Effects of acid mine drainage on a Southwestern Pennsylvania stream

Physicochemical parameters and benthic macroinvertebrate community structure were studied in a small valley stream in southwestern Pennsylvania. Sampling stations were located upstream and downstream of coal mine drainage input. Due to an alkaline discharge and significant downstream alkalinity the pH below the mine effluent remained between 5.8 and 7.0 throughout the course of this 18 mo study. The major factor affecting the benthic community seemed to be ferric hydroxide deposition. Certain taxa (Plecoptera and Ephemeroptera) were abundant at station sites above the mine discharge, while only those taxa tolerant of polluted conditions, such as Chironomidae and Tubifex, were prevalent at the downstream station sites. An analysis of benthic populations through changes in total numbers, species diversity, and species indicator organisms graphically demonstrated environmental stress within this aquatic ecosystem.     

Bacterial phylogenetic diversity in a constructed wetland system treating acid coal mine drainage

Microorganisms in acid mine drainage are typically acidophiles that mediate the oxidation of reduced compounds of iron and sulfur. However, microbial populations in wetland systems constructed to treat acid mine drainage are not well characterized. The purpose of this study was to analyze bacterial diversity, using cultivation-independent molecular ecological techniques, in a constructed wetland that received acid drainage from an abandoned underground coal mine. DNA was purified from Fe(III)-precipitates from the oxidized surface zone of wetland sediments and 16S rRNA gene sequences were amplified and cloned. A total of 200 clones were analyzed by restriction fragment length polymorphism (RFLP) and 77 unique RFLP patterns were obtained with four restriction enzymes. Of these patterns, 30 most dominant unique clones were selected for sequencing of their 16S rRNA genes. Half of these 30 clones could be matched with autotrophic iron- and sulfur-oxidizing bacteria (Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans). Several clones also formed a clade with heterotrophic iron-oxidizing bacteria (TRA2-10, TRA3-20, and TRA5-3) and heterotrophic bacteria (Stenotrophomas maltophilia, Bordetella spp., Alcaligenes sp., Alcaligenes faecalis, and Alcaligenes xylosoxidans). Approximately 40% and 35% of the analyzed RFLP restriction patterns were consistent with A. ferrooxidans and A. thiooxidans, respectively. The relatively high frequency of acidithiobacilli is consistent with the chemical and physical characteristics of this site—i.e., continuous, abundant supply of reduced iron and sulfur compounds, pH 3–4, ambient temperature, and limited organics originating from the coal seam and from vegetation or soil surrounding the inlet channel to the wetland. The RFLP results were consistent with our previous culture-independent PCR-DGGE and FISH study, showing relatively low bacterial diversity and predominance of mesophilic acidithiobacilli in oxic wetland sediments.     

The effects of dredging operations on the benthic community of a chalk stream

Sampling of the benthic fauna showed that dredging operations produced relatively short-term effects on invertebrate population levels. The behaviour of the animals was immediately affected, the differences between species were noted and the implications of dredging at different times of year are discussed.     

Deforesting the riverscape: the effects of wood on fish diversity in a Venezuelan piedmont stream

While deforestation of tropical ecosystems has been shown to have significant impacts on terrestrial habitats, its effects on aquatic habitats are poorly studied. Deforestation dramatically reduces the input of woody debris to streams, and given the importance of large woody debris to fish communities in temperate streams, this might be one mechanism by which logging could affect aquatic ecosystems in the tropics. To examine the effects of large woody debris on the diverse fish assemblage of a tropical stream, we surveyed pools with and without wood at Rio Las Marias, Venezuela. Pools containing wood contained greater numbers of individuals and more species of fish than pools without wood, and the two types of pools differed in their composition. To test whether these results were due to the presence of woody debris, we conducted an experimental wood addition. Pools to which wood was added showed marked increases in both fish abundance and species richness relative to wood-free pools, and the composition of the fish assemblage in experimental pools approached that of pools with naturally occurring woody debris. These results demonstrate that large woody debris plays a major role in structuring fish communities in tropical streams. As a consequence, logging practices that reduce the input of woody debris to tropical streams or directly remove wood from streams could have serious impacts on aquatic habitats, affecting both the diverse fish communities and local economies dependent on stream fisheries.     

Temporal and spatial variations in dominance,diversity and biotic indices along a limestone stream receiving a trout farm effluent

Benthic macroinvertebrate response to organic pollution generated by a trout farm, located in the upper Rio Tajuña (Central Spain), was evaluated by calculating Whittaker's and Camargo's dominance indices; Margalef s, Menhinick's, Camargo's, Shannon's and MacArthur's diversity indices; and several biotic indices, including the Trent Biotic Index (TBI), the Chandler Biotic Score (CBS), the Biological Monitoring Working Party (BMWP), the Average Score Per Taxon (ASPT) and the Overall Quality Rating (OQR). An upstream sampling site (S-1) and three downstream stations placed 10 (S-2), 150 (S-3) and 1000 (S-4) m below the fish farm outlet were selected along the study area. Site S-3 was situated just below a man-made waterfall (1.8 m in height). Winter, spring and summer macrobenthic surveys were conducted during 1986. Plecopterans, ephemeropterans, coleopterans, trichopterans, amphipods and planarians decreased in abundance or were basent at downstream sampling sites, whereas simuliids, leeches, chironomids and tubificid worms increased in abundance. All diversity and biotic indices had highest and lowest values at S-1 and S-2, respectively, and higher values at S-3 (below the waterfall) than at S-4. However, Shannon's and MacArthur's diversity indices and the TBI were less effective in quantifying differences among sampling sites, exhibiting the lowest positive coefficients of linear correlation with species richness and other diversity and biotic indices. Both dominance indices had highest values at S-2, but similar values at S-1, S-3 and S-4. Biotic indices (except the TBI) and Margalef s, Menhinick's and Camargo's diversity indices appear to be the most sensitive measures for assessing macroinvertebrate response to changes in environmental conditions downstream from the fish farm. In addition, temporal variation in species richness, Margalef s index and biotic indices was similar, exhibiting their highest coefficients of variation at S-4. It is concluded that small waterfalls may improve the streamns self-purification of organic pollution generated by trout farms.     

Transitory dynamic effects in the soil invertebrate community in a temperate deciduous forest: Effects of resource quality

The importance and strength of bottom-up forces in terrestrial soil systems are poorly understood. In contrast to aquatic systems, where trophic cascades and top-down forces dominate, it has been postulated that terrestrial systems are regulated mainly by bottom-up forces. We set up a 17 month field experiment to study the effects of addition of resources of different quality (wood, wheat bran, pet food, and glucose+phosphorous+nitrogen) on the soil micro-, meso- and macrofauna as well as on microbial biomass, ergosterol content and abiotic parameters (soil pH, water content, carbon and nitrogen content) in a beech forest (Fagus sylvatica) on sandstone. We hypothesized that bottom-up effects will be strong on lower trophic levels resulting in increased biomass of bacteria and fungi, and that this increase will propagate to higher trophic levels (microbivorous invertebrates, predators) but with decreasing intensity due to dampening of bottom-up forces at higher trophic levels by high connectivity, trophic-level-omnivory and generalist feeding. The results of the study in general did not support these hypotheses. Microbial biomass only moderately increased after resource addition, and while densities of several animal groups increased (lumbricids, nematodes, collembolans, gamasid mites, staphylinid beetles), densities of other groups declined (oribatid mites, prostigmate mites, lithobiids), and a large number of taxa remained unaffected (enchytraeids, diplopods, uropodine mites, pseudoscorpions, spiders). We conclude that (a) bottom-up forces are of limited importance in the soil system of temperate deciduous forests, (b) large primary decomposers, such as earthworms, do not depend on microorganisms as food but consume organic matter directly, (c) the link between microorganisms and microbivores, such as collembolans, is weak since collembolan density increased even though microbial biomass was unaffected, (d) habitat modification by ecosystem engineers, such as earthworms, is more important than resource availability for a number of soil invetebrates including prostigmate mites and centipedes, and (e) the soil food web in general is rather resistant responding little to changes in resource supply. The results also suggest that species which commonly are assigned to single trophic groups, such as collembolans, differently respond to changes of the base of the food web. Increased fungal biomass led to an increase in the density of Folsomia quadrioculata s.l. and Isotomiella minor, whereas the increased bacterial biomass was accompanied by an increase in density of Ceratophysella denticulata and Isotoma notabilis.     

Recovery of benthic invertebrate communities in silver bow creek,montana, following improved metal mine wastewater treatment

Silver Bow Creek, a tributary of the Clark Fork River in southwest Montana, has been affected by metal mining and domestic wastes for over 100 yr. The invertebrate community was monitored at five stations from 1972 through 1983 to determine both the longitudinal and temporal patterns of recovery following major improvements in mine wastewater treatment. This treatment dramatically reduced metal concentrations in the mine discharge. Despite markedly improved water quality, no invertebrates were collected in Silver Bow Creek until 1975, when small numbers of invertebrates (primarily chironomids) were collected at the furthest downstream stations. A few invertebrates (<75 m^?2) were collected for the first time at Stations 1 and 2 in 1981, although the lower stations still had much greater densities (> 1600 m^?2). The earliest colonizers at each station were chironomids, empidids, and oligochaetes. In 1982, 10 yr after initiation of improved water quality, aquatic insect populations were over 1800 m^?2 at all five stations. Populations dropped in 1983, but upper and lower stations had comparable densities suggesting that the stream is responding to a common stress such as high snowmelt runoff. The relatively long recovery time is partially attributed to the lack of an undisturbed headwater source of colonizers.     

Effects of experimental acidification on macroinvertebrate drift diversity in a mountain stream

A small stream (Norris Brook) within the Hubbard Brook Experimental Forest was acidified to determine what effect elevated H⁺ stress may have on the ecology of a mountain stream. The experiment was designed to simulate a pH level (4.0) that can occur during initial snowmelt (acute period) and during longer term (chronic period) acidification. Daily macroinvertebrate drift samples were collected from treatment and reference areas of Norris Brook. Drift diversity at the generic level was calculated using Brillouin's formula and partitioned hierarchically following macroinvertebrate classifications based on taxonomy (orders) and feeding strategies (functional groups or guilds). The rate of movement of individuals and genera was significantly greater for those organisms leaving the acid-stressed area during the first five days than for those entering, whereas no difference between the rate of macroinvertebrates entering or leaving the acid-stressed area was apparent for either numbers or genera over the remaining 25-day study period. For the acute period (first five days), the increased macroinvertebrate drift leaving the acidified area was significantly more diverse at the levels of aquatic insect orders and functional groups but less diverse at the generic level than the drift entering. For the chronic period (25-day period) no significant differences were detected in either major taxa, functional group (with the exception of collectors), or generic diversity between the drift entering and leaving the treatment reach. Mayflies and probably chironomids leaving the acid-stressed area during the acute period were generically more diverse than those entering, whereas stoneflies drifting out of the acidified reach were generically less diverse than those drifting in. The overall change in the normal pattern of spatial and temporal variation in drift rate and diversity provides quantitative evidence that H⁺ stress significantly altered the structure and function of the macrobenthic community.     

The effects of earthworm functional group diversity on earthworm community structure

A comprehensive understanding of how species/functional group interactions determine population dynamics, community composition and their effect on ecosystem functioning is necessary if we are to understand the consequences of species loss. This paper presents data from a mesocosm experiment, based on the simplex design, to examine the effect of interactions between earthworm functional groups, food supply and initial overall biomass on community structure. All communities containing anecic species moved towards domination by anecics. The survival of anecics remained constant irrespective of initial conditions, with no effect of initial community structure, food supply or initial biomass. The proportional biomass of epigeics increased when they were placed in communities dominated by anecics. Initial overall biomass had a significant effect on the survival of endogeics, with increased survival at low biomass. Juvenile production was significantly increased in communities that contained a higher initial abundance of epigeics. The anecics had significantly increased production of juveniles at lower levels of initial biomass. Overall, earthworm functional group diversity had an idiosyncratic effect on earthworm assemblage structure but the presence of synergistic interactions suggests that the persistence and optimal contribution of the earthworm assemblage to ecosystem service is dependent on the presence of a number of functional groups.     

转Bt基因棉对土壤无脊椎动物群落结构的影响

采用干、湿漏斗分离法,运用群落生态学方法,研究了转Bt基因棉"GK12"和"新棉33B"对棉田0～15 cm土层土壤无脊椎动物群落结构的影响.结果表明,线虫和螨类为棉田土壤无脊椎动物优势类群,其频度分别为54%以上和18%以上,与亲本常规棉"泗棉3号"相比,"GK12"提高了土壤线蚓数量,但降低了某些土壤无脊椎动物类群(如同翅目、目和双翅目)的数量;两种Bt棉田中,"新棉33B"棉田的同翅目昆虫数量显著高于"GK12",蜘蛛目数量显著低于"GK12"棉田,其他土壤无脊椎动物类群的数量则基本上无显著差异."GK12"显著降低了土壤无脊椎动物类群的丰富度、多样性和均匀度;两种Bt棉中,"新棉33B"棉田土壤无脊椎动物类群的丰富度、多样性和均匀度较高.Renyi多样性指数曲线也表明,"GK12"棉田各土层土壤无脊椎动物群落的多样性均显著低于"泗棉3号"棉田;"新棉33B"棉田各土层土壤无脊椎动物群落的多样性高于"GK12",但10～15 cm土层常见类群和优势类群的多样性较低.在各土层中,土壤无脊椎动物数量、多样性指数和均匀度指数动态在不同类型棉田趋势基本相同.7～11月期间,10月是土壤无脊椎动物数量的高峰期,此时在"泗棉3号"棉田土壤无脊椎动物在0～5 cm的表层和10～15 cm的深层土壤均较多,在"GK12"和"新棉33B"棉田则集中于10～15 cm的深层土壤.11月, "泗棉3号"土壤无脊椎动物类群的多样性和均匀度呈下降趋势,"GK12"则呈上升趋势.可见,种植Bt棉"GK12"可改变某些土壤无脊椎动物类群的数量,降低类群的丰富度、多样性和均匀度;两种Bt棉田的土壤无脊椎动物群落结构也有一定的差异,"新棉33B"棉田土壤无脊椎动物群落的多样性高于"GK12".     

毛竹入侵杉木林对土壤真菌群落多样性的影响

为揭示凤阳山毛竹入侵杉木林后土壤真菌群落结构组成和多样性的变化,采用Illumina Miseq 测序技术,分析杉木纯林、毛竹纯林及毛竹入侵后的杉木林真菌群落结构特征。结果表明:3 种林型的土壤真菌类群为26 门60 纲113 属415 OTU,子囊菌门和担子菌门是绝对优势的两个菌门。两者的丰度占真菌总量80.80% ～ 83.92%,在3 种林型间均不存在显著差异。识别出的1% 以上的优势菌纲有8 个,为古根菌纲、伞菌纲、粪壳菌纲、锤舌菌纲、银耳纲、球囊菌纲、散囊菌纲和酵母菌纲。古根菌纲和伞菌纲占真菌总量的50.82% ～ 75.40%。古根菌纲在毛杉混交林的相对丰度显著高于毛竹纯林(P<0.05),与杉木纯林无显著差异。Archaeorhizomyces 为优势菌属(20.07% ～ 51.51%)且在毛杉混交林中最高、在毛竹纯林最低,毛杉混交林中全氮、碱解氮和速效钾含量均显著低于杉木纯林和毛竹纯林。土壤真菌优势菌属水平丰度与土壤环境因子的斯皮尔曼相关性分析表明,全磷与Meliniomyces、毛壳菌属、Hodophilus、瓶霉属、Heterocephalacria 呈显著正相关(P<0.05),与Wickerhamomyces 呈极显著正相关(P<0.01)。毛竹入侵杉木林后土壤理化性质变化显著,全磷、有效磷、pH、速效钾和碳磷比是影响土壤真菌群落结构的主要环境因子,研究结果可为控制毛竹扩张,维护生态稳定和多样性提供科学依据。     

Conserving ground-dwelling beetles in an endangered woodland community: Multi-scale habitat effects on assemblage diversity

Patterns of biodiversity are influenced by habitat features at multiple spatial scales, yet few studies have used a multi-scale approach to examine ground-dwelling beetle diversity patterns. We trapped and quantified ground-dwelling beetle assemblages at two spatial scales: (1) microhabitat elements, represented by open ground, ground under trees and ground next to logs and (2) macrohabitat, represented by three vegetation types in a box-gum grassy woodland in south-eastern Australia. Species richness and evenness was highest at samples from under trees and lowest at samples in the open. At the macrohabitat scale, species richness and evenness did not differ among vegetation types. Assemblage composition was significantly different between trees, logs and open elements. Assemblage composition was different only between vegetation types with contrasting high and low shrub cover. Estimation of true species richness indicated assemblages at logs may have a higher number of species compared to trees and open elements, and implied greater spatial heterogeneity in assemblages at logs. Significant spatial autocorrelation in beetle assemblages was detected for logs at up to 400 m, but not for ground under trees or in the open. In agreement with previous studies, a mix of vegetation types at the macrohabitat scale is important for beetle conservation. Assemblage composition, however, appears to be more closely linked with habitat elements at the microhabitat scale, where logs support a high diversity of beetle species. This strongly supports the idea that restoring logs to box-gum grassy woodlands would be useful for increasing beetle species richness and assemblage heterogeneity.     

Ameba community dynamics and diversity in a desert ecosystem

A field study was conducted to monitor the effect of different desert shrub ecophysiological adaptations on the composition, size, and diversity of soil free-living amebae. Population diversity was also analyzed using four morphological types. Samples were collected seasonally under the canopy of the common desert shrubs Artemisia herba alba, Reaumuria negevensis, and Noea mucronata. Control samples were taken from exposed interspace areas between shrubs. The composition and diversity of the ameba population were significantly affected by both season and plant species. Types 3 and 4 amebae were found to create a complementary system of adaptation in which type 3 was resistant and adapted to the harsh environment, whereas type 4 was much more vulnerable and existed for short periods of time when the environment allowed. The Reaumuria negevensis ecophysiological adaptation had a negative effect on type 4 amebae by creating a stressed environment.     

Atmospheric deposition effects on the chemistry of a stream in Northeastern Georgia

A modeling study of the Allt a Mharcaidh catchment in the Cairngorm region of Scotland has been undertaken to investigate long term trends in acidification and model sensitivity to soil physical and chemical characteristics. The MAGIC model (Model of Acidification of Groundwater In Catchments) is used to demonstrate that the sulphate adsorption ability of the soil and quality and quantity of rainfall inputs have significant effects on model output. Optimal weathering rates and predicted present day ion concentrations in streamwater compare well with measured and observed values. The analysis shows that the catchment has become progressively acidified since pre-industrial times but major changes in stream acidity have yet to occur.     

Heavy metal contamination of agricultural soils around a chromite mine in Vietnam

Abstract

In Vietnam, the Co Dinh mine is the largest chromite mine in the country. Mining, ore dressing and disposal of the tailings provide obvious sources of heavy metal contamination in the mine area. The present study examined the influence of chromite mining activities on the adjacent lowland paddy field by investigating heavy metal and As levels in the mine tailings, sediments, paddy soils and water. At paddy fields located near the mine tailings, the total contents of Cr, Co and Ni were 5,750, 375 and 5,590?mg?kg^?1, and the contents of their water-extractable form were 12.7, 1.16 and 32.3?mg?kg^?1, respectively. These results revealed severe contamination of lowland paddy soils with Cr, Co and Ni as a result of mining activity, suggesting serious health hazards through agricultural products, including livestock in this area. The principal source of the pollution was sediment inflow owing to the collapse of the dike, which was poorly constructed by heaping up soil. Moreover, water flowing out from the mining area was also polluted with Cr and Ni (15.0–41.0 and 20.0–135?μg?L^?1, respectively). This might raise another problem of heavy metal pollution of watercourses in the area, indicating the need for further investigation and monitoring of fluctuations of water quality with seasonal changes.     

Effects of abandonment of subalpine hay meadows on plant and invertebrate diversity in Transylvania, Romania

Recent changes in agriculture (intensification or abandonment) have resulted in a critical reduction of semi-natural grasslands in Eastern Europe. Subalpine semi-natural grasslands in Transylvania, Romania, harbour a high diversity of plants and invertebrates, including endemics, and are considered refugia for numerous threatened open-land species. We investigated effects of land abandonment by examining species richness, species abundance, proportion of open-land, endemic and threatened vascular plants, gastropods, and diurnal and nocturnal Lepidoptera in extensive hay meadows (initial stage), and three seral stages of succession (early stage of abandoned hay meadow, naturally growing birch forest, and mature forest) in the mountainous region of Baisoara in Transylvania. A total of 626 species (225 vascular plants, 16 gastropods, 68 diurnal and 317 nocturnal Lepidoptera) were found in the 16 study sites (four replicates per successional stage). The four taxonomic groups differed in their response to the abandonment of hay meadows. Each stage of succession harboured the maximum species richness for one taxonomic group: extensive hay meadows for vascular plants, abandoned hay meadows for diurnal Lepidoptera, birch forests for nocturnal Lepidoptera, and mature forests for gastropods. In all four taxonomic groups the complementarity of species composition increased with successional age, whereas the number of characteristic open-land species decreased with successional age. The four successional stages did not differ in proportion of red-listed plant and diurnal Lepidoptera species. In nocturnal Lepidoptera, however, the proportion of red-listed species increased with successional age. Furthermore, successional stages did not differ in number of plant species endemic to the Carpathians and Eastern Europe. Our results indicate the high conservation value of all stages of subalpine grassland succession for the indigenous biodiversity of Transylvania. To prevent losses of characteristic species, we suggest a rotational grassland management program that maintains different successional stages.     

Effects of bacteria on metal bioavailability,speciation, and mobility in different metal mine soils: a column study

Purpose  

Successful phytoremediation depends mainly on the bioavailability of heavy metals in the soil. Recently, soil microbes possess several mechanisms that are able to change metal bioavailability in the soil, which provides a new strategy for investigating biogeochemical cycling of metals in contaminated soils. Three metal mines soils with elevated concentrations of Cd, Pb, and Zn from China were applied in this column study to (1) evaluate the effects of metal tolerant bacterial inoculation (Burkholderia cepacia, accession number: AB051408) on metal release, (2) monitor the migration of metals in the rhizospheric horizon (0–20 cm), and (3) investigate metal speciation and sequential fractions in soil.     

The decomposition of vegetation growing on metal mine waste

Aspects of the decomposition of metal tolerant vegetation growing on mine waste containing high concentrations of lead and zinc were studied and compared with those on an adjacent uncontaminated site. High concentrations of Pb and, to a lesser extent, Zn, accumulated in metal-tolerant grass. Retarded decomposition of this vegetation as compared with that on the uncontaminated site was indicated by a greater accumulation of litter, less humus formation, reduced soil urease activity and smaller microbial and microfaunal populations. Some evidence for increased metal tolerance in microbes from the mine waste was obtained. Concentrations of lead tolerated under laboratory conditions were much lower than those extracted from the mine waste and its vegetation, probably due to the lack of an accurate method for assessing the availability of lead in soil and vegetation.