Periphyton community responses to elevated metal concentrations in a Rocky Mountain stream

The effects of elevated metals on stream periphyton in the Eagle River, a mining impacted river in central Colorado, were assessed in 1991 and 1992 using assemblage information (taxa richness, community similarity) and non-taxonomic measures (biomass, chlorophyll a, autotrophic index). The number of periphyton genera collected ranged from 2 at a site adjacent to abandoned mining operations to 21 at a downstream site, but was not significantly correlated with dissolved metals concentrations. Fragilaria and Achnanthes were the dominant genera at all sites, with Fragilaria dominating the less impacted sites and Achnanthesdominating at the more impacted sites. Taxonomic similarity was greatest among those sites receiving the greatest inputs of metals from mining operations, where the coefficient of similarity ranged from 0.87 to 0.99. Cluster analyses revealed significant differences among sites adjacent to the mine and either the upstream or downstream sites. Chlorophyll a content of periphyton and the autotrophic index in both years showed significant downstream decreases associated with increasing dissolved metals concentrations. Overall, the periphyton community data were able to separate metal contaminated sites from reference or less impacted sites, and responded in predictable ways to increasing metal concentrations of Eagle River water.     

The effects of a new reservoir on the attached diatom communities in Huntington Creek,Utah, U.S.A.

A study was made to determine whether a new reservoir being constructed on Huntington Creek, Utah would have significant effects on the attached diatom communities of the stream. Cluster analysis and other statistical methods indicated only small differences in the diatom communities before and after construction of the dam.     

Leaf breakdown patterns in a NW Italian stream: Effect of leaf type, environmental conditions and patch size

We studied the decomposition process and macroinvertebrate colonisation of leaf packs to determine to what extent leaf consumption and invertebrate abundance depend on the pollution level, season, leaf type and patch size. We exposed 400 leaf packs made of two leaf types, alder and chestnut, at two sites of the Erro River (NW Italy) with different environmental alteration levels. Leaf packs were set out as three patch sizes (alone, or in groups of 6 or 12). A first experiment was carried out in winter and a second in summer. Leaf packs were retrieved after 15, 30, 45 and 60 days of submersion to determine the leaf mass loss and to quantify the associated macroinvertebrates. Natural riverbed invertebrates were collected in the same areas. Patch size, season, leaf type and pollution level significantly affected mass loss. The breakdown process was faster for alder leaves, during summer, at the unpolluted site, and in smaller patches. Leaf type and patch size did not affect macroinvertebrate density and richness, but the highest taxon richness was found in winter and at the unpolluted site. There were more shredders and predators than in the natural riverbed. Our study supports two recent ideas regarding leaf processing in streams: that patch size influences the leaf breakdown rate and that the breakdown rate can be used to evaluate water quality and environmental health.     

Biosynthesis of au nanoparticles by a marine bacterium and enhancing their catalytic activity through metal ions and metal oxides

The authors report that a marine Shewanella sp. CNZ-1 is capable of producing Au NPs under various conditions. Results showed that initial concentration of Au(III), pH values and electron donors affected nucleation of Au NPs by CNZ-1, resulting in different apparent color of the as-obtained bio-Au NPs, which were further characterized by UV-Vis, TEM, XRD, and XPS analyses. Mechanism studies revealed that Au(III) was first reduced to Au(I) and eventually reduced to EPS-coated Au⁰ NPs. FTIR and FEEM analyses revealed that some amides and humic acid-like matters were involved in the production of bio-Au NPs through CNZ-1 cells. In addition, the authors also found that the catalytic activity of bio-Au NPs for 4-nitrophenol (4-NP) reduction could be enhanced by various metal ions (Ca²⁺, Cu²⁺, Co²⁺, Fe²⁺, Fe³⁺, Ni²⁺, Sr²⁺, and Cr³⁺) and metal oxides (Fe₃O₄, Al₂O₃, and SiO₂), which is beneficial for their further practical application. The maximum zero-order rate constant k ₁ and first-order rate constant k₂ of all metal ions/oxides supplemented systems can reach 99.65 mg/(L^.min) and 2.419 min⁻¹, which are 11.3- and 12.6-fold higher than that of control systems, respectively. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2727, 2019.     

The effects of habitat complexity and hydraulic conditions on the establishment of benthic stream macroalgae

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Structural and functional responses of benthic macroinvertebrates to acid precipitation in two forested headwater streams (Vosges Mountains, northeastern France)

From December 1996 to August 1997, beech litter breakdown and stream benthic macroinvertebrate communities were investigated to assess the effects of acidic precipitation on community structure and function in two second-order headwater streams of the Vosges Mountains (NE France). Because of microscale changes in bedrock mineral composition, one of the streams was acidified (mean pH=4.53, mean total Al=421 g.l^-1) and the other circum-neutral (mean pH=7.23, mean total Al=36 g.l^-1). Results showed that both litter breakdown rate and macroinvertebrate community structure were drastically affected under acidic conditions. The rate of leaf litter breakdown decreased by nine times in the acidic stream. Benthic sampling showed that scrapers were totally eradicated and both gathering and filtering collectors were drastically reduced. Such drastic effects appear to be the consequences of the toxicity of acid water including both proton and aluminum toxicity. A decrease in shredder abundance and a shift from the efficient acid-sensitive Amphipoda Gammarus fossarum to acid-tolerant Nemouroidea (mainly Leuctra sp.) was observed in the acidic stream. Our results indicate that freshwater acidification significantly alters the action of shredders processing leaf litter in the acidic stream. Consequently, interactions between structural and functional responses to acidification probably have profound consequences on the efficiency of acidified stream ecosystems, which in return may alter downstream functioning.     

Species composition,abundance and emergence phenology of midges (Deiptera: Chironomidae) in a brown-water stream of West-Central Alberta,Canada

Sixteen floating, box type emergence traps, each covering 0.1 m², were placed along 150 m of a third-order stretch of the Bigoray River, a slow-flowing, vegetation-choked, brown-water muskeg stream. Effects of trap design, trap shading, length of sampling interval, and stream velocity on the number of midges caught was examined. Of the 112 species of Chironomidae caught, 32 species made up 90% of the catch and their emergence phenology is described in detail. There were more rare species than expected from Preston's lognormal distribution. Percentage of Bigoray species belonging to Tanypodinae, Orthocladiinae, Chironomini and Tanytarsini was 18%, 43%, 20%, and 19%, and was compared with 27 other studies on lotic chironomids. During the 140-day emergence period an average of 19.3 × 10³ chironomids emerged per square meter of stream. Based on changes in male:female ratios throughout a species emergence period, it was postulated that 30% of the Bigoray chironomid species were univoltine, 50% were bivoltine, and 20% were trivoltine.     

The impact of repeated insecticidal treatments on drift and benthos of a headwater stream

A small first-order, Appalachian Mountain stream received successive seasonal treatments with the insecticide, methoxychlor. Despite an application rate of 10 mg/1 methoxychlor for 4 hours, based on stream discharge, only a small fraction (1.6%) of the insecticide was exported to downstream reaches for a 31 h period during and following treatment. Most of the insecticide was incorporated into sediments of the streambed, which had residues ranging from 0.038 to 11.7 µg methoxychlor/g dry wt of sediments in June 1986 following treatments in December 1985 and March 1986. Despite low concentrations of methoxychlor measured in stream water (maximum = 128 µg/l) during the initial treatment, massive drift (> 950 000 organisms, and 70 g AFDM biomass) occurred from a stream area of about 144 m². Numerically, collector-gatherer taxa (primarily Chironomidae) dominated drift (63 %) followed by shredders and predators; however, biomass of drift was dominated by shredders (48.9%), followed by predators and collector-gatherers. Compared with pre-treatment benthic abundances, insects were reduced by 75% following the initial treatment in December 1985, and 85% following an additional treatment in March 1986. Benthic abundances of non-insect taxa showed no significant changes. Benthic abundances of shredder, collector-filterer, and scraper functional groups exhibited significant decreases in the first month following treatment. Although benthic abundances of collector-gatherer and predator taxa were reduced by 48.6 and 40.5%, respectively, the reduction was not statistically significant because of high-sample variance. Comparisons of drift composition during the initial treatment with successive quarterly treatments (March 1986 to January 1988) reflected of ongoing pesticide disturbance of the biota as the community structure shifted from one consisting of a diverse insect and non-insect fauna toward one dominated by copepods, oligochaetes, Collembola, and chironomids.     

Macroinvertebrate survival during cessation of flow and streambed drying in a lowland stream

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Suspended particulate oxides and organic matter interactions in trace metal sorption reactions in a small urban river

The relative scavenging abilities of suspended particulate oxides (SPOX), and organic matter (SPOM) for Cd, Zn and Cu were evaluated in a small, anthropogenically influenced river. In addition, the factor most important in influencing the sorption density (A_d: metal concentration associated with a given phase divided by the concentration of that geochemical phase in the suspended particulate pool) of each metal to SPOX and SPOM were identified through multiple linear regression analyses from the suite of: pH, temperature, dissolved metal concentration, and the concentration of the other particulate fraction. Results indicate that SPOX-SPOM interactions do occur in trace metal complexation reactions; and interactions are both phase and cation specific. Fe oxides are able to outcompete discrete organic binding sites for Cu and Zn as a relative decrease in the amount of these two cations sorbed to organic matter was observed with increasing particulate Fe oxides. SPOM concentration was identified as being most important in influencing Cu sorption densities associated with the SPOX fraction. Organic matter — oxide complexes are postulated to occur that enhance oxide sorption of Cu such that relatively more Cu is sorbed to particulate oxides with increasing particulate organic matter concentrations. Dissolved concentrations of Cd and Zn were found to be most important in influencing the sorption densities for these two metals associated with the oxides fraction. The sorption behaviour appears to follow Freundlich isotherm behaviour where the amount sorbed is a function of the dissolved concentration.     

The St. Lawrence River in winter: population structure,biomass, and pattern of its primary and secondary food web components

Plankton and benthic invertebrate populations were examined along a 160 km section of the St. Lawrence River between Lake Ontario and Waddington, New York during a period of ice cover. Algal biomass was low in winter with diatoms and cryptomonads the most prominent forms. Zooplankton biomass was about one-tenth the algal standing crop and cyclopoid copepods predominated. Phytoplankton and zooplankton biomass declined downriver providing evidence that most plankton was imported from Lake Ontario. Benthic invertebrate standing crop was greatest near Lake Ontario where molluscs were abundant. The downriver macroinvertebrate community shifted to coarse particle feeders, namely annelids and chironomids. Beds of accumulated detrital material derived primarily from dieback of macrophytes were particularly rich in benthic invertebrates.     

The effects of shrimps on benthic material in a Brazilian island stream

1. Shrimps are abundant in many tropical coastal streams. Studies in Central America and the Caribbean have demonstrated the importance of shrimps in removing sediments and altering the composition of the benthos. Previous work in our study area showed that ephemeropterans and not shrimps were important in removing benthic material. 2. Here we used an experimental exclusion to test the hypothesis that shrimps exert strong influence on sediment dynamics with direct and indirect effects on the benthic algal and faunal community at a site where they are the predominant element of macrofauna. We used electricity to exclude Macrobrachium olfersi and Potimirim glabra from small quadrats (0.135 m²) for 34 days in a stream located at Ilha Grande, Rio de Janeiro state, Brazil. We analysed benthic sediment dynamics and community colonisation during this period on artificial substrates in electrified and not‐electrified quadrats. 3. Significantly higher sediment accrual had occurred in the electrified treatment after 14 days and persisted for the 34‐day course of the experiment; substrates protected from shrimps contained about four times as much ash‐free dry mass (AFDM) as those of the controls. After 34 days, significantly more pennate diatoms were present in the exclusion treatment, but chlorophyll was not significantly different between treatments. Densities of baetid ephemeropteran nymphs were significantly higher in the presence of shrimps. 4. We attribute all these effects to the atyid P. glabra, the more abundant and active shrimp observed in the control treatment. Our results suggest that atyid shrimps played an important role related to sediment removal on hard substrate by direct ingestion and ‘bioturbation’. They reduced certain components of the periphyton (pennate diatoms) without affecting primary production (chlorophyll a). The activity of these shrimps on periphyton affected also faunal components such as baetid ephemeropterans and seems to determine the composition of the benthic community.     

基于河道-湿地-缓冲带复合指标的京郊河溪生态评价体系

河溪是陆地水环境的基本组成单位,对人类的生产,生活产生着重要的影响。河溪近自然生态评价是以自然状态河段为本底值,对人为活动或自然条件突变所造成的退化河溪生态系统的结构和功能作整体健康评判．基于河道-湿地-缓冲带复合指标的京郊河溪近自然生态评价体系以野外大量调查数据为基础,按照科学性、目标性、系统性、独立性、可操作性的原则,从生态、地貌、水文特征方面挑选相互匹配的22个定量指标和13个定性指标,将评价过程分为定性评价和定量评价,综合考虑两者的长处以避免评价结果过于主观．并由于该评价是基于多指标和多点调查得到的,评价的结果容易受到采样中随机性的影响,存在模糊性和概率性,因此,采用模糊概率评价的方法,构建该评价体系。并综合考虑一个平衡河溪水生生态系统的特点以及水环境特有的地形地质和群落状况等因素的差异,可以将河溪的近自然程度分为以下4个等级：Ⅰ自然状态;Ⅱ河溪受到轻微人类活动的侵扰（近自然状态）;Ⅲ河溪受到剧烈人类活动的侵扰（退化自然状态）;Ⅳ完全人工化,并在4个等级之间划分出3个过渡带,以表明河溪生态系统的动态转化过程．最后利用该评价体系对位于怀柔区二级水源保护区内的怀九河进行了分段近自然生态评价,以避免某调查点数值突变对整个河溪评价结果造成影响．     

Benthic community metabolism in four temperate stream systems: An inter-biome comparison and evaluation of the river continuum concept

Benthic community metabolism was studied on four stream systems located in different biomes in the United States: the eastern deciduous forest (Pennsylvania, PA, and Michigan, MI), the high desert (Idaho, ID), and the coniferous forest (Oregon, OR). Studies were designed to test the hypothesis advanced within the River Continuum Concept that a transition in community metabolism will occur from a predominance of heterotrophy in headwaters to a predominance of autotrophy in mid-sized reaches, with a return to heterotrophy further downstream. Both gross primary productivity (GPP) and community respiration (CR₂₄) increased with downstream direction on all systems. Net daily metabolism (NDM, or GPP – CR₂₄) shifted from heterotrophy (–NDM, GPP < CR₂₄) to autotrophy (+NDM, GPP > CR₂₄) with downstream direction at all sites, supporting the hypothesis. Annual metabolism in the most upstream reach of all sites was dominated by respiration; however, the farthest downstream reach was not necessarily the most autotrophic. Site-specific factors affected manifestation of the trend. Photosynthesis predominated annual metabolism in reaches (designated 1–4 in order of increasing size) 2–4 in ID, 3 and 4 in OR, and 4 in MI. In PA annual photosynthesis was slightly greater than respiration only at Station 3. Photosynthesis was predominant most consistently in ID and respiration most often in PA. About half the reaches that were heterotrophic annually were autotrophic at one or more seasons. Annual means of benthic GPP, CR₂₄ and NDM ranged from 0.16 to 3.37, 0.36 to 2.88 and –0.73 to 0.50 g O₂ · m² · d¹, respectively. Metabolic rates were usually high in PA and MI (and sometimes ID) and almost always lowest in OR. Parameters accounting for most variance in multiple linear regression analyses of the combined metabolism data from all sites were indicators of stream size, photosynthetically active radiation, temperature, and chlorophyll a concentration.     

Seasonal and temperature‐related movement of Colorado River cutthroat trout in a low‐elevation,Rocky Mountain stream

Mobile species will migrate considerable distances to find habitats suitable for meeting life history requirements, and stream‐dwelling salmonids are no exception. In April–October 2014, we used radio‐telemetry to examine habitat use and movement of 36 Colorado River cutthroat trout Oncorhynchus clarkii pleuriticus (CRCT) in a 14.9‐km fragment of Milk Creek, a relatively low‐elevation stream in the Rocky Mountains (Colorado). We also used a network of data loggers to track stream temperature across time and space. Our objectives were to (1) characterize distribution and movement of CRCT, (2) evaluate seasonal differences in distribution and movement of CRCT, and (3) explore the relationship between stream temperature and distribution and movement of CRCT. During the course of our study, median range of CRCT was 4.81 km (range = 0.14–10.94) and median total movement was 5.94 km (range = 0.14–26.02). Median location of CRCT was significantly further upstream in summer than in spring, whereas range and movement of CRCT were greater in spring than in summer. Twenty‐six of the 27 CRCT tracked through mid‐June displayed a potamodromous (freshwater migratory) life history, migrating 1.8–8.0 km upstream during the spring spawning season. Four of the seven CRCT tracked through July migrated >1.4 km in summer. CRCT selected relatively cool reaches during summer months, and early‐summer movement was positively correlated with mean stream temperature. Study fish occupied stream segments in spring and fall that were thermally unsuitable, if not lethal, to the species in summer. Although transmitter loss limited the scope of inference, our findings suggest that preferred habitat is a moving target in Milk Creek, and that CRCT move to occupy that target. Because mobile organisms move among complementary habitats and exploit seasonally‐unsuitable reaches, we recommend that spatial and temporal variability be accounted for in delineations of distributional boundaries.     

The effect of salmon redd excavation on stream substrate and benthic community of two salmon spawning streams in Canterbury,New Zealand

The effects of redd excavation by female quinnat salmon (Oncorhynchus tshawytscha walbaum) on the bentic invertebrate communities of two stable springfed spawning streams in the headwaters of the Rakaia River, South Island, New Zealand, were studied during January to September 1982. The gross effects of salmon spawning on the streams appear to be: the loss of instream macrophytes, algae and mosses, a loss of fines and detritus, and a modification of the pool-riffle character. Redd excavation may be associated with a reduction in benthic standing crop of up to 83.6%, with only a minor effect on the benthic community structure. Benthic recolonisation rates were similar for both spawning streams, with almost complete recovery after 95 days.     

Spatial and temporal occurrence of invertebrates in a chalk stream,Berkshire, England

The invertebrate assemblages of the River Lambourn and its tributary, the Winterbourne stream, were investigated as part of a broad ecological study prior to water resource development in the catchment. The longitudinal distribution of the invertebrate fauna within the Winterbourne stream was examined in detail and supporting data for the R. Lambourn revealed that the upstream intermittent section of each water course had an invertebrate assemblage which was distinct from the fauna downstream where flow was permanent. Within the perennial zone taxon richness tended to increase downstream.A one-year programme of monthly quantitative sampling on five distinct biotopes (Ranunculus, Berula, Callitriche, gravel and silt) at two contrasted sites (shaded and unshaded) was undertaken in the lower perennial of the R. Lambourn below the confluence with the Winterbourne. On each study site, the taxon richness, numerical abundance and biomass of invertebrates were significantly higher on the three macrophytes than on gravel and silt. There were also statistically significant seasonal changes in the biomass of invertebrates on each site. Estimates of total biomass of invertebrates per site revealed a late spring peak (May/June) and a late autumn (November/December) peak, neither of which coincided with the summer peak biomass of macrophytes. This suggested that, in the lower perennial, the level of food resources (epiphytic algae in late spring and fallen tree leaves plus decaying macrophytes in autumn) rather than available habitat, were a major influence on population levels for most of the year.Quantitative sampling of each biotope on each site continued in June and December only for a period of 8 years (1971–78), during which time the river experienced a minor drought (1973) and a severe drought (1976). The Chironomidae showed a strong positive response to conditions of low flow in June of 1973 and 1976, when exceptionally high densities of larvae were recorded. Although further between-year differences were recorded in several other major components of the invertebrate fauna, which may have been related to conditions of low discharge, they did not have long-term consequences for the fauna in the lower perennial of the R. Lambourn.In contrast, in the upper perennial, the prolonged drought of 1976 resulted in the loss of wetted perimeter and macrophytes, coupled with deposition of silt, all of which had deleterious effects on the invertebrate assemblages. The following year, despite a normal discharge regime and the removal of silt, some submerged macrophytes were slow to return to their pre-drought condition. In the intermittent section, the drought of 1976 resulted in the total loss of flow for a 16 month period instead of a more typical four month period of water loss.Thus, chalk streams encompass within a single system both stable and extreme hydrological regimes which offer unique opportunities for investigating the processes of community formation and maintenance.     

Decomposition and colonisation by invertebrates of native and exotic leaf material in a small stream in New England (Australia)

In many parts of south-eastern Australia, native riparian vegetation has been cleared and exotic willows planted. In order to evaluate some of the possible effects of this practice, the decomposition and colonisation by invertebrates of the leaves of three native plant species along with those of willow were examined.Decomposition of leaves of the willow Salix babylonica L. and the indigenous macrophyte Myriophyllum propinquum A. Cunn. was much faster than for leaves of the indigenous trees Eucalyptus blakelyi Maiden and Casuarina cunninghamiana Miq. Both macroinvertebrates and current were found to have a significant influence upon decomposition. The pattern of preferential colonisation suggested that plant detritus represented a primary food source for invertebrates and not simply a refuge. Colonisation was found to be a function of the stage of decomposition, regardless of plant species. The lower temporal availability of willow leaves compared to the native evergreen tree leaves appears to be insufficient to enhance the production of the benthic macroinvertebrates.     

Effects of omnivorous shrimp in a montane tropical stream: sediment removal,disturbance of sessile invertebrates and enhancement of understory algal biomass

Freshwater shrimp dominate the faunal biomass of many headwater tropical streams: however, their role in community organization is unclear. Enclosure/exclosure experiments in a montane Puerto Rican stream examined direct and indirect effects of two dominant taxa of atyid (Atyidae) shrimp, Atya lanipes Holthuis and Xiphocaris elongata Guerin-Meneville. Both shrimp taxa caused significant reductions in sediment cover on rock substrata, reducing sedimentation and enhancing algal biovolume on clay tiles in cages. When tiles incubated in shrimp exclosures for 2 wks were placed outside of cages, atyid shrimp removed 100% of the sediment cover within a 30 min observation period. Atyid shrimp appear to play an important role in stream recovery after high discharge events by rapidly removing sediments and detritus deposited on benthic substrata in pools. We evaluated the mechanism by which A. lanipes influences algae and benthic insects by comparing patterns of algal biomass, taxonomic composition, and insect abundance between shrimp-exclusion and shrimp-presence treatments both with and without manual sediment removal. The shrimp exclusion treatment without manual sediment removal bad significantly lower algal biomass and greater sedimentation than all other treatments. The treatment in which shrimp were excluded but sediment was manually removed, however, accrued almost the same algal biovolume as the shrimp enclosure treatment, supporting the hypothesis that sediment removal enhances the biovolume of understory algal taxa. Algal community composition was similar between stream bottom bedrock exposed to natural densities of shrimp and all experimental treatments for both Atya and Xiphocaris: a diatom community strongly dominated (78–95%) by the adnate taxon, Achnanthes lanceolata Breb ex. Kutz. Atyid shrimp are important in determining the distribution and abundance of benthic insects through both direct and indirect effects. Sessile, retreat-building chironomid larvae (Chironomidae: Diptera) are negatively affected by both A. lanipes and X. elongata, through direct removal by foraging activities and/or indirectly through depression of sediment resources available to larvae for the construction of retreats. In constrast, the mobile grazer, Cloeodes maculipes (Baetidae: Ephemeroptera) was not adversely affected and atyid shrimp have the potential to exert positive indirect effects on this taxon by facilitating its exploitation of algal resources and/or through enhancement of understory algal food resources through sediment removal.