Small Streams Research Articles

Restoring streams with large wood: An analysis of geomorphic changes 7 years post‐restoration in small coastal streams

AbstractIntroducing large wood (LW) into streams for restoration purposes is a common practice, as it creates habitat through processes like scouring, deposition and sediment sorting. However, while monitoring often focuses on short‐term (<3 years) or long‐term (>10 years) changes in habitat features, there is a lack of understanding regarding annual geomorphic changes over relatively long periods. In this study, we investigated annual geomorphic adjustments (channel geometry and substrate size) over 7 years in three tributaries of the Mill Creek watershed (Oregon, USA). The 7‐year period included moderate to high flows, with peak annual flow exceeding bankfull flow (Qbf) 2–5 times and flows being above half Qbf on average 4–20 days per year. Data included topographic surveys and surface pebble counts collected from 2014 (1 year before LW) to 2021 (6 years after LW). We quantified scour and deposition and estimated sediment grain sizes and sorting from topographic surveys and pebble counts. Our analysis revealed that stream size influenced geomorphic adjustment, with smaller streams experiencing more scouring compared with larger streams over the 6 years. LW structures promoted increased scouring at the cross‐section scale, with a strong relationship found between volumetric blockage ratio and scour. In our case, the most significant scouring changes were associated with volumetric blockage ratios between 35% and 50%; further research is needed to investigate scouring for higher blockage ratios. Instream changes in scour and deposition peaked around 3–4 years after LW introductions but persisted until the end of the monitoring period. Sediment size dynamics were influenced more by time since restoration than by proximity to LW jams. While LW introductions increased sediment sorting into patches, the degree of sorting declined 5–6 years post‐restoration at all sites. Our findings offer insights into the long‐term persistence and magnitude of instream changes associated with LW introductions.

Biogas Purification by Methane and Acetate Manufacturing

ABSTRACTWastewater treatment plants have two persistent financial and energetic drains, the carbon dioxide content of biogas, which limits its commercial sale, and the presence of trace organics in the wastewater effluent, which damages the aquatic ecosystem, like the Great Barrier Reef. Biogas is a renewable methane resource that is underutilized due to the variable CO2 content (~40%). Biogas is energy intensive to purify and limited by the economy of scale (> 8.85 GJ/h) to large‐scale purification methods, thus small‐scale processes require development. Electrocatalytic microbes native to wastewater have been shown to convert CO2 to CH4 and acetate, however complete conversion of the CO2 content to CH4 is energy intensive. Here we show a low power bioelectrochemical fuel cell design to purify biogas to pipeline quality methane (98%), manufacture methane and/or acetate, and remove trace organics, using HCO3− as the transport charge carrier from dissolved CO2 from the biogas through an anion exchange membrane. This decreased the power required to separate CO2 from methane in biogas on a molar basis, resulting in a net energy recovery similar to current industrial systems. Magnesium anode use resulted in an energy positive system. Tests evaluated the influence of cathode potential on the current density, HCO3− ion flux and the rates and efficiencies of methane production, resulting in optimization at −0.7 V versus standard hydrogen electrode (SHE). A techno‐economic analysis modeled a positive return on investment for scaled‐up production to purify small biogas streams that are otherwise financially unrecoverable. Carbon sequestration by production of methane, acetate and solid fertilizers demonstrated profitable and energy efficient waste‐to‐resource conversion.

Molecular Identification and Description of the Tadpole of Leptobrachella melanoleuca (Matsui, 2006) (Amphibia: Anura: Megophryidae)

Identifying tadpoles will significantly enhance future studies on life histories, behavior, ecology, and distribution of amphibian species. This study provides a detailed morphological and buccopharyngeal description of Leptobrachella melanoleuca tadpoles, utilizing DNA barcoding for accurate identification. Ten tadpoles, measuring 15.0±1.22 mm (range: 12.0–16.6 mm) in body length, were collected from Khlong Saeng Wildlife Sanctuary, Surat Thani Province, southern Thailand. Mitochondrial gene sequences, including 12S rRNA, tRNA-Val, and 16S rRNA, showed less than 0.1% divergence from adult L. melanoleuca in GenBank and our adult specimens, confirming the identification. Both tadpoles and adults were found in a small rocky stream. The tadpoles exhibit dark brown coloration with brown blotches in life, while preserved specimens show significant fading. The tadpoles’ external morphology includes a translucent abdomen, darkened throat, and dark gray chest. The tail musculature is gray with light brown spots, and the fins are slightly transparent. Buccopharyngeal anatomy revealed a semicircular prenarial arena with knobby projections, narrow choanae, and a densely pustular buccal roof arena. The buccal floor features triangular tongue anlage, trapezoidal prelingual arena, and large buccal floor arena papillae. The Keratodont Row Formula (KRF) is recorded as 1:2–2/0 or 2+2/0, with black jaw sheaths. These findings contribute significantly to our understanding of tadpole morphology in the genus Leptobrachella, providing a crucial reference for future taxonomic and ecological studies of this and related species.

The perennially ice-covered Lake Enigma, Antarctica supports unique microbial communities

Northern Foothills of Victoria Land, Antarctica contains numerous hydrological formations, ranging from small surface streams and ponds fed by glacial or snow meltwater to permafrost lakes containing briny pockets. Here we describe the discovery of a massive body of unfrozen stratified oligotrophic water in Lake Enigma, a permanently ice-covered lake previously thought to be frozen from top to bottom. A remarkable feature of the Lake Enigma microbial ecosystem is the presence, and sometimes even dominance, of ultrasmall bacteria belonging to the superphylum Patescibacteria, a group apparently absent from Antarctic lakes in the well-studied McMurdo Dry Valleys. Cyanobacteria are virtually absent from Lake Enigma ice and water column although they are well represented in its extensive and diverse benthic microbial mats. Collectively, these features reveal a new complexity in Antarctic lake food webs and demonstrate that in addition to phototrophic and simple chemotrophic metabolisms, both symbiotic and predatory lifestyles may exist.

Effects of Channelization on Macroinvertebrate Assemblages in a Small Stream: The Case of Awetu in Jimma City, Ethiopia

Freshwater ecosystems are increasingly modified worldwide by anthropogenic activities. Land use change is one of the leading factors responsible for stream ecosystem degradation. Physical habitat disturbance due to channelization is among the factors responsible for the loss of biodiversity and degradation of river water quality worldwide. Since 2020, Jimma City municipality has been beautifying the city and one of the activities is channelizing using concrete embankment, a part of the Awetu stream that runs through the city. The main aim of this study is to assess the effect of channelization on macroinvertebrate assemblages and the water quality of the Awetu stream. A cross-sectional study was conducted in April 2022. Macroinvertebrates, water samples, and habitat data were collected from 21 sampling sites along the three segments of the stream (upstream, channelized, and downstream). Data were analyzed for different macroinvertebrate metrics and water quality parameters. Canonical Correspondence Analysis was used to examine the overall relationship between macroinvertebrate assemblages and water quality parameters. The upstream site has better macroinvertebrate assemblages than channelized and downstream sites (p<0.05). The downstream site showed better assemblage compared to the channelized site, though it was not significant. Regarding water quality parameters, a significant variation was observed between channelized and, un-channelized sites (upstream and downstream) (p<0.05). The habitat condition score varied from 47 (poor) at channelization to 150 (suboptimal) upstream. Upstream sites were found to have relatively better macroinvertebrate assemblages, better water quality, and good habitat conditions. The downstream sites had lower macroinvertebrate assemblages, poor habitat conditions, and degraded water quality compared to the upstream sites. The channelized segment had the poorest habitat, with poor macroinvertebrate assemblages and water quality. Thus, the conservation of habitat conditions along the channelized segments of the Awetu stream is recommended to improve the water quality and macroinvertebrate assemblage.

Five new species of the genus Grouvellinus Champion, 1923 from Guizhou Province, China (Coleoptera, Elmidae).

The genus Grouvellinus Champion, 1923 comprises 60 described species distributed across the Oriental and Palearctic regions. Species diversity is very high in mainland China, with 28 recorded species. Here, the results of the aquatic beetle survey in Guizhou Province are presented; they began in 2021, when we collected more than 5000 specimens of riffle beetle. All specimens come from small ravine streams where inhabited submerged stones. Using morphological characters of adults such as body form and size, coloration, elytral, pronotal and ventral surface structures, and forms of male and female genitalia, five new species were discovered and are described: Grouvellinusloong sp. nov., G.buyi sp. nov., G.wangmoensis sp. nov., G.lihaitaoi sp. nov., G.muyinlini sp. nov. The species descriptions contain illustrations of diagnostic characters and measurements of metric characters such as body length, pronotal length, pronotal width, elytral length and width, and head length and width. The females are, on average, larger and have only slight differences in external morphology compared to the males. The comparative diagnoses discuss characters of the new and already known species. The results show that the existing species diversity requires more detailed research focusing on larger areas of South China in the future.

Population characteristics, seasonal distribution, and suppression potential of introduced Northern Pike in a Great Plains stream

AbstractObjectiveThe objectives of this study were to describe the population dynamics, reproductive characteristics, and movement of Northern Pike Esox lucius in the Niobrara River drainage of Wyoming. This information was used to estimate the necessary level of suppression to meaningfully reduce their abundance and thereby facilitate persistence of native nongame fishes.MethodsIn 2019 and 2020, Northern Pike were sampled to describe population size structure, age structure, growth, and mortality. An additional 42 gravid female Northern Pike were collected across 2020–2023 to determine a length–fecundity relationship. Vulnerability to recruitment overfishing was modeled with a static spawning potential ratio model. Finally, 15 mature fish were implanted with radio transmitters in 2021 and 2022 and tracked for 1 year to determine seasonal dispersal and spawning locations.ResultSampled Niobrara River drainage Northern Pike (n = 213) varied from 127 to 749 mm total length. Estimated ages of fish were between 0 and 8 years, and total annual mortality was estimated at 42% (95% confidence interval = 36–48%) in the presumed absence of fishing mortality. Recruitment was extremely stable, and growth was relatively fast through age 2. Some females matured at age 1, and all females were mature by age 2 and spawned annually. Estimated total fecundity for females between 297 and 914 mm total length varied from 3573 to 154,877 eggs. Most telemetered fish moved little throughout the year, but movements as large as 5.9 river kilometers were observed. Modeling suggests that exploitation of age‐1 and older Northern Pike should exceed 42% and exploitation of age‐2 and older fish should exceed 85% to meaningfully reduce the population's reproductive potential.ConclusionNorthern Pike growth and reproductive potential at older ages may be more limited in small prairie streams than within their native range. Observed annual home range was small, and spawning occurred annually in consistent locations. The necessary intensity of mechanical removal to achieve meaningful suppression in this system will likely require an intensive and ongoing interstate effort.

Lowland Interior-Forest Stream Habitat of Galictis vittata (Carnivora: Mustelidae) on the Las Piedras Tributary, Southeastern Peru.

Records of Galictis vittata (Greater Grison) from the Amazon basin are sparse, particularly in the Madre de Dios region, where only three records have been published. This study elaborates on seven observations of Galictis vittata within and near small interior forest streams of the Las Piedras tributary in Madre de Dios, Peru. While G. vittata inhabits terrestrial environments, it has also been observed in association with aquatic habitats in parts of its range. Although limited to seven observations, all documented sightings of G. vittata in the Las Piedras region have been associated with stream ecosystems. Based on our records, prior research from the region, and known natural history of the species, we hypothesize that streams are a preferred habitat in Amazon rainforests. Additionally, we provide behavioral notes associated with the encounters.

Migration patterns, habitat use and genetic origins of sea trout (Salmo trutta) in Norfolk chalk streams: implications for management of a mixed stock fishery

Sea trout, the anadromous ecotype of the species Salmo trutta, are subject to multiple threats, including exploitation and aquaculture impacts in the marine environment, habitat fragmentation and pollution in freshwaters, loss of genetic resilience due to interbreeding with hatchery strains and environmental change. Small streams contribute relatively little biomass to European sea trout stocks but are thought to be important in maintaining genetic diversity and therefore wider population resilience. The current study combined data from acoustic telemetry, stable isotopes, genetics and scalimetry to assess the current status of sea trout in the rivers Stiffkey and Glaven, two locally important chalkstreams in East Anglia, UK, to provide an evidence base for future management. The incidence of anadromy was low, and most sea trout were near migrants, residing in the lower reaches of rivers and close to the tidal outfalls. A small number migrated to the North Sea where they were vulnerable to exploitation in the coastal fishery, which comprises a mixed stock. Straying between the two rivers was recorded among 10% of sea trout, leading to apparent high gene flow. Nonetheless, genetic data also demonstrated structuring of River Glaven trout into two distinct groups. Quantification of patterns of freshwater and estuarine habitat use, and of passage at cross-channel obstructions, was used to identify where remedial measures such as habitat restoration would be most effectively targeted. Findings are discussed in the context of local supplementary stocking and the potential impact of the nearshore fishery on limited and vulnerable small stream anadromous trout populations.

The impact of repeated pyrethroid pulses on aquatic communities

Pesticides are considered to be one of the main causes of the decline in macroinvertebrate biodiversity in small streams. In particular, pyrethroids are detected in agricultural surface waters worldwide and pose a high risk to aquatic invertebrates. Due to their knock-down effect, even short pyrethroid exposure pulses can have significant short- and long-term effects on macroinvertebrate communities. Therefore, it is necessary to consider more realistic exposure scenarios for the environmental risk assessment of pyrethroids and, consequently, to obtain more realistic effect data by using multi-stressor test systems.In an experimental setup with artificial indoor streams (AIS), four pyrethroid pulses simulated the exposure scenario of heavy rainfall events. Effects of these 12 h-exposures at different concentrations of deltamethrin (0.64 ng/L, 4 ng/L, 16 ng/L, 64 ng/L) with intervening recovery periods of six days were assessed on an aquatic community consisting of Gammarus pulex, Ephemera danica, Lumbriculus variegatus and Potamopyrgus antipodarum with various lethal and sub-lethal endpoints.The mortality rate of G. pulex significantly increased with increasing deltamethrin concentrations, whereas the mean number of offspring significantly decreased (NOECoffspring: 16 ng/L, LOECoffspring: 64 ng/L). The biomass of L. variegatus decreased with increasing deltamethrin concentrations (NOECdry weight: 16 ng/L, LOECdry weight: 64 ng/L).The findings of this study clearly demonstrate that 12 h-deltamethrin pulses at environmentally relevant concentrations adversely affect an aquatic community. Based on the results of this study a RAC value of 5.33 ng/L is assumed, which is below the concentrations measured in rivers of up to 58.8 ng/L. Unacceptable effects on the entire freshwater environment can therefore not be ruled out. The experimental AIS approach is a useful tool for assessing the effects of repeated pulse exposures that occur during surface runoff events.

Flow analysis and optimization study of main components of flow-type small hydro turbine system

Abstract Small hydro power generation refers to the production of electricity by harnessing the kinetic energy of water in small rivers or streams, typically generating up to 10 MW of power. The optimal shape combination of the watercone and turbine, according to the water flow rate, is crucial for maximizing the power generated. In this study, flow analysis using computational fluid dynamics was performed on Kaplan turbines to examine the effects of blade angle, volume flow rate and rotational speed on power generation. To ascertain the impact of variables on power generation, the internal flow field was examined. The findings demonstrated that an increased blade angle perpendicular to the flow direction resulted in a reduced incidence of vortices and cavitation formations within the turbine wake. A predictive model was generated using a design of experiment and response surface methodology to generate a predictive model to find the power generation for flow rates, blade angles and rotational speed within the experimental range.

Temporal and Spatial Variations in Microplastic Concentrations in Small Headwater Basins in the Southern Blue Ridge Mountains, North Carolina, USA

Microplastics (MPs) are ubiquitous contaminants of emerging concern that require additional study in freshwater streams. We examined the spatial-temporal variations in MP concentrations and characteristics within two headwater basins in the Southern Appalachian Mountains of western North Carolina over ~1 year. Atmospheric samples were also collected to determine the significance of atmospheric MP deposition to these relatively small streams. MP concentrations in both basins were within the upper quartile of those reported globally, reaching maximum values of 65.1 MPs/L. Approximately 90% of MPs were fibers. MP composition was dominated by polystyrene, polyamides, and polyethylene terephthalate. Spatially, concentrations were highly variable and increased with development, indicating anthropogenic inputs from urbanized areas. MP concentrations were also elevated in forested tributary subbasins with limited anthropogenic activity, suggesting atmospheric deposition was an important MPs source. Significant atmospheric inputs are supported by high atmospheric depositional rates (ranging between 7.6 and 449.8 MPs/m2/day across our study sites) and similarities in morphology, color, and composition between atmospheric and water samples. Temporally, MP concentrations during storm events increased, decreased, or remained the same in comparison to base flows, depending on the site. The observed spatial and temporal variations in concentrations appear to be related to the complex interplay between precipitation and runoff intensities, channel transport characteristics, and MP source locations and contributions.

Small Streams Support Beta Diversity in Neotropical Fish Assemblages in the Upper Paraná River Basin

ABSTRACTVariation in species composition along an environmental gradient (β‐diversity) can inform our understanding of biodiversity patterns and species composition. Beta diversity can be partitioned into species contributions to beta diversity (SCBD) and local contributions to beta diversity (LCBD). While SCBD describes the variations in species composition among samples, LCBD measures the uniqueness of a biological community within a larger ecosystem. Recently developed metrics enabled the estimation of species contribution to total beta diversity (SCBD) and the contribution of individual sites to total beta diversity (LCBD). Utilising these metrics, a one‐time survey of 275 sampling points within four sub‐basins of the Upper Paraná River Hydrographic Basin (low‐flow streams, &lt; 5 m3/s) was conducted to assess fish community composition. Our results show that limnological influences at different scales contribute to higher LCBD. However, land use and species richness were not directly linked to this outcome, suggesting that sites with fewer fish species along sub‐basins contributed to higher beta diversity. It was concluded that beta diversity is more influenced by limnological characteristics and the position of sampling sites along the longitudinal gradient than that based on variations in species composition (SCBD). Moreover, high LCBD values were even found in portions of the gradient with lower species richness. This means that small streams in the sub‐basins of the upper Paraná River are unique and are comprised of varied habitats that contribute to increasing diversity. As such, they should be seen as a target in the development of environmental policies designed to conserve their pristine condition.

Assessing the effectiveness of “River Morphodynamic Corridors” for flood hazard mapping

In dynamic rivers the assessment of flood hazard related to geomorphological dynamics assumes crucial importance. Recently, some geomorphological approaches have been developed to assess channel dynamics in response to floods. In this study we explore the River Morphodynamic Corridors which include the current active channel and areas of the alluvial plain that may be (re)activated by channel dynamics during floods. In order to assess the effectiveness of such corridors for mapping flood hazard, we delineated the morphodynamic corridors along a river network of 74 km in the Cordevole River catchment (Italy) and compared the corridors with the channel changes that were triggered by a high-magnitude event (Vaia Storm) that hit the study area in October 2018. We observed that the morphodynamic corridors are capable to define areas where channel dynamics are most likely to occur and have proven satisfactorily effective in predicting channel widenings triggered by a severe flood. The results show that it is crucial to adopt different procedures for corridor delineation based on channel width, i.e., for small streams (width < 30 m) a more precautionary approach should be adopted that considers the entire alluvial plain as an area potentially affected by channel dynamics. The study highlighted an inherent limitation of the approach, since erosion that can affect valley slopes or fluvial terraces (i.e., widening of the alluvial plain) is not taken into account. This application represents the first validation of the River Morphodynamic Corridors approach through comparison with observed flood channel changes. Through this analysis, it can be inferred that, notwithstanding its relatively simple procedure, the approach allows a robust mapping and delineation of flood hazard due to river channel dynamics. The River Morphodynamic Corridors, when applied jointly with hydraulic model for assessing inundation processes, allow an overall assessment of flood hazard, particularly in dynamic river contexts.

Peculiarities of the Species Composition, Abundance and Biotope Distribution of Mollusks Fam. Sphaeriidae in Rivers with a Many Lakes in the Catchment Area (by the Example of Water Courses of the Onega Lake Basin)

Using the example of the rivers of the Onega Lake basin, the species composition of mollusks of the Sphaeriidae family, their abundance, biomass, and contribution to benthic communities in rivers with many lakes in the catchment areas were analyzed. Patterns of spatial distribution of species across biotopes and gradients of environmental variables were traced. 26 species of mollusks of this family were identified, among them European-Siberian species predominate. Most of the species of mollusks of the family Sphaeriidae found by us have wide ecological ranges and are found in water bodies of various types. It was found that the contribution of Sphaeriidae to the species richness and functioning of aquatic communities in rivers in the conditions of branched lake-river systems (Lake Onega basin) exceeds the values usual for rivers with a small number of lakes in the catchment area. Using the ANOSIM and PERMANOVA methods, it was proved that the species composition of rocky rapids and riffles, sandy rifts and soft bottom soils is different. Using the IndVal test, seven species were shown to have a statistically significant association with one of these biotopes, and four of them, with rocky bottoms of river rapids and riffles. Using the NMDS method, it was shown that the greatest changes in the species composition of representatives of Sphaeriidae are observed when environmental conditions change from small streams with slow current and brown water to large rivers with fast current and clear water.

Dynamic frequent subgraph mining algorithms over evolving graphs: a survey.

Frequent subgraph mining (FSM) is an essential and challenging graph mining task used in several applications of the modern data science. Some of the FSM algorithms have the objective of finding all frequent subgraphs whereas some of the algorithms focus on discovering frequent subgraphs approximately. On the other hand, modern applications employ evolving graphs where the increments are small graphs or stream of nodes and edges. In such cases, FSM task becomes more challenging due to growing data size and complexity of the base algorithms. Recently we see frequent subgraph mining algorithms designed for dynamic graph data. However, there is no comparative review of the dynamic subgraph mining algorithms focusing on the discovery of frequent subgraphs over evolving graph data. This article focuses on the characteristics of dynamic frequent subgraph mining algorithms over evolving graphs. We first introduce and compare dynamic frequent subgraph mining algorithms; trying to highlight their attributes as increment type, graph type, graph representation, internal data structure, algorithmic approach, programming approach, base algorithm and output type. Secondly, we introduce and compare the approximate frequent subgraph mining algorithms for dynamic graphs with additional attributes as their sampling strategy, data in the sample, statistical guarantees on the sample and their main objective. Finally, we highlight research opportunities in this specific domain from our perspective. Overall, we aim to introduce the research area of frequent subgraph mining over evolving graphs with the hope that this can serve as a reference and inspiration for the researchers of the field.

Estimation of tributary–mainstem migration of freshwater fishes by Sr isotope analysis of otoliths

AbstractThe study of fish movement patterns in freshwater ecosystems remains a major focus of contemporary research. Small freshwater fish are known to migrate between tributaries and mainstems at different stages of their life history, helping to avoid local extinctions and maintain genetic diversity. However, fitting small fish species with telemetry equipment is difficult, making it challenging to track their detailed migration history via conventional methods. We evaluated the suitability of otolith isotope analysis for verifying the migration histories of small fish species inhabiting small tributaries. In this study, we compared the 87Sr/86Sr values in stream water and the otoliths of two fish species (Nipponocypris temminckii and Rhinogobius flumineus) inhabiting small streams. The 87Sr/86Sr ratios in the stream waters within the study area displayed considerable variation among tributaries. Our findings indicate that only N. temminckii has high dispersal ability, showing movement between tributaries or between tributaries and the mainstem in some locations. In contrast, such movement was not generally observed for R. flumineus. These results show the potential of 87Sr/86Sr as a tool for estimating the migration patterns of small fishes that inhabit small tributaries.

Amazon severe drought in 2023 triggered surface water loss

Abstract The Amazon underwent a severe austral springtime drought attributed to the onset of El Niño in 2023 and the warmer North Atlantic, Indian, and North Pacific Oceans. The Amazon rivers, lakes, small streams, wetlands, and reservoirs quickly lowered their water level below historical records due to decreased rainfall and warmth in the region. Based on satellite imagery, this study presents the first estimate of the water loss extent in the 4.2 million km2 of the Brazilian Amazon biome (∼62% of the Amazon total biome) in 2023. We estimated the loss of 3.3 million hectares of surface water relative to 2022, with an overall accuracy of 92%. The surface water losses were concentrated in the states of Amazonas (59.4%) and Pará (25.5), adding up to 2.8 million hectares. The warmer and drier climate in the region affected the main rivers in the Amazon. Among them, the Solimões, Negro, Purus, Acre, and Branco suffered extreme drops in their levels in some regions, resulting in a high negative impact on the aquatic biodiversity, yet estimated only in local areas. A total of 1.14 million hectares of surface water loss (i.e. 35%) was detected within protected areas territories, affecting extractivist, indegenous, African-Brazilian, and fishing and traditional communities. Proximity analysis revealed that 75% of the 2023 surface water loss was within 25 km of small towns, 48% and 65.8% at 50 km from indigenous villages and urban areas, respectively. Our results reinforce people’s vulnerability to climate change, anticipating a plausible adverse impact scenario in the Amazon region and urging solutions to adaptation and mitigation. Therefore, an integrated monitoring system based on climate and water dynamics from satellite and ground stations is necessary to improve understanding of the problem for timing response of climatic change negative impacts.

Frog hepatic health and metal pollution: An assemblage-level approach in a hotspot in southeastern Brazil.

Chemical pollutants include the harmful effects of various substances on soils, water bodies, and biodiversity. Amphibians are one of the most endangered groups ofvertebrates and are impacted by chemical pollutants in various ways due to their complex life cycles. Since trace pollutant concentrations vary across environments, different frog ecomorphs (classified by their microhabitat use) may have different exposures. We aimed to determine the association between frog ecomorphs and the occurrence of histopathological hepatic lesions (HHLs) as an indicator of contaminant exposure. We focused on small forest streams near a large urban region in Brazil, heavily polluted in the 1980s. We examined 104 frog specimens from various families. All specimens exhibited HHLs, with melanomacrophages being the most common (n = 99). Arboreal frogs exhibited more vascular congestion, while terrestrial frogs showed structural hepatic damage. Higher cobalt levels were linked to increased liver necrosis in arboreal frogs and structural issues in both arboreal and terrestrial frogs. Cadmium was associated with hepatitis in terrestrial frogs. Although metal levels had no significant effects on rheophilic frogs, the prevalence of hepatitis and necrosis indicated complex exposure pathways. Iron and aluminum were linked to fewer lesions in rheophilic frogs, suggesting resilience. The high prevalence of HHLs signals an ongoing issue, with variations among ecomorphs suggesting differential exposure to pollutantsand posinga complex challenge for community conservation.

Water Column Nitrogen Removal During Storms in a Low‐Order Watershed

AbstractWater column removal in streams is a nitrogen (N) cycling pathway that has been historically overlooked. Studies filling this knowledge gap have focused on the role of water column N removal in mid‐to‐large‐order rivers with consistently high suspended sediment concentrations. However, smaller streams may provide comparable suspended sediment concentrations during and after storm events, creating favorable conditions for water column N removal. To assess the presence, magnitude, and control of water column N removal during storms in low‐order watersheds, we measured water column denitrification and heterotrophic assimilatory N uptake rates at three locations in a Mid‐Atlantic watershed during five storm events of different magnitude, sediment loads, and nutrient availability. We found large variations in water column denitrification (0–5.56 mg N g−1 d−1) and assimilatory uptake (0.003–1.67 mg N g−1 d−1). Higher rates of N removal occurred during flow recession, with a correlation between suspended sediment organic matter content and denitrification. On average, denitrification rates in the water column were higher when flashy responses to storm events occurred. In contrast to denitrification, water column N removal rates (as both denitrification and heterotrophic assimilation) during storm events were comparable to those measured at baseflow in larger rivers. However, water column denitrification could only account for less than 10% of potential reach‐scale N removal during most of the storm events. Our findings provide insight into the ecological relevance of small stream water columns and suggest that more research is needed to understand the magnitude of stream water column processing on watershed‐scale N removal.