Altered Stream Research Articles

Seasonal movements between main stem and tributaries may facilitate the persistence of Roundtail Chub and Flannelmouth Sucker within an altered stream system

AbstractObjectiveMovement enables animals to complete their life history by responding to changing environmental conditions. Linking movement behaviors to life history characteristics can allow more targeted management applications for declining native fish populations. We identified seasonal movement patterns of Roundtail Chub Gila robusta and Flannelmouth Sucker Catostomus latipinnis, two understudied species that currently occupy only a portion of their historical range in the Colorado River basin.MethodsWe coupled passive integrated transponder tag antenna systems with multistate capture–recapture models to quantify juvenile and adult movement between main‐stem and tributary habitats in the Blacks Fork subbasin of southwestern Wyoming during 2019–2021. We also evaluated how flow and temperature may cue the timing of seasonal movements.ResultAdults from both species made spring movements, likely associated with spawning, to reach upstream tributary habitat, though adult Flannelmouth Sucker movements were more common and longer. Roundtail Chub primarily moved into the Hams Fork, while Flannelmouth Sucker primarily moved into Muddy Creek, an intermittent tributary that was also identified as important for juvenile rearing. Juvenile movements occurred primarily during the fall months, with distance traveled comparable between species. Temperature and flow influenced the timing of spring movements for adult Flannelmouth Sucker, with rising temperatures triggering movement and low flow potentially limiting access to preferred spawning habitat.ConclusionIdentified movements likely contribute to Roundtail Chub and Flannelmouth Sucker persistence in this highly altered stream system and ultimately provide insights for management and recovery strategies to prevent further population declines.

Land use differentially alters microbial interactions and detritivore feeding during leaf decomposition in headwater streams

Abstract Human‐driven land conversion from forest to agriculture introduces nutrients, like nitrogen (N) and phosphorus (P), which upon entering nearby streams can stimulate growth and metabolism of microbial autotrophs (algae) and heterotrophs (fungi and bacteria). Recent evidence indicates that algae also can stimulate microbial heterotrophs associated with decaying plant litter by exuding labile carbon (C), defined as the priming effect on decomposition. These autotroph–heterotroph interactions may further alter detritivore feeding ecology, suggesting many complex mechanisms of land‐use change on stream ecosystem functions. In order to investigate the effects of land use on autotroph–heterotroph interactions, we used a full‐factorial design manipulating labile C (glucose and acetate) and nutrients (N and P) to test their effects during red maple litter decomposition within four forested and four pasture agriculture streams in the Point Remove catchment, Arkansas. We deployed nutrient‐diffusing substrates (NDS) containing litter and either agar, agar + labile C, agar + NP, or agar + CNP for 20 days and measured microbial biomass and metabolism, and detrital mass loss. Additionally, we fed litter to Tipula sp. to assess shifts in consumption and egestion rates. Both microbial heterotrophs and autotrophs responded to NDS manipulations, but not land use. Heterotrophic microbes showed evidence of nutrient limitation and negative priming, while algal biomass was negatively associated with heterotrophs. Tipula consumption and egestion rates were both elevated when feeding on litter incubated in agriculture streams, but only egestion responded to NDS manipulations, suggesting a change in assimilation efficiencies. Cumulatively, we suggest that altered stream conditions, such as those resulting from land‐use change, can alter food webs and detritivore feeding more heavily than microbial interactions during litter decomposition in stream ecosystems. These results add to the literature demonstrating shifts in autotroph–heterotroph interactions with anthropogenic nutrient pollution, and the implications for detritivore feeding and overall C cycling in streams.

Environmental DNA analysis confirms extant populations of the cryptic Irwin\u2019s turtle within its historical range

BackgroundApproximately 50% of freshwater turtles worldwide are currently threatened by habitat loss, rural development and altered stream flows. Paradoxically, reptiles are understudied organisms, with many species lacking basic geographic distribution and abundance data. The iconic Irwin’s turtle, Elseya irwini, belongs to a unique group of Australian endemic freshwater turtles capable of cloacal respiration. Water resource development, increased presence of saltwater crocodiles and its cryptic behaviour, have made sampling for Irwin’s turtle in parts of its range problematic, resulting in no confirmed detections across much of its known range for > 25 years. Here, we used environmental DNA (eDNA) analysis for E. irwini detection along its historical and contemporary distribution in the Burdekin, Bowen and Broken River catchments and tributaries. Five replicate water samples were collected at 37 sites across those three river catchments. Environmental DNA was extracted using a glycogen-aided precipitation method and screened for the presence of E. irwini through an eDNA assay targeting a 127 base pair-long fragment of the NADH dehydrogenase 4 (ND4) mitochondrial gene.ResultsElseya irwini eDNA was detected at sites within its historic distribution in the lower Burdekin River, where the species had not been formally recorded for > 25 years, indicating the species still inhabits the lower Burdekin area. We also found higher levels of E. iriwni eDNA within its contemporary distribution in the Bowen and Broken Rivers, matching the prevailing scientific view that these areas host larger populations of E. irwini.ConclusionsThis study constitutes the first scientific evidence of E. irwini presence in the lower Burdekin since the original type specimens were collected as part of its formal description, shortly after the construction of the Burdekin Falls Dam. From the higher percentage of positive detections in the upper reaches of the Broken River (Urannah Creek), we conclude that this area constitutes the core habitat area for the species. Our field protocol comprises a user-friendly, time-effective sampling method. Finally, due to safety risks associated with traditional turtle sampling methods in the Burdekin River (e.g., estuarine crocodiles) we propose eDNA sampling as the most pragmatic detection method available for E. irwini.

Ecological Impacts of Altered Stream Hydrogeomorphic Characteristics Extend Beyond the Channel Boundary: Evidence From Urban Streams of Columbus, OH, United States

Urbanization in stream catchments can have strong effects on stream channel hydrogeomorphic features including channel dimensions, channel-floodplain connectivity, and flood regime. However, the consequences of hydrogeomorphic alterations on aquatic-terrestrial subsidy dynamics are largely unexplored. We examined the associations among hydrogeomorphic characteristics, emergent aquatic insect assemblages, and the density and trophic dynamics of riparian spiders of the family Tetragnathidae at 23 small urban stream reaches in the Columbus, OH (United States) Metropolitan Area. Naturally abundant stable isotopes of 13C and 15N were used to quantify the relative contribution of aquatically derived energy (i.e., nutritional pathways deriving from algae) to tetragnathid spiders and their trophic position. Bankfull discharge was negatively related to both emergence rate and family richness. On average, tetragnathid spiders relied on aquatically derived energy for 36% of their nutrition, with the greatest reliance found for spiders next to channels with wider flood-prone widths and proportionally fewer emergent insects of the family Chironomidae. Mean emergent aquatic insect reliance on aquatically derived energy was 32% and explained 44% of the variation in tetragnathid aquatically derived energy. A positive relationship between δ13C of tetragnathid spiders and emergent insects provides additional evidence of tetragnathid reliance on emergent insects. Mean tetragnathid trophic position was 2.85 and was positively associated with channel sinuosity and negatively associated with aquatic insect emergence rate. Sinuosity was also positively related to aquatically derived energy of emergent aquatic insects; as well as emergent insect family richness; % Ephemeroptera, Plecoptera, and Trichoptera (EPT); and aquatic insect emergence rate; implicating instream habitat-mediated shifts in emergent aquatic insect communities as an indirect mechanistic link between hydrogeomorphic processes and spiders. Our findings underscore that the impacts of stream hydrogeomorphic alterations can cascade into terrestrial food webs. These results suggest that monitoring and restoration of fluvial geomorphic form and function (e.g., sinuosity, slope, and hydrology) confer benefits to both aquatic and terrestrial riparian ecosystems in urban catchments.

Detrusor urethral dyssynergy in dogs: 35 cases (2007-2019).

To evaluate clinical presentation, diagnosis, treatment and outcome of dogs diagnosed with detrusor urethral dyssynergy. Multicentre (n=3 UK referral clinics), retrospective, observational study. Database searches were performed (2007 to 2019) to identify dogs with detrusor urethral dyssynergy. Dogs with structural abnormalities or detectable neurological disorders affecting micturition were excluded. Clinical presentation, diagnostic procedures, treatment and outcome were evaluated. Thirty-five dogs were included. Middle-aged, large-breed, male neutered dogs were most frequently documented. Four female dogs were included. Fifteen breeds, including Labrador retrievers (8/35; 22.9%), golden retrievers (5/35;14.3%) and cross-breeds (5/35; 14.3%) were identified. Median duration of clinical signs was 152 days (range 0 to 1095). All dogs were dysuric at presentation with 17/35 (48.6%) reported to have an altered stream of urine and 17/35 (48.6%) to be stranguric. Follow-up data were available for 34 dogs (median 136 days, range 4 to 2188). Response was classified as good (20/34; 58.8%), partial (7/34; 20.5%) or poor (7/34; 20.5%). Overall time to response was known for 21 of 34 dogs (partial n=6, good n=15) with a median of 11 days (range 1 to 155). Four dogs had surgical intervention (castration n=4, cystostomy tube n=2). Three dogs were euthanased due to partial (n=1) or poor (n=2) response. Medications were discontinued in 11 of 20 (55.0%) dogs with a good response to therapy, two of these relapsed. Detrusor urethral dyssynergy is an uncommon micturition disorder in dogs, in particular females. Medical therapy with or without surgery resulted in a favourable prognosis in the majority of dogs, although many require long-term medication.

Urban planning for fishes: untangling a new project’s effects from old infrastructure and regional patterns

Urbanization has altered fish communities in many ways. However, as cities expand and redevelop, it is challenging to assess the impacts of new projects given existing alteration. We investigated how new and old infrastructure alters fish communities over a 4-year period in Metro Vancouver, British Columbia (Canada). We compared fish communities from a stream altered by a new rapid transit rail line and seven reference sites over 4 years, from before to after construction. We provide evidence that new and old projects depress the density, species richness, and diversity of fish communities. During and after construction, sections of the altered stream had one fewer species and lower density compared with preconstruction and reference streams. Streams without existing culverts had more species and greater diversity than those with culverts, but only in some years. Diversity was lower in 1 year of the study across all streams. We argue that most monitoring in Canada is insufficient to detect the incremental changes that new projects may cause and suggest improvements in monitoring and protecting reference streams.

Do changes in riparian zones affect periphyton growth and invertebrate colonization on rocky substrates in Atlantic Forest streams?

ABSTRACT: We evaluated the growth of periphyton and colonization of sterilized cobbles by invertebrates in three coastal streams of the Atlantic Forest (Southeast Brazil) that differ in the conservation level of riparian zones. Because of differences in light availability and water temperature, we hypothesized the growth of periphytic algae would be higher in the most altered stream. Consequently, invertebrate assemblages would differ among streams. Cobbles with similar sizes were ashed and incubated for 7, 15, 30, 45 and 60 days in the studied streams. Despite periphyton growth was faster in the most altered stream, contents of chlorophyll-a did not differ among streams. A total of 954 individuals (98% insects) belonging to 36 taxa was found. Invertebrate density was higher and increased throughout the experiment in the preserved stream, while invertebrate biomass was higher on the initial sampling intervals (7 and 15 days). A stream effect on invertebrate assemblages was observed after the 15th day and 17 taxa were found only in the preserved stream. Leptophlebiidae (Ephemeroptera), Hydroptilidae, Helichopsychidae, Leptoceridae (Trichoptera) and Orthocladiinae (Diptera) showed specificities with the assemblages found in the preserved stream and no taxa proved to be an indicator of the assemblages found in the altered streams. These results showed that changes in the riparian zones of Atlantic Forest streams did not affect the content of chlorophyll-a on rocky substrates, but the growth of periphyton influenced the density and structural composition of invertebrate assemblages. Our findings partially support the proposed hypothesis and conform to the notion of the importance of periphyton community for the colonization of exposed substrates by invertebrates and for evaluating the consequences of anthropogenic changes in ecosystem functioning and aquatic communities.

Stream of consciousness: Quantum and biochemical assumptions regarding psychopathology

The accepted paradigms of mainstream neuropsychiatry appear to be incompletely adequate and in various cases offer equivocal analyses. However, a growing number of new approaches are being proposed that suggest the emergence of paradigm shifts in this area. In particular, quantum theories of mind, brain and consciousness seem to offer a profound change to the current approaches. Unfortunately these quantum paradigms harbor at least two serious problems. First, they are simply models, theories, and assumptions, with no convincing experiments supporting their claims. Second, they deviate from contemporary mainstream views of psychiatric illness and do so in revolutionary ways. We suggest a possible way to integrate experimental neuroscience with quantum models in order to address outstanding issues in psychopathology. A key role is played by the phenomenon called the “stream of consciousness”, which can be linked to the so-called “Gamma Synchrony” (GS), which is clearly demonstrated by EEG data. In our novel proposal, a unipolar depressed patient could be seen as a subject with an altered stream of consciousness. In particular, some clues suggest that depression is linked to an “increased power” stream of consciousness. It is additionally suggested that such an approach to depression might be extended to psychopathology in general with potential benefits to diagnostics and therapeutics in neuropsychiatry.

Comparative swimming and station-holding ability of the threatened Rocky Mountain Sculpin (Cottus sp.) from four hydrologically distinct rivers.

Hydrologic alterations, such as dams, culverts or diversions, can introduce new selection pressures on freshwater fishes, where they are required to adapt to novel environmental conditions. Our study investigated how species adapt to natural and altered stream flow, where we use the threatened Rocky Mountain Sculpin (Cottus sp.) as a model organism. We compared the swimming and station-holding performance of Rocky Mountain Sculpin from four different hydrologic regimes in Alberta and British Columbia, including the North Milk River, a system that experiences increased flows from a large-scale diversion. We measured the slip (Uslip) and failure (Uburst) velocities over three constant acceleration test trials. Uslip was defined as the point at which individuals required the addition of bursting or swimming to maintain position. Uburst was defined as the point at which individuals were unable to hold position in the swimming chamber through swimming, bursting or holding techniques without fully or partially resting on the electrified back plate. We found individuals from the Flathead River in British Columbia (with the highest natural flow) failed at significantly higher Uburst velocities than fish from the southern Albertan populations. However, there was no relationship between peak hydrologic flow from the natal river and Uburst or Uslip. Further, Uburst velocities decreased from 51.8 cm s−1 (7.2 BL s−1) to 45.6 cm s−1 (6.3 BL s−1) by the third consecutive test suggesting the use of anaerobic metabolism. Uslip was not different between trials suggesting the use of aerobic metabolism in station-holding behaviours (Uslip). Moreover, we found no significant differences in individuals from the altered North Milk River system. Finally, individual caudal morphological characteristics were related to both slip and failure velocities. Our study contributes to the conservation of Rocky Mountain Sculpin by providing the first documentation of swimming and station-holding abilities of this benthic fish.

Evaluating Flow Diversion Impacts to Groundwater‐Dependent Riparian Vegetation with Flow Alteration and Groundwater Model Analysis

AbstractAn approach for assessing the potential ecologic response of groundwater‐dependent riparian vegetation to flow alteration is developed, focusing on change to groundwater. Groundwater requirements for riparian vegetation are reviewed in conjunction with flow alteration statistics. Where flow alteration coincides with groundwater‐related vegetation sensitivities, scenarios are developed for groundwater simulation. Groundwater depths and recession rates in the riparian zone are simulated for baseline and altered stream hydrographs, with changes to river stage and width represented with a transient, flow‐dependent boundary condition. Potential flow diversion from the Upper Gila River in New Mexico is examined. Statistical flow alteration analysis, applying prospective diversions to a 76‐year record of daily flow, shows that flows in the winter‐spring months and within the high‐pulse to small flood range are subject to greatest potential change. Groundwater simulation scenarios are developed for these flow conditions in representative dry, near‐average, and wet years. Differences in groundwater elevations, generally less than 0.25 m during the flow alteration period, dissipate rapidly following cessation of diversion. Relating groundwater depth, recession rates and range of fluctuations to riparian vegetation needs, we find adverse ecological response is not expected from groundwater impacts for the flow alteration examined.

Mid- and long-term effects of wildfire and debris flows on stream ecosystem metabolism

Wildfire is an important and prevalent agent of disturbance in vegetated landscapes across much of the Earth’s surface, including forested watersheds in the arid western USA. Between 1992 and 2003, >40% of the watersheds in the upper reaches of the Boise River watershed in central Idaho burned. The purpose of our study was to investigate the legacy effects of wildfire on stream ecosystems by analyzing the relationship between wildfire and resulting debris flows and their joint effects on stream ecosystem metabolism in 31 streams. The watersheds of ∼½ of these streams burned within the last 11 y, and some of these burned watersheds also experienced large-scale debris flows 1 y postfire. Streams with burned watersheds recovered quickly, and estimates of photosynthetically active radiation, gross primary production, and ecosystem respiration were indistinguishable from those in streams draining unburned watersheds. However, streams that experienced debris flows after their watersheds burned were remarkably different. They exhibited higher production and incident light and lower ecosystem respiration. Debris flows resulted in nearly complete removal of streamside vegetation, slowed recovery of the riparian canopy, and altered stream ecosystem metabolism. Our results suggest a synergistic interaction between wildfire and associated geomorphological processes whereby debris flows delay succession of stream ecosystems, possibly resulting in altered recovery trajectories, communities, and foodweb interactions.

Interactive effects of climate change with nutrients, mercury, and freshwater acidification on key taxa in the North Atlantic Landscape Conservation Cooperative region.

The North Atlantic Landscape Conservation Cooperative LCC (NA LCC) is a public-private partnership that provides information to support conservation decisions that may be affected by global climate change (GCC) and other threats. The NA LCC region extends from southeast Virginia to the Canadian Maritime Provinces. Within this region, the US National Climate Assessment documented increases in air temperature, total precipitation, frequency of heavy precipitation events, and rising sea level, and predicted more drastic changes. Here, we synthesize literature on the effects of GCC interacting with selected contaminant, nutrient, and environmental processes to adversely affect natural resources within this region. Using a case study approach, we focused on 3 stressors with sufficient NA LCC region-specific information for an informed discussion. We describe GCC interactions with a contaminant (Hg) and 2 complex environmental phenomena-freshwater acidification and eutrophication. We also prepared taxa case studies on GCC- and GCC-contaminant/nutrient/process effects on amphibians and freshwater mussels. Several avian species of high conservation concern have blood Hg concentrations that have been associated with reduced nesting success. Freshwater acidification has adversely affected terrestrial and aquatic ecosystems in the Adirondacks and other areas of the region that are slowly recovering due to decreased emissions of N and sulfur oxides. Eutrophication in many estuaries within the region is projected to increase from greater storm runoff and less denitrification in riparian wetlands. Estuarine hypoxia may be exacerbated by increased stratification. Elevated water temperature favors algal species that produce harmful algal blooms (HABs). In several of the region's estuaries, HABs have been associated with bird die-offs. In the NA LCC region, amphibian populations appear to be declining. Some species may be adversely affected by GCC through higher temperatures and more frequent droughts. GCC may affect freshwater mussel populations via altered stream temperatures and increased sediment loading during heavy storms. Freshwater mussels are sensitive to un-ionized ammonia that more toxic at higher temperatures. We recommend studying the interactive effects of GCC on generation and bioavailability of methylmercury and how GCC-driven shifts in bird species distributions will affect avian exposure to methylmercury. Research is needed on how decreases in acid deposition concurrent with GCC will alter the structure and function of sensitive watersheds and surface waters. Studies are needed to determine how GCC will affect HABs and avian disease, and how more severe and extensive hypoxia will affect fish and shellfish populations. Regarding amphibians, we suggest research on 1) thermal tolerance and moisture requirements of species of concern, 2) effects of multiple stressors (temperature, desiccation, contaminants, nutrients), and 3) approaches to mitigate impacts of increased temperature and seasonal drought. We recommend studies to assess which mussel species and populations are vulnerable and which are resilient to rising stream temperatures, hydrological shifts, and ionic pollutants, all of which are influenced by GCC.

Timing matters: species-specific interactions between spawning time, substrate quality, and recruitment success in three salmonid species.

Substratum quality and oxygen supply to the interstitial zone are crucial for the reproductive success of salmonid fishes. At present, degradation of spawning grounds due to fine sediment deposition and colmation are recognized as main factors for reproductive failure. In addition, changes in water temperatures due to climate change, damming, and cooling water inlets are predicted to reduce hatching success. We tested the hypothesis that the biological effects of habitat degradation depend strongly on the species-specific spawning seasons and life-history strategies (e.g., fall- vs. spring-spawners, migratory vs. resident species) and assessed temperature as an important species-specific factor for hatching success within river substratum. We studied the species-specific differences in their responses to such disturbances using egg-to-fry survival of Danube Salmon (Hucho hucho), resident brown trout (Salmo trutta fario), and migratory brown trout (Salmo trutta lacustris) as biological endpoint. The egg incubation and hatching success of the salmonids and their dependence on temperature and stream substratum quality were compared. Hatching rates of Danube salmon were lower than of brown trout, probably due to higher oxygen demands and increased interstitial respiration in spring. Increases in maximum water temperature reduced hatching rates of resident and migratory brown trout (both fall-spawners) but were positively correlated with hatching rates of Danube salmon (a spring-spawner). Significantly longer incubation periods of resident and migratory brown trout coincided with relatively low stream substratum quality at the end of the egg incubation. Danube salmon seem to avoid low oxygen concentrations in the hyporheic zone by faster egg development favored by higher water temperatures. Consequently, the prediction of effects of temperature changes and altered stream substratum properties on gravel-spawning fishes and biological communities should consider the observed species-specific variances in life-history strategies to increase conservation success.

The interactive effects of climate change, riparian management, and a nonnative predator on stream-rearing salmon.

Predicting how climate change is likely to interact with myriad other stressors that threaten species of conservation concern is an essential challenge in aquatic ecosystems. This study provides a framework to accomplish this task in salmon-bearing streams of the northwestern United States, where land-use-related reductions in riparian shading have caused changes in stream thermal regimes, and additional warming from projected climate change may result in significant losses of coldwater fish habitat over the next century. Predatory, nonnative smallmouth bass have also been introduced into many northwestern streams, and their range is likely to expand as streams warm, presenting an additional challenge to the persistence of threatened Pacific salmon. The goal of this work was to forecast the interactive effects of climate change, riparian management, and nonnative species on stream-rearing salmon and to evaluate the capacity of restoration to mitigate these effects. We intersected downscaled global climate forecasts with a local-scale water temperature model to predict mid- and end-of-century temperatures in streams in the Columbia River basin. We compared one stream that is thermally impaired due to the loss of riparian vegetation and another that is cooler and has a largely intact riparian corridor. Using the forecasted stream temperatures in conjunction with fish-habitat models, we predicted how stream-rearing chinook salmon and bass distributions would change as each stream warmed. In the highly modified stream, end-of-century warming may cause near total loss of chinook salmon-rearing habitat and a complete invasion of the upper watershed by bass. In the less modified stream, bass were thermally restricted from the upstream-most areas. In both systems, temperature increases resulted in higher predicted spatial overlap between stream-rearing chinook salmon and potentially predatory bass in the early summer (two- to fourfold increase) and greater abundance of bass. We found that riparian restoration could prevent the extirpation of chinook salmon from the more altered stream and could also restrict bass from occupying the upper 31 km of salmon-rearing habitat. The proposed methodology and model predictions are critical for prioritizing climate-change adaptation strategies before salmonids are exposed to both warmer water and greater predation risk by nonnative species.

Competitive release modifies the impacts of hydrologic alteration for a partially migratory stream predator

AbstractUnderstanding ecological effects of altered stream flows is an essential objective. In a comparative field study of juvenile steelhead trout (Oncorhynchus mykiss) that compared natural‐ and reduced‐flow sites, we used mark–recapture modelling and information theory to quantify spatially and temporally explicit patterns of density, specific growth rate, survival and outmigration; and test predictions for biotic and abiotic drivers. Densities were lower in water withdrawal treatments, resulting in lower intraspecific competition and, higher specific growth rate and survival. We observed yearly differences in density and intraspecific competition, with a negative relationship between density and specific growth rate over a wide range of densities, but reductions in survival only at the highest densities. Moreover, individual variability within sites was important. At high density (sites and years), survival related negatively to body size. In contrast, when overall density was lower, specific growth rate was negatively related to body size. Lastly, individuals were more likely to outmigrate when they had larger body size, lower survival or reared in habitats with reduced flows, and these patterns appeared mediated by the intensity of intraspecific competition. Our results underscore the harsh bioenergetic conditions induced by higher temperatures and densities during summer baseflow (relative to other seasons), particularly for larger fish demanding more resources, and suggest a density‐dependent mechanism for why this period is important for regulating salmonid populations. We found that a complex combination of natural (e.g., density) and anthropogenic (e.g., withdrawal) factors affected juvenile salmon populations and life history expression in the face of altered flows.

A salt on the bioenergy and biological invasions debate: salinity tolerance of the invasive biomass feedstock Arundo donax

AbstractArundo donax L., commonly known as giant reed, is promising biomass feedstock that is also a notorious invasive plant in freshwater ecosystems around the world. Heretofore, the salt tolerance of A. donax had not been quantified even though anecdotal evidence suggests halophytic qualities. To test whole‐plant and leaf level responses, we established a pot experiment on 80 scions propagated from an A. donax population that has naturalized on the shore of the San Francisco Bay Estuary. To quantify growth and physiological responses to salinity (NaCl), A. donax scions were divided into eight treatments and grown for 60 days across a range of salinities (0–42 dS m−1). Classic growth analysis showed >80% reduction in overall growth at the highest salinities. Yet, there was zero mortality indicating that A. donax is able to tolerate high levels of salt. Declining photosynthesis rates were strongly correlated (R2 > 0.97) with decreasing stomatal conductance, which was in turn closely related to increasing salinity. Leaf gas exchange revealed that stomata and leaf limitations of carbon dioxide were three times greater at high salinities. Nonetheless, even when salinities were 38–42 dS m−1 A. donax was able to maintain assimilation rates 7–12 μmol m−2 s−1. Further, by maintaining 50% relative growth at salinities ~12 dS m−1 A. donax can now be classified as ‘moderately salt tolerant’. A. donax leaf gas exchange and whole‐plant salt tolerance are greater than many important food crops (i.e. maize, rice), the bioenergy feedstock Miscanthus × giganteus, as well as some uncultivated plant species (i.e. Populus and Salix) that are indigenous in regions A. donax currently invades. The results of this study have implications for both agronomists wishing to expand A. donax to fields dominated by saline soils, and for others who are concerned about the spread of A. donax with altered stream hydrology or sea‐level rise.

Wildfire and the effects of shifting stream temperature on salmonids

The frequency and magnitude of wildfires in North America have increased by four‐fold over the last two decades. However, the impacts of wildfires on the thermal environments of freshwaters, and potential effects on coldwater fishes are incompletely understood. We examined the short‐term effects of a wildfire on temperatures and Steelhead/Rainbow Trout (Oncorhynchus mykiss) bioenergetics and distribution in a California coastal stream. One year after the wildfire, mean daily stream temperatures were elevated by up to 0.6°C in burned compared to unburned pools. Among burned pools, light flux explained over 85% of the variation in altered stream temperatures, and 76% of the variation in light flux was explained by an index of burn severity based on proximity of the pool to burned streamside. We estimated that salmonids of variable sizes inhabiting burned pools had to consume between 0.3–264.3 mg of additional prey over 48 days to offset the 0.01–6.04 kJ increase in metabolic demand during the first post‐fire summer. However, stomach content analysis showed that fish in the burned region were consuming relatively little prey and significantly less than fish in the reference region. Presumably due to starvation, mortality, or emigration, we found a significant negative relationship between the change in total salmonid biomass over the post‐fire summer and the average energy costs (kJ·g−1·day−1) within a burned pool. This study demonstrates that wildfire can generate thermal heterogeneity in aquatic ecosystems and drive short‐term increases in stream temperature, exacerbating bioenergetically stressful seasons for coldwater fishes.

Land Degradation Due To Mining: The Gunda Scenario

Several studies have been carried out on the effects of mining on the environment, these have been characterized by landscape devastation, deforestation, it has also exposed the land to both wind and water erosion, water pollution and other environmental hazards which poses threat to humans in diverse ways. The study is set out to examine land degradation due to mining in Gunda area of Biu plateau with emphasis on the landscape. Both primary and secondary data were used. The nature of the environment such as destruction to the landscape, lost in vegetation cover, scattered open pits, alteration of water courses etc were all considered. One of the findings revealed that mining has led to the discovery of diatomite in the pits along stream channels which they use locally for painting purposes in building. The findings further revealed that reclamation work may not likely take place soon, because there are no economic returns from it. The study therefore, recommended among others, that reclamation be encouraged by using some of the pits for wastes disposal with farm and household residues so as to refill it especially those on farmlands, also measures should be taken by the inhabitants in restoring back the altered stream channels to their former glory by filling the cuts.

The Conflict-Laden Multi-Functionality of the Kapuas River in Kalimantan, Indonesia

the Kapuas river in west-Kalimantan, indonesia's longest river, is a prime example illustrating the conflict-laden multi-functionality of water in south-east asia. diverse utilisations of the river and adjacent land areas by local residents as well as corporate and state-led environmental transformations affect the river in various ways and bear conflicts at different scales. water as fluid medium connects the various actors and utilisations upstream and downstream. the river is used as a space for living, for personal hygiene and washing clothes, for fishing and aquaculture, as source of water for industrial, agricultural, and domestic purposes, for the discharge of partly toxic domestic and industrial waste water and rubbish, for gold and sand mining, and as a route of transport for people and goods. in the frame of a research project that aims at a spatial theoretical analysis of upstream-downstream and rural-urban interrelations with regard to water as a fluid resource, we undertook an exploratory research trip on the Kapuas river in March 2012 to gain a first overview of the various actors and utilisations positioned along the river, and of related transformations and conflicts. the material presented here provides visual illustrations of selected aspects of human-nature interactions and the conflict-laden multi-functionality of the river. the photographic journey begins in the upstream areas and ends in the coastal city of Pontianak. with its economic and political primacy the city affects human-nature relations upstream, which in turn affect the city via the flow of water.[Sidebar]Citation Lukas, M. C., Julia, radjawali, i., flitner, M., & Pye, o. (2012). the Conflict-Laden Multi-functionality of the Kapuas river in Kalimantan, indonesia. ASEAS - Austrian Journal of South-East Asian Studies, 5(2), 359-368.[Sidebar]1 Life on water - Especially the villages of the Melayu people who advanced to the interior of West Kalimantan from the coastline along the waterways and mainly live from fishing and small-scale trading, are concentrated along the Kapuas river and lake network.2 3 Fishing And Nutrition - The upper Kapuas Basin with the Danau Sentarum region contributes the main portion of freshwater fish caught in West-Kalimantan. The fishers - both women and men - use various fishing gears. The fishing gear shown in Picture 3 allows catching small sized fish in small amounts for everyday consumption.4 Conflicts over nature conservation - Danau Sentarum, a unique ecosystem comprising interconnected seasonal lakes and swamp forests, is valued by the local population for its fish abundance. It also plays a crucial role in regulating the water flows of the Kapuas River. As in other national parks in the upper reaches of the Kapuas and its tributaries, conflicts have arisen between state-led conservation strategies and local residents' resource uses.5 Politicised Water Fl ows - Politicised land-river and upstream-downstream interactions are marked by widely unknown or disputed cause-effect relationships: Local residents blame the operations of a logging company, with which they are in conflict over land, for altered stream flows resulting in river bank erosion that begins to threaten their dwellings.6 HE alth And Sanitation - Throughout the entire catchment area, residents use the river for their daily hygiene, for brushing teeth, and for doing their laundry. The floating wooden huts with their attached platforms along the shoreline serve as toilets and as washing and bathing spots. In some villages, river water had also been used for human consumption until recently but was then replaced by alternative water sources to reduce the incidence of water borne diseases, like cholera and typhoid.7 Mining and Poll ution - Thousands of gold miners, both locals and people from other parts of West-Kalimantan, dig up sediments in many parts of the Kapuas River and its tributaries, thereby polluting the river with mercury and increasing riverine sediment transport. …

Modelling available habitat versus available energy flux: do PHABSIM applications that neglect prey abundance underestimate optimal flows for juvenile salmonids?

Common applications of models to predict the response of fish habitat to altered stream flow (such as the Physical Habitat Simulation Model; PHABSIM) assume that fish abundance is directly related to the area of suitable habitat for limiting life stages and usually ignore flow effects on prey abundance. However, if prey availability is flow sensitive, then fish production may be more closely related to the total flux of available prey than to habitat area. We compared instream flow predictions from PHABSIM to predictions of optimal energy flux to drift-feeding juvenile coho salmon ( Oncorhynchus kisutch ) estimated using a drift-foraging bioenergetics model. Flux of available energy to juvenile coho salmon declined much more rapidly with decreasing flow than suitable habitat area estimated using PHABSIM, so that, relative to the bioenergetic model, predictions from PHABSIM systematically overestimated productive capacity at very low flows (i.e., underestimated the negative consequences of simulated water withdrawal). Applications of habitat suitability based models like PHABSIM may systematically overestimate low-flow productive capacity for species that prefer low velocities (e.g., pools) but are dependent on energy fluxes generated in higher velocity habitats (e.g., riffles).