Longitudinal stream synoptic (LSS) monitoring to evaluate water quality in restored streams

Impervious surface cover increases peak flows and degrades stream health, contributing to a variety of hydrologic, water quality, and ecological symptoms, collectively known as the urban stream syndrome. Strategies to combat the urban stream syndrome often employ engineering approaches to enhance stream-floodplain reconnection, dissipate erosive forces from urban runoff, and enhance contaminant retention, but it is not always clear how effective such practices are or how to monitor for their effectiveness. In this study, we explore applications of longitudinal stream synoptic (LSS) monitoring (an approach where multiple samples are collected along stream flowpaths across both space and time) to narrow this knowledge gap. Specifically, we investigate (1) whether LSS monitoring can be used to detect changes in water chemistry along longitudinal flowpaths in response to stream-floodplain reconnection and (2) what is the scale over which restoration efforts improve stream quality. We present results for four different classes of water quality constituents (carbon, nutrients, salt ions, and metals) across five watersheds with varying degrees of stream-floodplain reconnection. Our work suggests that LSS monitoring can be used to evaluate stream restoration strategies when implemented at meter to kilometer scales. As streams flow through restoration features, concentrations of nutrients, salts, and metals significantly decline (p < 0.05) or remain unchanged. This same pattern is not evident in unrestored streams, where salt ion concentrations (e.g., Na+, Ca2+, K+) significantly increase with increasing impervious cover. When used in concert with statistical approaches like principal component analysis, we find that LSS monitoring reveals changes in entire chemical mixtures (e.g., salts, metals, and nutrients), not just individual water quality constituents. These chemical mixtures are locally responsive to restoration projects, but can be obscured at the watershed scale and overwhelmed during storm events.

Oil and gas produced waters fail to meet beneficial reuse recommendations for use as dust suppressants

Produced water from conventional oil and gas wells (O&G PW) is beneficially reused as an inexpensive alternative to commercial dust suppressants which minimize inhalable particulate matter (PM10) from unpaved roads. The efficacy and environmental impacts of using O&G PW instead of commercial products have not been extensively investigated, although O&G PW has been used for dust suppression for decades and often has elevated concentrations of environmental pollutants. In this study, the effectiveness of O&G PW is compared to commercial products under variable humidity conditions by measuring total generated PM10 emissions from treated road aggregate discs. To measure environmental impacts, model roadbeds were treated with six O&G PW and commercial products then subjected to a simulated two-year, 24-h storm event. Generated runoff water was collected and characterized. In efficacy studies, O&G PW offered variable dust reduction (10-85 %) compared to rainwater controls under high humidity (50 %) conditions but performed similarly or worse than controls when humidity was low (20 %). Conversely, all but two commercial products reduced dust emissions by over 90 % regardless of humidity. In rainfall-runoff experiments, roads treated with O&G PWs and CaCl2 Brine generated runoff that was hypersaline, indicating that mobilization of soluble salts could contribute to freshwater salinization. Though most runoff concentrations were highest from roadbeds treated with CaCl2 Brine, runoff from roadbeds treated with O&G PW had the highest concentrations of combined radium (83.6 pCi/L), sodium (3560 mg/L), and suspended solids (5330 mg/L). High sodium concentrations likely dispersed clay particles, which increased road mass loss by 47.2 kg solids/km/storm event compared to rainwater controls. Roadbeds treated with CaCl2 Brine, which had low sodium concentrations, reduced solid road mass loss by 98.1 kg solids/km/storm event. Based on this study, O&G PW do not perform as well as commercial products and pose unique risks to environmental health.

Do magnesium and chloride ameliorate high sodium bicarbonate concentrations? A comparison between laboratory and mesocosm toxicity experiments

Increasing salinity is a concern for biodiversity in many freshwater ecosystems globally. Single species laboratory toxicity tests show major differences in freshwater organism survival depending on the specific ions that comprise salinity types and/or their ion ratios. Toxicity has been shown to be reduced by altering ionic composition, despite increasing (total) salinity. For insistence, single species tests show the toxicity of sodium bicarbonate (NaHCO3, which commonly is a large proportion of the salts from coalbeds) to freshwater invertebrates is reduced by adding magnesium (Mg2+) or chloride (Cl-). However, it is uncertain whether reductions in mortality observed in single-species laboratory tests predict effects within populations, communities and to ecosystem processes in more complex multi-species systems both natural and semi-natural. Here we report the results of an outdoor multi-species mesocosm experiment to determine if the effects of NaHCO3 are reduced by increasing the concentrations of Mg2+ or Cl- on: a) stream macroinvertebrate populations and communities; b) benthic chlorophyll-a and; c) the ecosystem process of leaf litter decomposition. We found a large effect of a high NaHCO3 concentration (≈4.45 mS/cm) with reduced abundances of multiple taxa, reduced emergence of adult insects and reduced species richness, altered community structure and increased leaf litter breakdown rates but no effect on benthic chlorophyll-a. However, despite predictions based on laboratory findings, we found no evidence that the addition of either Mg2+ or Cl- altered the effect of NaHCO3. In semi-natural environments such as mesocosms, and natural environments, organisms are subject to varying temperature and habitat factors, while also interacting with other species and trophic levels (e.g. predation, competition, facilitation), which are absent in single species laboratory tests. Thus, it should not be assumed single-species tests are good predictors of the effects of changing ionic compositions on stream biota in more natural environments.

Can long-term salinity acclimation eliminate the inhibitory effect of salinization on anti-predation defense of Daphnia?

Freshwater salinization, due to road salt and other increased anthropogenic activities, has become a significant threat to freshwater organisms. However, whether freshwater salinization affects the response of aquatic organisms to their predators, especially prey that have been acclimated to salinity environments for a long time, remains unclear. In the present study, we investigated the changes in anti-predator defense of Daphnia magna with and without salinity acclimation at five different salinities (0, 0.6, 0.8, 0.10, and 0.12 M). Results showed that freshwater salinization weakened the induced defense response of D. magna, regardless of whether it had undergone long-term salinity acclimation. Specifically, induced defense traits such as smaller body size, higher relative spine length, more relative reproductive output, and smaller body size neonates disappeared at ≥ 0.08 M salinities. In addition, there were no significant differences in most traits of induced defense strength between D. magna with and without salinity acclimation at the same salinity. Importantly, the integrated induced defense response index decreased with increasing salinity. Our study showed that salinity-tolerant organisms do not recover their induced defense at high salinities, underlining the importance of incorporating interspecific interactions when estimating the effects of freshwater salinization on organisms.

An index for inferring dominant transport pathways of solutes and sediment: Assessing land use impacts with high-frequency conductivity and turbidity sensor data

Land use change threatens aquatic ecosystems through freshwater salinization and sediment pollution. Effective river management requires an understanding of the dominant hydrologic pathways of sediment and solute delivery. To address this, we applied hysteresis analysis, hydrograph separation, and linear regression to hundreds of events across a decade of specific conductance and turbidity data from three streams along a rural-to-urban gradient. Thereafter, we developed an index (β_runoff^') to quantify the relative influence of surface runoff to event-scale suspended sediment generation, where a value of '1' indicates complete alignment of suspended sediment generation with the temporal structure of runoff whereas '0' indicates total alignment with baseflow. Solute hysteresis results showed a predominance of dilution for the rural and mixed-use streams irrespective of road salt presence. On the other hand, urban stream behavior shifted from dilution to flushing following salt application, which was largely driven by greater runoff coefficients and the connectivity of distal solutes to the stream corridor. The newly developed index (β_runoff^') indicated that suspended sediment dynamics were more aligned with runoff in all three streams: rural stream (β_runoff^' = 0.70), mixed stream (β_runoff^' = 0.57), and urban stream (β_runoff^' = 0.64). The relative importance of baseflow to sediment generation grows slightly in urbanizing streams, as impervious surfaces disconnect upland sediment, which would otherwise transport with runoff, while piston-flow baseflow erodes exposed streambanks. Our findings emphasize the need to consider the impact of human modification of the landscape on solute and sediment transport in freshwater systems for effective water quality management. Further, our β_runoff^' index provides a useful tool for assessing the relative influence of surface runoff on event-scale solute or sediment generation in streams, supporting river management and conservation efforts.

Salinization and heavy metal cadmium impair growth but have contrasting effects on defensive colony formation of Scenedesmus obliquus

Driven by anthropogenic activities, freshwater salinization has become an emerging global environmental issue. Recent studies indicate that salinization increases the mobility of heavy metals in soil and causes higher flux into surface waterbodies. The present study assessed the combined effects of salinization (0, 3, 6 PSU) and the heavy metal Cd²⁺ (0, 0.2, 0.4 mg L^-1) on the anti-grazing colony formation and population growth of Scenedesmus obliquus, a common freshwater alga. The results showed that the increase in salinity promoted colony formation of S. obliquus with or without the presence of grazing cues and, in contrast, Cd²⁺ contamination depressed the defensive colony formation of S. obliquus to Daphnia filtrate. The increase in both salinity and Cd²⁺ concentration depressed the population growth of S. obliquus, including impaired photosynthesis and a decreased population growth rate. Salinization moderated the negative effects of Cd²⁺ on defensive colony formation of S. obliquus, suggesting increased absorption of Cd²⁺ ions by a thicker outer layer of the algal cell wall under saltier conditions. As a result, larger defensive colonies of S. obliquus under freshwater salinization may cause higher bioaccumulation of heavy metals by algal cells and heavier influence on zooplankton. This study provides evidence that freshwater salinization could interfere with plankton interactions by affecting algal defense and growth, which may lead to bottom-up cascading effects on freshwater food webs.

Microbial network complexity drives non-linear shift in biodiversity-nutrient cycling in a saline urban reservoir

Aquatic biodiversity is important in mediating ecosystem functioning, contributing to ecosystem sustainability and human wellbeing. However, how microbial network complexity affects the biodiversity-nutrient cycling relationship in saline freshwater ecosystems remains underexplored. Using high-resolution time-series data, we examined the relationships between microeukaryotic-bacterial community network complexity, biodiversity and multi-nutrient cycling in an urban reservoir undergoing a freshwater salinization-desalinization cycle. We found that low microbial diversity enhanced ecosystem multi-nutrient cycling under high salinity stress. In addition, multi-nutrient cycling declined with increased network complexity. Further, we found a non-linear relationship between salinity-induced shifts in the complexity of the microbial network and biodiversity-nutrient cycling (BNC) relationship of keystone taxa, i.e. the strength of the BNC relationship first became weak and then strong with increased network complexity. Together, these results highlighted the significant insight that there is not always positive relationship between biodiversity/network complexity and multi-nutrient cycling, even between network complexity and BNC relationship in real-world ecosystems, suggesting that preserving microbial association is important in aquatic health managing and evaluating the freshwater salinization problem.

A Novel Approach to Developing Thresholds for Total Dissolved Solids Using Standardized and Experimental Toxicity Test Methods

The increasing salinization of freshwater streams from anthropogenic land uses and activities is a growing global environmental problem. Increases in individual ions (such as sodium or chloride) and combined measures such as total dissolved solids (TDS) threaten drinking water supplies, agricultural and economic interests, and the ecological health of freshwater streams. Because the toxicity of high ionic strength waters depends on the specific ion composition, few water quality standards exist to protect freshwater streams from salinization. In the present study, we used a novel approach to develop site-specific and ecologically relevant TDS thresholds for the protection of aquatic life. The first step of the approach was to characterize the ion composition of the waterbody or region of interest and prepare artificial samples to match that composition. Using a combination of standardized toxicity test species and more ecologically relevant field-collected species, toxicity tests were then conducted on these artificial samples prepared at a range of TDS concentrations. The advantage of this approach is that water quality criteria can be developed for easy-to-measure generalized parameters such as TDS while ensuring that the criteria are protective of instream aquatic life and account for the complex interactions of the various ions contributing to salinization. We tested this approach in Sand Branch, Loudoun County, Virginia, USA, where salinization from hard rock mining and urban runoff has impaired aquatic life. Acute and chronic TDS thresholds of 938 and 463 mg/L, respectively, were developed in this stream and used for total maximum daily load development in the watershed. The approach provides a potential model for establishing protective thresholds for other waterbodies impacted by salinization. Environ Toxicol Chem 2022;41:2782-2796. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Stream bacterial diversity peaks at intermediate freshwater salinity and varies by salt type

Anthropogenic freshwater salinization is an emerging and widespread water quality stressor that increases salt concentrations of freshwater, where specific upland land-uses produce distinct ionic profiles. In-situ studies find salinization in disturbed landscapes is correlated with declines in stream bacterial diversity, but cannot isolate the effects of salinization from multiple co-occurring stressors. By manipulating salt concentration and type in controlled microcosm studies, we identified direct and complex effects of freshwater salinization on bacterial diversity in the absence of other stressors common in field studies using chloride salts. Changes in both salt concentration and cation produced distinct bacterial communities. Bacterial richness, or the total number of amplicon sequence variants (ASVs) detected, increased at conductivities as low as 350 μS cm^-1, which is opposite the observations from field studies. Richness remained elevated at conductivities as high as 1500 μS cm^-1 in communities exposed to a mixture of Ca, Mg, and K chloride salts, but decreased in communities exposed to NaCl, revealing a classic subsidy-stress response. Exposure to different chloride salts at the same conductivity resulted in distinct bacterial community structure, further supporting that salt type modulates responses of bacterial communities to freshwater salinization. Community variability peaked at 125-350 μS cm^-1 and was more similar at lower and upper conductivities suggesting possible shifts in deterministic vs. stochastic assembly mechanisms across freshwater salinity gradients. Based on these results, we hypothesize that modest freshwater salinization (125-350 μS cm^-1) lessens hypo-osmotic stress, reducing the importance of salinity as an environmental filter at intermediate freshwater ranges but effects of higher salinities at the upper freshwater range differ based on salt type. Our results also support previous findings that ~300 μS cm^-1 is a biological effect concentration and effective salt management strategies may need to consider variable effects of different salt types associated with land-use.

Road salt is more toxic to wood frog embryos from polluted ponds

Organisms that rely on aquatic habitats in roaded landscapes face a growing array of consequences from pollution, especially due to freshwater salinization. Critically, these consequences can vary from population to population depending on exposure histories and evolutionary responses. Prior studies using transplant and common garden experiments have found that aquatic-stage wood frogs (Rana sylvatica) from roadside populations are less fit in the wild and more sensitive to road salt than their counterparts from woodland populations away from roads. While this pattern is consistent with local maladaptation, unresolved insights into the timing and duration of these effects leave open the possibility that negative outcomes are countered during development. Here, we asked whether the survival disadvantage of roadside wood frogs is stage-specific, and whether this disadvantage reverses before metamorphosis. We used a common garden road salt exposure experiment and a field-based reciprocal transplant experiment to examine differences in survival across life-history stage and with respect to population type. In each experimental context, roadside embryos showed a survival disadvantage relative to woodland embryos, and this disadvantage was not reversed prior to metamorphosis. We also found that salt exposure delayed metamorphosis more strongly for roadside than woodland populations. Together, these results suggest that local maladaptation in aquatic-stage wood frogs is driven by embryonic sensitivity to salt and that roadside populations are further compromised by delayed developmental rates. Future studies should consider which embryonic traits fail to adapt to salt toxicity, and how those traits might correlate with terrestrial trait variation.

Salty water and salty leaf litter alters riparian detrital processes: Evidence from sodium-addition laboratory mesocosm experiments

Terrestrial and freshwater secondary salinization is a global phenomenon arising partially from anthropogenic activities. How low-level direct (e.g., sodium exposure through irrigation runoff) or indirect (e.g., sodium exposure through sodium-enriched leaves as riparian plants uptake sodium that via senescence enters detrital systems) impacts detrital processes in riparia have received little attention. Based on the sodium ecosystem respiration hypothesis, we predicted low-level salinization of an inland mesic riparia would result in increased detrital processing and increased leachate dissolved organic carbon (DOC) and conductivity. Two riparian soil mesocosm experiments tested how low-level salinization affects leachate chemistry and conductivity and riparian decomposition rates and detritivore community structure: 1) direct low-level NaCl deposition in water (weekly additions of 300 ml of 0.05% NaCl or just H₂O (controls)), and 2) indirect low-level NaCl deposition through Na-enriched artificial litter (0.05% NaCl or just H₂O (controls)). After three months, leachate Na⁺ concentrations were 12-fold and 1.5-fold higher in Na-addition than control mesocosms for direct and indirect Na-addition experiments, respectively. Contrary to predictions, decomposition rate was 1.3-fold lower in indirect Na-addition than control mesocosms but invertebrate communities were similar. Decomposition rate did not differ in direct Na-addition experiments, and although invertebrate abundance was lower, diversity was 1.4-fold higher in Na-addition than control mesocosms. Leachate DOC did not differ between Na-addition and control mesocosms for either direct or indirect Na-addition experiments. This study adds to the growing evidence that even low-level Na addition can stress inland mesic terrestrial systems and demonstrates that even Na-enriched detritus alone can induce salt-stress in riparian soil systems. These results suggest that even low-level salinization of riparia can impact riparian ecosystem function and leachate chemistry through direct exposure and indirectly through Na-enriched detritus, a previously overlooked pathway.

Trans-epithelial potential (TEP) response as an indicator of major ion toxicity in rainbow trout and goldfish exposed to 10 different salts in ion-poor water

Freshwater ecosystems are facing increasing contamination by major ions. The Multi-Ion Toxicity (MIT) model, a new tool for risk assessment and regulation, predicts major ion toxicity to aquatic organisms by relating it to a critical disturbance of the trans-epithelial potential (TEP) across the gills, as predicted by electrochemical theory. The model is based on unproven assumptions. We tested some of these by directly measuring the acute TEP responses to a geometric series of 10 different single salts (NaCl, Na₂SO₄, KCl, K₂SO₄, CaCl₂, CaSO₄, MgCl₂, MgSO₄, NaHCO₃, KHCO₃) in the euryhaline rainbow trout (Oncorhynchus mykiss) and the stenohaline goldfish (Carassius auratus) acclimated to very soft, ion-poor water (hardness 10 mg CaCO₃/L). Results were compared to 24-h and 96-h LC50 data from the literature, mainly from fathead minnow (Pimephales promelas). All salts caused concentration-dependent increases in TEP to less negative/more positive values, in patterns well-described by the Michaelis-Menten equation, or a modified version incorporating substrate inhibition. The ΔTEP above baseline became close to a maximum at the 96-h LC50, except for the HCO₃^- salts. Furthermore, the range of ΔTEP values at the LC50 within one species was much more consistent (1.6- to 2.1-fold variation) than the molar concentrations of the different salts at the LC50 (19- to 25-fold variation). ΔTEP responses were related to cation rather than anion concentrations. Overall patterns were qualitatively similar between trout and goldfish, with some quantitative differences, and also in general accord with recently published data on three other species in harder water where ΔTEP responses were much smaller. Blood plasma Na⁺ and K⁺ concentrations were minimally affected by the exposures. The results are in accord with most but not all of the assumptions of the MIT model and support its further development as a predictive tool.

Freshwater salinization increases survival of Escherichia coli and risk of bacterial impairment

Elevated levels of Escherichia coli (E. coli) are responsible for more designated freshwater stream impairments than any other contaminant in the United States. E. coli are intentionally used as a sentinel of fecal contamination for freshwaters because previous research indicates that salt concentrations in brackish or marine waters reduce E. coli survival, rendering it a less effective indicator of public health risks. Given increasing evidence of freshwater salinization associated with upland anthropogenic land-use, understanding the effects on fecal indicators is critical; however, changes in E. coli survival along the freshwater salinity range (≤ 1500 µS cm^-1) have not been previously examined. Through a series of controlled mesocosm experiments, we provide direct evidence that salinization causes E. coli survival rates in freshwater to increase at conductivities as low as 350 µS cm^-1 and peak at 1500 µS cm^-1, revealing a subsidy-stress response across the freshwater-marine continuum. Furthermore, specific base cations affect E. coli survival differently, with Mg²⁺ increasing E. coli survival rates relative to other chloride salts. Further investigation of the mechanisms by which freshwater salinization increases susceptibility to or exacerbates bacterial water quality impairments is recommended. Addressing salinization with nuanced approaches that consider salt sources and chemistry could assist in prioritizing and addressing bacterial water quality management.

The effect of salinity fluctuation in freshwater streams on the fecundity of post-diapause Chironomus dilutus

Much scientific research dedicated to understanding the effects of freshwater salinization caused by road de-icing salts has utilized static exposures, with many tests conducted at winter or spring temperatures. While relevant for lentic ecosystems, pulsed patterns of salinity occur in lotic environments, particularly in summer months where precipitation can decrease elevated salinity levels caused by retention of residual salts. The current study aimed to evaluate the effects of pulsed patterns of salinity on the emergence, sex ratio, and fecundity of Chironomus dilutus over two generations of laboratory exposure. Three road de-icing salt treatments, including a control, modeled after environmental monitoring data of two local streams, were used to determine the ecological effects of periodic declines in salinity on C. dilutus at summer temperatures. No significant effects were observed on emergence success or sex ratios within or across generations, but fecundity of C. dilutus in the high salt treatment was reduced regardless of generation (P < 2e-16), possibly due to increased osmoregulatory stress caused by increased salinities. The intermediate and decreasing salinities may account for the lack of negative effects on emergence success and sex ratios by protecting sensitive life stages. More research is needed on long-term effects of reduced fecundity on population viability. The current study suggests more research using a similar experimental design is needed to fully evaluate the influence of road de-icing salts in lotic environments, as static laboratory exposures may not accurately reflect environmental changes in salinity.

Effects of an hypersaline effluent from an abandoned potash mine on freshwater biofilm and diatom communities

Potash abandoned mines cause severe environmental damage to their bordering environment, with significant impacts on freshwater ecosystems mostly through uncontrolled discharge of hypersaline effluents. This study aimed to evaluate the ecological impact caused by a hypersaline effluent from an abandoned potash mine (Menteroda, Germany) on freshwater biofilms and, specifically, on diatom communities. Biofilm from a pristine stream was exposed under controlled conditions in microcosms to a mining effluent (ME), and its structural (algal biomass, community composition, diatom metrics) and functional (photosynthetic activity, nutrient uptake) responses were evaluated over time and compared with unexposed biofilms used as control. Biofilm exposed to ME showed drastic functional responses after one day of exposure, with a significant decrease in photosynthetic efficiency and nutrient uptake, that were recovered over time. Biofilm exposed to ME showed a progressive increase in diatom metrics (abundance, density and growth rate) over time, compared to the control. However, a significant decrease in diatom species diversity, richness and cell size was also observed in biofilm exposed to ME. This study revealed that the ME affected the biofilm causing short-term functional responses, which were recovered simultaneously with a drastic diatom community structure shift.

Chloride inputs to the North Saskatchewan River watershed: the role of road salts as a potential driver of salinization downstream of North America's northern most major city (Edmonton, Canada)

Multiple anthropogenic activities are driving the salinization of freshwater environments threatening water resources worldwide. Accordingly, this research will first examine the spatial and temporal variability of major ions (i.e. Ca²⁺, Mg²⁺, Na⁺, K⁺, SO₄^2-, CO₃^2-, and HCO₃^-) upstream and downstream of the northernmost major city in North America (Edmonton, Canada). Second, this research will estimate the relative contributions of the major sources of chloride (Cl), the main constituent of road deicers, to the sub-basin around Edmonton. Monthly water quality data was for three sites on the North Saskatchewan River (NSR): Rocky Mountain House (RMH - downstream of the Rocky Mountain headwaters), Devon Bridge (upstream of Edmonton) and Pakan Bridge (downstream of Edmonton). Change ratios investigate the downstream alterations of major ions at Pakan and Devon, relative to RMH. Seasonal Kendall tests examine temporal trends (1987-2017). A mass-balance approach then quantifies the major sources of Cl in the sub-basin of the NSR between Devon and Pakan. Progressing from the Rocky Mountain headwaters (at RMH) to downstream of Edmonton (at Pakan), Cl^- increased by >5.5 times, Na⁺ by 4.8 times and K by 2.7 times. No significant temporal trends for Cl^-, Na⁺ and K⁺ were evident at Devon (upstream of Edmonton), whereas all three significantly increased at Pakan (downstream of Edmonton). Deicers (54%), agriculture (20%), along with waste water treatment plant and industrial effluent (15%) were the largest Cl sources in the NSR Devon-Pakan sub-basin. In total, 77 Gg yr^-1 of Cl (or 6 t km² yr^-1) is added to the Devon-Pakan sub-basin, of which, 43 Gg yr^-1 is retained. Understanding and managing the major drivers of freshwater salinization will be of increasing importance in the 21^st century owing to the potential salinization of freshwater resources in the context of a changing climate.

Combined effects of NaCl and fluoxetine on the freshwater planarian, Schmidtea mediterranea (Platyhelminthes: Dugesiidae)

Increasing salinity levels in freshwaters due to natural and anthropogenic sources pose risk to exposed aquatic organisms. However, there is a paucity of information on how salinity may influence the effects of other chemical stressors especially psychiatric pharmaceuticals. Freshwater planarians which have been suggested as bioindicator species in aquatic habitats were used in this study to evaluate toxic effects of sodium chloride (NaCl) used here as a surrogate for increasing salinity, and its influence on the effects of the antidepressant, fluoxetine. Effects of NaCl on Schmidtea mediterranea were evaluated using survival, regeneration, locomotion, feeding, and reproduction as endpoints. Subsequently, combined effects of NaCl and fluoxetine on planarians' locomotion and reproduction were also evaluated. Result showed that exposure to increased NaCl concentrations is toxic to planarians with 48 and 96 h LC₅₀ of 9.15 and 7.55 g NaCl L^-1 respectively and exposure to sub-lethal concentrations led to reductions in feeding (LOEC of 0.75 g NaCl L^-1 or 1906 μS cm^-1 at 20 °C) and reproduction (LOEC 3.0 g NaCl L^-1 or 5530 μS cm^-1 at 20 °C), delayed head regeneration (LOEC of 1.5 g NaCl L^-1 or 3210 μS cm^-1 at 20 °C), and also slight decreases in locomotor activity. Moreover, some developmental malformations were observed in regenerating planarians, as well as delayed or inhibition of wound healing and degeneration after fissioning and during head regeneration. A significant interaction between fluoxetine and NaCl was observed for locomotor activity and unlike planarians exposed to fluoxetine alone, fissioned planarians and their pieces from the combined exposure treatments were also unable to regenerate missing portions. Results show that S. mediterranea can be highly sensitive to low NaCl concentrations and that this stressor can alter the effects of fluoxetine. The implication of these effects for planarian populations in the natural habitat is discussed as well as the need for more research on the effects of neuroactive pharmaceuticals under relevant exposure scenarios.

Toxicity testing of "eco-friendly" de-icing formulations using Chironomus dilutus

An influx of chloride ions from road de-icing solutions can result in toxicological effects to organisms in terrestrial and aquatic environments. As such, "eco-friendly" de-icing alternatives are sought to mitigate environmental impacts of de-icing impervious surfaces, while maintaining human safety. While many alternative de-icers are economically impractical for municipal use, the residential commercial market is flooded with de-icing formulations claiming to be "eco-friendly". Given the little regulation and guidance that surrounds eco-labeling, the meaning of "eco-friendly" remains unclear in the context of biological systems. The objective of the current study was to determine the toxicity of three "eco-friendly" de-icing formulations to Chironomus dilutus using 10 d toxicity tests. The toxicity of these three formulations was compared to a traditional formulation composed entirely of chloride salts. Two of the "eco-friendly" de-icers demonstrated LC₅₀s of 6.61 and 6.32 g/L, which were similar in toxicity to the traditional sodium chloride formulation with a LC₅₀ 6.29 g/L. The comparable toxicities of these formulations is likely due to the presence of chloride salts in each of the "eco-friendly" de-icers. The third "eco-friendly" formulation, a urea-based de-icer, demonstrated toxicity an order of magnitude higher than that of the traditional formulation with an LC₅₀ of 0.63 g/L. While C. dilutus may not have been the intended endpoint in consideration when marketing these products as "eco-friendly", consideration of how eco-labeling is utilized and the role of environmental scientists in determining the meaning of such claims must be considered to ensure continued and future protection of the environment.

Effects of brine contamination from energy development on wetland macroinvertebrate community structure in the Prairie Pothole Region

Wetlands in the Prairie Pothole Region (PPR) of North America support macroinvertebrate communities that are integral to local food webs and important to breeding waterfowl. Macroinvertebrates in PPR wetlands are primarily generalists and well adapted to within and among year changes in water permanence and salinity. The Williston Basin, a major source of U.S. energy production, underlies the southwest portion of the PPR. Development of oil and gas results in the coproduction of large volumes of highly saline, sodium chloride dominated water (brine) and the introduction of brine can alter wetland salinity. To assess potential effects of brine contamination on macroinvertebrate communities, 155 PPR wetlands spanning a range of hydroperiods and salinities were sampled between 2014 and 2016. Brine contamination was documented in 34 wetlands with contaminated wetlands having significantly higher chloride concentrations, specific conductance and percent dominant taxa, and significantly lower taxonomic richness, Shannon diversity, and Pielou evenness scores compared to uncontaminated wetlands. Non-metric multidimensional scaling found significant correlations between several water quality parameters and macroinvertebrate communities. Chloride concentration and specific conductance, which can be elevated in naturally saline wetlands, but are also associated with brine contamination, had the strongest correlations. Five wetland groups were identified from cluster analysis with many of the highly contaminated wetlands located in a single cluster. Low or moderately contaminated wetlands were distributed among the remaining clusters and had macroinvertebrate communities similar to uncontaminated wetlands. While aggregate changes in macroinvertebrate community structure were observed with brine contamination, systematic changes were not evident, likely due to the strong and potentially confounding influence of hydroperiod and natural salinity. Therefore, despite the observed negative response of macroinvertebrate communities to brine contamination, macroinvertebrate community structure alone is likely not the most sensitive indicator of brine contamination in PPR wetlands.

Seasonal pattern of anthropogenic salinization in temperate forested headwater streams

Salinization of freshwaters by human activities is of growing concern globally. Consequences of salt pollution include adverse effects to aquatic biodiversity, ecosystem function, human health, and ecosystem services. In headwater streams of the temperate forests of eastern USA, elevated specific conductance (SC), a surrogate measurement for the major dissolved ions composing salinity, has been linked to decreased diversity of aquatic insects. However, such linkages have typically been based on limited numbers of SC measurements that do not quantify intra-annual variation. Effective management of salinization requires tools to accurately monitor and predict salinity while accounting for temporal variability. Toward that end, high-frequency SC data were collected within the central Appalachian coalfield over 4 years at 25 forested headwater streams spanning a gradient of salinity. A sinusoidal periodic function was used to model the annual cycle of SC, averaged across years and streams. The resultant model revealed that, on average, salinity deviated approximately ±20% from annual mean levels across all years and streams, with minimum SC occurring in late winter and peak SC occurring in late summer. The pattern was evident in headwater streams influenced by surface coal mining, unmined headwater reference streams with low salinity, and larger-order salinized rivers draining the study area. The pattern was strongly responsive to varying seasonal dilution as driven by catchment evapotranspiration, an effect that was amplified slightly in unmined catchments with greater relative forest cover. Evaluation of alternative sampling intervals indicated that discrete sampling can approximate the model performance afforded by high-frequency data but model error increases rapidly as discrete sampling intervals exceed 30 days. This study demonstrates that intra-annual variation of salinity in temperate forested headwater streams of Appalachia USA follows a natural seasonal pattern, driven by interactive influences on water quantity and quality of climate, geology, and terrestrial vegetation. Because climatic and vegetation dynamics vary annually in a seasonal, cyclic manner, a periodic function can be used to fit a sinusoidal model to the salinity pattern. The model framework used here is broadly applicable in systems with streamflow-dependent chronic salinity stress.

Widespread legacy brine contamination from oil production reduces survival of chorus frog larvae

Advances in drilling techniques have facilitated a rapid increase in hydrocarbon extraction from energy shales, including the Williston Basin in central North America. This area overlaps with the Prairie Pothole Region, a region densely populated with wetlands that provide numerous ecosystem services. Historical (legacy) disposal practices often released saline co-produced waters (brines) with high chloride concentrations, affecting wetland water quality directly or persisting in sediments. Despite the potential threat of brine contamination to aquatic habitats, there has been little research into its ecological effects. We capitalized on a gradient of legacy brine-contaminated wetlands in northeast Montana to conduct laboratory experiments to assess variation in survival of larval Boreal Chorus Frogs (Pseudacris maculata) reared on sediments from 3 local wetlands and a control source. To help provide environmental context for the experiment, we also measured chloride concentrations in 6 brine-contaminated wetlands in our study area, including the 2 contaminated sites used for sediment exposures. Survival of frog larvae during 46- and 55-day experiments differed by up to 88% among sediment sources (Site Model) and was negatively correlated with potential chloride exposure (Chloride Model). Five of the 6 contaminated wetlands exceeded the U.S. EPA acute benchmark for chloride in freshwater (860 mg/L) and all exceeded the chronic benchmark (230 mg/L). However, the Wetland Site model explained more variation in survival than the Chloride Model, suggesting that chloride concentration alone does not fully reflect the threat of contamination to aquatic species. Because the profiles of brine-contaminated sediments are complex, further surveys and experiments are needed across a broad range of conditions, especially where restoration or remediation actions have reduced brine-contamination. Information provided by this study can help quantify potential ecological threats and help land managers prioritize conservation strategies as part of responsible and sustainable energy development.

Chloride and sulphate toxicity to Hydropsyche exocellata (Trichoptera, Hydropsychidae): Exploring intraspecific variation and sub-lethal endpoints

The rivers and streams of the world are becoming saltier due to human activities. In spite of the potential damage that salt pollution can cause on freshwater ecosystems, this is an issue that is currently poorly managed. Here we explored intraspecific differences in the sensitivity of freshwater fauna to two major ions (Cl(-) and SO4(2-)) using the net-spinning caddisfly Hydropsyche exocellata Dufour 1841 (Trichoptera, Hydropsychidae) as a model organism. We exposed H. exocellata to saline solutions (reaching a conductivity of 2.5mScm(-1)) with Cl(-):SO4(2-) ratios similar to those occurring in effluents coming from the meat, mining and paper industries, which release dissolved salts to rivers and streams in Spain. We used two different populations, coming from low and high conductivity streams. To assess toxicity, we measured sub-lethal endpoints: locomotion, symmetry of the food-capturing nets and oxidative stress biomarkers. According to biomarkers and net building, the population historically exposed to lower conductivities (B10) showed higher levels of stress than the population historically exposed to higher conductivities (L102). However, the differences between populations were not strong. For example, net symmetry was lower in the B10 than in the L102 only 48h after treatment was applied, and biomarkers showed a variety of responses, with no discernable pattern. Also, treatment effects were rather weak, i.e. only some endpoints, and in most cases only in the B10 population, showed a significant response to treatment. The lack of consistent differences between populations and treatments could be related to the high salt tolerance of H. exocellata, since both populations were collected from streams with relatively high conductivities. The sub-lethal effects tested in this study can offer an interesting and promising tool to monitor freshwater salinization by combining physiological and behavioural bioindicators.

Spatial and temporal relationships among watershed mining, water quality, and freshwater mussel status in an eastern USA river

The Powell River of southwestern Virginia and northeastern Tennessee, USA, drains a watershed with extensive coal surface mining, and it hosts exceptional biological richness, including at-risk species of freshwater mussels, downstream of mining-disturbed watershed areas. We investigated spatial and temporal patterns of watershed mining disturbance; their relationship to water quality change in the section of the river that connects mining areas to mussel habitat; and relationships of mining-related water constituents to measures of recent and past mussel status. Freshwater mussels in the Powell River have experienced significant declines over the past 3.5 decades. Over that same period, surface coal mining has influenced the watershed. Water-monitoring data collected by state and federal agencies demonstrate that dissolved solids and associated constituents that are commonly influenced by Appalachian mining (specific conductance, pH, hardness and sulfates) have experienced increasing temporal trends from the 1960s through ~2008; but, of those constituents, only dissolved solids concentrations are available widely within the Powell River since ~2008. Dissolved solids concentrations have stabilized in recent years. Dissolved solids, specific conductance, pH, and sulfates also exhibited spatial patterns that are consistent with dilution of mining influence with increasing distance from mined areas. Freshwater mussel status indicators are correlated negatively with dissolved solids concentrations, spatially and temporally, but the direct causal mechanisms responsible for mussel declines remain unknown.