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The amount and composition of organic carbon are major controls on water quality and ecological processes in streams. In this study we explored the fate of the quantity of dissolved organic carbon (DOC) and the composition of dissolved organic matter (DOM) in an agricultural hillslope - stream network system. We conducted our study in the 66 ha HOAL (Hydrological Open Air Laboratory) in Lower Austria. We measured DOC of the soil eluates from different land use units, water samples from the stream and from seven tributaries, and estimated DOM components by fluorescent spectrophotometry and PARAFAC analyses. Soil DOC shows the highest concentrations in summer, but DOC concentrations in the tributaries are lower in summer than in winter by between 19% and 31%. DOM composition of the soil eluate differs between land use units. The forest site exhibits the largest fractions of humic-like fluorophores and less labile DOM. DOM composition in the tributaries is, in addition to DOC, controlled by soil moisture. We estimated the DOC import from the tributaries into the stream as 125 kg during base flow conditions in the period February to December 2017 and the instream DOC production as 38 kg, considering mass balance and exchange with groundwater. Six out of seven DOM components have a positive net production along the stream, only aliphatic DOM with low molecular weight is consumed (65 % of its input). These findings suggest that agricultural land use increases DOC input into streams and alters their DOM quality. Instream processes modify DOM quality over short distances.

Murray-Darling Freshwater Research CentreMDFRC item.Urbanization leads to degradation in water quality and has a major effect on the biota of streams, but its effect on microbial communities is not as well understood. DNA-techniques that target functional genes are being used to examine microbial communities, but less frequently applied to freshwater aquatic systems. Our aim was to determine whether terminal restriction fragment length polymorphism and sequence analysis of polymerase chain reaction-amplified (PCR) nosZ gene sequences could be used to show if there were measurable differences in the denitrifying community in two urban streams in catchments with contrasting degrees of catchment urbanization. Community structure in the sediments and associated riparian zones were studied at the contrasting sites. We showed that the denitrifying community in the sediments and riparian soils of the two streams were significantly different. There were also significant differences between the sediment and riparian zone communities within each of the sites. Terminal restriction fragment length polymorphism analysis proved to be a valuable technique that could resolve patterns of the denitrifying community in streams of contrasting degrees of urbanization, but sequence analysis was required to confirm the identity of the amplified products.

Beginning with the first lampricide treatments of Lake Huron streams in 1960, applying lampricides and maintaining barriers to migration in Lake Huron tributaries continue to be the primary methods of controlling sea lampreys (Petromyzon marinus). In years leading up to the new millennium, sea lamprey abundance in Lake Huron remained at high levels, yet well below the pre-control adult abundance estimate of 700,000 adults. Two decades later, a variety of sea lamprey control strategies have been developed and employed to further reduce sea lamprey abundance in Lake Huron. In recent years, record low numbers have been achieved and continue to be at or near target levels for sea lamprey abundance. The St. Marys River continues to be one of the largest producers of sea lampreys to Lake Huron and additional actions have been taken to address this challenge. Controlling larval abundance in the St. Marys River along with increasing lampricide treatments throughout the basin and focusing on the largest sea lamprey producing streams have contributed to the decline in sea lamprey abundance. Lake trout (Salvelinus namaycush) restoration efforts along with increased sea lamprey control has facilitated natural reproduction and increase in wild stocks across the basin. The fish community objective for sea lampreys in Lake Huron has not been entirely met and efforts to achieve this objective are ongoing.

The sea lamprey (Petromyzon marinus) is an invasive species in the Laurentian Great Lakes which requires control to protect valuable fisheries. The Sea Lamprey Control Program (program) uses chemical methods (lampricides) each year to treat infested streams, but limited resources only allow control agents to target 100–125 streams annually. To provide the most cost-effective use of these resources, the program began using the Empiric Stream Treatment Ranking (ESTR) system in 2000 as a decision support tool for selecting streams for treatment. Following a comprehensive review of larval assessment techniques in 2002, the program transitioned from a labor-intensive quantitative technique to a more rapid catch-per-unit-effort based approach. Staff resources were re-allocated to lampricide control, allowing for treatment of more streams annually. Beginning in 2009, stream selection shifted to cost-per-kill of large larvae (>100 mm) and incorporated expert opinion along with targeted treatment strategies. This resulted in a greater number of treatments on an annual basis overall as well as increased treatment frequency for many individual streams. The average adult sea lamprey index decreased by 26% and lake trout wounding rates decreased by 21% across the Great Lakes basin during 2010 to 2017 when compared to 2000 to 2009. Recommended improvements to the stream selection model include: leveraging historic data and expert knowledge to identify streams for treatment, refining the accuracy of the ESTR decision tool, incorporating supplemental and alternative control methods into the treatment selection process, and identifying areas to improve larval assessment techniques that guide and evaluate lampricide control efforts.

Effective control of aquatic invasive species requires knowledge of the population throughout the infested area. Lake-wide assessments of invasive sea lampreys (Petromyzon marinus) are used to assess their status in the Laurentian Great Lakes, informing fisheries managers and decision makers in the sea lamprey control program. Initially these assessments focused on an estimate of absolute abundance, but later switched to an estimate of relative abundance as an index. In this paper, we describe the recently developed index of sea lamprey abundance and the reasons for its use. Rather than trying to estimate spawning run sizes of all Great Lakes tributaries, the index instead estimates run sizes of a small subset of index streams. Streams chosen for the index had large spawning runs and a history of trapping operations that consistently yielded mark-recapture estimates. This change enabled the sea lamprey control program to abandon a previously used regression model that predicted run size on streams with no sea lamprey traps. Further research is needed to determine how strongly correlated the index is with actual patterns in the lake-wide population of adult sea lampreys.

Natural reproduction of salmonids occurs in many Lake Michigan tributaries, yet little is known about abundance and the potential contribution of wild fish hatching in Wisconsin tributaries. The objectives of our study were to determine if: 1) abundance of wild juvenile salmonids (primarily adfluvial rainbow trout, Oncorhynchus mykiss, referred to as steelhead) varied among selected Wisconsin streams based on available spawning and age-0 habitat; 2) stream temperature regimes could limit survival of juvenile salmonids, and 3) wild juvenile salmonids outmigrate from Wisconsin tributaries into Lake Michigan or larger tributaries. In 2016 and 2017, juvenile salmonid abundance was estimated in six Wisconsin tributaries to Lake Michigan by multiple-pass depletion sampling using backpack electrofishing. Habitat assessments included steelhead redd surveys, age-0 habitat surveys, and stream temperatures were monitored using in-stream loggers. Passive integrated transponder (PIT) tagging and PIT antennas were used to detect outmigration from three streams (Willow, Stony and Hibbard creeks). Population estimates for individual streams ranged from 75 to 2276 for juvenile steelhead and from 0 to 243 for juvenile coho salmon, Oncorhynchus kisutch. No correlation was detected between juvenile steelhead abundance and quality age-0 habitat. Stream temperatures rarely exceeded the thermal limit for steelhead (27 °C). Outmigration rates for three streams ranged from 0.6% to 3.1%, but these estimates were considered minimum values. Low abundance of wild juvenile steelhead and coho salmon alone suggest that the contributions of these tributaries to Lake Michigan fisheries are likely small. Furthermore, relying on returns of wild steelhead produced in these streams is probably insufficient to maintain stream fisheries.

Above average precipitation from October 2018 through July 2019 in the Maumee River (R.) Basin resulted in 29% of cropland left fallow, providing a glimpse of potential effects from decreased nutrient application. Ongoing monitoring at 15 water-quality sites on the Maumee R. upstream from Defiance enabled comparison with 2017, which was hydrologically similar to 2019 in precipitation and streamflow. In 2019, nitrate (as nitrogen; NO3-N) for March-July was significantly less than previous years (2015–2018), but the response for phosphorus (P) was more complicated. Relative to 2017, total P (TP) was lower at 7 of 15 sites, but higher at 7, reflecting higher suspended sediment (SS). Dissolved P (DP) was generally lower, but less different than NO3; DP was higher at 3 sites. DP-P:NO3-N was generally higher in 2019, DP-P:TP was lower, and there was less TP relative to SS. Overall, less P was in the system in 2019. However smaller streams showed a large range of difference between 2019 and 2017 for all constituents, indicating variability in land management and physiography. In contrast, all constituents were lower in 2019 in larger (>5000 km2) streams, including the Maumee R. near Defiance, where the difference in NO3 (−37%) exceeded that for TP (−16%), DP (−10%), and SS (−20%). Differences in these relations among N, P, and SS indicate that P was available from legacy sources that are more difficult to distinguish during typical agricultural production years and that some material from 2019 was stored in the system upstream from the largest sites.

Nitrogen (N) legacies have built up in anthropogenic landscapes over decades of agricultural intensification, and these legacies lead to time lags in water quality change measurable even beyond the moment of application of N. It is important to understand these legacies to quantify the relationship between N inputs and N concentrations in streams and implement best management practices for water quality improvement; however, little is known about the magnitude of legacies in various landscape elements like soils and groundwater. Here, we have used the ELEMeNT (Exploration of Long-tErM Nutrient Trajectories) model to explore the buildup and depletion of N legacies over a 216-year period, across the Mondego River Basin, a 6645-km2 watershed in Portugal, where human interventions have considerably changed the characteristics of the basin to prevent floods and improve farming conditions in recent decades. The results show that the increase in the amount of inorganic fertilizer applied was the main driver for the anthropogenic N loads in the watershed from 1950 until the beginning of the 1990s. The N inputs have been decreasing since then, but N loads in the river did not document any decrease till the 1990s; after which there was a decline. This time lag between the N inputs to the watershed and the N loads in the river (about two decades) is a function of accumulation of N legacy.

Tills from moraines adjacent to major ice streams of the Weddell Sea Embayment contain distinct detrital zircon (n = 5304) and K-bearing mineral age populations (n = 323) that, when combined with pebble composition data, can be used to better understand Antarctica's subglacial geology and ice sheet history. Till representing the Institute, Foundation, Academy, Recovery and Slessor Ice Streams each have distinct detrital zircon age populations. Detrital Ar-Ar ages are mostly younger than zircon ages, and distinctive populations include 270–300 Ma (Institute), 170–190 Ma (Foundation), and 1200–1400 Ma (Recovery), which are not easily explained by known outcrops. Pebble fractions of the Foundation and Academy tills are most diverse with up to >40% exotic erratics. The southern side of the Recovery Glacier has fossiliferous limestone erratics. Mixing models created using a nonlinear squares curve-fitting approach were developed to evaluate contributors of zircons to Foundation Ice Stream till. These model results and pebble lithology data both indicate that unexposed (subglacial) bedrock is mixed with exposed rocks to produce the observed till. Notably, the model required limited local Patuxent Formation input to the Foundation till's zircon population. Our data suggest that sandstones underlie the Foundation Ice Stream and Recovery Glacier troughs, which has a bearing on basal ice flow conditions and results in geological controls on ice stream location. This geo- and thermo-chronological characterization of the ice streams will enable ice-rafted debris in Weddell Sea marine sediments to be traced back to its sources and interpreted in terms of ice stream dynamics.

The river continuum concept (RCC) predicts a downstream shift in the reliance of aquatic consumers from terrestrial to aquatic carbon sources, but this concept has rarely been assessed with longitudinal studies. Similarly, there are no studies addressing how forestry related disturbances to the structure of headwater food webs manifest (accumulate/dissipate) downstream and/or whether forest management alters natural longitudinal trends predicted by the RCC. Using stable isotopes of carbon, nitrogen and hydrogen, we investigated how: 1) autochthony in macroinvertebrates and fish change from small streams to larger downstream sites within a basin with minimal forest management (New Brunswick, Canada); 2) longitudinal trends in autochthony and food web length compare among three basins with different forest management intensity [intensive (harvest and replanting), extensive (harvest only), minimal] to detect potential cumulative/dissipative effects; and 3) forest management intensity and other catchment variables are influencing food web dynamics. We showed that, as predicted, the reliance of some macroinvertebrate taxa (especially collector feeders) on algae increased from small streams to downstream waters in the minimally managed basin, but that autochthony in the smallest shaded stream was higher than expected based on the RCC (as high as 90% for some taxa). However, this longitudinal increase in autochthony was not observed within the extensively managed basin and was weaker within the intensively managed one, suggesting that forest management can alter food web dynamics along the river continuum. The dampening of downstream autochthony indicates that the increased allochthony observed in small streams in response to forest harvesting cumulates downstream through the river continuum.The online version contains supplementary material available at 10.1007/s10021-021-00717-6.

Wildfire is a major driver of nitrogen (N) cycling and export from terrestrial to aquatic systems. While fire is a natural process in many watersheds, it can still degrade water quality by rapidly flushing N to streams. This can be particularly problematic in watersheds that experience high levels of N deposition or where climate change is promoting larger and more severe fires. The extent and duration of postfire N export, and the potential consequences for downstream water quality, depend on how N inputs, internal cycling, and outputs vary before, during, and after fire. Here we review the major factors controlling N cycling and retention in forests and adjacent shrublands, and how fire modifies these controls. We connect burned slopes to streams to describe how fire exports N to aquatic environments. We also consider the implications for municipal watersheds and water resources management. We close by identifying critical knowledge gaps in projecting how fire will affect watershed N cycling and retention in the future.

The last decade increasing attention to litter accumulation in the marine environment revealed the issue of the terrestrial fluxes of plastic pollution into the oceans. However, limited studies investigate the macro-litter abundance and composition particularly in freshwater ecosystems and the adjusted coastal environment. In this study, we conducted an empirical analysis of anthropogenic litter (AL) in two freshwater streams and their estuaries of Lesvos island (Greece), strongly affected by the waste mismanagement in the Moria refugee camp. A total of 1,622 litter items were collected from five sites during the field campaign between the 3rd and 6th of June 2019. Among these, artificial polymer items (mainly drink bottles, single-use plastic bags, cutlery, and trays) irrespective of the site location constituted the major part ranging from 46 to 91% of total AL by mass. Drink bottles and plastic cutlery are found in higher percentage at Moria camp river and its estuary, while packaging and bag litter are more abundant at upstream sites. The operation of the camp has increased the AL abundance 13 times more than the reference site, causing severe threat to human health and to freshwater and marine environment. It is therefore important to improve the waste management system at (inter)national (change in production and packaging policy) and local scale (introducing sustainable solutions to refugee camp design) by promoting recycling and circular economy projects to diminish AL pollution.

Glaciers represent important biomes of Earth and are recognized as key species pools for downstream aquatic environments. Worldwide, rapidly receding glaciers are driving shifts in hydrology, species distributions and threatening microbial diversity in glacier-fed aquatic ecosystems. However, the impact of glacier surface snow-originating taxa on the microbial diversity in downstream aquatic environments has been little explored. To elucidate the contribution of glacier surface snow-originating taxa to bacterial diversity in downstream aquatic environments, we collected samples from glacier surface snows, downstream streams and lakes along three glacier-fed hydrologic continuums on the Tibetan Plateau. Our results showed that glacier stream acts as recipients and vectors of bacteria originating from the glacier environments. The contributions of glacier surface snow-originating taxa to downstream bacterial communities decrease from the streams to lakes, which was consistently observed in three geographically separated glacier-fed ecosystems. Our results also revealed that some rare snow-originating bacteria can thrive along the hydrologic continuums and become dominant in downstream habitats. Finally, our results indicated that the dispersal patterns of bacterial communities are largely determined by mass effects and increasingly subjected to local sorting of species along the glacier-fed hydrologic continuums. Collectively, this study provides insights into the fate of bacterial assemblages in glacier surface snow following snow melt and how bacterial communities in aquatic environments are affected by the influx of glacier snow-originating bacteria. This article is protected by copyright. All rights reserved.

Riparian vegetation provides a wide range of ecosystem services including water quality regulation, flooding avoidance, and the natural control of stream temperatures. Changes in land use and the increase of anthropogenic activities in the proximity of rivers affect the growth and development of riparian buffers. The aim of the work was to assess the effects of riparian vegetation on the evapotranspiration processes and the water quality of small plain streams using remote sensing resources and in-situ monitoring. The area of study considered two neighboring basins of small plain streams (Glavacioc and Ilfov) from Romania. The data obtained from in-situ monitoring performed in 2019 was used in the Penman-Monteith algorithm to calculate the potential evapotranspiration (PET) based on a series of specific parameters. The Green Normalized Difference Vegetation Index (GNDVI), computed from LANDSAT 8 images, has been used to assess the vegetation status at the basin scale. The GNDVI fluctuations were linked to the variations in precipitation regimes and land use modifications. Remote sensing data have shown changes in GNDVI between June and September 2019 in both riparian areas resulting in an intense spread of cattail (Typha spp.). Surface waters arriving at the entrance control sections had a basic pH and were loaded with nitrates and ammonium ion (NH4+), which had decreased at the downstream section after passing the cattail phytosociological associations and the riparian patches, thus acting as buffer areas. The current anthropogenic pressures on the riparian areas might have degenerative effects on the integrity of the vegetation structure. Thus, for effective and sustainable management, it is essential to identify the main stressors and to assess to what extent they affect the riparian ecosystem as a whole.

Groundwater pumping can reduce streamflow by reducing groundwater discharge and/or inducing streamflow infiltration, which together are referred to as streamflow depletion. Recently, analytical depletion functions (ADFs) have been suggested as rapid and accurate tools for streamflow depletion assessment, but their performance has only been tested in a few hydrogeological settings. To evaluate whether they will be useful tools for other regions with contrasting stream network and hydrogeological characteristics, we compared ADFs to calibrated MODFLOW models in BX Creek and Peace Region with distinct hydrogeological settings (interior plateaus & highlands, and boreal plains, respectively) and spatial scales (165 km2 and 1952 km2, respectively) in British Columbia, Canada. Results showed that ADFs can accurately identify streams most affected by pumping for 100% and 83% of wells in the BX Creek and Peace Region, respectively, and had small prediction errors compared with MODFLOW. Specifically, the mean absolute error of predicted depletion ranged from 2% to 14% of the highest simulated pumping rate over the study period of 30 years, with improved accuracy during the pumping season. We also found contrasting responses of ADF performance to hydrostratigraphic properties such as hydraulic conductivity, aquifer thickness, streambed conductance, and well depth across two domains, indicating that different drivers control ADF accuracy in different hydrogeological settings. Therefore, we conclude that ADFs are useful tools for conjunctive water management, but a good understanding of local hydrogeological conditions is needed to address the potential uncertainty of ADFs for decision-making.

Human activities have increasingly impacted rivers globally and influence environmental factors at multiple scales: proximal factors (e.g., light and nutrients) and distal controls (e.g., riparian cover and forest area in the basin) that affect benthic metabolism or algal assemblage structure. Function and structure have been studied separately and thus the linkage between them is not well understood. Furthermore, how much of the variability of benthic metabolism can be explained by changes in the environmental variables is inconclusive. We measured the structural and metabolism of epilithic algae in streams across gradients of catchment forest cover (3.5 to 88.6%) and riparian zone canopy cover (0 to 91.0%) in South East Queensland, Australia. Overall net daily metabolism (NDM) on cobbles was positive (gross primary production, GPP exceeded respiration, R) for all but three of the 34 sites. Chl a biomass of benthic algae on cobbles ranged from 1.37 to 178.05 mg m−2. Shaded streams had the highest percentage of diatoms (95.4%), while the least shaded streams were dominated by cyanobacteria (82.2%). Partial least squares (PLS) regression modeling showed that most of the variation in GPP, R, and NDM was explained by light intensity (photosynthetic photon flux density, PPFD), phosphorus concentration in water, water temperature, and the percentage of mid-dense forest upstream of the site. Path analysis (structural equation modeling, SEM) indicated that, as a surrogate for metabolism, diatom (Bacillariophyta) density was the best predictor of GPP and NDM when we assessed the environmental process in the streams. In comparison, Chl a, which has been traditionally used as a surrogate for measurements of GPP or NDM, performed well only when the percentage of diatoms in the epilithic algal community exceeded 75%. Our results also indicated that both the structure and function of benthic algal communities were sensitive to anthropogenic modifications, including riparian vegetation and forest cover in the catchment in river ecosystems.

Aim : This study aimed at investigating the taxonomic resolutions (TRs) of benthic macroinvertebrates for freshwater assessments in the scope of the functional trait approach (FTA). Location: Macroinvertebrate samples were collected in 22 locations within the Paute River Basin (PRB), Ecuador, over three years (2010, 2011 and 2012). Methods: Biological traits were allocated as scores to the macroinvertebrate data (at genus level) through fuzzy coding, using published data. The scores of each genus were used to derive scores for the corresponding family. These two sets of scores were standardized and compared, they were similar in 82% of the cases. Functional diversity (FD) was described by the rRao index, which showed no significant differences between coarse (family level) and fine (genus level) TRs. Cluster analyses using the K-means algorithm were performed to determine similarities between both rRao data sets. The WQ cluster number (K) was varied between 2 and 5 to determine a threshold K value (Kth), after which a WQ assessment differed as a function of the TR being used. Results: Kth was 3. Family-level identification in the framework of the FTA in the PRB was suitable in detecting changes of macroinvertebrate assemblages (until Kth = 3). Main conclusions: The proposed methodology could be implemented in other basins where decision-makers could decide whether the level of functional trait data similarity is sufficient for WQ management purposes and whether the defined Kth is acceptable. The reliability of the key methodological steps was assessed using performance statistics that have rarely been applied to ecological studies. Despite related research performed in other regions, the present study is the first South American attempt to investigate the effects of TR of benthic macroinvertebrates on freshwater bioassessments using functional traits.

In a warming climate, land-to-water carbon mobilization is increasing in glacier and permafrost area. To identify the connection between exported river carbon content and the permafrost or glacier condition in the high-altitude mountain area, we studied the dissolved organic carbon and dissolved inorganic carbon concentration in three streams of Qinghai–Tibet Plateau (QTP), which were located in the continuous permafrost, seasonal permafrost and glacial basin, respectively. It was found that the DIC and DOC concentrations were lower in the glacial rivers compared with the permafrost derived rivers; but more DOC would be exported from glacier due to the large amount of melted glacier water in the high mountainous area. DIC/DOC ratio in rivers reflected the watershed landscape types. In the permafrost area, the river recharged by seasonal permafrost had higher DIC concentration than the river in the continuous permafrost region, suggesting that increased DIC concentration could be a precursor of permafrost degradation. Research is meaningful to estimate the DOC and DIC export from high mountain area.

Documenting flow regimes and the ecology of source headwater streams has gained considerable attention for scientific and regulatory purposes. These streams do not appear on standard maps, and local physiographic and climatologic conditions can control their origins. We investigated macroinvertebrate assemblages seasonally and in relation to flow duration, catchment and habitat variables within 14 source headwaters (< 1 ha) in the Western Allegheny Plateau over a 19-month period. We classified 6 perennial (P) and 8 intermittent (I) streams directly with continuous flow data loggers. Several biological and trait-based metrics could distinguish flow class, but few instream physical measures could. Macroinvertebrate metrics and assemblage dispersion varied seasonally and responded significantly along a gradient of total flow duration. Separate indicator species analyses generated 22 genera and 15 families with significant affinities to P streams. Richness of P-indicator taxa was also strongly correlated with flow duration gradients, and we estimated a total flow duration changepoint at 77% (3 indicator families) followed by a sharp increase in richness. Two rapid field-based flow duration methods (NC Stream Identification index and OH Headwater Habitat Evaluation index) could distinguish upstream ephemeral reaches from P and I reaches, but misclassified P as I more frequently. Our findings highlight that diverse coldwater macroinvertebrate assemblages inhabited extremely small, low-discharge springs in the region, and responded with flow duration. These source headwater habitats are susceptible to human disturbance and should be monitored as is routinely done in larger lotic systems.

Glacier-dependent streams and irrigation systems in the Hood River Watershed (HRW) are particularly vulnerable to climate change, as glaciers retreat and snowpack declines. We developed a system dy...

A vortex tube is a simple device with no moving parts that has the inherent capability of separating the high pressure inlet stream into two low pressure outlet streams. One of the outlet streams i...

We have found out the general patterns in the elemental composition of ash ejected by the Kuril volcanoes Alaid and Ebeko. The ashes show persistent exceedances in the concentrations of K, Bi, U, Cs, Th, Na, and Yb relative to the mean concentrations for the respective types of volcanic rock. The deficient elements (Kk < 1) include Mg, Ag, Sn, Nb, Ta, Ni, and Cr. Inspection of the range of ashes ejected by different volcanoes of Kamchatka (Klyuchevskoi, Tolbachik, Ksudach, Bezymyannyi, Koryaksky, Shiveluch, and Kizimen) showed that the ejecta of Shiveluch and Kizimen are the most similar in elemental composition to the ashes discharged by the volcanoes of the Kuril Islands studied here. The ashes of Alaid and Ebeko volcanoes differ from most Kamchatka ashes in having higher concentrations of radioactive elements (U, Th). We have found a comparatively high potential of biological productivity for the Kuril ashes. The potential fertility index considered here (PFI) when compared with the most productive ash on the Kamchatka Peninsula whose PFI was taken to be unity is 0.72 and 0.66 for Alaid and Ebeko, respectively. The PFI shows a persistent dependence on the concentration of silicon in the ashes: the higher the basicity of an ash, the greater is its potential fertility. It is for the first time that we have discovered fractionation of rare earth elements occurring in all volcanic ashes under study here (both those for the Kuril Islands and for Kamchatka) in the form of a positive europium anomaly with E/Er* varying between 1.2 and 1.8. The estimation of the elemental composition for the surface waters of a brook that flowed on Ebeko Volcano did not reveal any tendency of active transfer of radioactive elements from ashes to naturally occurring solutions. A comparative analysis of the waters of this brook and the streams around the Kamchatka volcanoes studied here showed that the relationship between their compositions is largely controlled by the time factor. Streams near different volcanoes show similarities at the time of an eruption, and their water very actively receives rare earth elements (REE), their concentrations in brooks exceed the mean REE concentrations for fresh waters in continents by two orders of magnitude. When the volcanic event comes to an end, the relationship between the geochemical compositions of water in areas of ashfalls due to different volcanoes becomes weaker. The waters of small streams near volcanoes during eruptions can be regarded as natural liquid REE-bearing fertilizers.

Trichoptera is one of the most important components of freshwaters used in biomonitoring studies to determine the different degradations in aquatic ecosystems. Though such works are necessary, there is a huge gap in ecological studies on Trichoptera larvae in northeastern Turkey. We examined the effects of some environmental variables on the distribution of caddisfly larvae inhabiting the streams arising above the tree line. To determine the relationships between larvae distribution and environmental variables (riparian forest, riparian vegetation, stream size -width-, altitude, pH, substrate, electrical conductivity, temperature, dissolved oxygen), 66 sites were selected from five different streams (Aksu, Degirmendere, Solakli, Iyidere, Firtina) in 2008, 2009, and 2011. In total, 22 caddisfly genera belonging to 13 Trichoptera families were identified. It was found that riparian forest was the most important variable affecting the distribution of caddisfly larvae in open canopy headwater streams. Larvae exhibiting shredder feeding behavior were found both in the stations above and below the tree line. It is supposed that shredders can utilize both allochthonous materials coming from trees and riparian vegetation. Since this region is a biodiversity hotspot, it is becoming increasingly important to determine the ecological preferences of macroinvertebrates as soon as possible to use them in biomonitoring studies in the future.

Florida spring complexes (springs and their associated runs) represent patches of clear, cool freshwater habitat in a landscape of tannin-stained wetlands, streams, and rivers. These spring...

Invasive species are a widespread threat to stream ecosystems across the planet. In Southern California, USA, the invasive red swamp crayfish Procambarus clarkii (Girard, 1852) poses a significant threat to native aquatic fauna. Studies have suggested that artificial refuge traps (ARTs) resembling crayfish burrows can be used to remove invasive crayfish, but, to date, no studies have focused on optimizing ART design and deployment to maximize crayfish catch. This month-long study tested the effect of modifications on ART diameter, color, and soak time on P. clarkii catch effectiveness across 160 traps. We evaluated catch data by creating multiple candidate generalized linear mixed models predicting P. clarkii catches with different modeling parameterizations and a priori hypothesized predictor variables. During the study period, ARTs removed a total of 240 red swamp crayfish with no incidental bycatch. Larger P. clarkii (2–6-cm carapace length) were found more frequently in 5.1-cm-diameter traps, and smaller P. clarkii (1–4 cm) were found more frequently in 2.5-cm-diameter traps. Catch numbers varied between trap types, with black-colored 5.1-cm-diameter traps removing the greatest amount of the total P. clarkii caught in the study (mean = 0.27, SD = 0.29; 35% of the total caught) and black-colored 2.5-cm-diameter traps removing the least amount (mean = 0.09, SD = 0.55; 12% of the total). Further, ART deployment duration was an important predictor variable for candidate models, where ARTs with 4-d and 7-d deployment durations had lower catch/unit effort than traps with 1-d and 2-d deployments. This factorial experiment is the 1st study to suggest specific design modifications to ARTs that optimize invasive red swamp crayfish removal without incurring non-target incidental bycatch. This study demonstrates that ARTs can be a valuable tool for conservation managers interested in restoring streams through invasive crayfish removal, especially where there are sensitive biological resources.

Forested riparian corridors are a key management solution for halting the global trend of declining ecological status of freshwater ecosystems. There is an increasing body of evidence related to the efficacy of these corridors at the local scale, but knowledge is inadequate concerning the effectiveness of riparian forests in terms of protecting streams from harmful impacts across larger scales. In this study, nationwide assessment results comprising more than 900 river water bodies in Finland were used to examine the importance of adjacent land use to river ecological status estimates. Random forest models and partial dependence functions were used to quantify the independent effect of adjacent land use on river ecological status after accounting for the effects of other factors. The proportion of adjacent forested land along a river had the strongest independent positive effect on ecological status for small to medium size rivers that were in agricultural landscapes. Ecological quality increased by almost one status class when the adjacent forest cover increased from 10 to 60%. In contrast, for large rivers, adjacent forested land did not show an independent positive effect on ecological status. This study has major implications for managing river basins to achieve the EU Water Framework Directive (WFD) goal of obtaining good ecological status of rivers. The results from the nationwide assessment demonstrate that forested riparian zones can have an independent positive effect on the ecological status of rivers, indicating the importance of riparian forests in mitigating the impacts of catchment-level stressors. Therefore, forested buffer zones should be more strongly considered as part of river basin management.

The coastal flanks of Mt Etinde is wedged between the sea and the southwestern slope of Mt Cameroon. The only fresh water resources available for multipurpose uses in this area are mountain springs and streams that drain volcanic materials. To access the sources, processes and assess the ecological risk associated with hydrochemicals and heavy metals in these mountain water resources, 18 water samples were collected in different seasons at 4 locations between may 2009 and december 2010 for major ions and heavy metals determination. The sampled waters ranged from neutral to slithly alkaline, weakly mineralized and dominated by Ca–Mg–HCO3 water type irrespective of season. The hydrochemical ratios revealed ions chemistry mostly influenced by geogenic source of silicate rock weathering and atmospheric inputs. Sampled waters had low concentration of heavy metals which are less mobile in the aqueous phase, controlled by hydraulic condition. Geochemical processes of mineral dissolution and reverse ion exchange coupled with hydrodynamic processes of flushing at the weathering front and soil leaching are the main controls on the water chemistry in the area. Despite agricultural and other anthropogenic activities, quality indices in the study area indicate the absence of anthropogenic inputs. Key words: Major ions, heavy metals, rocks weathering, soil leaching, water quality assessment.

Several recent studies were conducted concerning species richness and spatial-temporal distribution of Simuliidae (Diptera: Culicomorpha), but there are still gaps in knowledge regarding these species, mainly when it comes to their local abundance and regional distribution patterns. The aim of this study was to investigate the distribution and diversity of Simuliidae in a watershed located in the Pampa biome of southern Brazil. Abiotic factors were evaluated during two seasons, spring and autumn, and at two spatial scales. These spatial scales consisted of three regions of the Piratinim river drainage basin (upper basin, middle, and lower courses) and three stretches of tributary streams (upstream, intermediate, and downstream). Immature stages, consisting of larvae and pupae, were sampled in six streams encompassing a total of 18 sampling points. The results indicated the occurrence of nine simuliid species along the studied area, with the three most abundant being Simulium pertinax, Simulium orbitale, and Simulium incrustatum. It was verified that the structure of the assemblage was mostly influenced by local factors, i.e., stream stretches, but also by those of a wider scale, i.e., watershed regions. Some species showed spatial distribution patterns; Simulium orbitale and S. jujuyense were associated with downstream areas, while S. pertinax was associated with upstream areas. Concerning regions, S. pertinax was less frequent in the lower region of the basin. Environmental variables such as temperature and stream width were also important. Our results show new and relevant information regarding the structure of simuliid assemblages in the Pampa biome.

Microplastics (MP) have several negative effects on biodiversity, from the ecosystem to individual levels, and can be easily consumed by small invertebrates and fish. The increased production of plastic and absence of efficient management systems for these residues facilitate their presence in aquatic environments. In this study, we evaluated the presence of MP in the stomach contents of four species of Characidae in rural streams in the upper portion of the Uruguay River watershed (northern Rio Grande do Sul). Among the total of collected organisms (n=121), the presence of MP was observed in 72% of the analyzed stomach contents. Bryconamericus iheringii had the highest occurrence of MP (85.7%), followed by Astyanax lacustris (69.4%), Astyanax henseli (69.1%) and Oligosarchus breviostris (66.7%). Our results demonstrate the high occurrence of MP in freshwater aquatic environments, especially rural streams. The results observed in this study confirm the importance of conservation of streams, from the maintenance of riparian vegetation as a way to reduce the input of MP in these ecosystems. Os microplásticas (MP) causam vários efeitos negativos sobre a biodiversidade, desde o ecossistema até os níveis individuais, podendo ser facilmente consumidos por pequenos invertebrados e peixes. O aumento da produção de plástico e a ausência de sistemas eficientes de gerenciamento desses resíduos facilitam sua presença em ambientes aquáticos. Neste estudo, avaliamos a presença de MP no conteúdo estomacal de quatro espécies de caracídeos em riachos rurais na porção superior da bacia hidrográfica do rio Uruguai (norte do Rio Grande do Sul). Dentre o total de organismos coletados (n = 121), observou-se a presença de MP em 72% do conteúdo estomacal analisado. Bryconamericus iheringii apresentou a maior ocorrência de MP (85,7%), seguida por Astyanax lacustris (69,4%), Astyanax henseli (69,1%) e Oligosarchus breviostris (66,7%). Nossos resultados demonstram a alta ocorrência de MP em ambientes aquáticos de água doce, especialmente riachos rurais. Os resultados observados neste estudo reafirmam a importância da conservação dos riachos, a partir da manutenção da vegetação ripária como uma forma de reduzir a entrada de MP nesses ecossistemas.

Morphometric analysis is the measurement and mathematical analysis of the configuration of the surface, shape, and dimension of landforms. The objective of this study is to characterize the Aynalem and Illala streams using the morphometric parameter. The topographic map at a scale of 1:50,000 taken from the Ethiopian National Mapping Agency was used to characterize the linear and areal aspects. ASTER Digital Elevation Model with 10m resolution was used to characterize the relief aspect. The Arc GIS 10.4.1 was used during the morphometric analysis. The analysis result of the streams is summarized based on the linear, areal, and relief aspects. The area is characterized by a dendritic drainage pattern which is characteristics of massive hard rock terrain. The Aynalem and Illala streams are 4th and 5th order streams. Considering the number of streams in the Aynalem (75.81%) and Illala (74.66%) is composed of first-order streams that indicate a flashy flood and the mean bifurcation value of Aynalem (6.8) and Illala (4.7) shows that the Aynalem area is more structurally affected than Illala but both show less stream integration. The analysis of areal aspects such as elongation ratio, circularity ratio, and form factor has indicated that both streams are characterized as elongated streams, this implies that both streams are flowing in heterogeneous rock material, presences of structural effect, and slow runoff discharge. The other areal aspect such as drainage density, stream frequency, infiltration number, and length of overland flow all show smaller values in both streams. This implies that the streams are characterized by a relatively permeable rock material with a higher infiltration capacity. The relief aspect of the Aynalem and Illala was also analyzed using basin relief, relief ratio, ruggedness number, hypsometric curves, and Hypsometric integral. The streams are characterized by a lower relief ratio and ruggedness number which implies a relatively flat slope and lower relief. The hypsometric curves and the Hypsometric Integral of the streams indicate that the Aynalem and Illala are at the maturity stage. This shows the area is characterized by higher erosion but less affected by recent structures. Based on the morphometric parameter analysis result it is possible to conclude that the stream development is dependent on the topography and geology of the study area and both streams show similar morphometric character.

Existing data in the United States are insufficient for estimating pesticide-treated crop areas at the watershed scale. The objective of this research was to evaluate an approach for estimating simazine usage on corn (Zea mays L.) based on its transport to streams of the Salt River Basin (SRB) of Missouri, USA. Annual loads of total simazine and atrazine (parent + metabolites) were quantified for seven SRB watersheds from 2005 to 2017. Simazine-treated corn area was computed as the total simazine load (g) divided by total atrazine load (g ha-1 ) on a treated area basis; atrazine was used as surrogate in the absence of treated area simazine load data. From 2005 to 2010, an estimated 3.8-31% of the corn area within SRB watersheds was treated with simazine, and four of six watersheds had

The lampricide 3-trifluoromethyl-4-nitrophenol (TFM) has been used in liquid form to control larval sea lamprey (Petromyzon marinus) in Great Lakes tributaries since the late 1950s. In the 1980s a dissolvable TFM bar was developed as a supplemental tool for application to small tributaries as a deterrent to larvae seeking water not activated with TFM. The size, mass, and number of bars needed in some streams, as well as the location of the streams, limit the utility of a TFM bar. The development and use of an alternative niclosamide bar has the potential to use fewer bars to achieve similar results. However, the use of a niclosamide bar is dependent upon its larval deterrent capability compared to the TFM bar. In this study, we developed a laboratory-scale, simulated stream fluvarium with several avoidance areas including two side channels and a seep. The objective was to evaluate the deterrent capabilities of TFM and niclosamide. We found similar behavioral responses, with TFM and niclosamide having similar capabilities to prevent sea lamprey from seeking refuge in side channels and seep avoidance areas. TFM-treated side channels and seep increased sea lamprey occupancy in the main channel 2.56 times more than the untreated-controls (95% CI 1.63–4.14) whereas niclosamide-treated side channels and seep increased sea lamprey occupancy of the main channel 2.68 times more than the untreated-controls (95% CI 1.72–4.32). These responses indicate a niclosamide bar would effectively prevent sea lamprey escapement into freshwater during a lampricide treatment at concentrations unlikely to harm aquatic organisms.

Overriding the underthrusting Indian plate along the low angle detachment surface of the Main Himalayan Thrust (MHT), the entire Himalayan wedge, consisting of several allochthonous and autochthonous sheets is actively deforming due to ongoing India-Asia convergence. However, the information on active tectonics of autochthonous sheets exposed in tectonic windows has often been eluded due to lack of directed investigations. The present study pertains to the active tectonics of the eastern part of an autochthonous sheet exposed in Kullu-Larji-Rampur window of the Lesser Himalaya. Geomorphic features and statistically analyzed geomorphic indices of Drainage Basin Shape (Bs), Hypsometric Integral (HI), Stream Length-Gradient Index (SL), Transverse Topography Symmetry Factor (T), and Basin Asymmetry Factor (AF) reveal active crustal deformation in the window caused by tectonic activities of spatially varying magnitudes. While the spatial distribution of Bs, HI, and SL suggest differential uplift of the anticlinally folded autochthonous sheet along the MHT, the spatial distributions of AF and T suggest an overall southeastward preferential shifting of the trunk streams of 3rd-order drainage basins of the terrane; the hinge zone and northwestern part of the sheet are experiencing relatively faster uplift. The faster uplift in the northwest has caused an overall southeastward down-tiling of the terrane, and thus preferential stream migration in that direction. The faster uplift of the hinge zone is considered to indicate active tightening of the fold.

The results of the present study show that the highest elevation point is (912) meters (a.s.l.) inside Wadi Al-Khur basin while the lowest elevation point is (6) meters (a.s.l.) inside Wadi Abu-Talha basin. The biggest catchment area is represented by Wadi Al-Khur (48840 km²) whereas the smallest catchment area is Wadi Taqtaq (1748 km²). The stream direction of all streams trends from South-West towards North-East. The soil available water capacity (AWC) (Moisture Deficit) in the studied area was15 mm. The average annual rainfall was133.11 mm, the average annual temperature was 25.65 Co, the total depth amount of E Apanwas 3691.85 mm/year, the relative humidity was 40 %, the average annual sunshine is 7.9 hrs., and the average annual wind speed is 2.7 m/s. The water surplus of the total studied area 46800 km) was about 488.592 m³⁄year, while the runoff amount was about 442.190 m³ ⁄year.

The landslides of the Lagam escarpment, Kaben Location, Marakwet, Elgeyo Marakwet County, are not only recurrent but are highly cataclysmic; causing mayhem whenever they occur. The first known landslides on the Lagam escarpment of Kaben location -Marakwet, happened during the 1961 El-Nino, when a major rainstorm hit the area (Kiptungu). These landslides re-fashioned Embosumer River and left huge boulders scattered over many farmlands. In 2010, a catastrophic landslide hit Kaben location and again, Embosumer River was the perpetrator, having broken its banks due to excessive water inflow. Many lives were lost and lots of property was destroyed. In 2020, heavy rains pounded the area causing massive mudslides that involved many rivers and streams; such as Embosumer, Emboreberwo and Karengor. As a result, twenty-six (26) lives were lost, homes, schools and farmlands were washed away and to date, there are several bodies believed to be trapped in the mudslide material. This study is geared towards investigating the causes of the recurrent landslides and proposing possible mitigation measures. Data was collected through secondary data analysis and has been presented in the form of ground photographs, satellite images and discussions made thereon. It is hoped that this preliminary study of the Lagam escarpment landslides will create awareness pertaining to the recurrent landslides and draw positive action from the area residents and all concerned.

Replanting riparian vegetation can improve ecological health but there are few guidelines that help stakeholders achieve shade targets cost-effectively. A computer model was extended to calculate a...

Climate change is altering hydrologic regimes globally. In the Mediterranean climate region of south-western Australia (SWA), climate drying has caused many perennial streams to switch to intermittent flow regimes. Shifts in flow regime are expected to alter physical and biological processes in streams, including litter decomposition, which is the basis of detrital food webs. Decomposition of jarrah (Eucalyptus marginata) leaves and associated macroinvertebrates, were measured over 320 days in 2018–19 using leaf bags in four headwater streams in SWA. Two streams retained perennial reaches and two were formerly perennial streams that are now intermittent. Pre-planned comparisons that formed a partial multiple before–after, control–impact design were used to compare the results to an experiment conducted in 1982–83 in some of the same streams when all were perennially flowing. Both experiments used coarse and fine-mesh bags containing 10 g of dry leaves. In one perennial stream, coarse bags lost more weight than fine bags at the last sampling time only, when shredding caddisflies arrived on the leaf bags. In the other perennial stream, leaf-mining chironomids entered fine-mesh bags and accelerated decomposition so that they lost more weight than the coarse-mesh bags. There was no difference in weight loss between fine and coarse-mesh leaf bags in the two intermittent streams. In 2018–19, decomposition was slower in dry reaches of intermittent streams than in perennial reaches. Leaf weight loss increased with the resumption of flow in intermittent streams, so that by the end of the experiment, similar amounts of leaf weight had been lost in intermittent and perennial reaches. Thus, although the temporal pattern of decomposition differed between intermittent and perennial reaches, after 320 days, they had reached a similar endpoint. Over similar experimental duration, mean leaf weight remaining in perennial reaches at the end of the experiment did not differ between the 1982–83 study and 2018–19, showing that leaf decomposition had not changed in reaches that retained perennial flow. As mean leaf weight remaining also did not differ between intermittent and perennial streams in 2018–19, leaf decomposition was robust to flow regime change. However, since 1982–83, these streams have lost populations of shredding caddisflies and stoneflies, which were replaced by other shredders (e.g. leaf mining chironomids Stenochironomus sp.), showing that there was some redundancy amongst shredder species. As climate change progresses, drying flow regimes will become commonplace in Mediterranean (and other) climate regions globally. This study indicates that litter decomposition may be maintained as streams transition to intermittency although shredder species may change. However, the impact of shredding species on leaf decomposition varies amongst studies, so effects of the loss of shredder species sensitive to drying may also vary, and in some cases their loss may substantially alter ecosystem processes.

In streams and rivers, wood from riparian vegetation contributes to habitat complexity and substrates for stream biota, influences channel geomorphology, alters flow, retains sediment and organic matter, and enhances nutrient uptake. A few studies have shown that wood amounts in urban streams may be lower than in rural streams or that wood amounts in streams are inversely related to watershed impervious surface cover (ISC). To determine if these patterns occur more broadly, we compared wood amounts in urban and non-urban streams in the South Carolina Piedmont and Blue Ridge Provinces. We measured wood abundance in 20 streams draining urbanized (15–68% ISC) or non-urbanized (≤ 2.5% ISC) watersheds. Our results did not support the hypothesis that urban streams would have less wood than rural streams, and we found no relationship between wood amounts and watershed ISC. Indeed, one urban stream bordered by large riparian trees had the greatest wood volume of all streams in our study. Instead, large wood amounts were best explained by tree canopy cover and length of unobstructed tree-lined channel upstream. These results suggest that the presence of numerous riparian trees influences wood amounts positively even in urban streams where wood amounts might be expected to be low.

The three contiguous National Estuary Programs of southwest Florida, along with partners from six coastal counties, have developed a tidal creek water quality assessment framework to help prioritize natural resource investigations across a large population of tidal creeks between Tampa Bay and Estero Bay, Florida. The assessment framework is based on outcomes of a multidisciplinary study and includes a nutrient based report card that characterizes nutrient conditions relative to regional numeric nutrient criteria developed for contributing freshwater streams, identification of site-specific water quality indicators of tidal creek condition, and an online open science dashboard to display the assessment framework and provide access to all information relevant to its implementation. Application of the assessment framework has provided an actionable list of southwest Florida tidal creeks prioritized for further research and potential management action along with a host of site-specific indicator results that provide insights into drivers of tidal creek condition. The open science dashboard provides a platform for dissemination of this information in a readily accessible and reproducible format and a means to incorporate new data and indicators as they become available. Local resource managers are in need of tools to help prioritize natural resource investigations and management actions that achieve the greatest resource benefit with limited available resources. This assessment framework informs these efforts and builds capacity for future research to identify and refine management tools for these creeks where management resources, data, and sentinel biological response endpoints are limited.

A critical component of water-resources management in the irrigated agriculture landscape, particularly those landscapes dependent on groundwater availability, is determining groundwater recharge rates from streams and other channels. In California, flows in many such channels are “controlled” by upstream reservoir releases to meet downstream urban, irrigation and environmental water requirements. Seepage volumes from these channels and how they might vary during controlled release periods is a key component of meeting downstream riparian and groundwater-pumping needs. Understanding annual seepage from streamflow channels is also important in developing water budgets as part of the management of groundwater resources under the Sustainable Groundwater Management Act (SGMA) in California. However, direct measurements of channel seepage rates are infrequent or unavailable, and these rates, or associated volumes, are most often only estimated. Here we describe direct point- and reach-scale field measurements of channel seepage rates in Lower Putah Creek (Solano County) and in distribution lateral channels of the Oakdale Irrigation District on the east side of the San Joaquin Valley (San Joaquin and Stanislaus counties). We measured overall average seepage rates of about 2 feet (610 mm) per day at both locations and determined how these rates varied spatially and temporally during the summer when channel flows are controlled for downstream requirements.

Mercury (Hg) export from glacierized watersheds is poorly understood, with very few studies worldwide on Hg concentration and speciation in glacier snow, ice, and meltwater, and on Hg fluxes to downstream freshwater and coastal ecosystems. In addition to bedrock-derived geogenic Hg, glaciers may be releasing legacy accumulations of natural and anthropogenically-sourced Hg trapped in glacier ice melt each summer season. Our prior work showed that a glacierized stream in southeast Alaska had the highest reported flux of inorganic mercury of all known non-mining impacted streams, highlighting the strong ability of glaciers to mobilize the trace metal. Here we present data on Hg concentrations, speciation, partitioning, and fluxes from two more glacierized watersheds (Herbert and Mendenhall Rivers), and we compare them to an adjacent non-glacierized, forested-wetland stream (Peterson Creek). Results show that the glacierized streams carried Hg largely in the particulate form, whereas the forested-wetland stream carried it largely in the filtered fraction, at 20 fold higher concentration than in the glacierized streams, and with a higher percent of Hg in its methylated form. Yet, considering the higher water and sediment yields (as mass per watershed area per year) of the glacierized streams during the summer melt season, the yield of total Hg (unfiltered) from the Mendenhall glacier was approximately 80 times higher than from the Herbert glacier and 50 times higher than in Peterson Creek and presents the highest watershed yields of total Hg and methyl-Hg reported in the literature to date. Incongruous yields out of the two glacierized streams can likely be explained by differences in underlying bedrock geology. Based on the sediments entrained in Mendenhall meltwater, the late Paleozoic to Paleocene metasedimentary and volcanic rocks being eroded in the terminal 3 km of the Mendenhall are elevated above mean crustal concentrations by at least 4–17 fold. Differences in speciation between the glacierized and non-glacierized streams are likely accounted for by glacial and watershed geochemical conditions that variably promote Hg methylation.

Surface waters are under pressure from diffuse pollution from agricultural activities, and groundwater is known to be a connection between the agricultural fields and streams. This paper is one of the first to calculate long-term in-stream concentrations of tritium, chloride, and nitrate using dynamic groundwater travel time distributions (TTDs) derived from a distributed, transient, 3D groundwater flow model using forward particle tracking. We tested our approach in the Springendalse Beek catchment, a lowland stream in the east of the Netherlands, for which we collected a long time series of chloride and nitrate concentrations (1969–2018). The Netherlands experienced a sharp decrease in concentrations of solutes leaching to groundwater in the 1980s due to legislations on the application of nitrogen to agricultural fields. Stream measurements of chloride and nitrate showed that the corresponding trend reversal in the groundwater-fed stream occurred after a time lag of 5–10 years. By combining calculated TTDs with the known history of nitrogen and chloride inputs, we found that the variable contribution of different groundwater flow paths to stream water quality reasonably explained the majority of long-term and seasonal variation in the measured stream nitrate concentrations. However, combining only TTDs and inputs underestimated the time lag between the peak in nitrogen input and the following trend reversal of nitrate in the stream. This feature was further investigated through an exploration of the model behaviour under different scenarios. A time lag of several years, and up to decades, can occur due to (1) a thick unsaturated zone adding a certain travel time, (2) persistent organic matter with a slow release of N in the unsaturated zone, (3) a long mean travel time (MTT) compared to the rate of the reduction in nitrogen application, (4) areas with a high application of nitrogen (agricultural fields) being located further away from the stream or drainage network, or (5) a higher presence of nitrate attenuating processes close to the stream or drainage network compared to the rest of the catchment. By making the connection between dynamic groundwater travel time distributions and in-stream concentration measurements, we provide a method for validating the travel time approach and make the step towards application in water quality modelling and management.

Functional feeding group (FFG) is an approach that classifies macroinvertebrates based on their utilization of organic matter food resources. Across streams and rivers, variations in the distribution of FFGs reflect the unequal distribution of food resources, which are affected by varying environmental conditions and disturbances to the ecosystem. In the tropics, the distribution of FFGs does not follow the pattern observed in temperate streams. This study aims to (1) determine the FFGs present in selected Philippine tropical streams, (2) assess the variations in FFG distributions and how the distributions vary across space, and (3) evaluate how FFG distributions are affected by certain environmental factors and habitat structure. Benthic macroinvertebrates were collected in 2010 from five sites and assigned to their primary FFG based on published literature. Across study sites, the macroinvertebrates collected were classified into gathering collectors (total n = 4,640), scrapers (n = 1,670), filtering collectors (n = 1,545), predators (n = 632), and shredders (n = 270). Within and between sites, these FFGs varied significantly. Variations explained the upstream-downstream and north-south variations in the mean of FFG abundance in width and depth of the stream, discharge, temperature, pH, riparian vegetation, and habitat stability and variability. This study reveals that the FFG approach is a useful bioassessment tool in tropical aquatic systems. However, there is still a need for verification of the findings in other streams and seasons.

Initial Odonata larval distributions are primarily influenced by adult females at the moment of oviposition. However, after oviposition, the larvae are strongly associated with environmental conditions. In the case of both adults and larvae, anthropogenic disturbances that change these conditions may alter the composition and structure of Odonata assemblages. Therefore, based on the differing environmental requirements of Zygoptera and Anisoptera adults and larvae, together with their morphological and physiological differences, we suspected differing riparian preferences of larvae and adults for each suborder. We evaluated the richness and abundance of Odonata larvae. We hypothesized that Zygoptera larvae would have greater richness and abundance in streams with canopy shading, lower temperature ranges, and high physical habitat heterogeneity. On the other hand, Anisoptera larvae would be more abundant in streams without canopy cover. We sampled 186 headwater stream sites in the Neotropical Savanna along an anthropogenic disturbance gradient and used a model selection approach to test our hypotheses, correlating environmental metrics with Odonata larval richness and abundance. We found higher richness of Zygoptera larvae in shaded sites with canopy cover > 5 m high, whereas bare ground without riparian vegetation was important for Anisoptera richness and abundance. Our results indicated that Odonata larvae follow the same distribution, richness and abundance patterns as adults. Anthropogenic disturbances related to the removal or reduction of riparian vegetation can favor Anisoptera over Zygoptera larval assemblages in streams. Preserving riparian canopy cover is needed to maintain the richness of Zygoptera larvae in Neotropical Savanna streams.

Knowing how cave lithology influences the benthic macroinvertebrate fauna is important for conservation and management of subterranean aquatic systems. However, those influences are still poorly understood, especially in the Neotropics. This study aimed to understand how cave lithology can influence benthic EPT assemblages by assessing the differences in the EPT genera structure in caves of two distinct lithologies (quartzite and limestone) and determining possible differences in the lithology habitats. To achieve this, hydrochemistry data and biological samples were collected in six allogenic cave streams from the two aforementioned lithologies. Results showed that both the assemblages from different lithologies and within the same lithology are statistically different, thus indicating probable regional influences beyond local ones. Our results also pointed out an effect of lithology on the substrate parameters, which in turn affected the EPT composition. Cave lithology affects water chemical and physical characteristics, thus supporting different EPT assemblages. The results of this study provide a foundation for future investigation on how the lithology can influence the benthic macroinvertebrate fauna and should lead to means of predicting such fauna on the basis of the cave lithology and water chemistry.

The underlying spatial and environmental processes shape the freshwater fish assemblage of streams and rivers. Due to dispersal barriers between the river basins, species filtering is associated with longitudinal environmental gradients resulting in distinct assemblages. This study primarily aims to assess the freshwater fish beta diversity profile inhabiting two rivers of the Upper Brahmaputra basin of Eastern Himalayas, namely River Teesta (large-scale) and Murti (small-scale). The beta profile is further disintegrated into three components, i.e., beta turnover, beta nestedness, and local contribution to beta diversity (LCBD). River Teesta has higher beta diversity and beta turnover values, while River Murti has a higher nestedness in community composition. LCBD is found to be higher in altitudinal extremities, and River Murti seems to have higher values. However, turnover in River Teesta is highly correlated (r > 0.5) with 17 environmental factors, while in River Murti, 15 of them seem to be significantly correlated (r > 0.5). Similarly, nestedness in River Teesta is correlated with stream slope while with water velocity and river width in River Murti.

The relief of the ice-sheet bed predetermines the location of the valleys both in vast regions and in local, relatively limited areas. The influence of the relief in a large region on the formation of valleys occurs in lowland, more dissected northern and western regions of Belarus. Here, the bedrock relief plays a key role in appearance the hollow-like Vidzovsky, Polotsk and Surazh glacial erosion depressions and in isolation of the elevations separating them. The distribution of these largest forms of glacial erosion is associated with the regional picture of the glacial ice flow in topographic depressions, increased erosion of the ice bed, which developed under the glacial streams and lobes of the Scandinavian ice sheet. The degree and character of the relief dissection, the size, surface slope and orientation of the depressions, river paleo-valleys, elevations, and escarps had a leading role in the location of valleys in local, relatively limited areas. Their significance for the formation of valleys was to determine the local picture of the glacial flow and the areas where stresses were concentrated at the bed and glacial erosion intensified. The formation of tunnel valleys was possible in depressions and in the dissected relief of the glacial bed, which contributed to the accumulation of meltwater, the formation of subglacial lakes, as well as the concentration of meltwater in the subglacial channels.

Globally, wetlands have declined in area by over 50% since 1900, due to changes in land-use patterns, converting them into farmlands, human settlements, urban centers, and infrastructure development. Land-use changes also impact negatively on the water area (streams, rivers, lakes, reservoirs, and sea) of an area. In this study, the threats of land use changes on wetland and water areas in Murang’a County, Kenya, were assessed, in a bid to understand the main causes for the rapid decline in wetland and water areas in the County. Landsat images of 2001 and 2018 were analyzed using a supervised classification technique to produce Land-use maps in ArcGIS and detect associated changes. Between 2001 and 2018, the wetland area in Murang’a County declined by over 48% while the water area declined by over 25%. Bare-soil/built-up area posed the greatest threat to the conservation of wetlands in the County, taking up 161 ha of the wetland area during the period. The growth of woody shrubs posed the greatest threat to the loss of water areas taking up 152 ha of the water area during the period. Mean total threats facing wetlands differed significantly from mean total threats facing water areas in the County (t = 0.682; p