Article

Five-year legacy of wildfire and salvage logging impacts on nutrient runoff and aquatic plant, invertebrate, and fish productivity

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  • Okanagan Kootenay Sterile Insect Release Board
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Abstract

Ecohydrological linkages between phosphorus (P) production, stream algae, benthic invertebrate, and fish communities were studied for 4 years after severe wildfire in the Rocky Mountains (Alberta, Canada). Mean concentrations of all forms of P (soluble reactive, total dissolved, particulate, and total) were 2 to 13 times greater in burned and post-fire salvage-logged streams than in unburned streams (p < 0.001). Post-disturbance recovery of P was slow with differences in P-discharge relationships still evident 5 years after the fire (p < 0.001). Coupled P and sediment interactions were likely responsible for slow recovery of P regimes in fire-disturbed watersheds. P loading was associated with strong ecological responses in stream biota. Annual algal productivity was 5 to 71 times greater in streams within burned watersheds than in reference watersheds and persisted for 5 years after the fire (p < 0.001). Elevated algal production was associated with strong differences in benthic invertebrate community structure, including greater invertebrate densities, biomass, species diversity, and shifts in species composition. Monotonic shifts in invertebrate stable carbon and nitrogen isotope ratios indicated increased consumption of autochthonous food sources and effects on energy pathways for invertebrates from fire-affected streams. Wildfire-related changes at lower trophic lead to increases in size (weight and length) and growth rate (weight : age ratios) of cutthroat trout (Oncorhynchus clarki). This cascading series of effects of wildfire on stream productivity (primary production, secondary invertebrate consumers, and fish) may be long-lived legacies of wildfire because of the slow recovery of P regimes.

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... Rainfall can subsequently leach or transport the nutrients from the burned terrestrial landscape to adjacent streams [14]. Many studies have measured elevated nitrogen (N) concentrations (i.e., nitrate, ammonium, and nitrite) in stream water in response to severe wildfire [15][16][17][18], and concentrations may remain elevated for years due to the loss of vegetation that disrupts nutrient processes [19,20]. High concentrations of phosphorus (P) and other ions (i.e., soluble reactive P, SO 4 2− , and Cl − ) have also occurred after wildfire [20][21][22]. ...
... Many studies have measured elevated nitrogen (N) concentrations (i.e., nitrate, ammonium, and nitrite) in stream water in response to severe wildfire [15][16][17][18], and concentrations may remain elevated for years due to the loss of vegetation that disrupts nutrient processes [19,20]. High concentrations of phosphorus (P) and other ions (i.e., soluble reactive P, SO 4 2− , and Cl − ) have also occurred after wildfire [20][21][22]. Nitrogen losses to streams are usually much larger than phosphorus losses because forms of N are more soluble and mobile than P [4,14]. Increased nutrient loads to streams often exacerbate water quality by increasing algal concentrations and lowering dissolved oxygen [23,24]. ...
... − losses from disturbed forests are usually much higher than other forms of N and P because of rapid nitrification following fire and the high mobility of this anion [6]. As a result, many researchers measured large increases in NO 3 − concentrations in streams following wildfire [15,17,20]. For example, Mast and Clow studied a large wildfire in Glacier National Park, Montana, USA and reported NO 3 − concentrations exceeding 800 µg/L, which were >10 times higher than an unburned reference stream [46]. ...
Article
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Wildfires in the western U.S. have increased in severity and duration in recent decades. Severe wildfires can enhance the rates of nutrient mineralization, causing large exports of inorganic nitrogen and other ions from forests to streams. Measuring the degree to which streams respond to severe, stand-replacing wildfires is critical to estimate in ecosystems prone to disturbance. In 2003, two severe crown wildfires burned in Yellowstone National Park, WY, USA. We studied the extent to which these fires increased nitrogen (ammonium, nitrate and nitrite), sulfate, chloride, and total dissolved phosphorus concentrations and export in three watersheds prior to and during the first four years post-fire. We measured higher concentrations of most ions after wildfire, and nitrate and chloride concentrations increased the most, increasing > 1000 µg/L. Concentrations of nitrate (≤146 times pre-fire concentrations), total dissolved nitrogen (≤11 times), chloride (≤9 times), and total dissolved phosphorus (≤7 times) were higher four years post-fire than before the wildfires burned. Exports of nitrate (≤1392 times), sulfate (≤14 times), and chloride (≤37 times) were also higher after wildfire, while nitrite (≤2.9 times) and ammonium (≤6.4 times) increased to a lesser degree. Stream concentrations of most ions were higher in watersheds that had a larger percent of the area burned. Comparing ion concentrations in streams before and after severe wildfires provides critical information to managers as the climate warms and the frequency of fire-conductive weather increases.
... Much of what is known about wildfire impacts on aquatic ecosystems is from freshwater habitats, particularly montane streams. Freshwater studies comparing reference catchments to burnt catchments have found differences in the abundance, diversity and composition of macroinvertebrates (Minshall, 2003;Martens et al., 2019;Musetta-Lambert et al., 2019), primary producers (Silins et al., 2014;Klose et al., 2015) and microbial communities (Musetta-Lambert et al., 2020) as well as shifts in food web structure (Spencer et al., 2003;Cooper et al., 2015). Extents of effects may be related to intensity of fires, that correspond to the degree of catchment vegetation lost and subsequent increases in water temperatures (Minshall, 2003;Dunham et al., 2007;Cooper et al., 2015). ...
... While both eukaryotic and bacterial communities similarly shifted in community composition in response to burn category, fewer eukaryotic families (5/24 abundant families) changed significantly in relative abundance compared to bacterial orders (16/28 abundant orders). This may be due to a delayed response or greater resilience to changes in environmental conditions as has been shown for terrestrial and freshwater mesofauna (Silins et al., 2014;Pressler et al., 2019). While it's possible that the eukaryotic communities here are more resilient to change than bacterial communities, we suggest that these systems may be primed for further biological shifts, given the significant changes in environmental variables. ...
... While it's possible that the eukaryotic communities here are more resilient to change than bacterial communities, we suggest that these systems may be primed for further biological shifts, given the significant changes in environmental variables. Changes in abundances of stream invertebrates have been found up to five years following wildfire events due to stimulated productivity and enhanced phosphorous concentrations in burnt streams (Silins et al., 2014). The increase in green algae and nutrients observed in estuaries from highly burnt catchments here could cause further stimulation of biological productivity, particularly as temperatures increase in warmer weather. ...
Article
Novel combinations of climatic conditions due to climate change and prolonged fire seasons have contributed to an increased occurrence of “megafires”. Such large-scale fires pose an unknown threat to biodiversity due to the increased extent and severity of burn. Assessments of wildfires often focus on terrestrial ecosystems and effects on aquatic habitats are less documented, particularly in coastal environments. In a novel application of eDNA techniques, we assessed the impacts of the 2019–2020 Australian wildfires on the diversity of estuarine benthic sediment communities in six estuaries in NSW, Australia, before and after the fires. Estuaries differed in area of catchment burnt (0–92%) and amount of vegetative buffer that remained post-fire between burnt areas and waterways. We found greater dissimilarities in the composition and abundance of eukaryotic and bacterial sediment communities in estuaries from burnt catchments with no buffer compared to those with an intact buffer or from unburnt catchments. Shifts in composition in highly burnt catchments were associated with increased concentrations of nutrients, carbon, including fire-derived pyrogenic carbon, and copper, which was representative of multiple trace metals that were highly correlated. Changes in the relative abundances of certain taxonomic groups, such as sulfate-reducing and nitrifying bacterial groups, in the most impacted estuaries indicate potential consequences for the functioning of sediment communities. These results provide a unique demonstration of the use of eDNA to identify wildfire impacts on ecological communities and emphasize the importance of vegetative buffers in limiting wildfire-associated impacts.
... Pre-fire studies are based on simulation models that predict fire regime metrics and the degree to which watershed functioning might be altered given a number of wildfire scenarios, the end goal being the creation of prevention measures within a risk-reduction logic (Elliot, Miller, and Enstice 2016;Gannon, Wei, and Thompson 2020). Post-fire studies, on the other hand, are driven by the collection and analysis of observational data for impact analysis and monitoring of wildfire effects (Silins et al. 2014); these observations might also be fed to simulation models for the purpose of emergency watershed restoration Neris et al. 2021). Both WWR categories are, however, co-dependent: observational datasets are paramount to developing simulation models that project the expected effects and their influence on risk levels. ...
... The role of fire for sustaining aquatic biodiversity thus remains a matter of debate across the various regions of Canada (Gresswell 1999;Carignan and Steedman 2000;Robinne et al. 2020). But studies have provided widespread evidence of post-fire changes in aquatic ecosystems, including short-term negative impacts on primary productivity, invertebrate communities, and fisheries, especially salmonids (Rieman et al. 2003;Silins et al. 2014). Although many salmonid species are listed under the Species At Risk Act (SARA), existing population data deficiencies hinder in-depth understanding of wildfire-fish interactions, and, thus, the development of appropriate conservation actions (Rieman and Clayton 1997;Turcotte et al. 2021). ...
... Biomonitoring is a useful aquatic monitoring tool because biological communities are often impacted by chemicals and contaminants, invasive species, habitat degradation, climate change, as well as changes in annual water yields, peak flows, low flows, and timing of availability (Friberg et al. 2011;Environment and Climate Change Canada 2018). Organisms like benthic invertebrates are useful to show environmental change (Chadd and Extence 2004), like those triggered by wildfires (Spencer, Gabel, and Hauer 2003;Silins et al. 2014), especially when monitoring occurs consistently (i.e., repeated over years to decades), allowing for a deeper understanding of the ecological community and its relationship to external pressures. ...
Article
Awareness of wildfire risks to water security, or wildfire-watershed risks (WWR) for short, has been growing in Canada (Robinne et al. 2020; Coogan et al. 2019; Pomeroy et al. 2019). This comes from the realisation that watersheds are increasingly vulnerable to compound stressors, including more seasonal variation in water availability (Ireson et al. 2015; Bonsal et al. 2020), increased occurrence of droughts and extreme precipitation events (Bush and Lemmen 2019), and a changing nature and exacerbating impact of fire activity (Hanes et al. 2019; Coops et al. 2018). Although water resource protection is a top priorityies for wildfire management agencies across the country (Tymstra et al. 2019), baseline information on the vulnerability of source waters to wildfire remains limited despite the high potential for water supply disruption (Hohner et al. 2019; Martin 2016; Robinne et al. 2021). As climatic and hydrologic -climatic extremes conducive to water security issues are expected to grow in magnitude and frequency, increasing the risk of water security issues, there is an urgent need for greater access to baseline WWR information. represents an urgent need Improved access can facilitate towards the development of more targeted watershed management policies and strategies, especially for communities relying on water coming originating from upstream forests, to protect source water supply and security.
... Juvenile fishes tend to benefit from an increased primary productivity (e.g. greater access to food, improved growth; Koetsier et al., 2007;Silins et al., 2014), but larger fish can be negatively affected (Rosenberger et al., 2015;Tonn et al., 2003). This review found that no studies have directly examined the impact of elevated light quantity (or elevated PAR) on aquatic taxa within the context of wildfires. ...
... smoke) from fires outside the catchment (Earl & Blinn, 2003;Spencer et al., 2003). post-wildfire (Silins et al., 2014;Spencer et al., 2003). High levels of nutrients (coupled with elevated light and water temperature levels) ...
... The most well-documented impact of elevated nutrient concentrations on freshwater systems is the stimulation of algal growth and altered food web interactionsMalison & Baxter, 2010;Rodriguez-Lozano et al., 2015;Spencer et al., 2003). For instance, isotopic analyses (mainly nitrogen, δ 15 N; carbon, δ 13 C; and hydrogen, δD stable isotope signatures) of fish and macroinvertebrates from fire-affected sites showed a consistent shift towards algal-derived dietary resources compared to organisms from reference sitesMoreno et al., 2016;Silins et al., 2014;Spencer et al., 2003). Similarly,Carvalho et al. (2019) reported a significant reduction in the activity of microbial decomposers and invertebrate shredders suggesting that wildfires can have major impacts on detrital food webs in streams. ...
Article
Climate and land-use changes are expected to increase the future occurrence of wildfires, with potentially devastating consequences for freshwater species and ecosystems. Wildfires that burn in close proximity to freshwater systems can significantly alter the physicochemical properties of water. Following wildfires and heavy rain, freshwater species must contend with complex combinations of wildfire ash components (nutrients, polycyclic aromatic hydrocarbons, and metals), altered light and thermal regimes, and periods of low oxygen that together can lead to mass mortality events. However, the responses of aquatic fauna to wildfire disturbances are poorly understood. Here we provide a systematic review of available evidence on how aquatic animals respond to and recover from wildfire disturbance. Two databases (Web of Science and Scopus) were used to identify key literature. A total of 83 studies from across 11 countries were identified to have assessed the risk of wildfires on aquatic animals. We provide a summary of the main ecosystem-level changes associated with wildfires and the main responses of aquatic fauna to such disturbances. We pay special focus to physiological tools and biomarkers used to assess how wildfires impact aquatic animals. We conclude by providing an overview of how physiological biomarkers can further our understanding of wildfire-related impacts on aquatic fauna, and how different physiological tools can be incorporated into management and conservation plans and serve as early warning signs of wildfire disturbances.
... The importance of scale-specific connectivity where unburned areas between the wildfire or ash deposition can ameliorate impacts on the aquatic ecosystem (e.g., reducing the effect of reduced evapotranspiration (ET)) has been observed by Hallema et al. (2017) and Collar et al. (2023). In both Wyoming (U.S.) and Southwestern Alberta (Canada), streamflow, suspended sediment concentrations, and total phosphorus concentrations increased relative to pre-wildfire baselines in streams located within burned watersheds, especially if rainstorms occurred during the snowmelt season (Ryan et al., 2011;Silins et al., 2014). However, similar results were not observed in a New Mexico (U.S.) watershed where the snowmelt season is shorter compared to northern latitudes (Hall et al., 2022). ...
... These activities may systematically impede recovery in a burned watershed. Silins et al. (2014) reported up to a 13-fold increase of phosphorus in salvage-logged watersheds. Particulate phosphorus production in salvage-logged watersheds was two-fold higher than what was observed in unburned watersheds, during storm and snowmelt events, indicating that seasonal variation is controlled, in part, by anthropogenic activities. ...
Article
Full-text available
Wildfire substantially alters aquatic ecosystems by inducing moderate to catastrophic physical and chemical changes. However, the relations of environmental and watershed variables that drive those effects are complex. We present a Driver‐Factor‐Stressor‐Effect (DFSE) conceptual framework to assess the current state of the science related to post‐wildfire water‐quality. We reviewed 64 peer‐reviewed papers using the DFSE framework to identify drivers, factors, stressors, and effects associated with each study. A total of five drivers were identified and ranked according to their frequency of occurrence in the literature: atmospheric processes > fire characteristics > ecologic processes and characteristics > land surface characteristics > soil characteristics. Commonly reported stressors include increased nutrients, runoff, and sediment transport. Furthermore, although several different factors have been used at least once to explain water‐quality effects, relatively few factors outside of precipitation and fire characteristics are frequently studied. We identified several gaps indicating the need for long‐term monitoring, multi‐factor studies, consideration of organic contaminants, consideration of groundwater, and inclusion of soil characteristics. This assessment expands on other reviews and meta‐analyses by exploring causal linkages between influential variables and overall effects in post‐wildfire watersheds. Information gathered from our assessment and the framework itself can be used to inform future monitoring plans and as a guide for modeling efforts focused on better understanding specific processes or to mitigate potential risks of post‐wildfire water quality.
... We found that nutrient concentrations generally showed the expected, short-term responses to basin-scale upland burn patterns. These responses were related to some of the same processes engendering fire-induced geomorphic change, including vegetation destruction, soil alterations, and increased runoff and sediment transport (because some P is adsorbed to sediment, but then solubilizes; Coombs and Melack, 2013;Silins et al., 2014;Aguilera and Melack, 2018;Hampton et al., 2022). However, nutrients are also biologically active, so nutrient concentrations and fluxes also depend on uptake and transformation by microbes and plants (Hanan et al., 2016a(Hanan et al., , 2016bGoodridge et al., 2018). ...
... The dominant invertebrate functional feeding group in our streams was collector-gatherers (primarily quickcolonizing baetid mayflies), which were associated with, and consumed epiphytic diatoms growing on, macroalgal surfaces (Dudley et al., 1986). Algal biomass and macroalgal cover showed short-term responses to local riparian burning at M-H severities, which resulted in the loss of canopy cover and, therefore, increased light and nutrient inputs (Silins et al., 2014;Klose et al., 2015). The dominant algivores in our system (tolerant baetid mayflies and hylid tadpoles) also increased with the proliferation of algae. ...
Chapter
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Wildfire biogeomorphology is an integrative science fundamental in understanding the dynamic processes of adjustment that occur after wildfires. This volume draws together interdisciplinary studies that highlight key insights important to support heterogeneity, biodiversity, and resilience in fluvial ecosystems. Post-wildfire sediment pulses that change the physical elements of fluvial habitat may be transitory or long-lasting, for example, depending on variations in post-wildfire climate conditions. How biological processes and feedback alter post-wildfire geomorphic responses is also important to enhance ecosystem resilience. The syntheses point to greater emphasis on integrated approaches to advance strategies for ecosystem management toward conservation, restoration, and sustainable practices, in particular, to accommodate multiple possible postfire disturbance and recovery trajectories.
... The primary consumer trophic level, then, appeared to occupy the fulcrum between top-down and bottom-up interactions, being reduced by invertebrate predators but increasing with algal availability. Although bottom-up and top-down interactions occur simultaneously for trophic levels below the top level, the relative magnitude and impacts of these interactions vary greatly across different ecosystems, depending on interconnected environmental conditions and the abundances, behaviour, and traits of organisms at different trophic levels (Nyström et al., 2003;Peckarsky et al., 2013Peckarsky et al., , 2015Power, 1992a), emphasising the importance of disentangling the effects of both consumers and resources on different trophic levels (Peckarsky et al., 2013(Peckarsky et al., , 2015Silins et al., 2014;Wootton & Power, 1993). ...
... By contrast, our results suggest that bottom-up effects and relationships between abiotic and biotic variables accounted for the structure of the detrital-based food web with shredder abundance being positively related to leaf litter mass, which, in turn, was positively related to riparian canopy cover and negatively related to flow. Although there were direct effects of post-fire floods and drought on invertebrate assemblages via impacts on flow, sediment, and/or hydrochemical conditions (first axis in NMS analyses, see also Cooper et al., 2015Cooper et al., , 2021McMahon et al., 2023;Silins et al., 2014), changes in invertebrate and amphibian assemblages after disturbance also partly were owing to the local extirpation of trout, which led to increases in tadpoles and OCH taxa within a year or two after disturbance events, with possible repercussions for invertebrate primary consumers depending on disturbance impacts on algal resource levels . ...
Article
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Climate change is increasing the frequency, severity, and extent of wildfires and drought in many parts of the world, with numerous repercussions for the physical, chemical, and biological characteristics of streams. However, information on how these perturbations affect top predators and their impacts on lower trophic levels in streams is limited. The top aquatic predator in southern California streams is native Oncorhynchus mykiss , the endangered southern California steelhead trout (trout). To examine relationships among the distribution of trout, environmental factors, and stream invertebrate resources and assemblages, we sampled pools in 25 stream reaches that differed in the presence (nine reaches) or absence (16 reaches) of trout over 12 years, including eight reaches where trout were extirpated during the study period by drought or post‐fire flood disturbances. Trout were present in deep pools with high water and habitat quality. Invertebrate communities in trout pools were dominated by a variety of medium‐sized collector–gatherer and shredder invertebrate taxa with non‐seasonal life cycles, whereas tadpoles and large, predatory invertebrates (Odonata, Coleoptera, Hemiptera [OCH]), often with atmospheric breather traits, were more abundant in troutless than trout pools. Structural equation modelling of the algal‐based food web indicated a trophic cascade from trout to predatory invertebrates to collector–gatherer taxa and weaker direct negative trout effects on grazers; however, both grazers and collector–gatherers also were positively related to macroalgal biomass. Structural equation modelling also suggested that bottom‐up interactions and abiotic factors drove the detritus‐based food web, with shredder abundance being positively related to leaf litter (coarse particulate organic matter) levels, which, in turn, were positively related to canopy cover and negatively related to flow. These results emphasise the context dependency of trout effects on prey communities and of the relative importance of top‐down versus bottom‐up interactions on food webs, contingent on environmental conditions (flow, light, nutrients, disturbances) and the abundances and traits of component taxa. Invertebrate assemblage structure changed from a trout to a troutless configuration within a year or two after trout were lost owing to post‐fire scouring flows or drought. Increases in OCH abundance after trout were lost were much more variable after drought than after fire. The reappearance of trout in one stream resulted in quick, severe reductions in OCH abundance. These results indicate that climate‐change induced disturbances can result in the extirpation of a top predator, with cascading repercussions for stream communities and food webs. This study also emphasises the importance of preserving or restoring refuge habitats, such as deep, shaded, perennial, cool stream pools with high habitat and water quality, to prevent the extirpation of sensitive species and preserve native biodiversity during a time of climate change.
... Contemporary wildfire disturbance has minor direct effects on freshwater communities, with postfire indirect effects (changes in runoff, nutrient loads, and channel alteration) affecting macroinvertebrate assemblages (Minshall 2003). In addition to immediate effects, forest salvaging following fire can lead to large increases in nutrient and sediment flux, with the consequences of increasing algae production and increased macroinvertebrate numbers and production (Silins et al. 2014). These effects lasted at least 5 years postfire in streams of the Canadian Rockies (Silins et al. 2014). ...
... In addition to immediate effects, forest salvaging following fire can lead to large increases in nutrient and sediment flux, with the consequences of increasing algae production and increased macroinvertebrate numbers and production (Silins et al. 2014). These effects lasted at least 5 years postfire in streams of the Canadian Rockies (Silins et al. 2014). Depending on the severity of the fire, riparian system vegetation responds rapidly with a flush of nutrients, although more intense crown fires are slower to recover . ...
... In 2003, the Lost Creek Wildfire, one of the most severe wildfires to occur in the region, burned 21,000 ha of nearly contiguous forest land, leading to significant impacts on sediment delivery regimes (Silins et al., 2009). Such land alterations have resulted in legacy impacts in the region, such as changes in sediment and associated pollutant (contaminants and nutrients) export, ecological status, and stream productivity Martens et al., 2019;Silins et al., 2014Silins et al., , 2008Stone et al., 2021bStone et al., , 2014Watt et al., 2021). The study reaches of the Crowsnest River are oligotrophic (Watt et al., 2021), generally presenting high water quality, except during infrequent extreme precipitation and flood events (Oldman Watershed Council, 2010). ...
... Article distribution, composition, and productivity, facilitating an increased importance of periphyton in fire-affected stream food webs. 47,104,105 For these reasons, wildfire and other watershed disturbances appear to have a more pronounced effect on periphyton and reliant consumer MeHg concentrations than is observed for taxa reliant on terrestrial litter inputs. 97,106−108 Filterers and collectors had greater MeHg concentrations in burned watersheds compared to reference watersheds (48 and 251% higher, respectively; p ≤ 0.0097; Figure 5C). ...
Article
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The increasing frequency and severity of wildfires are among the most visible impacts of climate change. However, the effects of wildfires on mercury (Hg) transformations and bioaccumulation in stream ecosystems are poorly understood. We sampled soils, water, sediment, in-stream leaf litter, periphyton, and aquatic invertebrates in 36 burned (one-year post fire) and 21 reference headwater streams across the northwestern U.S. to evaluate the effects of wildfire occurrence and severity on total Hg (THg) and methylmercury (MeHg) transport and bioaccumulation. Suspended particulate THg and MeHg concentrations were 89 and 178% greater in burned watersheds compared to unburned watersheds and increased with burn severity, likely associated with increased soil erosion. Concentrations of filter-passing THg were similar in burned and unburned watersheds, but filter-passing MeHg was 51% greater in burned watersheds, and suspended particles in burned watersheds were enriched in MeHg but not THg, suggesting higher MeHg production in burned watersheds. Among invertebrates, MeHg in grazers, filter-feeders, and collectors was 33, 48, and 251% greater in burned watersheds, respectively, but did not differ in shredders or predators. Thus, increasing wildfire frequency and severity may yield increased MeHg production, mobilization, and bioaccumulation in headwaters and increased transport of particulate THg and MeHg to downstream environments.
... There are also studies demonstrating that the exposure of fish to ashes causes major cytological and genetic damage (Ré et al., 2021), behavioral changes (Gonino et al., 2019b), bioaccumulation of contaminants (e.g., metals) (Pracheil et al., 2016), and on an ecosystem scale, decreases fish diversity (Lallement et al., 2016). In contrast, some studies are showing that the input of ashes in the water did not elicit conspicuous changes in fish traits Riggs et al., 2017;Yofukuji et al., 2021), and even positive associations with ashes exposure in some specific biological attributes were reported (e.g. higher growth rates; Silins et al., 2014). Despite these known effects, a compilation of available evidence on how freshwater fish respond to ashes remains largely unexplored (but see Isaza et al., 2022). ...
Article
Full-text available
Ash runoff into freshwater systems from fire events, coal combustion, and volcanic activities threatens to biodiversity conservation, given its toxicity to various aquatic organisms. However, despite many studies reporting a negative relationship between ash exposure and the biological traits of freshwater fish, non-significant and even positive associations can also be found in the literature. Here, a systematized review was conducted to explore patterns and biases in studies examining the impacts of ash on freshwater fish. Out of the 43 studies included in this review, 38 reported harmful effects of ash exposure on fish traits. The median lowest concentration of ashes capable of inducing negative effects on fish traits was found to be 2 g/L. Diet restrictions (84.6%), behavioral changes (83.3%), cytological and genetic damages (64.7%), and bioaccumulation of toxic compounds (57.1%) exhibited the highest proportions of negative results in statistical evaluations testing ash effects on fish traits. In contrast, biomarkers related to reproduction (94.7%) and metabolism (66.4%) had the highest proportion of non-significant associations between fish traits and ash exposure. Statistical models indicate that the ash source does not determine the direction (positive or negative) of its effect on fish traits. Furthermore, no evidence supports the hypothesis of similar sensitivity levels to ash exposure among phylogenetically closely related fish species. Together, the evidence provides a cohesive perspective on the detrimental effects of ash on fish, highlighting the effective necessity to manage the influx of ash into watercourses. Graphical Abstract
... There is some evidence that the impacts of fire on stream food webs bear some similarities to those of clear-cut riparian forestry. From a land management perspective, it is clear that there is a need for a much greater understanding of the interactions between fire and forestry practices, with evidence that post-fire salvage logging may have considerable consequences on riverine ecosystems (e.g., Silins et al. 2014). ...
Thesis
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The frequency and intensity of extreme wildfire events have increased globally. The impact of extreme wildfires on stream temperatures and subsequent stream invertebrate survival is not well understood and very few studies have focused on temperature spikes during the combustion phase of these wildfire. Stream invertebrates are essential for maintaining the overall health and functions of stream ecosystems. However, as ectotherms, stream invertebrates are vulnerable to increasing temperatures, dying from heat stress when lethal thresholds are exceeded. This thesis investigates the immediate response of stream invertebrates to acute short-term stream temperature spikes, specifically those resembling spikes caused during the combustion phase of extreme wildfire events. The research examined stream invertebrate mortality, population changes, and overall ecosystem resilience during and immediately after simulated acute short-term extreme temperature events. The first component of this research used highly controlled laboratory mesocosm temperature disturbance experiments to explore the effects of 45°C and 55°C acute short-term temperature spikes on natural stream invertebrate assemblage. The results showed that a 55°C temperature spike caused a 95.9% reduction in abundance and functional feeding group diversity was reduced to scrapers and shredders. Conversely, the 45°C temperature spike had no significant impact on either abundance or richness of functional feeding groups. Individual families responded differently to the temperature spike, with some families being very sensitive to the increase in temperature and two being tolerant of the spike and the resulting reduction in abundance and diversity will influence post fire recovery. The second component of this thesis investigated, for the first time, the specific Upper Lethal Temperature (ULT) (LT50) of five Australian subtropical stream invertebrate taxa (four species and one genus). These taxa were chosen based on their identified sensitivity or tolerance to higher temperatures observed during the mesocosm experiments. The aim was to gain insights into the lethal thresholds of these taxa in response to temperature extremes. The ULTs ranged from 35.2°C for the shrimp Paratya spinosa to 37.2°C for the adult beetle Macrogyrus oblongus. The ULTs were all below the temperature spikes of 55°C and 45°C investigated in the mesocosm experiments. The results highlight the importance of refugia areas in stream ecosystems. The availability and maintenance of thermal refugia, such as the hyporheic zone, play a fundamental role in providing shelter and buffering against extreme water temperatures for stream invertebrates. Invertebrates inhabiting subtropical streams appear to be living closer to their ULT than those identified in previous studies in temperate zones, making them more susceptible to extreme heat events. Finally, the thesis explored the potential for the thermal plasticity of the shrimp Paratya spp. as an adaptive mechanism in response to changing thermal conditions. Results showed warm-water acclimated shrimp had a significantly higher LT50 of 36.1°C than winter acclimated shrimp at 34.6°C. Paratya spp. had a potential critical temperature (LT90) of ~37°C, beyond which the shrimp could not survive. This critical limit underscores the vulnerability of Paratya spp. to extreme heat events and highlights the need for more understanding of the impacts of increasing stream temperatures. The research completed in this thesis helps to fill gaps in knowledge by evaluating stream invertebrate assemblage dynamics and providing insights into lethal temperature thresholds for different taxa. It also highlights the potential for adaptive responses and resilience in stream ecosystems. This research thesis improves and enhances our knowledge of the vulnerability of stream invertebrates to extreme water temperature spikes and future thermal extreme events.
... These results do not discard other possible responses of microbial decomposers and detritivores in the longer term. For example, after a wildfire, other known long-term legacies for stream ecosystems are the reduction in the quantity and quality of terrestrial organic matter supplies (Bixby et al. 2015;Warren et al. 2022), greater solar radiation (Veraverbeke et al. 2012), and a sustained increase in nutrient availability over time (Silins et al. 2014). All these changes could bring alterations in the structure and functioning of headwater streams (Jankowski et al. 2021;Pérez et al. 2013) that would make them more similar to mid-low reaches (Martínez et al. 2016b;Vannote et al. 1980) but that cannot be detected in a short-term microcosm experiment like the present one. ...
Article
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Background Wildfires have strong impacts on terrestrial and aquatic ecosystems, whose frequency, severity, and intensity are increasing with climate change. Moreover, the expansion of exotic monoculture plantations, such as those of eucalypts, increases this risk. When wildfires do not cause the disappearance of riparian vegetation, they still imply the fall of leaf litter exposed to the fire (i.e., crown scorch), which consequences for ecosystems are unknown. Experimental design To explore how these leaf litter inputs may affect stream ecosystem functioning, we conducted a microcosm experiment where we quantified the decomposition of leaf litter from three tree species (alder, oak, and eucalypt) under two conditions (control litter simulating natural entries and litter subjected to 150 °C for 3 h mimicking exposure to fire). We also examined the interaction between this factor and a temperature rise (which is often associated to the loss of riparian vegetation caused by the wildfire) by manipulating water temperature (10, 12.5, and 15 °C). Finally, we explored the effects of these variables on the growth of a common detritivore, the caddisfly Sericostoma pyrenaicum . Results Control alder presented the highest decomposition rates, which were notably reduced due to fire exposure. On the contrary, eucalypt litter decomposition was even slower than that of oak and hardly showed any effect derived from fire exposure. The different leaf litter types determined detritivore growth, to a greater extent than variation related to warming, which generally had negligible effects. Conclusions Our study shows the negative effects of wildfires on stream ecosystem functioning even when they only involve brief exposure of leaf litter to the fire. Effects are greater on the most palatable native species, which represents the highest quality input in streams of the study area. Our results highlight the importance of protecting riparian forests, especially those composed of native species, against wildfires.
... Allochthonous organic matter contributes significantly to food webs in many aquatic systems, including estuaries, but relative contributions can vary widely depending on geographic location and climate [17,[32][33][34]. A shift from terrestrial to aquatic food web pathways can bolster productivity, resulting in subsequent enhancements to carrying capacity and fish consumer growth [35][36][37]; however, a food web based entirely on autochthonous pathways may be less resilient to perturbations and detrimental environmental conditions such as nutrient imbalances, elevated temperatures, lower dissolved oxygen levels, and poor prey quality [36,[38][39][40]. The inherent interconnectivity of estuarine systems makes it difficult to parse out the relative contributions of allochthonous and autochthonous organic matter and the potential effects these different food web pathways could have on pelagic and demersal fish consumers. ...
Article
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Terrestrial organic matter is believed to play an important role in promoting resilient estuarine food webs, but the inherent interconnectivity of estuarine systems often obscures the origins and importance of these terrestrial inputs. To determine the relative contributions of terrestrial (allochthonous) and aquatic (autochthonous) organic matter to the estuarine food web, we analyzed carbon, nitrogen, and sulfur stable isotopes from multiple trophic levels, environmental strata, and habitats throughout the estuarine habitat mosaic. We used a Bayesian stable isotope mixing model (SIMM) to parse out relationships among primary producers, invertebrates, and a pelagic and demersal fish species (juvenile Chinook salmon and sculpin, respectively). The study was carried out in the Nisqually River Delta (NRD), Washington, USA, a recently-restored, macrotidal estuary with a diverse habitat mosaic. Plant groupings of macroalgae, eelgrass, and tidal marsh plants served as the primary base components of the NRD food web. About 90% of demersal sculpin diets were comprised of benthic and pelagic crustaceans that were fed by autochthonous organic matter contributions from aquatic vegetation. Juvenile salmon, on the other hand, derived their energy from a mix of terrestrial, pelagic, and benthic prey, including insects, dipterans, and crustaceans. Consequently, allochthonous terrestrial contributions of organic matter were much greater for salmon, ranging between 26 and 43%. These findings demonstrate how connectivity among estuarine habitat types and environmental strata facilitates organic matter subsidies. This suggests that management actions that improve or restore lateral habitat connectivity as well as terrestrial-aquatic linkages may enhance allochthonous subsidies, promoting increased prey resources and ecosystem benefits in estuaries.
... Postfire differences in aquatic environments include decreases in the diversity and abundance of sensitive organisms (Rinne, 1996;Minshall et al., 1997;Vieira et al., 2004;Bêche et al., 2005;Oliver et al., 2012), including benthic macroinvertebrates (Hall and Lombardozzi, 2008;Mellon et al., 2008). Benthic macroinvertebrates can exhibit rapid recovery following a wildfire (e.g., Monaghan et al., 2019Monaghan et al., , 2020Robson et al., 2018), but when combined with other disturbances, such as salvage logging, impacts to aquatic communities can persist for longer periods of time (Martens et al., 2019;Silins et al., 2014). ...
Chapter
Wildfire biogeomorphology is an integrative science fundamental in understanding the dynamic processes of adjustment that occur after wildfires. This volume draws together interdisciplinary studies that highlight key insights important to support heterogeneity, biodiversity, and resilience in fluvial ecosystems. Post-wildfire sediment pulses that change the physical elements of fluvial habitat may be transitory or long-lasting, for example, depending on variations in post-wildfire climate conditions. How biological processes and feedback alter post-wildfire geomorphic responses is also important to enhance ecosystem resilience. The syntheses point to greater emphasis on integrated approaches to advance strategies for ecosystem management toward conservation, restoration, and sustainable practices, in particular, to accommodate multiple possible postfire disturbance and recovery trajectories.
... ). Further study site descriptions can be found inSilins et al. (2014) andWatt et al. (2021). ...
Article
Excess” interstitial fine sediment (<2 mm) is known to cause deleterious impacts on streambed ecosystems. Current methodologies available to assess ingress and its vertical and horizontal components still lack standardization, and the accuracy of commonly used assessments is still debatable. Here, we evaluate three fine sediment trap designs that measure only vertical (V), only horizontal (H), and both vertical and horizontal (HV) ingress mechanisms. Sediment traps were deployed in triplicates to: (i) evaluate measurement variability within traps of the same type; (ii) evaluate the effects of trap design on particle size distributions of infiltrated fine sediment and; (iii) assess methodologies used to calculate vertical and horizontal ingress mechanisms. Ingress rates were recorded for each sediment trap during seven deployment periods (lasting from 2 to 10 days) at a range of flow conditions at four sites. A total of 252 traps were deployed. Results from the triplicate assessment of traps with the same design showed that most measurements presented high variability and that particle size distributions were significantly affected by trap design. Here, different sediment traps were able to estimate directional ingress mechanisms. However, direct comparison between HV with either H or V traps led to an overestimation of horizontal or vertical ingress mechanisms, respectively. Better estimations were found when comparing HV observations to half the accumulation in either H or V, due to the proportional trap volume available for each accumulation mechanism according to trap design.
... We also expected that responses in trematode community structure to wildfire disturbance may depend on timescale, as parasite responses can lag several years behind environmental changes (Huspeni and Lafferty 2004). We predicted that snail density may decrease immediately after fire due to direct mortality from disturbance, but then may increase two years following fire due to bottom-up effects from increased light, nutrients, and primary productivity within the stream (Silins et al. 2014). While snail hosts are necessary to support trematodes (i.e., loss of snails would result in loss of trematodes), we did not necessarily expect snail density to correlate with trematode infection prevalence, as a previous study in the same study system found no correlation between these variables . ...
Article
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Increases in the intensity and frequency of wildfires highlight the need to understand how fire disturbance affects ecological interactions. Though the effects of wildfire on free-living aquatic communities are relatively well-studied, how host–parasite interactions respond to fire disturbance is largely unexplored. Using a Before-After-Control-Impact design, we surveyed 10 stream sites (5 burned and 5 unburned) in the Willamette River Basin, Oregon and quantified snail host infection status and trematode parasite community structure 1 year before and two years after historic wildfires. Despite the severity of the wildfires, snail host populations did not show significant shifts in density or size distributions. We detected nine taxa of trematode parasites and overall probability of infection remained consistent over the three-year study period. However, at the taxon-specific level, we found evidence that infection probability by one trematode decreased and another increased after fire. In a larger dataset focusing on the first year after fire (9 burned, 8 unburned sites), we found evidence for subtle differences in trematode community structure, including higher Shannon diversity and evenness at the burned sites. Taken together, host–parasite interactions were remarkably stable for most taxa; for trematodes that did show responses, changes in abundance or behavior of definitive hosts may underlie observed patterns. These results have implications for using parasites as bioindicators of environmental change and suggest that aquatic snail-trematode interactions may be relatively resistant to wildfire disturbance in some ecosystems.
... The characteristics of natural disturbances (i.e., spatial extent, frequency, intensity, and severity) are influenced by geography, vegetation structure and composition, weather, and climate (Dale et al. 2001;Flannigan et al. 2009), resulting in a range of potential ecological outcomes for a single disturbance type (Seidl et al. 2017). The spatial legacies that disturbances leave behind in the form of residual forest structure, altered ecological function, and successional vegetation trajectories can affect future disturbances well after the original disturbance event has passed (James et al. 2011;Silins et al. 2014). These spatial legacies can interact with other disturbances to amplify or attenuate future disturbance behavior and associated outcomes (Turner 2010;Buma 2015;Seidl et al. 2017). ...
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Context The mountain pine beetle (MPB; Dendroctonus ponderosae) is a native bark beetle whose outbreaks leads to widespread conifer forest mortality. Of particular concern to forest and wildfire managers is the influence of MPB outbreaks on wildfire via spatial legacies left in impacted forest stands. There is, however, limited consensus in the literature regarding how MPB outbreaks affect wildfire across western North America. Objectives This meta-analysis aims to (1) summarize available evidence regarding MPB-wildfire interactions, and (2) identify environmental and methodological indicators associated with various wildfire responses (i.e., amplified, neutral, or dampened) post-outbreak. Methods We include peer-reviewed publications focusing on MPB outbreaks and subsequent wildfire activity in forests across western Canada and the USA between 2000 and 2021. A classification scheme was used to examine attributes of each publication to assess which indicators contribute most to their associated wildfire response. Results We found that spatial scale, forest fuels, and weather are main drivers of variation in wildfire response post-outbreak. Metrics of forest fuels and inclusion of weather data on a stand-scale are related to amplified fire responses, whereas dampened responses correspond to landscape-scale analyses. Furthermore, red-stage stands are associated with amplified fire response, whereas other stages are associated with dampened response—supporting current conceptual models of the importance of outbreak stage on wildfire. Conclusions Advancing our understanding regarding drivers of wildfire responses post-MPB outbreak is key to developing accurate, and comparative research studies. These findings provide crucial information for wildfire, and forest management agencies, especially in forests newly exposed to this disturbance interaction under climate change.
... 14 Longer-term releases of bioavailable phosphorus from sediments to the water column also have been observed in some areas. 15,16 They promote primary productivity and the proliferation of algae, 10 including cyanobacteria, that can produce toxins of human health concern 17 �these effects are magnified when they converge with those from anthropogenic landscape disturbances. 18 Collectively, these impacts underscore that wildfires can challenge treatment plants beyond their operational capacity, ultimately resulting in increased infrastructure and operating costs, service disruptions, or outages. ...
Article
Elevated/altered levels of dissolved organic matter (DOM) in water can be challenging to treat after wildfire. Biologically mediated treatment removes some DOM; here, its ability to remove elevated/altered postfire dissolved organic carbon (DOC) resulting from wildfire ash was investigated for the first time. Treatment of wildfire ash-amended (low, moderate, high) source waters by bench-scale biofilters was evaluated in duplicate. Turbidity and DOC were typically well-removed (effluent turbidity ≤0.3 NTU; average DOC removal ∼20%) in all biofilters during periods of stable source water quality. Daily DOC removal across all biofilters (ash-amended and controls) was generally consistent, suggesting that (i) the biofilter DOC biodegradation capacity was not deleteriously impacted by the ash and (ii) the biofilters buffered the ash-associated increases in water extractable organic matter. DOM fractionation indicates this was because the biodegradable low molecular weight neutral fractions of DOM, which increased with ash addition, were reduced by biofiltration while humic substances were largely recalcitrant. Thus, biological filtration was resilient to wildfire ash-associated DOM threats to drinking water treatment, but operational resilience may be compromised if the balance between readily removed and recalcitrant fractions of DOM change, as was observed during brief periods herein.
... Such effects may not occur for trematode taxa that only infect aquatic hosts, particularly if disturbance was not strong enough to cause direct mortality of stream biota (e.g., snails, other invertebrates, sh). Furthermore, we predicted that snail density may decrease immediately after re due to direct mortality from disturbance, but then may increase two years following re as a result of bottom-up effects from increased light, nutrients, and primary productivity within the stream (Silins et al. 2014). While snail hosts are necessary to support trematodes (i.e., loss of snails would result in loss of trematodes), we did not necessarily expect snail density to correlate with trematode infection prevalence, as a previous study in the same study system found no correlation between these variables . ...
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Increases in the intensity and frequency of wildfires highlight the need to understand how fire disturbance affects ecological interactions. Though the effects of wildfire on free-living aquatic communities are relatively well-studied, how host-parasite interactions respond to fire disturbance is largely unexplored. Our study investigated the effects of wildfire on trematode parasites and their intermediate snail hosts using a Before-After-Control-Impact design. We surveyed 10 stream sites (5 burned and 5 unburned) in the Willamette River Basin, Oregon and quantified host infection status and trematode community structure one year before and two years after historic wildfires. Despite the severity of the wildfires, snail host populations appeared resilient, without significant shifts in population characteristics. We detected nine taxa of trematode parasites and overall prevalence of infection remained consistent over the three-year study period. However, at the taxon-specific level, we found evidence that infection probability by one trematode decreased and one increased after fire. In a larger dataset focusing on the first year after fire (9 burned, 8 unburned sites), we found evidence for subtle differences in trematode community structure, including higher Shannon diversity and evenness at the burned sites. Taken together, our results suggest that host-parasite interactions were remarkably stable for most taxa; for trematodes that did show responses, changes in abundance or behavior of definitive hosts that input infectious stages to the aquatic environment may underlie observed patterns. These results provide a useful first step in evaluating the broader utility of parasites as bioindicators of ecosystem changes following wildfire disturbance.
... Increased turbidity decreases the light penetration to the lower depth of laker and rivers which affect the photosynthesis of vegetation in lower depth. Increased water temperature initiates thermal pollution in lakes and rivers which can increase the biological activity of lake that may result in increased biological oxygen demand (DeBano et al., 1998;Aregai and Neary, 2015) and decreased dissolved oxygen (Silins et al., 2014), affects badly the aquatic faunal survival and population. Further, forest fire increases the nutrient concentration of lakes and rivers (Chorover et al., 1994;Aregai and Neary, 2015) through the ash deposit (Aregai and Neary, 2015). ...
Article
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Fire is a common hazard in forest which plays an important role in shaping a community with its ecosystem components. Recent fire records show an increasing trend in fire incidents with manipulated fire regime due to anthropogenic activity. Changes in the fire regime cause a negative impact on forest vegetation and ecosystem process. Broad range of literature on forest fire ecology gives information on the characteristics of fire effects on vegetation cover, composition, density and functions of forest ecosystem for better management of ecosystem and its process. Understanding the patterns of effects of forest fire on forest ecosystem will help to critically reduce the risk of unpredicted wildfires and suitable use of fire as a forest management tool. This review is a synthesis of impact of forest fire on forest ecosystem, effect on vegetation, soil, water and air relations closely discussed with priority on fire as a major cause. Fire can clearly alter the vegetation composition, density, diversity by encouraging fire adapted species, change the soil properties through addition of ash and changing the nutrient level, change the water quality through addition of chemicals. Effects of fire depend on the fire regime, climate and vegetation type.
... This is a common question asked by scientists, resource managers, and the public, but it does not have a simple answer. Wildfires can have complex effects on aquatic ecosystems (Bixby et al., 2015;Jager et al., 2021;Silins et al., 2014), and the nature of fish responses to wildfires may depend on the time scale of the observations (Gresswell, 1999), severity of the fire, or on the ecological context of where the fire occurs, which collectively can lead to notably different and highly variable short-and long-term responses (Bixby et al., 2015;Gomez Isaza et al., 2022;Jager et al., 2021). The response of fish will also depend on the focal species, with some groups potentially responding positively while others may respond negatively (LeMoine et al., 2020). ...
Article
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Native salmonid fishes-cutthroat trout (Oncorhynchus clarkii) and steelhead/rainbow trout (Oncorhynchus mykiss)-are ecologically, culturally, and economically important species distributed across western North America. These fish are generally considered "cold-water" adapted species. As such, recent studies have speculated about the potential effects of climate change on these native salmonids if stream temperature thresholds exceed 16-20 C during the summer. However, the magnitude of stream thermal responses to the slow but steady increases in regional temperatures associated with climate change remains uncertain and hard to predict. Comparatively, abrupt disturbances , such as wildfire, may produce almost instantaneous and substantial increases in stream temperatures that may persist for multiple years until near-stream vegetation becomes re-established. In the first summer following a severe wildfire in western Oregon, we observed the initial persistence of populations of O. clarkii clarkii (coastal cutthroat trout) and O. mykiss (rain-bow/steelhead trout). The fire burned the entire catchment, including the riparian area (~76% of the watershed area burned at moderate or high severity), resulting in stream temperature that regularly exceeded 20 C and represented increases of 6-7 C relative to prefire conditions. However, the mechanisms enabling the persistence of cold-water fishes despite the dramatic increases in stream temperature remain unclear and require further investigation. Nevertheless, wildfires represent acute natural disturbances that can substantially alter stream thermal regimes and provide unique insights that allow us to better understand how native fishes in natural systems cope with projected increases in stream temperatures.
... Campbell, 1970). Wildfire can increase the diversity and abundance of arthropods and other invertebrates (Bess et al., 2002;Buddle et al., 2006;Ferrenberg et al., 2019;Jackson et al., 2012), and high-severity fires can result in an extended "fire pulse" characterized by a flux of invertebrate prey to aquatic and terrestrial habitats (Harris et al., 2018;Malison & Baxter, 2010;Silins et al., 2014). Post-fire increases in prey availability therefore may have stimulated the growth of boreal toads between 2019 and 2020 at burned sites in our study area. ...
Article
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Global wildfire regimes are changing rapidly, with widespread increases in the size, frequency, duration, and severity of wildfires. Whereas the effects of wildfire on ecological state variables such as occupancy, abundance, and species diversity are relatively well documented, changes in population vital rates (e.g., survival, recruitment) and individual responses (e.g., growth, movement) to wildfire are more limited because of the detailed information needed on the same individuals both pre‐ and post‐fire. We capitalized on the 2018 Roosevelt wildfire, which occurred during our 6‐year (2015–2020) capture–mark–recapture study of boreal toads (Anaxyrus boreas boreas; n = 1415) in the Bridger‐Teton National Forest, USA, to evaluate the responses of population vital rates and individual metrics to wildfire. We employed robust design capture–recapture models to compare the growth, dispersal, survival, and recruitment of adult boreal toads pre‐ and post‐fire at burned versus unburned sites. At burned locations, growth increased 2 years post‐fire compared with the year directly following wildfire and was higher 2 years post‐fire than any other interval during our study period. Boreal toads dispersed to alternative breeding patches more at burned sites than unburned sites and dispersal increased 2 years post‐fire compared with the year directly following wildfire. Annual survival and recruitment neither differed between pre‐ and post‐fire years nor among pre‐fire years, the year following wildfire, and 2 years post‐fire. We demonstrate that, in certain contexts, dispersal can play a major role in changes to state variables (e.g., abundance) after wildfire, as opposed to other vital rates such as survival and recruitment. Our study represents an important step toward understanding the biological processes that underlie observed patterns in state variables following wildfire, which ultimately will be critical for the effective management of species in landscapes experiencing shifts in fire activity.
... [1][2][3] After wildland fire, vegetation is reduced or absent and more precipitation reaches the land surface, 4 leading to increased erosion and solids runoff; 5,6 even at large basin scales in systems with already deteriorated water quality. 7 Accordingly, solid-associated metals, 8 nutrients, [9][10][11] and other contaminants 12,13 also can be elevated-or transformed in the case of natural organic matter (NOM)-in wildfire-impacted waters. 14 Longer-term releases of bioavailable phosphorus from sediments to the water column also have been observed in some areas. ...
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Elevated/altered levels of dissolved organic matter (DOM) in water can be challenging to treat after wildfire. Biologically-mediated treatment removes some DOM; its ability to remove elevated/altered post-fire dissolved organic carbon (DOC) resulting from wildfire ash was therefore investigated. The treatment of low, medium, and high wildfire ash-amended source waters by bench-scale biofilters was evaluated in duplicate. Turbidity and DOC were typically well-removed during periods of stable operation (effluent turbidity ≤ 0.3 NTU in 93% of samples, average DOC removal ~20% in all biofilters during periods of non- impaired DOC removal). Daily DOC removal across all biofilters was generally consistent, suggesting that the wildfire ash and associated water extractable organic matter did not reduce the DOC biodegradation capacity of the biofilters. DOM fractionation indicated that this was because the low molecular weight neutral (which are known to be readily biodegradable) and biopolymer fractions of DOM were reduced; however, humics were largely recalcitrant. Thus, biological filtration may be resilient to wildfire ash-associated DOM threats to drinking water treatment. However, operational resilience may be compromised if the balance between readily removed and recalcitrant fractions of DOM change, as was observed when baseline source water quality fluctuated for brief periods during the investigation.
... The LWR showed that A. testudineus was in a desirable growth rate and demonstrated they were doing better compared to T. trichopterus in the oil palm plantation system. 20 resources due to anthropogenic causes [2][3][4][5]. The major threats to fish biodiversity are intense. ...
Article
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The cultivation of oil palm on peat swamps in Malaysia has changed the water quality and aquatic ecosystems. We determined the fish species composition and water quality conditions at a disturbed peat swamp, i.e., oil palm plantation, in Kuala Langat peat swamp reserve forest, Selangor. Fishes were collected via gill net in five selected drains during dry and wet seasons between August 2014 and January 2015. In-situ (electrical conductivity (EC), dissolved oxygen (DO), pH, turbidity and temperature) and ex-situ (dissolved organic carbon (DOC)) physicochemical parameters of water quality were measured bimonthly. The length-weight relationship (LWR) of fish related to seasonal and spatial variation was also examined. A total of 336 individuals belonging to five families of fish were found with Trichopodus trichopterus and Anabas testudineus were the two abundant species. The DOC ranges at drainage with established palm trees area (i.e., 15-yo(A) 1stG, 3-yo 2ndG, and 9-yo 2ndG) was much greater than at cleared-felled (CF 2ndG) suggested that these plantation areas have carbon leaching due to high supply of labile leaf litter produced by palm trees. The observed EC and temperature were 5% higher in the dry season compared to the wet season. The A. testudineus showed highly adaption with high DOC levels particularly in 15-yo 1stG, and 9-yo 2ndG drains during the wet season. The LWR showed that A. testudineus was in a desirable growth rate and demonstrated they were doing better compared to T. trichopterus in the oil palm plantation system.
... Although an increase in nutrient availability is often shown to have the greatest impact at the base of food webs, the stimulation to autotrophic production can have cascading effects to the highest trophic levels (Bumpers et al., 2017), making it relevant in the context of fisheries management. These effects can arise through natural causes, as when the P inputs arising from alpine woodland wildfires led to increased algal and macroinvertebrate biomass, resulting in an increase in the size and weight of cutthroat trout (Onchorhynchus clarki) (Silins et al., 2014); however, of greater current interest is the concept of deliberate manipulation of nutrient levels. ...
Article
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1. Freshwater catchments can experience nutrient deficits that result in reduced primary and secondary productivity. The most commonly limiting nutrients are nitrogen and phosphorus, either separately or together. This review considers the impact of increasing nutrient limitation in temperate basin stream and river systems, focusing on upland areas that currently or previously supported wild Atlantic salmon (Salmo salar) populations. 2. Anthropogenic changes to land use and increases in river barriers have altered upland nutrient dynamics, with particular impacts on salmon and other migratory fish species which may be net importers of nutrients to upland streams. Declining salmon populations may further reduce nutrient sources, reducing ecosystem and fisheries productivity below desired levels. 3. Experimental manipulations of nutrient levels have examined the impacts of this cultural oligotrophication. There is evidence that growth and biomass of juvenile salmon can be increased via appropriate additions of nutrients, offering potential as a conservation tool. However, further research is required to understand the long-term effects of these additions on salmon populations and stream ecosystems, and to assess the vulnerability of downstream habitats to eutrophication as a result. 4. Although purposeful nutrient addition with the aim of enhancing and conserving salmonid populations may be justified in some cases, it should be undertaken in an adaptive management framework. In addition, nutrient addition should be linked to nutrient retention and processing, and integrated into large-scale habitat restoration and recovery efforts. 5. Both the scientific and the management community should recognize that the ecological costs and benefits associated with adding nutrients to salmon streams may change in a non-stationary world.
... Finally, it should not be dismissed the potential contribution of the intense wildfires registered in the Vigo area in October 2017 to fuel plankton growth in 2018. Unfortunately, there is a lack of studies of wildfire impacts in marine ecosystems in comparison with those in freshwater habitats, especially on streams (Silins et al., 2014;Bixby et al., 2015). Increased soil erosion and sediment loss after wildfires can greatly disturb aquatic ecosystems, for instance through an excess of nutrients leading to algal blooms. ...
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Alexandrium minutum blooms generally occur in semi-enclosed sites such as estuaries, harbours and lagoons, where enhanced stratification, restricted circulation and accumulation of resting cysts in the sediment set suitable habitat conditions for the proliferation of this paralytic shellfish poisoning toxigenic species. In the Galician Rías Baixas (NW Iberian Peninsula), according to weekly time-series between 1994 and 2020, blooms of A. minutum were recurrent in small, shallow estuarine bays inside the Rías de Vigo and Pontevedra, but rarely detected, and if so at low concentrations, out of these environments. However, from May to July 2018 it developed as usual in the small inner bays but then spread over both Rías (Vigo and Pontevedra) causing discoloured waters during one month and prolonged harvesting closures. Meteorological conditions during that period (rains / runoff higher than climatological averages, sustained temperature increment and oscillating wind pattern –i.e., series of upwelling-relaxation cycles), fostered optimal circumstances for the development of that extensive and massive proliferation: strong vertical stratification and the alternation of retention and dispersion processes. Simulations from a particle tracking model portrayed the observed bloom development phases: onset and development inside a small inner bay; transport within the surface layer, from these sites towards the interior parts of the Ría; and dispersion all over the embayment. Seedbeds with high concentrations of resting cysts were detected several months after the bloom, which may have favoured flourishment of A. minutum in the following two years, markedly in 2020. The present work contributes to the general understanding of the dynamics of harmful algal blooms (HABs), from which surveillance indicators of the state of marine ecosystems and their evolution can be derived. We hypothesize that the intensity and frequency of A. minutum proliferations in the Galician Rías could increase under projected climate trends.
... The AR has been exposed to a growing number of environmental threats (Spaling et al., 2000(Spaling et al., , 2013. The anthropogenic activities of concern include: i) agricultural, industrial and urban development (Cessna et al., 2011;Forrest et al., 2011); ii) logging (Kreutzweiser et al., 2008;Silins et al., 2014); iii) pulp and paper mills (Wrona et al., 2000;Chambers et al., 2006); iv) coal mining (Casey, 2005); v) bitumen mining plus refining (Kelly et al., 2010), and vi) municipal wastewaters (Chambers et al., 1997;Bonnell and Storey, 2000;Schindler and Donahue, 2006;Squires et al., 2010;Shotyk et al., 2017;Lima and Wrona, 2019). Among these activities, mining and upgrading of bitumen from the Athabasca Bituminous Sands (ABS) have received the most attention, and concern has been expressed regarding TE contributions from this industry to the AR and its tributaries (Timoney, 2007;Kelly et al., 2010;Schindler, 2013;Guéguen et al., 2016). ...
Article
With a wide variety of natural and potential anthropogenic inputs, the Athabasca River (AR) has been the focus of recent attention. In addition to natural inputs of trace elements (TEs) from tributaries, industrial activities such as mining and upgrading of bitumen have been viewed as additional, potentially important anthropogenic sources, but evidence is limited. To quantify the spatiotemporal variations of TE concentrations and their forms, water samples were gathered along a 125-km stretch of the river from upstream to downstream of the industrial region, and at three points across the river, along five transects perpendicular to the flow. The samples were collected in the autumn of 2017 and the spring of 2018, using novel, metal-free sampling methods. The concentrations of total (i.e. acid-extractable), and dissolved (i.e., < 0.45 µm) TEs were measured to compare with water quality guidelines, and their size-based distribution amongst major colloidal forms was determined to better assess their biological significance. The results quantify spatiotemporal variation in total and dissolved concentrations of TEs along and across the AR. In both seasons the majority of TEs occurred in the particulate fraction. None of the TEs were significantly enriched in the particulate fraction, relative to crustal abundance. The average concentrations of TEs were below the CCME surface water quality guidelines. The PCA analysis identifies tributary contributions of total and dissolved TEs to the AR.
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Background The increasing frequency, severity and intensity of wildfire globally is generally recognised as a significant threat to freshwater biodiversity. Fires impact streams through a range of mechanisms including geomorphological change, altered resource availability and direct impacts on biota. The magnitude and duration of fire impacts on stream ecosystems vary widely. Reasons for this variation are hypothesised to include the effects of fire can be from upstream catchment disturbance, disturbance at the site, or both. Additionally, many studies have sub-optimal designs as they are poorly replicated, short term, lack before data, and/or lack unburnt controls, which may further contribute to this variations in impacts. Here, we use a before-after-control-impact (BACI) design in sub-alpine woodlands in south-eastern Australia with 7 years of before data and 8 years of after data, to determine the effects of landscape-scale fires on stream macroinvertebrate community structure at local and landscape scales. Results Catchment scale disturbance had greater impacts for a longer duration (up to 4 years) on macroinvertebrate communities than local site scale disturbance (up to 1 year). Fire-induced changes in in-stream habitat and resources (e.g., substrate composition) were associated with the greatest changes in macroinvertebrate communities. Macroinvertebrate diversity was lower post fire at burnt sites and catchment burnt sites because of both reduced taxa richness and increased evenness. Differences between burnt and unburnt sites were predominantly a consequence of changes to the abundances of Coleoptera and Diptera taxa. Recovery in macroinvertebrate communities, including those downstream of fire, was associated with recovery of riparian vegetation cover at burnt sites. Conclusions Larger scale disturbance to the upstream catchment was more important for the macroinvertebrate community than local site scale disturbance. Post-fire management to minimise and ameliorate fire effects on stream macroinvertebrates should focus on limiting the downstream effects of fire on in-stream habitat caused by sediment movement and geomorphic changes.
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As wildfire regimes shift, resource managers are concerned about potential threats to aquatic ecosystems and the species they support, especially fishes. However, predicting fish responses can be challenging because wildfires affect aquatic ecosystems via multiple pathways. Application of whole-ecosystem approaches, such as food web modeling, can act as heuristic tools that offer valuable insights that account for these different mechanisms. We applied a dynamic food web simulation model that mechanistically linked stream trophic dynamics to the myriad effects that wildfires can have on aquatic and riparian ecosystems at a local stream reach-scale. We simulated how wildfires of different severity may influence short- (months to years) and long-term (years to decades) periphyton, aquatic invertebrate, and fish biomass dynamics in forested headwater streams of the western Pacific Northwest (USA). In many cases, wildfire increased modeled periphyton, invertebrate, and fish biomass over both short- and long-time periods. However, modeled responses varied extensively in their direction (that is, positive or negative), magnitude, and duration depending on fire severity, time since fire, and trophic level. The shapes of these response trajectories were especially sensitive to predicted wildfire effects on water temperature, canopy cover, riparian shading, and instream turbidity. Model simulations suggest a single fire could result in a wide range of aquatic ecosystem responses, especially in watersheds with mixed burn severity. Our analysis highlights the utility of whole-ecosystem approaches, like food web modeling, as heuristic tools for improving our understanding of the mechanisms linking fire, food webs, and fish and for identifying contexts where fires could have deleterious impacts on fishes.
Chapter
Disinfection by-product (DBP) precursors are inextricably linked to the landscapes and waters on which they originate and transform. Warming global temperatures, hydroclimatic change, and climate shocks alter key landscape characteristics (e.g., land cover and soil characteristics) and responses (e.g., erosion and runoff), altering the mobilization and delivery of disinfection by-product (DBP) precursors to water supplies. In this chapter, the inter-relationships between (1) global warming, (2) hydroclimatic change and climate shocks, (3) landscape characteristics, (4) landscape responses to changes in landscape characteristics, and (5) DBP precursor delivery and change in aquatic systems are discussed.
Article
Wildfires induce changes in soil and vegetation composition, significantly impacting the hydrological cycle and altering future runoff and infiltration patterns. Ash residue on the ground can infiltrate the subsoil along with water, leading to modifications in groundwater hydrochemistry. Climate change and summer heatwaves can create favourable conditions for severe wildfires, such as the one that occurred in Zamora, Spain, in 2022. Fourteen simultaneous points of origin across various locations in Zamora triggered the worst environmental disaster in this province, as well as the largest fire recorded in the history of Spain. Following the severe wildfires in Sierra de la Culebra, Zamora, groundwater samples were obtained to compare the hydrochemistry with pre-fire background data spanning several years. A general decline in pH across all sampling points was observed, most notably at Z1, likely due to its very high permeability and leaching of organic acids from burned vegetation. Increases in major ions such as SO42− and NO3− were detected at Z1-2, while HCO3− levels decreased, indicating possible oxidation of soil organic matter and the introduction of wildfire-derived organic acids into the groundwater system. Elevated concentrations of Na+, K+, Mg2+, and Ca2+ were observed at Z3, suggesting possible ash residue infiltration. Despite the severity of the wildfires, the results indicate that there were no significant long-lasting impacts on groundwater quality overall. This finding suggests that the groundwater systems in the study area are resilient to such environmental catastrophes.
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Background: Wildfire plays an important role in determining ecosystem processes, composition, structure and condition, and is forecast to play a greater role under climate change. Wildfire affects the physicochemical and habitat characteristics of waterways, and the response in freshwater systems depends on characteristics of the fire, landscape and climate. Knowledge of fire effects on freshwater physiochemistry and habitat is predominantly based on suboptimal designed and short-medium term studies. Using a rigorous before-after-control-impact (BACI) study design and up to 28-years timeseries data, we examined if physicochemical and habitat variables changed following wildfire, and the duration of changes relative to unburnt sites in sub-alpine (hereafter alpine) and montane and sub-montane (montane hereafter) environments in south-eastern Australia. Results:Of the variables hypothesised to change in response to fire, 8 out of 33 variables at alpine sites, and 7 out of 12 variables at montane sites, changed in line with our predictions. Four variables changed in the opposite direction to predictions. Of 11 variables measured at both sites in alpine and montane environments, 3 variables responded to the fire in only one environment (montane zone) and 1 variable (electrical conductivity) responded in both environments but in different directions. For 90% of response variables examined at both alpine sites (33 variables) and montane sites (12 variables) effects were not detectable beyond 2 years post-fire. The remaining 10% of variables examined were detected up to 8 years post fire at alpine sites, and for 2.5 years at montane sites. The duration of detectable effects was greater at alpine sites than montane sites. Conclusions: We found no single consistent effect of fire on stream physicochemistry. Although some variables were found to respond to wildfire in a consistent way, the magnitude and duration of effects varied by site group (alpine versus montane) and site type (site burnt versus catchment burnt), illustrating the complexity of responses to wildfire. The complexity and inconsistency of responses of water physicochemical and habitat variables to wildfires reinforces the need for a better mechanistic understanding of the effects of fire on streams.
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Freshwater ecosystems host disproportionately high biodiversity and provide unique ecosystem services, yet they are being degraded at an alarming rate. Fires, which are becoming increasingly frequent and intense due to global change, can affect these ecosystems in many ways, but this relationship is not fully understood. We conducted a systematic review to characterize the literature on the effects of fires on stream ecosystems and found that (1) abiotic indicators were more commonly investigated than biotic ones, (2) most previous research was conducted in North America and in the temperate evergreen forest biome, (3) following a control‐impact (CI) or before‐after (BA) design, (4) predominantly assessing wildfires as opposed to prescribed fires, (5) in small headwater streams, and (6) with a focus on structural and not functional biological indicators. After quantitatively analyzing previous research, we detected great variability in responses, with increases, decreases, and no changes being reported for most indicators (e.g., macroinvertebrate richness, fish density, algal biomass, and leaf decomposition). We shed light on these seemingly contradicting results by showing that the presence of extreme hydrological post‐fire events, the time lag between fire and sampling, and whether the riparian forest burned or not influenced the outcome of previous research. Results suggest that although wildfires and the following hydrological events can have dramatic impacts in the short term, most biological endpoints recover within 5–10 years, and that detrimental effects are minimal in the case of prescribed fires. We also detected that no effects were more often reported by BACI studies than by CI or BA studies, raising the question of whether this research field may be biased by the inherent limitations of CI and BA designs. Finally, we make recommendations to help advance this field of research and guide future integrated fire management that includes the protection of freshwater ecosystems.
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Severe wildfire is altering the natural and the built environment and posing risks to environmental and societal health and well-being, including cascading impacts to water systems and built water infrastructure. Research on wildfire-resilient water systems is growing but not keeping pace with the scale and severity of wildfire impacts, despite their intensifying threat. In this study, we evaluate the state of knowledge regarding wildfire-related hazards to water systems. We propose a holistic framework to assess interactions and feedback loops between water quality, quantity, and infrastructure hazards as determinants of post-fire water availability and access. Efforts to address the evolving threat of wildfires to water systems will require more interdisciplinary research on the complex relationships shaping wildfire’s threat to water availability and access. To support this, we need reliable long-term data availability, consistent metrics, greater research in shared contexts, more extensive research beyond the burn area, and multistakeholder collaboration on wildfire risks to water systems.
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Understanding how wildfires affect food web structure and function remains an important challenge, especially at high elevations that historically have burned infrequently. In particular, fires may alter the magnitude of reciprocal cross‐ecosystem subsidies, leading to indirect effects on aquatic and terrestrial consumers. We quantified characteristics of high‐elevation (2500–3000 m) stream‐riparian food webs at 10 locations in the southern Rocky Mountains less than one year following high‐intensity, stand‐replacing wildfires. Using a paired ‘burned−unburned' stream survey design, we assessed benthic periphyton, aquatic macroinvertebrate community structure, trout population characteristics, trout stomach contents, inputs and emergence of insects to and from streams, and abundance of predatory riparian spiders that consume aquatic insects. Benthic macroinvertebrate density, flux of emerging aquatic insects, and riparian spider abundances were lower at burned sites. Fluxes of insect inputs entering the stream did not differ with burn status, despite the loss of riparian vegetation due to fire. Trout were somewhat less abundant, but larger on average at burned sites and did not differ in body condition. These results suggest mortality of smaller trout from fire disturbance and/or recolonization of burned sites by larger individuals. Trout showed subtle changes in diet composition with burn status, but no change in biomass or number of prey consumed. In general, burned sites showed greater variation in community characteristics than unburned sites, which may reflect differences in the timing and magnitude of post‐fire flooding, erosion, and scouring of the stream bed. Taken together, our results suggest that short‐term effects of fire disturbance strongly altered some food web responses, but others appeared relatively resilient, which is notable given the high severity of the wildfires in the study area.
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Wildfire activity is increasing in the continental U.S. and can be linked to climate change effects, including rising temperatures and more frequent drought conditions. Wildfire emissions and large fire frequency have increased in the western U.S., impacting human health and ecosystems. We linked 15 years (2006-2020) of particulate matter (PM2.5) chemical speciation data with smoke plume analysis to identify PM2.5-associated nutrients elevated in air samples on smoke-impacted days. Most macro- and micro-nutrients analyzed (phosphorus, calcium, potassium, sodium, silicon, aluminum, iron, manganese, and magnesium) were significantly elevated on smoke days across all years analyzed. The largest percent increase was observed for phosphorus. With the exception of ammonium, all other nutrients (nitrate, copper, and zinc), although not statistically significant, had higher median values across all years on smoke vs. non-smoke days. Not surprisingly, there was high variation between smoke impacted days, with some nutrients episodically elevated >10 000% during select fire events. Beyond nutrients, we also explored instances where algal blooms occurred in multiple lakes downwind from high-nutrient fires. In these cases, remotely sensed cyanobacteria indices in downwind lakes increased two to seven days following the occurrence of wildfire smoke above the lake. This suggests that elevated nutrients in wildfire smoke may contribute to downwind algal blooms. Since cyanobacteria blooms can be associated with the production of cyanotoxins and wildfire activity is increasing due to climate change, this finding has implications for drinking water reservoirs in the western United States, and for lake ecology, particularly alpine lakes with otherwise limited nutrient inputs.
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Purpose Multimodal effective particle size distributions (EPSDs) develop as flocculation and particle breakage occur dynamically in a fluid shear and such distributions have been previously reported in coastal and estuarine waters to understand flocculation processes. Here, we use time varying multimodal EPSDs and hydraulic parameters (discharge and bed shear stress) to assess freshwater flocculation in a gravel-bed river in southern Alberta, Canada. Methods Instantaneous discharge, volume concentration (VC), and EPSD of suspended solids were measured during three high discharge events at four study sites in a 10 km reach of the Crowsnest River. The EPSD and VC of suspended solids (< 500 µm) were measured in the centroid of flow with a LISST-200x. Bed shear stress for measured discharge was obtained using a flow model, MOBED. Results Multimodal EPSDs consisted of primary particles, flocculi, microflocs, and macroflocs. Shear dependent flocculation was consistently observed for all sites and events, due to low and high shear stress flocculation, particle breakage, and mobilization of tributary sub-catchment derived particles. Higher shear stress limited flocculation to smaller floc sizes, while lower bed shear stress conditions created higher volumes of macroflocs. Conclusion Flocculation and particle breakage processes based on relationships between particle size and hydraulic properties presented herein have implications for advancing fine sediment transport models by a variable cohesion factor as a function of floc size class.
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Fishes are considered as a good source of proteins, essential fatty acids and minerals. People with high fish intake have lower rates of acute myocardial infarctions and atherosclerosis, better cognitive functions and better neural and visual development in fetus. In the present work, it was evaluated that the seasonal variations in nutritional components of Channa striatus fish with respect to three different seasons during year 2021 i.e. pre-monsoon (Summers), post-monsoon and winter season taken from Aliganj, Narmada Ghat flowing through Raisen district of Madhya Pradesh was seen. Nutritional components like carbohydrate, protein and lipids are severely influenced with the change in season and water quality parameters. The nutritional analysis showed that all the main three nutritional components i.e. Protein, carbohydrate and lipid content of Channa striatus was seen maximum in the winter season (i.e. 33.64 µg/gm, 526.51 mg/l and 24.07mg respectively) followed by post-monsoon season (28.51 µg/gm, 523.4 mg/l and 22.12 mg respectively) and pre-monsoon (24.66 µg/gm, 502.1mg/l and 19.07 mg respectively).In general results suggested that the Channa striatus fish species of Narmada River of winter season contains the best nutritive value as compared to pre monsoon and post-monsoon. Hence consumption is more beneficial in winter season
Article
Determining the seasonal alterations in the essential nutritional constituents of Channa striatus fish will be important to estimate their nutritive value with different seasons so as to plan the most beneficial consumption time period, commercial processing and storage for future. In the present work, it was evaluated that the seasonal variations in nutritional value of Channa striatus including total carbohydrate, protein and lipid content with respect to three season’s i.e winter, pre-monsoon and post monsoon from Halali Reservoir in the Raisen district, of Madhya Pradesh. Nutritional components like carbohydrate, protein and lipids are severely influenced with the change in season and water quality parameters. Total carbohydrate, protein and lipid were estimated by phenol-sulphuric acid method, Follin’s-Lowry method and Folch et al. method respectively. The nutritional analysis showed that the nutritional value of Channa striatus in the winter sample (January to February) was maximum as compared to post monsoon (October to November) and pre-monsoon (Juneto July) sample. So, it is suggested that the consumption of Channa striatus fish of Halali reservoir in the winter season must be increased for obtaining maximum nutritional benefits
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Forested watersheds supply over two thirds of the world’s drinking water. The last decade has seen an increase in the frequency and intensity of wildfires that is threatening these source watersheds, and necessitating more expensive water treatment to address degrading water quality. Given increasing wildfire frequency in a changing climate, it is important to understand the magnitude of water quality impacts following fire. Here, we conducted a meta-analysis to explore post-fire changes in the concentrations of nitrogen (N) and phosphorus (P) species, dissolved organic carbon (DOC), and total suspended sediments (TSS) in 121 sites around the world. Changes were documented over each study’s respective duration, which for 90% of sites was 5 years or fewer. We find concurrent increases in C, N and P species, highlighting a tight coupling between biogeochemical cycles in post-fire landscapes. We find that fire alters N and P speciation, with median increases of 40-60% in the proportion of soluble inorganic N and P relative to total N and P. We also found that fire decreases C:N and C:P ratios, with median decreases ranging from 60-70%. Finally we observe a “hockey stick”-like response in changes to the concentration distribution, where increases in the highest concentration ranges are much greater than increases at lower concentrations. Our study documents strong heterogeneity in responses of water quality to wildfire that have been unreported so far in the literature.
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Continental-scale increases in aquatic system eutrophication are linked with increased cyanobacteria threats to recreational water use and drinking water resources globally. While some guidance regarding monitoring is available, it is largely reactive and insufficient for proactive risk mitigation and management, which necessarily requires an understanding of the composition and dynamics of cyanobacterial communities in the aquatic system. Their distribution is impacted by several factors, including water column mixing and buoyancy regulation responses to light availability that create oscillatory diurnal migration patterns within the water column, creating challenges in the ability to accurately describe and quantify cyanobacterial densities. These dynamic fluctuations are not typically reflected in monitoring protocols, which frequently focus on surface depths and either ignore sampling time or recommend large midday timeframes (e.g., 10AM-3PM), thereby precluding accurate characterization of cyanobacterial communities. While diurnal vertical migration of cyanobacteria has been reported in marine and eutrophic freshwater systems, reports in oligotrophic freshwater lakes are scant and characterization have focused on individual 24-hour periods neglecting to consider day-to-day variability. These dynamics must be better understood and reflected in water quality monitoring guidance to advance drinking water risk management and source water protection approaches. To evaluate the impact of diurnal migrations and water column stratification on cyanobacterial abundance, communities were characterized using a multi-time point sampling series across a 48-hour period in a shallow well-mixed lake interconnected to a thermally stratified lake in the Turkey Lakes Watershed (Ontario, Canada). Amplicon sequencing of the V4 region in the 16S rRNA gene was performed to characterize microbial community composition. Cyanobacteria were significantly represented in the microbial community in the midday and afternoon sampling times in the thermally stratified lake, but not in the well-mixed lake. Although the lakes in this study are interconnected, the cyanobacterial communities within them exhibited unique composition and distribution trends, thereby underscoring the importance of developing detailed sampling guidance to maximize the utility of cyanobacteria monitoring and better characterize and mitigate risk. Highlights ▪ Water column stability impacts diurnal migrations of cyanobacteria ▪ Gas vacuolate taxa are more abundant at surface, but also present at depth ▪ Rain events can impact cyanobacteria distribution and impact detection ▪ Cyanobacteria distribution can vary significantly between interconnected lakes ▪ Cyanobacteria monitoring for risk management should incorporate time and depth
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Forested land plays an essential role in water supply across the United States (US). Smoldering commonly existing in wildfires contributes significantly to biomass consumption and gas emission, but its influence on source water quality has been rarely studied. Here, we investigated the impact of smoldering temperature (i.e., no burn, 250, 400, and 600 °C) on the nutrients, elements, and dissolved organic matter (DOM) of water extracts from the residues of the leaf needles and woody trunks of pine (Pinus jeffreyi) under the lab-simulated smoldering fire. Results showed the increase of pH and the yields of the dominated exchangeable cations of K⁺ and Mg²⁺, P, PO4³⁻-P, and SO4²⁻ with increasing temperature increasing from 250 to 600 °C, whereas significant decreases in the fraction of dissolved organic C in residue C with increasing temperature and the yields of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) after burnings. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) presented consistent results with UV/fluorescence, suggesting that the unburned materials contained more biodegradable tyrosine/tryptophan/soluble microbial byproduct-like compounds with high molecular weight (MW), whereas the 600 °C-smoldering materials composed of more aromatic, humified, fulvic/humic acid-like, and oxidized compounds with a potentially high density of C=C bonds had less reactivity in forming trihalomethanes (THMs) and haloacetonitriles (HANs). Our study indicates the smoldering-dominated prescribed fire as a potential forest management strategy for reducing biomass fuel and disinfection byproducts (DBPs) precursors in source water from forested lands.
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High-severity wildfires can increase sediment mobility and erosion rates in burned landscapes which increase the delivery of fine sediment to receiving streams. The downstream propagation of these pyrogenic materials can have significant implications for ecosystem and human health implications. The identification of areas prone to differing levels of sediment erosion is necessary for watershed managers to prioritize critical areas that may require best management practices to reduce sediment transfer from hillslopes to receiving streams. Knowledge of sediment erodibility and runoff rates at the site scale and incorporation of these data in watershed scale sediment erosion models such as the Revised Universal Soil Loss Equation (RUSLE) is critical for landscape managers to mitigate the effects of soil erosion. The objectives of this study are to 1) quantify runoff and sediment erosion rates for dominant soil textures using a rainfall simulator at the plot scale to provide estimates of sediment erodibility and yield, 2) model post-wildfire erosion at the watershed-scale to identify critical areas of sediment erosion and 3) identify priority management zones in Waterton Lakes National Park and recommend management options for the implementation of best management practices. Runoff and sediment erosion rates of various soil textures were measured using a rainfall simulator using an I10 rainfall intensity. The rainfall simulation data were used in RUSLE to determine watershed-scale sediment yields and to identify priority management areas. In the present study, a low rainfall intensity (33 mm hr-1) produced runoff and sediment erosion over a range of soil textures following a wildfire. Finer soil textures produced higher runoff rates and sediment yields compared to coarse soil textures on burned soils. RUSLE provided first-order sediment erosion estimates following wildfire and has the potential to identify areas of varying erosion rates at the watershed-scale, in a GIS environment, for use by land managers that may want to reduce sediment from potentially entering nearby streams.
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Following a wildfire in southeastern Australia that burnt over 1 million hectares of forested land in early 2003, two former research catchments (136 and 244 ha), in the East Kiewa valley, Victoria, were re-instrumented. Discharge, suspended sediment, bedload and nitrogen (N) and phosphorus (P) were measured for 3 years post-fire. The nutrient data consisted of 15-min estimation of particulate P and total Kjeldahl N via a regression with turbidity, and dissolved forms of P and N estimated from over 1100 water samples. The regression-based estimation allowed rigorous estimation of errors, seldom reported in water quality data. The fire appears to have increased the total P and N exports by around 5-6-fold, peaking at 1.6 kg ha À1 of P and 15.3 kg ha À1 of total combined N. Nutrients transported as particulate matter dominated the first post-fire year, with 94% of total combined P and 69% of total combined N. Although dissolved forms increased in importance, the particulate load comprised 86% of the total combined P load and 68% of the total combined N load over the three post-fire years. Concentrations and loads of P and N exhibited a rapid recovery to unburnt levels during the second post-fire year. Particulate forms declined sharply through a reduction in sediment delivery. Nitrate had the slowest relaxation time, suggesting a persistent subsurface pathway and the effect of nitrification. Notably, dissolved N fluxes were predominantly in baseflow even in the first post-fire year. The errors calculated for this study indicate the uncertainty that can exist in water quality estimation despite high resolution experimental design. Loads estimated from intermittent sampling should be treated with caution. A simple model with time as the single parameter proved to be a good predictor of mean three monthly concentrations. ª
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This state-of-knowledge review about the effects of fire on soils and water can assist land and fire managers with information on the physical, chemical, and biological effects of fire needed to successfully conduct ecosystem management, and effectively inform others about the role and impacts of wildland fire. Chapter topics include the soil resource, soil physical properties and fire, soil chemistry effects, soil biology responses, the hydrologic cycle and water resources, water quality, aquatic biology, fire effects on wetland and riparian systems, fire effects models, and watershed rehabilitation.
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Stable isotope enrichment experiments offer a potentially powerful way to examine the base of aquatic food webs, but interpretation of the data from these experiments may be confounded by problems such as selective ingestion/assimilation of bulk food sources by consumers, variable tracer enrichment over time, and the failure of consumers to approach isotopic equilibrium with the tracer in their diets over the course of the experiment. Our study examined data from a stable isotope addition experiment in which 15N-labeled NH4+ was added to a midwestern US stream. A compartment model was used to provide insights into the kinetics of 15N uptake and release from algae, heterotrophic microbes colonizing detritus, and invertebrate consumers. The model accounted for temporal variation in the degree of isotopic enrichment and did not require the assumption of isotopic equilibrium between consumers and their diets. The importance of instream production (i.e., growth of algae and microbes within the study reach during the experiment) relative to allochthonous and upstream inputs was ∼38 to 50% for heptageniids and Psephenus, 10 to 20% for Orconectes propinquus, Gammarus, hydropsychids, and larval Stenelmis, and <10% for the filter-feeding Similium and the unionid mussel Pleurobema sintoxia. The alternative choices of algae or heterotrophic microbes as the basis of consumer diets made little difference in these estimates, even though the microbes became more 15N-enriched than the algae because microbes had higher turnover rates. These results were subject to a number of caveats, and guidelines for experimental design are suggested for future studies to help address some of these problems.
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The trophic ecology of 11 benthic macroinvertebrate taxa found in Cache Creek, Yellowstone National Park (YNP) was studied to determine if burned organic matter is an important resource and how resource utilization patterns may be altered in post-fire streams. Laboratory food quality experiments were conducted to determine the growth response of each species when grown on several resource types: burned organic matter, periphyton, unburned coarse particulate material (CPM), and unburned fine particulate material (FPM). The central hypothesis of this research was that benthic macroinvertebrates cannot use burned organic matter as a resource. A secondary hypothesis was that some benthic macroinvertebrates are facultative in trophic function, with the ability to use both allochthonous and autochthonous resources for growth. Of the 11 taxa studied, only one (Paraleptophlebia heteronea) could grow on burned organic matter as a resource, indicating that post-fire food webs probably do not exhibit major shifts in resource utilization to burned material. Two species were generalist detrivores (P. heteronea, Ameletus cooki) able to use both natural FPM and CPM resources. Two species were specialist detritivores (Oligophlebodes sigma, Ephemerella infrequens) growing only on unburned CPM resources, and two (Cinygmula mimus, Epeorus albertae) were specialist herbivores utilizing only periphyton. Five species were generalist herbivore-detritivores (Baetis bicaudatus, Drunella doddsi, D. coloradensis, D. spinifera, Zapada columbiana), exhibiting growth on both detritus and periphyton resources. Based on the experimental results, trophic generalists are common food web components in Yellowstone streams. Two of the most abundant benthic macroinvertebrates during post-fire recovery, B. bicaudatus and Z. columbiana, were trophic generalists, indicating that some generalists may be disturbance adapted. In this study, published functional feeding group classification did not indicate obligate resource utilization (growth on only one resource type) for most taxa studied. Comparison of a food web for Cache Creek based on functional feeding group classification and one based on the results of this study indicates that the inclusion of generalists in the web results in a more realistic approximation of food web relationships such as the link-species scaling law. Our results suggest that future research should include spatial and temporal aspects of resource switching and generalist resource utilization by individual lotic primary consumers.
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A field experiment was used to test whether stream periphyton was nutrient limited, and if so, whether the grazing insects that consumed this resource were food limited. Eight replicate wooden flumes were placed in an unshaded riffle in Augusta Creek, a third-order, hardwater trout stream in southwestern Michigan (USA). Phosphorus, in the form of Ca(H2PO4)2, was added to four of these flumes for 105 d. The average concentration of soluble reactive phosphorus (SRP) maintained in P-enriched flumes (85 @mg/L) was >5 times as great as in control flumes (15 @mg/L). After 77 d of nutrient enrichment, periphyton biomass per unit area on substrates with reduced grazer densities was 1.8 x as great in P-enriched flumes as in control flumes. The larvae of two species of grazing caddisflies (Leucotrichia pictipes and Psychomyia flavida) in P-enriched flumes also had higher individuals mass, developmental rates, and population densities. These responses resulted in standing crops of final-instar larvae in P-enriched flumes that were 2.1x and 1.5x as great as those in control flumes for Psychomyia and Leucotrichia, respectively. This demonstration of food limitation supplements previous behavioral studies showing that both grazer species aggressively defend feeding territories, and contributes to a growing body of evidence suggesting that resource limitation is more important in some stream food webs than previously recognized. Resource limitation of these grazer populations may be due in part to the rarity of catastrophic flooding and drying in Augusta Creek. Such stable flows could permit consumer populations to reach higher densities than in frequently disturbed streams.
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The Mortar Creek Fire burned 26 000 ha of mixed-conifer Rocky Mountain forest in July–August 1979. Changes in burn stream conditions were examined relative to reference streams for various ecological factors on two to six occasions, from October 1979 to August 1980. Factors included major ions and nutrients, suspended and benthic particulate matter, periphyton (algae), and macroinvertebrates. Elevated levels of most dissolved chemicals in the burn streams were evident soon after the fire and again during spring runoff. However, there were no major disruptions in the relative composition of cations (and presumably of anions also) in the burn streams during the study. Concentration (mg/L) and load (g/s) of some constituents were higher (e.g. NO 3 -N) and of others (e.g. Ca) were lower in the burn than in the reference streams during spring runoff, depending on whether they were normally under biological or geological control, respectively. Suspended sediment and particulate organic matter generally were higher in burn streams, especially during snow-melt runoff or following heavy rain storms. Benthic organic matter was higher in burn streams and was mainly charcoal, compared to the usual leaf litter found in the reference streams. Fine sediments increased and periphyton decreased in the burn streams. The fire increased the sensitivity of the burn streams to more routine smaller-scale disturbances, such as rainstorms, which had major impacts on the burn streams but not on the reference streams. The macroinvertebrate assemblage showed little direct effect from the fire but was severely altered in composition and abundance by the subsequent runoff, scouring, and channel alteration initiated by spring runoff. The burn streams showed considerable individuality in their response to fire depending on the particular set of conditions to which they were exposed.
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Research into post-wildfire effects began in the United States more than 70 years ago and only later extended to other parts of the world. Post-wildfire responses are typically transient, episodic, variable in space and time, dependent on thresholds, and involve multiple processes measured by different methods. These characteristics tend to hinder research progress, but the large empirical knowledge base amassed in different regions of the world suggests that it should now be possible to synthesize the data and make a substantial improvement in the understanding of post-wildfire runoff and erosion response. Thus, it is important to identify and prioritize the research issues related to post-wildfire runoff and erosion. Priority research issues are the need to: (1) organize and synthesize similarities and differences in post-wildfire responses between different fire-prone regions of the world in order to determine common patterns and generalities that can explain cause and effect relations; (2) identify and quantify functional relations between metrics of fire effects and soil hydraulic properties that will better represent the dynamic and transient conditions after a wildfire; (3) determine the interaction between burned landscapes and temporally and spatially variable meso-scale precipitation, which is often the primary driver of post-wildfire runoff and erosion responses; (4) determine functional relations between precipitation, basin morphology, runoff connectivity, contributing area, surface roughness, depression storage, and soil characteristics required to predict the timing, magnitudes, and duration of floods and debris flows from ungaged burned basins; and (5) develop standard measurement methods that will ensure the collection of uniform and comparable runoff and erosion data. Resolution of these issues will help to improve conceptual and computer models of post-wildfire runoff and erosion processes.
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Research highlights ► Wildfire effects on water quality vary substantially. ► Large post-fire increases to sediment, nutrient and trace element fluxes reported. ► Wildfires may disrupt the supply of potable water from forest catchments.
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A Large Fire Database (LFDB), which includes information on fire location, start date, final size, cause, and suppression action, has been developed for all fires larger than 200 ha in area for Canada for the 1959-1997 period. The LFDB represents only 3.1% of the total number of Canadian fires during this period, the remaining 96.9% of fires being suppressed while <200 ha in size, yet accounts for ∼97% of the total area burned, allowing a spatial and temporal analysis of recent Canadian landscape-scale fire impacts. On average ∼2 million ha burned annually in these large fires, although more than 7 million ha burned in some years. Ecozones in the boreal and taiga regions experienced the greatest areas burned, with an average of 0.7% of the forested land burning annually. Lightning fires predominate in northern Canada, accounting for 80% of the total LFDB area burned. Large fires, although small in number, contribute substantially to area burned, most particularly in the boreal and taiga regions. The Canadian fire season runs from late April through August, with most of the area burned occurring in June and July due primarily to lightning fire activity in northern Canada. Close to 50% of the area burned in Canada is the result of fires that are not actioned due to their remote location, low values-at-risk, and efforts to accommodate the natural role of fire in these ecosystems. The LFDB is updated annually and is being expanded back in time to permit a more thorough analysis of long-term trends in Canadian fire activity.
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Various studies report changes in phosphorus and nitrogen concentrations in surface waters after wildfires; however, we have found no reports which include nutrient data collected during actual wildfire activity. We had an opportunity to collect water chemistry data from several streams as a large (15,500 ha) intense firestorm passed through their watersheds. Phosphorus and nitrogen concentrations increased from 5 to 60 fold over background levels within the first two days of the fire with maximum recorded concentrations for dissolved nutrients reaching as high as 135 μg/L soluble reactive phosphorus, 261 μg/L ammonium, and 61 μg/L nitrate + nitrite. Total phosphorus and total nitrogen levels increased up to 206 μg/L and 349 μg/L respectively. Nutrient concentrations declined to background levels typically <5-10 μg/L within several days to several weeks. Experimental evidence suggests that the primary source of phosphorus was from leaching of ash deposited directly into the streams during the firestorm while the primary source of nitrogen appeared to be from diffusion of smoke gases into the stream waters.
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Based on the general premise that the genus represents an ecological, as well as a morphological type, a number of generalizations are developed concerning the use of food resources in fresh waters by Trichoptera and some other aquatic orders of the Nearctic fauna. There are more genera of the Nearctic order Trichoptera (144) than in the orders Ephemeroptera (59), Odonata (84), or Plecoptera (88). Trichoptera have a wide range of habitats and a broader range of trophic categories than any of these other wholly aquatic orders. This relatively high ecological diversity is attributed to the many uses of silk by trichopteran larvae. Genera of 3 families of filter-feeding Trichoptera show differences in distribution which are correlated with the type of food particle. Most of these genera are found in the eastern deciduous forest biome and all sizes of organic particles are filtered. In the western montane forest biome, generalist filter feeders are absent or underrepresented; predacious genera or those filtering very fine particles have been more successful. Possibly there are differences in the quality and quantity of fine particulate detritus between eastern and western forest which account for the above distributions. In the trichopteran family Limnephilidae, genera of the detritivorous shredders have exploited lotic, lentic, and even terrestrial habitats; grazer genera are mostly confined to cool lotic habitat. Grazers in other families of Trichoptera are also more diverse in upstream areas, and grazer genera are particularly well-represented in the western montane forest biome. In streams of the eastern deciduous forest biome, the relative proportions of feeding categories shown by trichopteran genera appear to agree with a general trophic model of benthic invertebrate communities in that dominance of shredder-collector genera in upstream sections gives way to grazer-collector dominance downstream. In western montane streams, trichopteran generic distributions conform to the model downstream, but show relatively more grazers than the model would predict for upstream areas. Periphyton growth, and thus food for grazers, may be more abundant in the western coniferous forest than in the shaded streams of the eastern deciduous forest. In general, an ecological analysis of Nearctic Trichoptera at the generic level appears to provide a reasonable indication of the energy resources available in aquatic habitats.