and their habitats

Despite extensive urbanization of its watershed, the Detroit River still supports diverse fish and wildlife populations. Conflicting uses of the river for waste disposal, water withdrawals, shipping, recreation, and fishing require innovative management. Chemicals added by man to the Detroit River have adversely affected the health and habitats of the river's plants and animals. In 1985, as part of an Upper Great Lakes Connecting Channels Study sponsored by Environment Canada and the U.S. Environmental Protection Agency, researchers exposed healthy bacteria, plankton, benthic macroinvertebrates, fish, and birds to Detroit River sediments and sediment porewater. Negative impacts included genetic mutations in bacteria; death of macroinvertebrates; accumulation of contaminants in insects, clams, fishes, and ducks; and tumor formation in fish. Field surveys showed areas of the river bottom that were otherwise suitable for habitation by a variety of plants and animals were contaminated with chlorinated hydrocarbons and heavy metals and occupied only by pollution-tolerant worms. Destruction of shoreline wetlands and disposal of sewage and toxic substances in the Detroit River have reduced habitat and conflict with basic biological processes, including the sustained production of fish and wildlife. Current regulations do not adequately control pollution loadings. However, remedial actions are being formulated by the U.S. and Canada to restore degraded benthic habitats and eliminate discharges of toxic contaminants into the Detroit River.Contribution 738 of the National Fisheries Research Center-Great Lakes, 1451 Green Road, Ann Arbor, MI 48105, U.S.A.     

Environmental Variability, Historical Contingency, and the Structure of Regional Fish and Macroinvertebrate Faunas in Ouachita Mountain Stream Systems

In 1990–1992, the United States Forest Service sampled six hydrologically variable streams paired in three different drainage basins in the Ouachita Mountains, Arkansas, U.S.A. Fishes, macroinvertebrates, and stream environmental variables were quantified for each stream. We used these data to examine the relationship between regional faunas (based on taxonomy and trophic affiliation of fishes and macroinvertebrates) and measured environmental variables. Because fishes are constrained to their historically defined drainage basins and many insect taxa are able to cross basin barriers, we anticipated that both groups would respond differently to environmental variability. Fishes were influenced more by environmental variability that was unique to their historical drainage basins, but macroinvertebrates were associated more strongly with environmental variability that was independent of drainage basins. Thus, the individual drainage basins represented a historical constraint on regional patterns of fish assembly. For both fishes and macroinvertebrates, groupings based on taxonomy and trophic affiliation showed a similar response to environmental variability and there was a high degree of association between taxonomic and trophic correlation matrices. Thus, trophic group structure was highly dependent on the taxonomic make-up of a given assemblage. At the basin-level, fish and macroinvertebrate taxa were associated more strongly with environmental variability than the trophic groups, and these results have implications for basin-level studies that use trophic groupings as a metric to assess ecological patterns. Trophic categories may not be a useful ecological measure for studies at large spatial scales.     

Invertebrate communities associated with a native (Vallisneria americana) and an alien (Trapa natans) macrophyte in a large river

1. We used a corer and a Downing box sampler to sample macroinvertebrates living on and beneath the introduced Trapa natans and the native Vallisneria americana in the freshwater tidal Hudson River, New York. 2. Densities of macroinvertebrates were higher in Trapa than in Vallisneria, and higher in the interior of plant beds than at their edges. These effects were largely a result of high plant biomass in Trapa beds and in bed interiors (the plants have similar surface area per unit mass). 3. The composition of both epiphytic and benthic macroinvertebrates differed distinctly between Trapa and Vallisneria, and also seasonally. 4. These compositional differences were not easily interpretable as rising from possible differences in oxygen concentrations, fish predation, or water circulation in the two macrophytes. 5. Sida crystallina (Cladocera) collected from Trapa contained more haemoglobin than those collected from Vallisneria. 6. The replacement of Vallisneria by Trapa in the Hudson probably increased system‐wide biodiversity and food for fish, although macroinvertebrates in Trapa beds may not be readily available to fish because of low oxygen concentration there.     

雅鲁藏布江流域底栖动物多样性及生态评价

雅鲁藏布江起源于喜马拉雅山,是世界上海拔最高的河流之一,是流经我国西藏境内重要的国际河流,其河流生态系统具有特殊地貌及生态条件。研究该流域底栖动物多样性分布特征及其影响因子,是科学评价该区域河流生态系统健康状况,实现资源可持续开发利用的基础。2009年10月—2010年6月期间,以底栖动物作为指示物种,对雅江流域干支流及堰塞湖的14个采样断面进行河流生态评价。采用Alpha及Beta生物多样性指数分别指示局部采样河段及全区域的底栖动物多样性。对采样断面底栖动物组成分析发现:14个采样断面共采集到底栖动物110种,隶属57科102属。雅江干流底栖动物种类数最高为29,平均为19。支流年楚河种类数为17。支流拉萨河,尼洋河,帕龙藏布的最高种类数分别为25,33,36;平均种类数分别为21,21,22,生物多样性普遍高于干流。整个流域中底栖动物平均种类数相差不大,但种类组成和密度相差较大。调查区域的Beta多样性指数β高于低海拔地区的相似的山区河流,说明雅江流域内底栖动物群落差异性高于正常海拔地区。对14个采样断面的物种组成进行除趋势对应分析表明:影响雅江流域底栖动物多样性的主要因素为河型,河床阻力结构,堤岸结构,水流流速。保持稳定的阶梯-深潭结构和自然堤岸结构,以及适宜的流速有利于保护雅江河流生态。     

Trophic ecology of a nonnative population of suckermouth catfish (<Emphasis Type="Italic">Hypostomus plecostomus</Emphasis>) in a central Texas spring-fed stream

Introduced suckermouth catfishes (Family Loricariidae) are now established in a number of spring-influenced streams in North America but their impacts on native biota are not well documented. Purposes of this study were to quantify gut contents of the loricariid Hypostomus plecostomus from the San Marcos River in central Texas and to evaluate the role of H. plecostomus in the San Marcos River food web using stable isotope analysis. Gut content analysis indicated that H. plecostomus (N = 36) primarily consumed amorphous detritus (87% in biovolume), filamentous red algae (5.4%), and picoplankton (4.1%). Macrophytes, macroinvertebrates, and fish eggs were not found in gut contents. Stable isotopes demonstrate that H. plecostomus occupies a trophic position indicative of an herbivore and likely utilizes detritus of algal origin. The results from our study suggest that large populations of H. plecostomus in the San Marcos River may directly compete with several native herbivorous fishes and may be disrupting trophic flows and nutrient cycling in spring-influenced streams of central and west Texas.     

长江宜昌段桥边河大型底栖动物功能摄食类群时空分布特征

研究河流生境时空变化对大型底栖动物功能摄食类群的影响,分析底栖动物功能摄食类群对环境因子的响应关系,对评估河流生态系统健康具有重要意义。以长江支流桥边河为研究对象,基于2020年8月、2021年1月和2021年4月对桥边河大型底栖动物和水体理化因子的调查数据,分析了大型底栖动物功能摄食类群的构成以及时空分布特征。结果表明：共采集到大型底栖动物3门38种,包括节肢动物门23种、软体动物门13种、环节动物门2种。桥边河大型底栖动物功能摄食类群中滤食者占绝对优势,其次为刮食者、捕食者、撕食者和收集者。滤食者的优势种为闪蚬和河蚬,刮食者的优势种为方格短沟蜷、铜锈环棱螺和卵萝卜螺,捕食者的优势种为河蟌,撕食者的优势种为秀丽白虾,收集者的优势种为黄色羽摇蚊。冗余分析（RDA）表明,影响桥边河大型底栖动物功能摄食类群的主要环境因子为溶解氧（DO）、氨态氮（NH₄⁺-N）、水深（Dep）、pH、温度（T）和硝态氮（NO₃^--N）。研究大型底栖动物功能摄食类群组成和时空分布特征,可为河流生态系统修复提供参考依据。     

Coexistence of Fish Species in a Large Lowland River: Food Niche Partitioning between Small-Sized Percids,Cyprinids and Sticklebacks in Submersed Macrophytes

In the spring and summer of each year, large patches of submersed aquatic macrophytes overgrow the bottom of the alluvial Warta River downstream of a large dam reservoir owing to water management practices. Environmental variables, macroinvertebrates (zoobenthos and epiphytic fauna, zooplankton) and fish abundance and biomass were assessed at this biologically productive habitat to learn intraseasonal dynamics of food types, and their occurrence in the gut contents of small-sized roach, dace, perch, ruffe and three-spined stickleback. Gut fullness coefficient, niche breadth and niche overlap indicated how the fishes coexist in the macrophytes. Chironomidae dominated in the diet of the percids. However, ruffe consumed mostly benthic chironomids, while perch epiphytic chironomids and zooplankton. The diet of dace resembled that in fast flowing water although this rheophilic species occurred at unusual density there. The generalist roach displayed the lowest gut fullness coefficient values and widest niche breadth; consequently, intraspecific rather than interspecific competition decided the fate of roach. Three-spined stickleback differed from the other fishes by consuming epiphytic simuliids and fish eggs. The diet overlap between fishes reaching higher gut fullness coefficient values was rather low when the food associated with the submersed aquatic macrophytes was most abundant; this is congruent with the niche overlap hypothesis that maximal tolerable niche overlap can be higher in less intensely competitive conditions.     

香溪河大型底栖无脊椎动物空间分布

2005年7月至2006年6月,通过对大型底栖无脊椎动物的量化检测,对三峡水库湖北库区最大河流香溪河的大型底栖无脊椎动物空间分布进行了研究.结果表明：四节蜉、高翔蜉、短尾石蝇为香溪河水系大型底栖动物优势类群;香溪河各支流间生境特征及大型底栖无脊椎动物群落结构差异较大;功能摄食类群密度相对丰度的变化能够反映不同的栖境特征.对生物多样性指数及优势类群耐污值的比较表明,大型底栖动物栖境为九冲河最好,香溪河干流次之,高岚河和古夫河较差.典型对应分析表明：铵态氮对香溪河大型底栖动物群落结构影响显著;pH值、浊度、水深、二氧化硅、电导和碱度对九冲河大型底栖动物群落结构影响显著;浊度对高岚河大型底栖动物群落结构影响显著;铵态氮和硝酸盐氮对古夫河大型底栖动物群落结构影响显著.     

Limnological aspects of the St. Clair River

The St. Clair River is a major navigable waterway transporting water southwards for 63 km from Lake Huron to Lake St. Clair at an average flow of 5 100 m3 s^-1. Water entering the river is low in suspended solids, organic carbon, phosphorus and nitrates, typical of clear, oligotrophic waters. In contrast to many large rivers, dissolved and colloidal solids account for 90 to 95 percent of the total solids load transported by the river, giving the river a turquoise colour common of glacial meltwater streams.The river supports a diverse floral and faunal community that includes 20 taxa of submergent macroflora, at least 300 benthic macroinvertebrates and 83 fishes. A number of exotic (European) species, including 3 plants, 4 molluscs and 11 fishes, occur in the river with the macroalga, Nitellopsis obtusa, zebra mussel (Dreissena polymorphora), Asian clam (Corbicula fluminea), and white perch (Morone americana) being the most recent invaders. Production is estimated to be 200 g m^-2 a^-1 ash-free dry mass for submergent macrophytes and periphyton, 7 g for macroinvertebrates and 5 g for fishes.The river also supports a variety of water-oriented recreational activities, is a source of municipal and industrial water, a receiver of municipal and industrial wastes, and a shipping corridor. Industrial discharges have adversely affected aquatic life, particularly in the nearshore areas along the Canadian shoreline south of Sarnia, Ontario. In addition, channel dredging and shoreline modifications (bulk-heading and backfilling) have destroyed large areas of valuable habitat in the main channel and along the shoreline. Improvements in the nearshore benthic macroinvertebrate community of the river over the past 20 years show that the river will respond to reductions in contaminants loadings.     

Ontogenetic patterns in prey use by pallid sturgeon in the Missouri River, South Dakota and Nebraska

The pallid sturgeon ( Scaphirhynchus albus ) is an endangered species native to the Missouri and Mississippi rivers. To date, recovery efforts have focused on stocking juvenile fish, but little is known about ontogenetic changes in diet composition. Although diet composition for pallid sturgeon is believed to change from macroinvertebrates to fish, it is unclear at what size and/or age these ontogenetic diet shifts occur. To evaluate diet composition, 29 hatchery-stocked pallid sturgeon (range 356–720 mm fork length [FL]; mean = 549; SE = 23) were collected from the Missouri River downstream of Fort Randall Dam, South Dakota and Nebraska during summer 2006. The majority of pallid sturgeon (72%) were captured within a large delta region formed by the Niobrara River in the headwaters of Lewis and Clark Lake. Predominant prey of pallid sturgeon based on percent occurrence was Ceratopogonidae (81%), Isonychiidae (67%), Chironomidae (52%), and fishes (24%). Percent composition by wet weight showed that diets were composed of fishes (68%), Ephemeroptera (23%), Decapoda (6%), and Diptera (3%). Graphical analysis of combined data showed that mayflies, particularly Isonychiidae, were an important component of pallid sturgeon diets. Nonetheless, the percent composition of fishes in the diet increased with pallid sturgeon body size; for fish > 600 mm FL (5–7 years of age) diets were composed primarily of fish prey (66%, mostly johnny darters Etheostoma nigrum ). These findings highlight the importance of ontogenetic changes in diet composition for pallid sturgeon. Moreover, the unique habitat formed in the delta region is characterized by higher fish and invertebrate densities that may enhance foraging opportunities and thus improve recovery efforts for stocked pallid sturgeon.     

Relating macroinvertebrate community structure to environmental characteristics and sediment contamination at the scale of the St. Lawrence River

There is still no assessment of the impact of sediment chemicals and environmental conditions on macroinvertebrates at the scale of the St. Lawrence River. In order to assess these impacts in the fluvial section of the St. Lawrence River including the Montreal harbour, the community structure of macroinvertebrates using different taxonomic aggregations (genus and family) and taxa attributes (abundance, presence–absence, indicator taxa) was assessed. The goal of the study was to determine the indicator taxa of macroinvertebrates along the fluvial continuum and relate changes in macroinvertebrate community to sediment chemical conditions and environmental characteristics of habitats using variance partitioning. This study also evaluated which taxonomic level and taxa attributes of macroinvertebrates were the most suitable for bioassessment of quality of sediments and habitat environment in the St. Lawrence River. Four different macroinvertebrate assemblages were found distributed along the fluvial continuum using either abundance or presence–absence data and genus or family levels. Indicator taxa characteristic of the different macroinvertebrate communities were associated with the sediment contamination gradient. However, habitat environmental characteristics (water masses, sulphur and DOC in sediments) had more influence on macroinvertebrate assemblages than sediment contamination. Our study confirms that family level analysis can give information comparable to the genus level analysis using presence–absence or abundance of macroinvertebrates, yet a higher number of indicator taxa were detected at the genus level.     

An application of different bioindicators for assessing water quality: a case study in the rivers Alfeios and Pineios (Peloponnisos, Greece)

A number of bioindicators and biotic indices and scores based on benthic macroinvertebrates, diatoms, fishes, aquatic and riparian vegetation in relation to physicochemical parameters have been applied in assessing the water quality of the rivers Alfeios and Pineios (Peloponnisos, Greece). According to the findings, the water quality in both rivers varied from very poor to very good. Among the bioindicators used, the benthic macroinvertebrates seem to be the most reliable. The BBI and IBE were the most applicable indexes while the applicability of the IBMWP and IASPT in the Greek region can be enforced with the inclusion of the Diptreran family Rhagionidae and the Coleopteran family Elminthidae.     

中国东部沿海中小型河流鱼类的整体遗传多样性评价——以曹娥江为例

研究将曹娥江作为东部沿海中小型河流代表, 基于线粒体细胞色素b基因(Cyt b)分子标记对其鱼类的整体遗传多样性水平进行了评估。结果表明, 21个种26个群体鱼类Cyt b基因的单倍型多样性指数(h)和核苷酸多样性指数(π)水平分别为0.074—0.987和0.00019—0.00520, 物种间遗传多样性水平差异较大; 比较不同江段鱼类遗传多样性水平发现, 曹娥江鱼类的单倍型多样性指数水平从河口到中下游再到上游逐渐降低(P<0.05)。比较同一物种的遗传多样性水平发现, 曹娥江鱼类的核苷酸多样性指数水平低于长江、珠江等大型河流鱼类的相应指数水平(P<0.05), 提示曹娥江鱼类的整体遗传多样性处于中等偏下水平, 鱼类资源亟需科学的保护和修复。进一步分析人为扰动因素对曹娥江鱼类遗传多样性水平的影响发现, 敏感型鱼类的单倍型多样性指数水平显著低于中等耐受型鱼类(P<0.05); 麦穗鱼(Pseudorasbora parva)、光泽黄颡鱼(Pelteobagrus nitidus)和刺鳅(Mastacembelus aculeatus)3种鱼类的上游镜岭群体单倍型多样性指数和核苷酸多样性指数水平均低于其中游仙岩群体的相应指数水平。结果提示, 水体污染、过度捕捞可能是造成目前曹娥江鱼类遗传多样性水平较低的主要原因。研究结果将为曹娥江乃至东部中小河流的鱼类资源的管理、保护和开发利用提供重要的理论依据。     

The effects of heavy metals pollution of the upper Arkansas River on the distribution of aquatic macroinvertebrates

Water quality, types, and diversity of aquatic macroinvertebrates show that heavy metal pollution of the upper Arkansas River is presently moderately severe and conditions for aquatic life are generally poor, particularly in the Leadville area. A 2 year study was done on a 30 km section of the upper Arkansas River, Colorado, to determine the effects of heavy metals pollution on the distribution of the aquatic macroinvertebrates. Physical and chemical water parameters were measured, and aquatic macroinvertebrates were collected. The major sources of heavy metal-laden inflows are Leadville Drain, California Gulch, and a number of intermittent flows entering the Arkansas River between Lake Fork and Lake Creek. Important freshening flows are Tennessee Creek, Lake Fork (containing Halfmoon Creek), and Lake Creek.