Comparing the Fish and Benthic Macroinvertebrate Diversity of Restored Urban Streams to Reference Streams

Urbanization is associated with substantial losses to stream biological diversity throughout the United States' mid‐Atlantic. Stream restoration has been used to improve stream conditions and, in part, to ameliorate these losses. However, the relationship between restoration and recovery of biological diversity is unclear. Our objective was to critically examine the efficacy of urban stream restorations with regard to biological diversity. We compared restored urban streams to urban nonrestored, nonurban, and reference (minimally degraded) streams using five measures each of fish and benthic macroinvertebrate diversity. Both multivariate and univariate statistical analyses show biological diversity of restored urban streams to be similar to nonrestored urban streams and lower than nonurban and reference streams. Restored urban sites showed no apparent increase in biological diversity through time, while diversity decreased at two of the reference streams coincident with increased urban development within their catchments. Our results indicate that restoration approaches commonly used regionally as in these urban streams are not leading to recovery of native stream biodiversity. Evidence from several sources indicates a need for dramatic changes in restoration approach, and we argue for a watershed‐scale focus including protection of the least impacted streams and adopting other land‐based actions within the watershed where possible.     

Temperature Responses to Infrared-Loading and Water Table Manipulations in Peatland Mesocosms

We initiated a multi-factor global change experiment to explore the effects of infrared heat loading (HT) and water table level (WL) treatment on soil temperature (T) in bog and fen peatland mesocosms. We found that the temperature varied highly by year, month, peatland type, soil depth, HT and WL manipulations. The highest effect of HT on the temperature at 25 cm depth was found in June for the bog mesocosms (3.34-4.27℃) but in May for the fen mesocosms (2.32-4.33℃) over the 2-year study period. The effects of WL in the bog mesocosms were only found between August and January, with the wet mesocosms warmer than the dry mesocosms by 0.48-2.03 ℃ over the 2-year study period. In contrast, wetter fen mesocoams were generally cooler by 0.16-3.87℃. Seasonal changes of temperatures elevated by the HT also varied by depth and ecosystem type, with temperature differences at 5 cm and 10 cm depth showing smaller seasonal fluctuations than those at 25 cm and 40 cm in the bog mesocosrns. However, increased HT did not always lead to warmer soil, especially in the fen mesocosms. Both HT and WL manipulations have also changed the length of the non-frozen season.     

Temporal Patterns and Environmental Correlates of Macroinvertebrate Communities in Temporary Streams

Temporary streams are characterised by short periods of seasonal or annual stream flow after which streams contract into waterholes or pools of varying hydrological connectivity and permanence. Although these streams are widespread globally, temporal variability of their ecology is understudied, and understanding the processes that structure community composition in these systems is vital for predicting and managing the consequences of anthropogenic impacts. We used multivariate and univariate approaches to investigate temporal variability in macroinvertebrate compositional data from 13 years of sampling across multiple sites from autumn and spring, in South Australia, the driest state in the driest inhabited continent in the world. We examined the potential of land-use, geographic and environmental variables to predict the temporal variability in macroinvertebrate assemblages, and also identified indicator taxa, that is, those highly correlated with the most significantly associated physical variables. Temporal trajectories of macroinvertebrate communities varied within site in both seasons and across years. A combination of land-use, geographic and environmental variables accounted for 24% of the variation in community structure in autumn and 27% in spring. In autumn, community composition among sites were more closely clustered together relative to spring suggesting that communities were more similar in autumn than in spring. In both seasons, community structure was most strongly correlated with conductivity and latitude, and community structure was more associated with cover by agriculture than urban land-use. Maintaining temporary streams will require improved catchment management aimed at sustaining seasonal flows and critical refuge habitats, while also limiting the damaging effects from increased agriculture and urban developments.     

Wood‐Associated Macroinvertebrate Fauna in Central European Streams

An overview of macroinvertebrates associated with wood debris is given, with the main focus on Central European fauna. In general, three categories of macroinvertebrate wood relations are distinguished: taxa frequently associated with wood but not xylophagous, facultative xylophagous taxa and obligate xylophagous taxa. The adaptations in the life history, ethology and physiology of species representing these three groups are reviewed. From literature and our own investigations, 15 taxa inhabiting Central European freshwater ecosystems are known to be obligate xylophagous, 22 taxa are facultatively xylophagous. From field observations another 41 taxa presumably feed on wood although no gut content analyses and laboratory experiments have yet been carried out. From 25 taxa other forms of close association to CWD are known (feeding on epixylic biofilm, use as a refuge, or as an attachment point). Possible pathways of xylophagy evolution are discussed and unresolved aspects of aquatic invertebrate wood relations are listed.     

Spatial and Temporal Variation of Macroinvertebrate Drift in Two Neotropical Streams1

The detection of spatial variation in macroinvertebrate drift depends on the spatial scale of investigation in streams of the La Selva Biological Station, Costa Rica. Drift samples were taken in a spatially nested design, with two streams, two reaches per stream, two riffles per reach, and four replicate samples per riffle. Drift showed little variation among streams, but varied significantly at the scales of reach and riffle, with variation among samples also high. In addition, sampling took place at two temporal scales: diel and at two different periods that differed in rainfall conditions. Drift diel periodicity was a clear pattern, while only density of individuals varied among sampling periods. This is the first study of macroinvertebrate drift at multiple spatial scales, despite the recognition that multi‐scale studies are essential for a more complete understanding of community patterns and processes.     

Bacterial Communities in Acidic and Circumneutral Streams

The relationship between pH and the abundance and activity of bacteria in streams was examined as part of a study of the effect of acidification on stream communities. Of the bacterial communities examined, the epilithic community appeared to be the most significantly affected by acidification. Microbial biomass, as quantified by measuring the ATP level, on rock surfaces was significantly correlated with pH. Also, bacterial production by the epilithic bacteria, indicated by incorporation of tritiated thymidine into DNA, was always higher at high-pH sites than at low-pH sites of the same stream order and elevation. Bacterioplankton concentrations varied between 0.53 × 10⁵ and 9.42 × 10⁵ cells · ml⁻¹ in the first- to fourth-order streams examined. The bacterioplankton concentration in one sample from a spring was 0.17 × 10⁵ cells · ml⁻¹. Bacterioplankton concentrations were not correlated with pH but were significantly correlated with seston concentrations. The correlation with seston is a result of increases in particle-associated bacteria at high seston concentrations. The proportion of bacterioplankton attached to particles varied from 0 to 70%. Bacterial numbers and production in the sediments were significantly correlated with the organic content of the sediment rather than with the pH of the overlying water. Thus, reduced abundance and activity of bacteria as a result of acidification could be detected only for the relatively active community on rock surfaces; this community was exposed to the low pH because of the unbuffered nature of its environment.     

Links Between Anthropogenic Perturbations and Benthic Macroinvertebrate Assemblages in Afromontane Forest Streams in Uganda

Relationships between environmental variables and benthic macroinvertebrate assemblages were investigated among several sites that varied in disturbance history in Bwindi Impenetrable National Park, an Afromontane site in East Africa. Environmental variables were correlated with the level of past catchment disturbance – logging, agricultural encroachment, and present tourism activity. For example, sites in medium and high disturbance categories had higher values of specific conductance and lower water transparency than low disturbance category sites, these environmental variables may therefore act indicators of ecological quality of rivers. Environmental variables such as conductivity and water transparency were found to be good predictors of benthic macroinvertebrate assemblages, with anthropogenically stressed sites having lower diversity than the reference sites. Impacted sites were dominated by tolerant taxa such as chironomid and leeches, while ‘clean water’ taxa such as Ephemeroptera, Plecoptera and Trichoptera dominated at minimally impacted sites. Comparison of sites with different disturbance histories provided evidence for differences in benthic macroinvertebrate communities that reflect the state of forest restoration and recovery. We recommend quarterly monitoring of water quality to act as an early warning system of deterioration and tracking ecological recovery of previously impacted sites.     

Macroinvertebrate Responses to Mitigative Liming of Dogway Fork, West Virginia

Dogway Fork, West Virginia, is a second–order stream affected by acid precipitation. One goal of the Acid Precipitation Mitigation Program was to determine if the composition or population levels of benthic macroinvertebrates were affected by limestone neutralization of the acidic waters (pH 4.5). Two techniques were used to determine any effects: seasonal Surber samples and in situ bioassays with selected genera. Prior to treatment, macroinvertebrate densities were low but represented a diverse group of acidtolerant taxa. During treatment, fewer macroinvertebrates were collected in the treated segment than in the untreated control. This appears to be a result of a number of factors, including substrate, flows, drift, fish predation, accumulation of limestone fines, and changes in water chemistry. Bioassays suggest that the limestone fines were not directly detrimental to the organisms but may have limited available habitat in the mixing zone. Limestone treatment affected the species composition of Dogway Fork. During four years of treatment, several new acid-sensitive taxa were collected in the treated segment. Data suggest that, with continued treatment, populations of these taxa can be expected to increase.     

Application of Fungal and Bacterial Production Methodologies to Decomposing Leaves in Streams

As leaves enter woodland streams, they are colonized by both fungi and bacteria. To determine the contribution of each of these microbial groups to the decomposition process, comparisons of fungal and bacterial production are needed. Recently, a new method for estimating fungal production based on rates of [(sup14)C]acetate incorporation into ergosterol was described. Bacterial production in environmental samples has been determined from rates of [(sup3)H]leucine incorporation into protein. In this study, we evaluated conditions necessary to use these methods for estimating fungal and bacterial production associated with leaves decomposing in a stream. During incubation of leaf disks with radiolabeled substrates, aeration increased rates of fungal incorporation but decreased bacterial production. Incorporation of both radiolabeled substrates by microorganisms associated with leaf litter was linear over the time periods examined (2 h for bacteria and 4 h for fungi). Incorporation of radiolabeled substrates present at different concentrations indicated that 400 nM leucine and 5 mM acetate maximized uptake for bacteria and fungi, respectively. Growth rates and rates of acetate incorporation into ergosterol followed similar patterns when fungi were grown on leaf disks in the laboratory. Three species of stream fungi exhibited similar ratios of rates of biomass increase to rates of acetate incorporation into ergosterol, with a mean of 19.3 (mu)g of biomass per nmol of acetate incorporated. Both bacterial and fungal production increased exponentially with increasing temperature. In the stream that we examined, fungal carbon production was 11 to 26 times greater than bacterial carbon production on leaves colonized for 21 days.     

Non-Additive Increases in Sediment Stability Are Generated by Macroinvertebrate Species Interactions in Laboratory Streams

Previous studies have shown that biological structures such as plant roots can have large impacts on landscape morphodynamics, and that physical models that do not incorporate biology can generate qualitatively incorrect predictions of sediment transport. However, work to date has focused almost entirely on the impacts of single, usually dominant, species. Here we ask whether multiple, coexisting species of hydropsychid caddisfly larvae have different impacts on sediment mobility compared to single-species systems due to competitive interactions and niche differences. We manipulated the presence of two common species of net-spinning caddisfly (Ceratopsyche oslari, Arctopsyche californica) in laboratory mesocosms and measured how their silk filtration nets influence the critical shear stress required to initiate sediment grain motion when they were in monoculture versus polyculture. We found that critical shear stress increases non-additively in polycultures where species were allowed to interact. Critical shear stress was 26% higher in multi-species assemblages compared to the average single-species monoculture, and 21% greater than levels of stability achieved by the species having the largest impact on sediment motion in monoculture. Supplementary behavioral experiments suggest the non-additive increase in critical shear stress may have occurred as competition among species led to shifts in the spatial distribution of the two populations and complementary habitat use. To explore the implications of these results for field conditions, we used results from the laboratory study to parameterize a common model of sediment transport. We then used this model to estimate potential bed movement in a natural stream for which we had measurements of channel geometry, grain size, and daily discharge. Although this extrapolation is speculative, it illustrates that multi-species impacts could be sufficiently large to reduce bedload sediment flux over annual time scales in streams where multiple species of caddisfly are present.     

Abundance of Three Bacterial Populations in Selected Streams

The population sizes of three bacterial species, Acinetobacter calcoaceticus, Burkholderia cepacia, and Pseudomonas putida, were examined in water and sediment from nine streams in different parts of the United States using fluorescent in situ hybridization (FISH). Population sizes were determined from three sites (upstream, midstream, and downstream) in each stream to compare differences in the occurrence and distribution of the species within each stream and among streams. Physical and chemical variables measured reflected differences in environmental conditions among the streams. In the water, B. cepacia numbers were highest in the agricultural, Iowa stream. P. putida numbers were highest in the southern coastal plain streams, Black Creek (GA) and Meyers Branch (SC). Compared to the other two species, the abundance of A. calcoaceticus was similar in all the streams. In sediment, the greatest abundance of all three species was found in the Iowa stream, while the lowest was in Hugh White Creek (NC). Detrended correspondence analysis (DCA) explained 95.8% and 83.9% of the total variation in bacterial numbers in water and sediment of the streams, respectively. In sediments and water, B. cepacia numbers were related to nitrate concentrations. A. calcoaceticus in water clustered with several environmental variables (i.e., SRP, pH, and conductivity) but benthic populations were less well correlated with these variables. This study reveals the potential influence of various environmental conditions on different bacterial populations in stream communities.     

Rumen Bacterial and Protozoal Responses to Insecticide Substrates

Insecticides containing organophosphate, chlorinated hydrocarbon, and carbamate were tested with bovine ruminal ingesta fractions. Rumen bacteria exposed to insecticide levels of 0 to 500 ppm in rumen fluid for 4 hr were inoculated into rumen fluid-starch feed extract medium. No apparent significant bacterial count inhibitions were noted. Also, when insecticides were used as carbon sources at concentrations of 500 ppm in carbohydrate-limited media, no increases in bacterial counts were indicated. Warburg manometric data showed that paraffin oil-Triton X-155 preparations of dimethoate, Diazinon, lindane, Thiodan and Sevin stimulated gas production in holotrich protozoa. Entodinium simplex, an oligotrich, produced less gas with insecticide substrates per unit of dry weight than did an Isotricha sp. Rumen bacteria and plant debris fractions from ruminal ingesta provided with insecticides did not give increased manometric responses over the endogenous control vessels. Washed suspensions of I. intestinalis produced volatile fatty acids in excess of the endogenous suspensions when provided insecticide substrates. Thiodan dissimilation by I. intestinalis was followed colorimetrically with 15% loss in substrate in 1 hr of incubation at 39 C. Diazinon-C¹⁴ substrate uptake was demonstrated with suspensions of E. simplex and I. intestinalis. Rumen ciliates are suggested as a possible means for screening out useful insecticides susceptible to microbial dissimilation for use on forage and other cattle-feed crops.     

The Extent of Algal and Bacterial Endosymbioses in Protozoa1,2

Long neglected has been the extensive and more or less intimate association of protozoa with a wide variety of other cells, either prokaryotic or eukaryotic in nature. Yet study of such relationships can provide important information concerning certain basic aspects of cellular evolution in general. A survey is offered here of the whole range of such symbiotic associations (i.e. with species of protozoa serving as hosts) with the purposes of drawing attention to the exciting possibilities of such research and of reviewing significant findings made to date. Because of the vastness of the overall field, examples and discussion are primarily limited to consideration of the following major studies: methanogenic bacteria in certain ciliates, bacterial endosymbionts of the large freshwater amoeba Pelomyxa palustris (itself an amazing organism from an evolutionary/phylogenetic point of view), the rod-shaped bacteria found in Amoeba proteus, the “Greek-letter” prokaryotes of Paramecium species, the xenosomes (sensu stricto) of the marine scuticociliate Parauronema acutum, and the diverse algal endosymbionts of similarly diverse protozoan taxa–ciliates, flagellates, radiolarians, acantharians, and foraminifera.     

Quantifying Macroinvertebrate Responses to In-Stream Habitat Restoration: Applications of Meta-Analysis to River Restoration

The assumption that restoring physical habitat heterogeneity will increase biodiversity underlies many river restoration projects, despite few tests of the hypothesis. With over 6,000 in-stream habitat enhancement projects implemented in the last decade at a cost exceeding $1 billion, there is a clear need to assess the consistency of responses, as well as factors explaining project performance. We adopted an alternative approach to individual case-studies by applying meta-analysis to quantify macroinvertebrate responses to in-stream habitat restoration. Meta-analysis of 24 separate studies showed that increasing habitat heterogeneity had significant, positive effects on macroinvertebrate richness, although density increases were negligible. Large woody debris additions produced the largest and most consistent responses, whereas responses to boulder additions and channel reconfigurations were positive, yet highly variable. Among all strategies, the strength and consistency of macroinvertebrate responses were related to land use or watershed-scale conditions, but appeared independent of project size, stream size, or recovery time. Overall, the low quality and quantity of pre- and post-project monitoring data reduced the robustness of our meta-analysis. Specifically, the scope and strength of conclusions regarding the ubiquity of macroinvertebrate responses to restoration, as well as the identification of variables controlling project performance was limited. More robust applications of meta-analysis to advance the science and practice of river restoration will require implementing rigorous study designs, including pre- and post-project monitoring replicated at both restored and control sites, collection of abiotic and biotic variables at relevant spatiotemporal scales, and increased reporting of monitoring results in peer-reviewed journals and/or regional databases.     

Factors Affecting Macroinvertebrate Richness and Diversity in Portuguese Streams: a Two‐Scale Analysis

We analysed the spatial patterns in macroinvertebrate taxon richness and abundance at two scales: sampling unit and basin. We sampled 12 stream sites in three zones of Portugal, differing in climate geomorphology and water chemistry. At a sampling unit scale, substratum organic matter content, depth and the dominant size of substratum particles were correlated with numbers of taxa and individuals. We propose that the number of taxa at a small scale depends on the number of individuals, which in turn is the result of organic matter accumulation, hydrologic and substratum characteristics. The environmental parameters better explaining the large‐scale biological data were temperature, minimum size of substratum particles and pH. Regardless of the relative importance of variable types and mechanisms regulating stream invertebrates along the climatic gradient, rivers from the North and Centre appeared to be richer in taxa than the typically Mediterranean streams in the South.     

Bacterial Responses to a Simulated Colon Tumor Microenvironment

One of the few bacteria that have been consistently linked to colorectal cancer (CRC) is the opportunistic pathogen Streptococcus gallolyticus. Infections with this bacterium are generally regarded as an indicator for colonic malignancy, while the carriage rate of this bacterium in the healthy large intestine is relatively low. We speculated that the physiological changes accompanying the development of CRC might favor the colonization of this bacterium. To investigate whether colon tumor cells can support the survival of S. gallolyticus, this bacterium was grown in spent medium of malignant colonocytes to simulate the altered metabolic conditions in the CRC microenvironment. These in vitro simulations indicated that S. gallolyticus had a significant growth advantage in these spent media, which was not observed for other intestinal bacteria. Under these conditions, bacterial responses were profiled by proteome analysis and metabolic shifts were analyzed by ¹H-NMR-spectroscopy. In silico pathway analysis of the differentially expressed proteins and metabolite analysis indicated that this advantage resulted from the increased utilization of glucose, glucose derivates, and alanine. Together, these data suggest that tumor cell metabolites facilitate the survival of S. gallolyticus, favoring its local outgrowth and providing a possible explanation for the specific association of S. gallolyticus with colonic malignancy.The human intestine is the habitat for several hundred different bacterial species with an increasing bacterial concentration and variability toward the distal colon (1). The resident gut microbiota is essential for human health by making dietary nutrients available to the host and preventing the invasion of pathogens by competitive colonization and nutrient competition (2, 3). Strikingly, the part of the intestine with the highest bacterial colonization, the colon, is also most affected by cancer, with 146,970 annual cases in the United States of America (4). In a healthy colonic environment, the host has several defense mechanisms to shield itself from bacterial infection, such as the viscous mucus layer overlaying the epithelium. However, the progression of CRC¹ is accompanied by changes in the integrity of the colon, including reduced mucus production (5) and increased epithelial permeability (6). These physiological changes can drive the intestinal ecosystem, which is relatively stable during adult life, into dysbiosis (7, 8). As a consequence, the host may become more susceptible to opportunistic bacterial infections (9–11).One of the few bacteria that have been consistently linked to CRC is the opportunistic pathogen Streptococcus gallolyticus (previously known as Streptococcus bovis biotype I). In CRC patients the fecal carriage rate of this bacterium is increased from 10% to about 50% (12), which suggests that this disease facilitates the colonic survival of S. gallolyticus. Importantly, ∼60% of patients that present with S. gallolyticus endocarditis have concomitant CRC (both adenomas and carcinomas) (13, 14), which largely exceeds the rates reported in the general population (∼25%) (15). These patients had no gastro-intestinal signs or clinical symptoms of malignancy and CRC was only detected because this bacterial infection guided the physician to perform a colonoscopy.Several mechanisms for this apparent association between S. gallolyticus and CRC can be envisaged. Recently, we postulated a model in which the collagen binding ability of S. gallolyticus contributes to the specific colonization of malignant colonic sites (16). However, the altered microenvironment of the tumor may also provide conditions that favor survival and outgrowth of S. gallolyticus in this newly formed intestinal niche. For example, Hirayama et al. have shown that glucose-1-phosphate and fructose-1-phophate levels as well as amino acid concentrations were significantly higher in tumor tissue than in normal tissue (17). To investigate if this altered nutritional status of the CRC microenvironment could facilitate the foraging of S. gallolyticus, we simulated the influence of colon tumor cell metabolites on S. gallolyticus growth by incubating this bacterium in spent medium of malignant cells. Subsequently, the bacterial responses were profiled by two-dimensional proteome analysis, and metabolic shifts in the culture medium were assessed by ¹H-NMR-spectroscopy. In silico pathway analysis and further in vitro simulations showed that, unlike other intestinal bacteria, S. gallolyticus had a growth advantage under these conditions, which could mainly be attributed to increased glycolysis. These results provide the first molecular support that tumor metabolites may facilitate the local outgrowth of tumor-foraging bacteria, such as S. gallolyticus.     

Functional Differences Among Benthic Macroinvertebrate Communities in Reference Streams of Same Order in a Given Biogeographic Area

Ecological theory (Southwood, 1977. Journal of Animal Ecology 46: 337–365, 1988. Oikos 52: 3–18; Townsend, 1989. Journal of the North American Benthological Society 8: 36–50; Townsend & Hildrew, 1994. Freshwater Biology 31: 265–275) considers that spatio-temporal variations in habitats act as evolutionary forces on organisms, selecting for traits that maximize fitness. As a consequence, communities developed under same environmental conditions should present the same combination of species bio-ecological characteristics. The objective was to verify, using data from the same biogeographical zone, (1) if there was a unique suite of bio-ecological profiles for reference macrobenthic communities of `comparable' rivers or (2) if the distribution of bio-ecological traits within reference communities was significantly influenced by geology. The variability of 22 bio-ecological traits in 12 different sites was tested to evaluate the potential influence of geological substrate on biological and ecological features of reference stream communities. Observed patterns suggested that communities displayed highly stable bio-ecological profiles among sites (within a given biogeographical zone) whatever the substrate was, even if communities on clayey substrate exhibited slightly different bio/ecological characteristics than on others geologies. Nevertheless, the functional structure of macrobenthic communities in reference sites was quite stable in this biogeographical area. This study was restricted to the selected stream types and its results may not directly be transferred to other biogeographical areas and stream types. However, the perspective of a unique functional reference for streams of the same order in a given biogeographical area, improve functional comparison between observed vs. reference communities. This could simplify and objectively define the ecological status of a given site.