Search

Land use intensification has led to conspicuous changes in plant and animal communities across the world. Shifts in trait‐based functional composition have recently been hypothesized to manifest at lower levels of environmental change when compared to species‐based taxonomic composition; however, little is known about the commonalities in these responses across taxonomic groups and geographic regions. We investigated this hypothesis by testing for taxonomic and geographic similarities in the composition of riverine fish and insect communities across gradients of land use in major hydrological regions of the conterminous United States. We analyzed an extensive data set representing 556 species and 33 functional trait modalities from 8023 fish communities and 1434 taxa and 50 trait modalities from 5197 aquatic insect communities. Our results demonstrate abrupt threshold changes in both taxonomic and functional community composition due to land use conversion. Functional composition consistently demonstrated lower land use threshold responses compared to taxonomic composition for both fish (urban p = 0.069; agriculture p = 0.029) and insect (urban p = 0.095; agriculture p = 0.043) communities according to gradient forest models. We found significantly lower thresholds for urban versus agricultural land use for fishes (taxonomic and functional p < 0.001) and insects (taxonomic p = 0.001; functional p = 0.033). We further revealed that threshold responses in functional composition were more geographically consistent than for taxonomic composition to both urban and agricultural land use change. Traits contributing the most to overall functional composition change differed along urban and agricultural land gradients and conformed to predicted ecological mechanisms underpinning community change. This study points to reliable early‐warning thresholds that accurately forecast compositional shifts in riverine communities to land use conversion, and highlight the importance of considering trait‐based indicators of community change to inform large‐scale land use management strategies and policies. [ABSTRACT FROM AUTHOR]

Recent waves of illegal deforestation for cattle pasture are damaging the Indio Maíz Biological Reserve and Rama-Kriol Territory of Nicaragua, with negative consequences to aquatic ecosystems and the people they support. This study creates a framework for how deforestation from cattle ranching causes shifts in stream community structure, mediated by changes in stream habitat over time. It integrates temporally explicit land use information with stream habitat, macroinvertebrate, freshwater shrimp, and fish community data to assess impacts of cattle ranching on 15 headwater streams. The deforestation history measure (DHM), a product of deforestation amount and time since deforestation for each catchment, strongly predicted stream habitat and biotic responses. Delayed effects of land-use change such as decreased allochthonous inputs (large wood, debris) and increased bank destabilization, sedimentation, flashiness, and the scouring effect were apparent in longer deforested catchments, causing lower richness and density and higher evenness of macroinvertebrates; lower shrimp abundance; and distinct changes in fish and invertebrate community composition. Both recently and longer deforested catchments had degraded riparia and smaller sized game fish. Otherwise, recently deforested catchments were more similar to forested catchments. Nicaragua's understudied primary rainforest ecosystems should be high priority for research and conservation before they are lost. [ABSTRACT FROM AUTHOR]

Eutrophication is a common phenomenon in aquatic ecosystems caused by human disturbance and is regarded as one of the major threats to biodiversity in rivers throughout the world. However, no consistent pattern explains the relationship between eutrophication and biodiversity in rivers. In the present work, we explored fieldwork in connection to the influence of eutrophication on biodiversity in nine streams in a boreal river ecosystem in China. We aimed to test the intermediate disturbance hypothesis (IDH) in our model, which predicts that biodiversity reaches its maximum at intermediate disturbance. We used total phosphorus (TP) as a direct indicator of eutrophication and divided TP concentration into five levels of eutrophication, which represented anthropogenic disturbance of varied intensity. The results obtained from periphyton, macroinvertebrate, and fish assemblages showed that species richness was higher at intermediate eutrophication levels, and the pattern was not impacted by other factors. Our findings may provide important insights into the influence of anthropogenic disturbance on biodiversity in stream ecosystems. [ABSTRACT FROM AUTHOR]

River flow regimes face increasing pressure from human activities including water resource management operations and climate change. Consequently, extreme hydrological events are becoming more severe and commonplace, and there is a pressing need to understand and manage their ecological effects. Extreme low flows (ELFs)—those displaying significantly greater magnitudes and durations than typical low‐flow conditions—are being increasingly experienced globally. Fish and macroinvertebrate responses to ELFs have been more widely researched relative to other organism groups in riverine environments, although such studies have employed variable methodological techniques. In this perspective piece, we identify field‐based assessments and controlled experiments as two key research paradigms used to examine riverine faunal responses to ELFs. Field‐based assessments are often explorative and can benefit from utilising large‐scale and long‐term datasets. Alternatively, controlled experiments typically employ more hypothesis‐driven approaches and can establish strong cause and effect linkages through high replication and control over potentially confounding parameters. Each paradigm clearly possesses their respective strengths, which we highlight and discuss how these could be better harnessed to optimise scientific advancements. To date, studies examining faunal responses to ELFs in these two research paradigms have largely been undertaken in parallel. Here, we argue that future research should seek to develop closer synergies to optimise the quality and quantity of evidence to better understand riverine faunal responses to ELFs. Such scientific advances are of paramount importance given the vulnerability of riverine fauna, and the ecosystems they comprise, to a new era of ELFs in many global regions. [ABSTRACT FROM AUTHOR]

Abstract Background Urban areas are often built along large rivers and surrounded by agricultural land. This may lead to small tributary streams that have agricultural headwaters and urbanized lower reaches. Our study objectives assessed are as follows: (1) landscape, geomorphic, and water quality variables that best explained variation in aquatic communities and their integrity in a stream system following this agricultural-to-urban land use gradient; (2) ways this land use gradient caused aquatic communities to differ from what would be expected for an idealized natural stream or other longitudinal gradients; and (3) whether the impacts of this land use gradient on aquatic communities would grow larger in a downstream direction through the agricultural and urban developments. Our study area was an impaired coldwater stream in Michigan, USA. Results Many factors structured the biological communities along the agricultural-to-urban land use gradient. Instream woody debris had the strongest relationship with EPT (Ephemeroptera, Plecoptera, and Trichoptera) abundance and richness and were most common in the lower, urbanized watershed. Fine streambed substrate had the strongest relationship with Diptera taxa and surface air breather macroinvertebrates and was dominant in agricultural headwaters. Fish community assemblage was influenced largely by stream flow and temperature regimes, while poor fish community integrity in lower urban reaches could be impacted by geomorphology and episodic urban pollution events. Scraping macroinvertebrates were most abundant in deforested, first-order agricultural headwaters, while EPT macroinvertebrate richness was the highest downstream of agricultural areas within the urban zone that had extensive forest buffers. Conclusion Environmental variables and aquatic communities would often not conform with what we would expect from an idealized natural stream. EPT richness improved downstream of agricultural areas. This shows promise for the recovery of aquatic systems using well-planned management in watersheds with this agricultural-to-urban land use pattern. Small patches of forest can be the key to conserving aquatic biodiversity in urbanized landscapes. These findings are valuable to an international audience of researchers and water resource managers who study stream systems following this common agricultural-to-urban land use gradient, the ecological communities of which may not conform with what is generally known about land use impacts to streams.

The Weihe River is the largest tributary of the Yellow River. The health of the river water ecosystem in the Weihe River Basin is closely related to the high-quality development of the Yellow River. Four times were carried out in the Weihe River Basin from 2011 to 2013. In the field sampling survey, a total of 77 sampling points were set up to collect information on fish, benthic animals, living algae and water environmental factors, analyze the characteristics of the aquatic ecosystem of the Weihe River Basin, and adopt The biological integrity index method evaluates the health of the aquatic ecosystem in the Weihe River Basin. A total of 51 species of fish, 116 species of benthic animals, and 248 species of living algae were collected in the Weihe River Basin. The environmental factor of the fish community structure in the Weihe River Basin is altitude, and the environmental factors that affect the structure of the benthic community are river width, electrical conductivity and hardness, which affect the structure of the algae community. The environmental factor is the width of the river. The results of the health assessment of the aquatic ecosystem show that the health status of benthic animals and living algae is better than that of fish, and more than 80% of the sampling points are in normal or above healthy water. The overall trend of the health evaluation results of the three biological water ecosystems is the same. The upper reaches of the Weihe River and the right bank tributaries, the source of the Jinghe River, and the middle reaches of the Beiluo River are in good health conditions. The middle and lower reaches of the river, most of the Jinghe River and the upper reaches of the Beiluo River are in poor health. [ABSTRACT FROM AUTHOR]

Wetland restoration or re-establishment is a common conservation goal, and the ability of a wetland community to recover from events such as drought are key to its long-term success. At the mouth of the Waiau River in Southland, New Zealand, a series of wetland ponds have been created by diverting water from the river. A period of particularly low river flows resulted in the wetland drying out entirely, except for a few deep channels. A subsequent flood inundated the ponds, creating an opportunity to study recolonisation of the system. The deep channels provided an important refuge habitat for eels (Anguilla spp.) during dry periods, with significantly higher numbers close to the channels immediately after refilling than at sites further away. Smaller fish (Gobiomorphus and Galaxias spp.) took much longer to reappear in the ponds. The macroinvertebrate community showed no significant variation over the short term or up to a year post-refill, although individually snail and water bug taxa increased and microcrustaceans decreased in abundance. Daphnia and ostracods were observed soon after refilling and dominated the community. This study highlights the importance of spatial heterogeneity in constructed wetland systems, as this habitat variation likely increases the recovery rate after drying. [ABSTRACT FROM AUTHOR]

Background: Urban areas are often built along large rivers and surrounded by agricultural land. This may lead to small tributary streams that have agricultural headwaters and urbanized lower reaches. Our study objectives assessed are as follows: (1) landscape, geomorphic, and water quality variables that best explained variation in aquatic communities and their integrity in a stream system following this agricultural-to-urban land use gradient; (2) ways this land use gradient caused aquatic communities to differ from what would be expected for an idealized natural stream or other longitudinal gradients; and (3) whether the impacts of this land use gradient on aquatic communities would grow larger in a downstream direction through the agricultural and urban developments. Our study area was an impaired coldwater stream in Michigan, USA. Results: Many factors structured the biological communities along the agricultural-to-urban land use gradient. Instream woody debris had the strongest relationship with EPT (Ephemeroptera, Plecoptera, and Trichoptera) abundance and richness and were most common in the lower, urbanized watershed. Fine streambed substrate had the strongest relationship with Diptera taxa and surface air breather macroinvertebrates and was dominant in agricultural headwaters. Fish community assemblage was influenced largely by stream flow and temperature regimes, while poor fish community integrity in lower urban reaches could be impacted by geomorphology and episodic urban pollution events. Scraping macroinvertebrates were most abundant in deforested, first-order agricultural headwaters, while EPT macroinvertebrate richness was the highest downstream of agricultural areas within the urban zone that had extensive forest buffers. Conclusion: Environmental variables and aquatic communities would often not conform with what we would expect from an idealized natural stream. EPT richness improved downstream of agricultural areas. This shows promise for the recovery of aquatic systems using well-planned management in watersheds with this agricultural-to-urban land use pattern. Small patches of forest can be the key to conserving aquatic biodiversity in urbanized landscapes. These findings are valuable to an international audience of researchers and water resource managers who study stream systems following this common agricultural-to-urban land use gradient, the ecological communities of which may not conform with what is generally known about land use impacts to streams. [ABSTRACT FROM AUTHOR]

Subaqueous dredging is a management activity undertaken globally to improve navigation, remove contaminants, mitigate flood risk and/or generate aggregate. Water Injection Dredging (WID) is a hydrodynamic technique involving the turbation and downstream displacement of fine sediments using vessel-mounted water jets. Despite the technique being widely applied internationally, the environmental and ecological effects of WID are poorly understood. For the first time, this study used a Before-After-Control-Impact (BACI) experimental design to assess the effects of WID on water physicochemistry, and macroinvertebrate and fish communities within a 5.7 km-long reach of tidal river. WID targeted the central channel (thalweg) to avoid disturbance of the channel margins and banks. Mean but not peak turbidity levels were substantially elevated, and dissolved oxygen levels were reduced during periods of WID, although effects were relatively short-lived (≈3 h on average). Dredging resulted in significant reductions in benthic macroinvertebrate community abundance (particularly taxa that burrow into fine sediments), taxonomic richness and diversity. In contrast, minor changes were detected in marginal macroinvertebrate communities within and downstream of the dredged reach following WID. Reductions in fish taxonomic richness and diversity were recorded downstream of the dredged reach most likely due to behavioural avoidance of the sediment plume. No visibly stressed or dead fish were sampled during dredging. Results suggest that mobile organisms and marginal communities were largely unaffected by thalweg WID and that the technique represents a more ecologically sensitive alternative to traditional channel margin mechanical dredging techniques.

Although freshwater ecosystems support a disproportionately large number of species, decision-support tools for prioritizing protected area efforts have mostly been implemented in marine and terrestrial environments. Systematic conservation planners rely on surrogate metrics to represent unsampled elements of biodiversity, yet few studies have considered the potential benefits associated with prioritizing multiple dimensions of freshwater biodiversity across multiple organism groups. In this study, we first evaluated relationships among patterns of taxonomic richness, functional diversity, functional redundancy, and biotic integrity for freshwater fish and benthic macroinvertebrate communities in the Congaree Biosphere Region, South Carolina, USA. We then used the decision-support tool Marxan to explore a potential trade-off between the number of organism groups sampled (i.e., taxonomic extent) and the multidimensional nature of biodiversity. Our central findings indicated that the processes driving patterns of taxonomic and functional diversity among organism groups were complementary, with direct implications for the evaluation of surrogate performance. Our results also suggest that within-taxa variation among measures of taxonomic and functional diversity may be more important to consider than the taxonomic representation of multiple organism groups. That is, we may be able to enhance the efficiency of conservation planning efforts by using available datasets in a more comprehensive way, as surrogate performance was largely mediated by the variation among metrics. Through the continued development of functional trait databases, we may be able to enhance the efficiency of data collection efforts and promote the timely and sustainable development of conservation strategies.

Mangrove litter is continuously supplied to coastal water systems in and around Southeast Asian mangrove forests, often floating or drifting in surface layer water and likely providing ecological benefits for aquatic animals. As a first step toward clarification of possible roles of such litter in coastal ecosystems, associated fish/macroinvertebrate fauna in a shallow coastal area in Trang Province, Thailand, were examined by scoop-netting. During the study period, 398 individual fishes (35 species), 33 macrocrustaceans (8 species) and 30 squid (1 species) were collected. Larval/juvenile Zenarchopterus sp. 1 (cf. Z. dunckeri) were the most abundant fish (31.4% of total fishes), followed by Butis butis (16.3%) and Terapon jarbua (13.3%). A pygmy squid, Idiosepius sp., was the most abundant macroinvertebrate (47.6% of total). The majority of specimens collected were small-sized individuals. The mangrove litter, which adds a structured microhabitat to the non-structured surface water layer, probably functions (for small animals) in reducing energy costs for movement, including migration to other areas, as well as reducing predation risk and increasing food catchability, resulting in enhanced affinity of small animals for the litter. [ABSTRACT FROM AUTHOR]

Despite their ecological and economic importance, coastal biological communities and ecosystem processes in large lakes have been understudied compared to those offshore. We investigated temporal variability in the abundance and assemblage composition of coastal organisms in northern Lake Michigan. We sampled nutrients, phytoplankton, zooplankton, periphyton, benthic invertebrates, and fish along the east coast of Beaver Island, Michigan, USA, with high temporal frequency (every d to every 2 wk) over 2 summers. We also examined connectivity between coastal and offshore habitats with both hourly water current data from the Great Lakes Coastal Forecasting System and sampling offshore 2 to 3× per summer. The abundance of littoral zone organisms varied markedly on daily to weekly timescales for both benthic invertebrates and water-column organisms (phytoplankton, zooplankton, fish). For example, zooplankton abundance changed by a mean of 297% between sampling dates at the same location. Within-season peaks in plankton abundance also differed among years. Specifically, peak chlorophyll a (Chl a) concentrations were observed 1 mo earlier in 2016 than 2015, and early summer (Jun) zooplankton abundance was 333% higher in 2016 than 2015. Furthermore, our data suggest that water currents may influence the abundance and assemblage composition of plankton, possibly by altering the flux of nutrients and organisms from offshore to coastal habitats. Specifically, zooplankton abundance increased by a mean of 194% when surface currents moved eastward before we sampled, and eastward surface velocity significantly altered zooplankton assemblage composition. Chl a concentration increased by a mean of 106% when surface currents moved northward prior to sampling. In contrast, the abundance and composition of benthic invertebrates and fish differed among sites and was not significantly related to water currents. The abundance of these organisms also declined throughout the summer. Therefore, benthic and water-column organisms are controlled by different processes, so patterns in their local abundance are out of sync. Understanding variability in coastal communities may enhance monitoring and design of effective protocols for investigating large lake ecology. Further, understanding the importance of regional movement of nutrients and organisms may be key to understanding community and ecosystem structure in coastal areas. [ABSTRACT FROM AUTHOR]

Abstract Environmental concentrations of Pb have been increased due to anthropogenic activities, which have provoked the released of this element to the environment in large amounts. To understand how Pb behaves in remote southern marine ecosystems, we measured Pb concentrations and isotope ratios in biota from coastal marine ecosystems of the Chilean Patagonia and the Antarctic Peninsula area. Lead concentrations in the aquatic organisms ranged from 0.02 to 1.19 mg kg−1 d.w. In Patagonia, higher Pb levels were found in fish than in invertebrates (crab, shrimp, porifera, limpet and shellfish). In comparison with the baseline reference values from other parts of the world, fishes exhibited lower Pb levels. The results of Pb isotopic compositions indicated that the bioaccumulation of Pb in marine organisms come from different anthropogenic sources. These Pb levels might be useful for further studies that allow a deeper evaluation of sources for Pb contamination in these remote ecosystems. Highlights • Lead was measured in tissues of macroinvertebrates and fishes from Patagonia and Antarctica. • Lead concentrations in the aquatic organisms are lower than those measured at lower latitudes. • Pb in marine ecosystems studied are due mainly to anthropogenic activities instead of natural sources. [ABSTRACT FROM AUTHOR]

Identifying ecological niche filters that shape species community composition is a critical first step in understanding the relative contributions of deterministic and stochastic processes in structuring communities. Systems with harsh ecological filters often have a more deterministic basis to community structure. Although these filters are often treated as static, investigations into their stability through time are rare, particularly in combination with extreme forms of environmental change such as drought.We examined the richness and composition of aquatic macroinvertebrate communities from 36 ponds over 4 years during the onset of a megadrought to answer the following questions: (a) what are the relative influences of non‐native fish presence and pond permanence in structuring communities? And (b) how do the magnitudes of such filters vary through time?As predicted, fish presence had a strong, negative effect on both alpha and gamma diversity, lowering average invertebrate richness in pond communities by 23%. However, fish presence and sample year interacted to determine both richness and taxa composition: as drought conditions intensified, the effects of fish weakened such that there were no differences in the richness or composition between fish and fishless ponds by the later sampling years. Moreover, large‐bodied invertebrate groups—often considered highly vulnerable to fish predation—were detected within fish‐occupied sites by the final year of the study.This pattern was associated with progressive decreases in precipitation due to a severe drought in California, emphasising the importance of exogenous, regional factors in moderating the strength of biotic niche filters on local community structure over time. Given that all detected fish species were non‐native, these results also have application to understanding and forecasting changes in the diversity of aquatic invertebrates in response to biological invasions. [ABSTRACT FROM AUTHOR]

Land use changes usually lead to the deterioration of freshwater ecosystems and reduced biodiversity. Aquatic organisms are considered valuable indicators for reflecting the conditions of freshwater ecosystems. Understanding the relationship between organisms and land use type, as well as physiochemical conditions, is beneficial for the management, monitoring and restoration of aquatic ecosystems. In this study, fish, macroinvertebrates, and diatoms were investigated at 60 sampling sites in the Wei River basin from October 2012 to April 2013 to determine the relationships between the environment and aquatic organisms. The richness, abundance, Shannon diversity, evenness, Margalef diversity, and Simpson diversity were selected as biological indices for analyzing the correlation between these communities and environmental variables according to Pearson’s coefficient. Canonical correspondence analysis (CCA) was used to analyze the relationship between the biotic communities and environmental variables. The results showed that three diatom indices were weakly correlated with chemical oxygen demand (COD), qualitative Habitat Evaluation Index (QH), and dissolved oxygen (DO). Four macroinvertebrate indices were associated with total phosphorus (TP) while total nitrogen (TN), and agricultural land (AL) had a significant influence on assemblages, suggesting that macroinvertebrates could respond to nutrient levels in the Wei River basin. All land use types had a strong effect on fish indices except AL, indicating that fish would be better used as indicators of spatial changes in the aquatic ecosystem. In conclusion, fish and macroinvertebrates have the potential for use in routine monitoring programs in the Wei River basin.

Zinc (Zn) bioaccumulation and trophic transfer were analyzed in the food web of Lake Nahuel Huapi, a deep, unpolluted ultraoligotrophic system in North Patagonia. Benthic macroinvertebrates, plankton, and native and introduced fish were collected at three sites. The effect of pyroclastic inputs on Zn levels in lacustrine food webs was assessed by studying the impact of the eruption of Puyehue-Cordón Caulle volcanic complex (PCCVC) in 2011, by performing three sampling campaigns immediately before and after the PCCVC eruption, and after 2 years of recovery of the ecosystem. Zinc trophodynamics in L. Nahuel Huapi food web was assessed using nitrogen stable isotopes (δ15N). There was no significant increase of Zn concentrations ([Zn]) in L. Nahuel Huapi biota after the PCCVC eruption, despite the evidence of [Zn] increase in lake water that could be associated with volcanic ash leaching. The organisms studied exhibited [Zn] above the threshold level considered for dietary deficiency, regulating Zn adequately even under a catastrophic situations like PCCVC 2011 eruption. Zinc concentrations exhibited a biodilution pattern in the lake’s food web. To the best of our knowledge, present research is the first report of Zn biodilution in lacustrine systems, and the first to study Zn transfer in a freshwater food web including both pelagic and benthic compartments. [ABSTRACT FROM AUTHOR]

Many large European rivers have undergone multiple pressures that have strongly impaired ecosystem functioning at different spatial and temporal scales. Global warming and other environmental changes have favored the success of invasive species, deeply modifying the structure of aquatic communities in large rivers. Some exogenous species could alter trophic interactions within assemblages by increasing the predation risk for potential prey species (top-down effect) and limiting the dynamics of others via resource availability limitation (bottom-up effect). Furthermore, large transboundary rivers are complex aquatic ecosystems that have often been poorly investigated so that data for assessing long-term ecological trends are missing. In this study, we propose an original approach for investigating long-term combined effects of global warming, trophic resource decrease, predation risk, and water quality variations on the trait-based structure of macroinvertebrate and fish assemblages over 26 yr (1985-2011) and 427-km stretch of the river Meuse (France and Belgium). The study of temporal variations in biological, physiological, and ecological traits of macroinvertebrate and fish allowed identifying community trends and distinguishing impacts of environmental perturbations from those induced by biological alterations. We provide evidence, for this large European river, of an increase in water temperature (close to 1°C) and a decrease in phytoplankton biomass (−85%), as well as independent effects of these changes on both invertebrate and fish communities. The reduction of trophic resources in the water column by invasive molluscs has dramatically affected the density of omnivorous fish in favor of invertebrate feeders, while scrapers became the major feeding guild among invertebrates. Macroinvertebrate and fish communities have shifted from large-sized organisms with low fecundity to prolific, small-sized organisms, with early maturity, as a response to increased predation pressure. [ABSTRACT FROM AUTHOR]

Freshwater littoral zones harbor diverse ecological communities and serve numerous ecosystem functions that are controlled, in part, by natural water level fluctuations. However, human alteration of lake hydrologic regimes beyond natural fluctuations threaten littoral zone ecological integrity. One type of hydrologic alteration in lakes is winter water level drawdowns, which are frequently employed for hydropower, flood control, and macrophyte control, among other purposes. Here, we synthesize the abiotic and biotic responses to annual and novel winter water level drawdowns in littoral zones of lakes and reservoirs. The dewatering, freezing, and increased erosion of exposed lakebeds drive changes in the littoral zone. Shoreline-specific physicochemical conditions such as littoral slope and shoreline exposure further induce modifications. Loss of fine sediment decreases nutrient availability over time, but desiccation may promote a temporary nutrient pulse upon re-inundation. Annual winter drawdowns can decrease taxonomic richness of macrophytes and benthic invertebrates and shift assemblage composition to favor taxa with r-selected life history strategies and with functional traits resistant to direct and indirect drawdown effects. Fish assemblages, though less directly affected by winter drawdowns (except where there is critically low dissolved oxygen), experience negative effects via indirect pathways like decreased food resources and spawning habitat. We identify eight general research gaps to guide future research that could improve our understanding about the complex effects of winter drawdowns on littoral zone ecology. [ABSTRACT FROM AUTHOR]

Global demand for timber products is increasing. Despite high interest in the environmental impacts of forestry and efforts to improve management practices, little synthesis of these impacts exist. This systematic review unifies the literature on timber harvest impacts on stream biota, quantifies temporal, geographical and taxonomic trends in this forestry research, and appraises widespread methodological approaches. Our findings highlight heterogeneity across studies regarding the response of aquatic biota to timber harvest. Overall we found few consistent responses of taxa to forestry, with variation in the direction and magnitude of observed responses across studies. We also show that the number of publications on this topic increased through till 2008 and has declined since that time. The majority of this research has been conducted in North America with a focus on invertebrates. Additionally, the majority of studies have been retrospective surveys conducted on a stream reach scale over a period of less than five years. We suggest that the most critical gaps for forestry research on aquatic fauna are in underrepresented areas with increasing levels of forestry, particularly in Asia, and on understudied taxa. We also propose that greater emphasis should be placed on gaining more mechanistic understandings of biotic responses to disturbance, through experimentation and more powerful statistical approaches. This will be necessary to improve understanding and predictive capacity of the responses of aquatic biota to increasing global timber harvest. This information is vital for effective management in the face of intensified use of forests. [ABSTRACT FROM AUTHOR]

Flow alteration is widespread in streams, but current understanding of the effects of differences in flow characteristics on stream biological communities is incomplete. We tested hypotheses about the effect of variation in hydrology on stream communities by using generalized additive models to relate watershed information to the values of different flow metrics at gauged sites. Flow models accounted for 54-80% of the spatial variation in flow metric values among gauged sites. We then used these models to predict flow metrics in 842 ungauged stream sites in the mid-Atlantic United States that were sampled for fish, macroinvertebrates, and environmental covariates. Fish and macroinvertebrate assemblages were characterized in terms of a suite of metrics that quantified aspects of community composition, diversity, and functional traits that were expected to be associated with differences in flow characteristics. We related modeled flow metrics to biological metrics in a series of stressor-response models. Our analyses identified both drying and base flow instability as explaining 30-50% of the observed variability in fish and invertebrate community composition. Variations in community composition were related to variations in the prevalence of dispersal traits in invertebrates and trophic guilds in fish. The results demonstrate that we can use statistical models to predict hydrologic conditions at bioassessment sites, which, in turn, we can use to estimate relationships between flow conditions and biological characteristics. This analysis provides an approach to quantify the effects of spatial variation in flow metrics using readily available biomonitoring data. [ABSTRACT FROM AUTHOR]

We examined patterns of concordance between macroinvertebrate and fish communities among adventitious and ordinate tributaries of the Monongahela River in southwestern Pennsylvania in order to determine their efficacy as mutual surrogates for the assessment of ecosystem integrity. Fish, macroinvertebrates, and 19 water quality parameters were sampled from 20 streams. Collected data were analyzed by principal components analysis, redundancy analysis, and Ward’s distance clustering matrices to determine degrees of community concordance and similarity. Fish and macroinvertebrate communities were assessed utilizing Indices of Biotic Integrity (IBI) in order to compare stream ecosystem health as expressed by each index. Adventitious and ordinate macroinvertebrate communities largely clustered in like groups with adventitious tributaries dominated by the crustacean Gammarus sp. and ordinate streams dominated by the trichopteran, Hydropsyche sp. Adventitious communities were strongly influenced by elevated total alkalinity and total suspended solids; ordinate communities by contrast to elevated total organic carbon and specific conductance. Fish communities showed no significant relationship to water quality parameters among either tributary type, but often grouped with their nearest geographic neighbor. The respective indices revealed a discord between the two communities suggesting that neither community serves as a surrogate for the other as an indicator of stream health in this basin. Both communities appeared to be driven by differences in local environmental conditions. [ABSTRACT FROM AUTHOR]

Habitat heterogeneity can influence biological communities by providing a diversity of areas that can be occupied by different species. Sandy beach surf zones are often considered homogenous environments; however, sand bars moved by currents and waves can produce trench-like shapes or troughs that provide heterogeneity. The influence of habitat heterogeneity produced by sand movement is unclear despite the fact that surf zones are an important habitat for larval and juvenile fish and macrocrustaceans. To determine if, and how, the fish and macroinvertebrate communities present in trough and non-trough or flat areas of Oregon surf zones differ, we compared species assemblages in both areas at three beaches adjacent to estuary mouths over 2 years. Troughs had different communities compared with flat areas, with higher total catch (mean ± SD = 123.2 ± 122.1 versus 43.6 ± 44.5 individuals × 100 m−2) and taxon richness (6.7 ± 2.7 versus 4.0 ± 2.3 taxa); these differences were potentially due to water movement, prey availability and sediment size. The fish and macroinvertebrate communities did not vary between years but there were significant differences among beaches, with the most distinct community present at the only beach adjacent to an estuary without a jetty at its mouth, which was possibly due to higher species movement between the surf zones and estuary. Fish and macrocrustacean surf zone communities varied spatially within and among beaches in relation to habitat heterogeneity provided by sand movement and, potentially, the influence of adjacent habitats. [ABSTRACT FROM AUTHOR]

Freshwater streams are critical resources that provide multiple benefits to humans and aquatic biota alike. As climate changes, it is projected that changes to the hydrological cycle and water temperatures will affect individual biota and aquatic ecosystems as a whole. The goal of this study was to determine the extent of climate change impacts on stream ecosystems as represented by four commonly used stream health indicators (Ephemeroptera, Plecoptera, and Trichoptera taxa (EPT), Family Index of Biotic Integrity (FIBI), Hilsenhoff Biotic Index (HBI), and fish Index of Biotic Integrity (IBI)). Seven watersheds in Michigan were selected based on stream thermal regimes. The Soil and Water Assessment Tool was used to simulate streamflow and pollutant loads. Important variables for each thermal class were selected using a Bayesian variable selection method and used as inputs to adaptive neuro-fuzzy inference systems models of EPT, FIBI, HBI, and IBI. Finally, an ensemble of climate models from the Coupled Model Intercomparison Project Phase 5 were used to determine the impacts of climate on the stream health in 2020–2040 compared to 1980–2000. The risk of declining stream health was determined using cumulative distribution functions. A stream temperature regression model was also developed to assess potential changes in stream thermal regimes, which could cause shifts in composition of aquatic communities. Several flow regime variables, including those related to flow variability, duration of extreme events, and timing were mainly affected by changing climate. At the watershed scale, most indicators were relatively insensitive to changing climate and the magnitude of stream health decline was low. However, at the reach scale, there are many instances of high risk and large magnitude of declines in the stream health indicators. At the same time, several streams experienced changes in thermal class, mostly transitioning from cold-transitional and cool streams to warm streams. This research demonstrated the applicability of the stream health modeling process in performing a climate change impacts assessment. [ABSTRACT FROM AUTHOR]

Ecohydrological models are frequently used to assess the biological integrity of unsampled streams. These models vary in complexity and scale, and their utility depends on their final application. Tradeoffs are usually made in model scale, where large-scale models are useful for determining broad impacts of human activities on biological conditions, and regional-scale (e.g. watershed or ecoregion) models provide stakeholders greater detail at the individual stream reach level. Given these tradeoffs, the objective of this study was to develop large-scale stream health models with reach level accuracy similar to regional-scale models thereby allowing for impacts assessments and improved decision-making capabilities. To accomplish this, four measures of biological integrity (Ephemeroptera, Plecoptera, and Trichoptera taxa (EPT), Family Index of Biotic Integrity (FIBI), Hilsenhoff Biotic Index (HBI), and fish Index of Biotic Integrity (IBI)) were modeled based on four thermal classes (cold, cold-transitional, cool, and warm) of streams that broadly dictate the distribution of aquatic biota in Michigan. The Soil and Water Assessment Tool (SWAT) was used to simulate streamflow and water quality in seven watersheds and the Hydrologic Index Tool was used to calculate 171 ecologically relevant flow regime variables. Unique variables were selected for each thermal class using a Bayesian variable selection method. The variables were then used in development of adaptive neuro-fuzzy inference systems (ANFIS) models of EPT, FIBI, HBI, and IBI. ANFIS model accuracy improved when accounting for stream thermal class rather than developing a global model. [ABSTRACT FROM AUTHOR]

Given predicted increases associated with human-induced climate change, stream temperatures are likely to approach upper tolerance limits of aquatic biota within the coming decades. Little information is available regarding thermal tolerance limits of lotic fauna or mechanisms allowing fauna to persist following high temperature events (e.g. use of thermal refuges). Cold-water refuges can facilitate survival of fish in the Northern Hemisphere, but little evidence of similar refuges exists elsewhere. Planned releases of hypolimnetic, or a mixture of top and bottom, waters from reservoirs have recently been touted as a novel method to potentially ameliorate extreme temperature events. However, the feasibility of this technique has not been fully discussed in the published literature. Therefore, we present a literature review, an analysis of thermal data for some large dams in southern Australia in relation to known thermal tolerances of native fauna, and an assessment of current management practices regarding the technique. We show that hypolimnetic releases have variable impacts on water temperatures downstream of a dam, depending on size, off-take infrastructure and management practices but, even where there is an effect, knowledge gaps are too numerous for this technique to be currently feasible. Furthermore, hypolimnetic releases generally evoke negative connotations among natural resource managers, due to the occurrence of cold-water shock in some species. If knowledge gaps and limitations can be addressed, it is possible that the technique may be considered in future, so we present potential tools for future assessment, capacities and limitations and discuss potential scenarios where environmental managers might consider this technique. [ABSTRACT FROM AUTHOR]

Variable selection is a critical step in development of empirical stream health prediction models. This study develops a framework for selecting important in-stream variables to predict four measures of biological integrity: total number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa, family index of biotic integrity (FIBI), Hilsenhoff biotic integrity (HBI), and fish index of biotic integrity (IBI). Over 200 flow regime and water quality variables were calculated using the Hydrologic Index Tool (HIT) and Soil and Water Assessment Tool (SWAT). Streams of the River Raisin watershed in Michigan were grouped using the Strahler stream classification system (orders 1–3 and orders 4–6), k -means clustering technique (two clusters: C1 and C2), and all streams (one grouping). For each grouping, variable selection was performed using Bayesian variable selection, principal component analysis, and Spearman's rank correlation. Following selection of best variable sets, models were developed to predict the measures of biological integrity using adaptive-neuro fuzzy inference systems (ANFIS), a technique well-suited to complex, nonlinear ecological problems. Multiple unique variable sets were identified, all which differed by selection method and stream grouping. Final best models were mostly built using the Bayesian variable selection method. The most effective stream grouping method varied by health measure, although k -means clustering and grouping by stream order were always superior to models built without grouping. Commonly selected variables were related to streamflow magnitude, rate of change, and seasonal nitrate concentration. Each best model was effective in simulating stream health observations, with EPT taxa validation R 2 ranging from 0.67 to 0.92, FIBI ranging from 0.49 to 0.85, HBI from 0.56 to 0.75, and fish IBI at 0.99 for all best models. The comprehensive variable selection and modeling process proposed here is a robust method that extends our understanding of watershed scale stream health beyond sparse monitoring points. [ABSTRACT FROM AUTHOR]

Summary The dynamics and relationships between society and nature are complex and difficult to predict. Anthropogenic activities affect the ecological integrity of our natural resources, specifically our streams. Further, it is well-established that the costs of these activities are born unequally by different human communities. This study considered the utility of integrating stream health metrics, based on stream health indicators, with socio-economic measures of communities, to better characterize these effects. This study used a spatial multi-factor model and bivariate mapping to produce a novel assessment for watershed management, identification of vulnerable areas, and allocation of resources. The study area is the Saginaw River watershed located in Michigan. In-stream hydrological and water quality data were used to predict fish and macroinvertebrate measures of stream health. These measures include the Index of Biological Integrity (IBI), Hilsenhoff Biotic Index (HBI), Family IBI, and total number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa. Stream health indicators were then compared to spatially coincident socio-economic data, obtained from the United States Census Bureau (2010), including race, income, education, housing, and population size. Statistical analysis including spatial regression and cluster analysis were used to examine the correlation between vulnerable human populations and environmental conditions. Overall, limited correlation was observed between the socio-economic data and ecological measures of stream health, with the highest being a negative correlation of 0.18 between HBI and the social parameter household size. Clustering was observed in the datasets with urban areas representing a second order clustering effect over the watershed. Regions with the worst stream health and most vulnerable social populations were most commonly located nearby or down-stream to highly populated areas and agricultural lands. [ABSTRACT FROM AUTHOR]

The meanders and floodplains of the Kushiro River were restored in March 2011. A1.6-km stretch of the straightened main channel was remeandered by reconnecting the cutoff former channel and backfilling the straightened reach, and a 2.4-km meander channel was restored. Additionally, flood levees were removed to promote river-floodplain interactions. There were four objectives of this restoration project: to restore the in-stream habitat for native fish and invertebrates; to restore floodplain vegetation by increasing flooding frequency and raising the groundwater table; to reduce sediment and nutrient loads in the core wetland areas; to restore a river-floodplain landscape typical to naturally meandering rivers. In this project, not only the natural landscape of a meandering river but also its function was successfully restored. The monitoring results indicated that these goals were likely achieved in the short term after the restoration. The abundance and species richness of fish and invertebrate species increased, most likely because the lentic species that formerly inhabited the cutoff channel remained in the backwater and deep pools created in the restored reach. In addition, lotic species immigrated from neighboring reaches. The removal of flood levees and backfilling of the formerly straightened reach were very effective in increasing the frequency of flooding over the floodplains and raising the water table. The wetland vegetation recovered rapidly 1 year after the completion of the meander restoration. Sediment-laden floodwater spread over the floodplain, and approximately 80-90% of the fine sediment carried by the water was filtered out by the wetland vegetation. [ABSTRACT FROM AUTHOR]

This study compares the relative influences of physiography and anthropogenic pressures on river biota at catchment, riparian corridor, and reach scales. Environmental data, catchment and riparian corridor land use, anthropogenic modifications and biological data were compiled for 301 French sites sampled from 2005 to 2008. First, relationships between anthropogenic pressures and fish and macroinvertebrate assemblages were analysed using redundancy analysis. Second, the influences of physiography and the three scales of human pressures on biological assemblages were measured using variance partitioning. Distributions of fish and macroinvertebrate taxa along the pressure gradients agreed with bio-ecological knowledge. At the reach scale, assemblage variability among the 301 French sites was related to the presence of an impoundment and to poor water quality, while at larger scales it was linked to a gradient from forest to agricultural covers. In addition, a large proportion of the explained variability in assemblage composition was related to complex interactions among factors (~40%) and to physiographic variables (~30%). Furthermore, our results highlight that catchment land use better reflects local water quality impairments than hydromorphological degradations. Finally, this study supports the idea that human pressure effects on river communities are linked at several spatial scales and must be considered jointly. [ABSTRACT FROM AUTHOR]

Abstract: Biotic indices for algae, macroinvertebrates, and fish assemblages can be effective for monitoring stream enrichment, but little is known regarding the value of the three assemblages for detecting perturbance as a consequence of low-level nutrient enrichment. In the summer of 2006, we collected nutrient and biotic samples from 30 wadeable Ozark streams that spanned a nutrient-concentration gradient from reference to moderately enriched conditions. Seventy-three algal metrics, 62 macroinvertebrate metrics, and 60 fish metrics were evaluated for each of the three biotic indices. After a group of candidate metrics had been identified with multivariate analysis, correlation procedures and scatter plots were used to identify the four metrics having strongest relations to a nutrient index calculated from log transformed and normalized total nitrogen and total phosphorus concentrations. The four metrics selected for each of the three biotic indices were: algae—the relative abundance of most tolerant diatoms, the combined relative abundance of three species of Cymbella, mesosaprobic algae percent taxa richness, and the relative abundance of diatoms that are obligate nitrogen heterotrophs; macroinvertebrate—the relative abundance of intolerant organisms, Baetidae relative abundance, moderately tolerant taxa richness, and insect biomass; fish—herbivore and detritivore taxa richness, pool species relative abundance, fish catch per unit effort, and black bass (Micropterus spp.) relative abundance. All three biotic indices were negatively correlated to nutrient concentrations but the algal index had a higher correlation (rho=−0.89) than did the macroinvertebrate and fish indices (rho=−0.63 and −0.58, respectively). Biotic index scores were lowest and nutrient concentrations were highest for streams with basins having the highest poultry and cattle production. Because of the availability of litter for fertilizer and associated increases in grass and hay production, cattle feeding capacity increases with poultry production. Studies are needed that address the synergistic effect of poultry and cattle production on Ozark streams in high production areas before ecological risks can be adequately addressed. [Copyright &y& Elsevier]

This study assessed the heavy metals particularly total cadmium, total lead and total chromium in the waters, fish and macroinvertebrates in Manila Bay, Philippines. The heavy metals monitoring in the waters of Manila Bay were carried out for six consecutive months, September to February of 2007-2008, covering both wet and dry periods. The collection of fishes and macroinvertebrates in this investigation lasted from September to November 2007. Results showed that the heavy metals particularly total chromium, total lead and total cadmium were evident in the waters, fish and macroinvertebrates. Significant differences on the total cadmium and total lead in the waters were noted for both the wet and dry periods. Accumulation of heavy metals in the aquatic organisms was species dependent. Highest heavy metal concentrations among the tissues in the studied fishes were evident in the liver as compared to the muscle. Continuous heavy metals monitoring is encouraged to effectively analyze the risk and impact of heavy metals on the environment and on the general public's welfare. [ABSTRACT FROM AUTHOR]

Lessons learned from the development, implementation, and initial 8 y of study findings from a long-term study to assess the effects of pulp and paper mill effluents on receiving waters are summarized as a conclusion to a series of articles (this issue) on study findings. The study, based on industry-defined information needs, was developed via a science-based experimental design into a long-term (>10 y) watershed-scale monitoring program that integrated in-stream population/ community assessment, laboratory chronic bioassays, and fathead minnow full life-cycle assays as well as water quality and effluent quality monitoring and habitat assessment in addressing the presence of effluent effects. The 4 study streams (Codorus Creek, PA; Leaf River, MS; and the McKenzie and Willamette rivers, OR) represented both bleached and unbleached kraft mill processes and effluent concentrations that ranged from near typical for the United States (0.4%) to very high (Codorus Creek=32%). Following 8 y of monitoring, the weight of evidence suggests an absence of biological differences at stations downstream of the mill discharges for periphyton or macroinvertebrates and, with the exception of 1 of 9 large-bodied fish and 1 of 7 small-bodied fish community structure metrics for 1 river (McKenzie), an absence of differences for fish communities. Laboratory bioassay and fathead minnow full-life cycle tests supported a substantial "margin of safety" in that, depending on the effluent, adverse responses did not occur until effluent concentrations were from 2 times to more than 150 times in-stream concentrations. The incorporation of a watershed spatial scale illustrated that each sample site tended to be unique over the 28 to 50 km monitored segments with respect to habitat and that knowledge of these variables permitted accurate evaluations of effluent effects. Similarly, the multiyear study framework provided information regarding the natural seasonal and year-to-year variability in fish communities and consequently a better understanding of how potential effluent effects signals could be expressed within this variability. The study incorporated an adaptive management strategy that provided for study design and monitoring modifications over time as a way of benefiting from practical experience and knowledge gained through time and to optimize the use of study resources. Results from this initial 8 y of monitoring, to our knowledge, represent the longest-known population/community-level assessment of the in-stream effects of pulp and paper mill effluents. Beyond the lessons learned with respect to effluent effects are those related to the design and conduct of long-term watershed-scale studies that may be of use to others in developing watershed assessment or management programs. [ABSTRACT FROM AUTHOR]

The article presents a study on the hydroecological reaction of river systems to shrinking glaciers. It mentions that aquatic ecosystems in high latitude and altitude environments are deeply influenced by cryospheric and hydrological process because of links between atmospheric forcing like glacier mass-balance and biota. It notes that the results of shrinking glaciers will alter spatial and temporal dynamics in bulk basin runoff associated with important changes in the relative contributions of snowmelt, glaciermelt and groundwater to stream flow. It suggests that glacier shrinkage and associated changes will be a major driver of the future biodiversity of stream communities in cold environments.

Monitoring pesticides in the environment requires the use of sensitive analytical methods. However, existing methods are generally not suitable for analyzing small organisms, as they require large matrix masses. This study explores the development of a miniaturized extraction protocol for the monitoring of small organisms, based on only 30 mg of matrix. The miniaturized sample preparation was developed using fish and macroinvertebrate matrices. It allowed the characterization of 41 pesticides and transformation products (log P from −1.9 to 4.8) in small samples with LC-MS/MS, based on European guidelines (European Commission DG-SANTE, 2019). Quantification limits ranged from 3 to 460 ng g−1 dry weight (dw) for fish and from 0.1 to 356 ng g−1 dw for invertebrates, with most below 60 ng g−1 dw. Extraction rates ranged from 70% to 120% for 35 molecules in fish. Recoveries ranged from 70% to 120% for 37 molecules in macroinvertebrates. Inter-day precision was below 30% for 32 molecules at quantification limits. The method was successfully applied to 17 fish and 19 macroinvertebrates collected from two ponds of the French region of Dombes in November and May 2018, respectively. Both sample matrices were nearly always contaminated with benzamide, imidacloprid-desnitro, and prosulfocarb at respective concentrations of 42–237, 3, and 30–165 ng g−1 dw in fish, and 62–438, 2–6, and 15–29 ng g−1 dw in macroinvertebrates. Results show that this method is an effective tool for characterizing polar pesticides in small biotic samples. [Display omitted] • Miniaturization of an extraction protocol for molecules with large polarity range. • Protocol validation on fish and macroinvertebrates. • Most limits of quantification were better than 10 ng g−1 dry weight. • Most of extraction recoveries were comprised between 70 and 120%. [ABSTRACT FROM AUTHOR]

We sampled 41 sites on 34 nonwadeable rivers that represent the types of rivers in Wisconsin, and the kinds and intensities of nutrient and other anthropogenic stressors upon each river type. Sites covered much of United States Environmental Protection Agency national nutrient ecoregions VII—Mostly Glaciated Dairy Region, and VIII—Nutrient Poor, Largely Glaciated upper Midwest. Fish, macroinvertebrates, and three categories of environmental variables including nutrients, other water chemistry, and watershed features were collected using standard protocols. We summarized fish assemblages by index of biotic integrity (IBI) and its 10 component measures, and macroinvertebrates by 2 organic pollution tolerance and 12 proportional richness measures. All biotic and environmental variables represented a wide range of conditions, with biotic measures ranging from poor to excellent status, despite nutrient concentrations being consistently higher than reference concentrations reported for the regions. Regression tree analyses of nutrients on a suite of biotic measures identified breakpoints in total phosphorus (~0.06 mg/l) and total nitrogen (~0.64 mg/l) concentrations at which biotic assemblages were consistently impaired. Redundancy analyses (RDA) were used to identify the most important variables within each of the three environmental variable categories, which were then used to determine the relative influence of each variable category on the biota. Nutrient measures, suspended chlorophyll a, water clarity, and watershed land cover type (forest or row-crop agriculture) were the most important variables and they explained significant amounts of variation within the macroinvertebrate ( R 2 = 60.6%) and fish ( R 2 = 43.6%) assemblages. The environmental variables selected in the macroinvertebrate model were correlated to such an extent that partial RDA analyses could not attribute variation explained to individual environmental categories, assigning 89% of the explained variation to interactions among the categories. In contrast, partial RDA attributed much of the explained variation to the nutrient (25%) and other water chemistry (38%) categories for the fish model. Our analyses suggest that it would be beneficial to develop criteria based upon a suite of biotic and nutrient variables simultaneously to deem waters as not meeting their designated uses. [ABSTRACT FROM AUTHOR]

1. Intermittent streams in the semi-arid region of Brazil are distinctive landscape features existing as dry watercourses for most of the time. It has been recognized that the extremes of flooding and total absence of water flow are the principal hydrological characteristics of rivers and streams in this region. This is a consequence of complex climatic patterns that lead to an irregular distribution of the small amount of rainfall and low thermal amplitude. The latter is the main climatic difference between the Brazilian semi-arid region and other semi-arid lands. 2. The expansion of water resource development has been a threat to the natural flow regime and the ecological integrity of rivers and streams in semi-arid Brazil. Efforts to manage and conserve the natural flow regime of these systems are hampered by limited scientific information on the ecological processes driving their flora and fauna and the responses of biota to the high natural variability in flow regime. 3. The most important issues in the conservation of streams in semi-arid Brazil are the need for their recognition as important sites of biodiversity and that this diversity is closely associated with natural patterns of flow and the hydrological disturbances. Without the understanding of how the extremes of flooding and drought affect the aquatic fauna, the conservation strategies for Brazilian semi-arid streams and their fauna will not be effective. 4. Therefore, conservation efforts in semi-arid Brazil must ensure that the processes sustaining biodiversity are maintained at multiple-scale and landscape levels and that the natural integrity of the riparian zone is maintained [ABSTRACT FROM AUTHOR]

1. The River Styles® framework is a geomorphic approach to the classification of river types, assessment of the physical condition of rivers, and planning of physical rehabilitation. However, the linkages between River Styles and aquatic biodiversity conservation are still only weakly developed. 2. In this study, 41 sites in the Bega River basin in New South Wales, Australia, were classified according to River Style and geomorphic condition, and surveyed for four biological assemblages: diatoms, aquatic and semi-aquatic macrophytes, aquatic macroinvertebrates and fish. 3. Each assemblage differed significantly among River Styles. However, in the case of diatoms and fish, these differences could be accounted for by geographic clustering of sites in the same River Style, and a tendency for River Styles to occupy particular altitudinal zones and sizes of streams. This result was attributed to the overriding influences of water quality on diatoms and of altitude-related variation in water temperature and distance from the ocean on fish. For macrophytes and macroinvertebrates, geomorphic river type appeared to exert a direct influence, probably via variation in physical habitat characteristics. 4. Geomorphic condition, judged as good, moderate or poor by reference to the inferred natural condition of each River Style, was also significantly associated with differences in biological assemblages other than fish. Twice as many taxa appeared to favour sites in good geomorphic condition as favoured sites in poor condition. Many of the taxa associated with sites in poor condition are alien taxa introduced to Australia since European settlement. 5. These findings imply that protection of reaches that are in good geomorphic condition is likely to be critical for the maintenance of indigenous biodiversity, and that rehabilitation of geomorphic condition can assist in the rehabilitation of native riverine biota. [ABSTRACT FROM AUTHOR]

New highways are pervasive, pernicious threats to stream ecosystems because of their short- and long-term physical, chemical, and biological impacts. Unfortunately, standard environmental impact statements (EISs) and environmental assessments (EAs) focus narrowly on the initial direct impacts of construction and ignore other long-term indirect impacts. More thorough consideration of highway impacts, and, ultimately, better land use decisions may be facilitated by conceptualizing highway development in three stages: initial highway construction, highway presence, and eventual landscape urbanization. Highway construction is characterized by localized physical disturbances, which generally subside through time. In contrast, highway presence and landscape urbanization are characterized by physical and chemical impacts that are temporally persistent. Although the impacts of highway presence and landscape urbanization are of similar natures, the impacts are of a greater magnitude and more widespread in the urbanization phase. Our review reveals that the landscape urbanization stage is clearly the greatest threat to stream habitat and biota, as stream ecosystems are sensitive to even low levels ( [ABSTRACT FROM AUTHOR]

We conducted a field study to examine the influence of hydroperiod and concomitant changes in abiotic (wetland size, pH, conductivity, dissolved oxygen and water temperature) and biotic (predatory fish presence) characteristics on macroinvertebrate communities in isolated wetlands in southern New Hampshire. Invertebrates were sampled using dipnet sweeps in 42 wetlands with short (<4 months), intermediate (4–11 months) or long (permanent) hydroperiods in 1998 and 1999. We found that invertebrate genera richness, and to a lesser degree abundance, increased linearly along the hydrological gradient, and in response to temperature and dissolved oxygen. Relative abundance of genera also differed markedly with respect to hydroperiod. Most notably, invertebrate communities changed from Acilius-dominated communities to Notonecta-dominated communities. Invertebrate relative abundances in permanent wetlands also differed with respect to the occurrence of predatory fish. Some genera (e.g., Libellula, and Dytiscus) were more likely to occur in permanent wetlands without fish, whereas other genera (e.g., Buena, and Basiaeshna) were more likely to occur in wetlands with predatory fish. Because aquatic invertebrate communities differed markedly with respect to wetland hydroperiod, and in relation to the occurrence of predatory fish, it is essential to retain a diversity of wetlands in the landscape to ensure the long-term persistence of aquatic invertebrate biodiversity. [ABSTRACT FROM AUTHOR]