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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Water Quality and Contamination".

Deadline for manuscript submissions: closed (15 October 2022) | Viewed by 29560

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Special Issue Editor

Dr. Christopher Nietch

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Guest Editor

U.S.EPA, Office of Research and Development, Center for Environmental Measurement and Modelling, Watershed and Ecosystem Characterization Division, Watershed Management Branch, Cincinnati, OH, USA
Interests: aquatic systems ecology; stormwater management; water quality modeling; watershed-scale nutrient management; watershed modeling; carbon and nutrient biogeochemistry; ecotoxicology; mesocosm studies; agricultural best management practices; aquatic life criteria

Special Issue Information

Dear Colleagues,

Applied ecology research considers fundamental ecological process and function to inform environmental policy and practice. In the field of water quality management, applied aquatic ecology provides the mechanisms, or causes-and-effects, that characterize the quality of water. Waters cannot be protected or restored without considering and accounting for ecological principles and interactions in the project planning, design, and implementation phases of such effort. Under the rapidly changing climate regime there are numerous interacting ecologies, some yet to be realized, that are increasing the uncertainty of water quality management and affecting the ability to assess the success of management effort along with the confidence that program managers can have that spent funds will result in improvements. In this special issue I am seeking contributions that bring new ecological insight to water quality managment. Contributions might describe how water quality mangement uses aquatic ecology to: enhance engineering design of best management practices; guide the development, implementation, and analysis of policies and programs; establish water treatment processes; set objectives for water use; determine effective strategies for public health risk assessment; or help account for the potential benefits and anticipate unintended consequences of management alternatives.

Dr. Christopher Nietch
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

ecosystem services
harmful algae blooms (HABs)
nutrient management
best management practices (BMPs)
wetlands
water quality benefits
aquatic life criteria
numeric nutrient criteria
mixtures
ecotoxicology
invasive species
public policy
ecological structure and function
point and nonpoint sources

Published Papers (11 papers)

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Research

26 pages, 3438 KiB

Open AccessArticle

Using Single-Species and Whole Community Stream Mesocosm Exposures for Identifying Major Ion Effects in Doses Mimicking Resource Extraction Wastewaters

by Christopher T. Nietch, Nathan J. Smucker, Leslie Gains-Germain, Christopher P. Peck, Stefania Guglielmi, Susanna DeCelles, James Lazorchak, Brent Johnson and Paul Weaver

Water 2023, 15(2), 249; https://0-doi-org.brum.beds.ac.uk/10.3390/w15020249 - 06 Jan 2023

Viewed by 1886

Abstract

Wastewaters and leachates from various inland resource extraction activities contain high ionic concentrations and differ in ionic composition, which complicates the understanding and effective management of their relative risks to stream ecosystems. To this end, we conducted a stream mesocosm dose–response experiment using two dosing recipes prepared from industrial salts. One recipe was designed to generally reflect the major ion composition of deep well brines (DWB) produced from gas wells (primarily Na⁺, Ca²⁺, and Cl⁻) and the other, the major ion composition of mountaintop mining (MTM) leachates from coal extraction operations (using salts dissociating to Ca²⁺, Mg²⁺, Na⁺, SO₄²⁻ and HCO₃⁻)—both sources being extensive in the Central Appalachians of the USA. The recipes were dosed at environmentally relevant nominal concentrations of total dissolved solids (TDS) spanning 100 to 2000 mg/L for 43 d under continuous flow-through conditions. The colonizing native algal periphyton and benthic invertebrates comprising the mesocosm ecology were assessed with response sensitivity distributions (RSDs) and hazard concentrations (HCs) at the taxa, community (as assemblages), and system (as primary and secondary production) levels. Single-species toxicity tests were run with the same recipes. Dosing the MTM recipe resulted in a significant loss of secondary production and invertebrate taxa assemblages that diverged from the control at all concentrations tested. Comparatively, intermediate doses of the DWB recipe had little consequence or increased secondary production (for emergence only) and had assemblages less different from the control. Only the highest dose of the DWB recipe had a negative impact on certain ecologies. The MTM recipe appeared more toxic, but overall, for both types of resource extraction wastewaters, the mesocosm responses suggested significant changes in stream ecology would not be expected for specific conductivity below 300 µS/cm, a published aquatic life benchmark suggested for the region. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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12 pages, 888 KiB

Open AccessArticle

Evaluation of Nitrogen and Carbon Stable Isotopes in Filter Feeding Bivalves and Surficial Sediment for Assessing Aquatic Condition in Lakes and Estuaries

by James L. Lake, Jonathan R. Serbst, Anne Kuhn, Michael Charpentier and Nathan J. Smucker

Water 2022, 14(22), 3712; https://0-doi-org.brum.beds.ac.uk/10.3390/w14223712 - 16 Nov 2022

Cited by 1 | Viewed by 1783

Abstract

Excessive inputs of nitrogen from anthropogenic activities in watersheds can cause detrimental effects to aquatic ecosystems, but these effects can be difficult to determine based solely on nitrogen concentrations because of their temporal variability and the need to link human activities to ecological responses. Here, we (1) tested the use of stable isotopes of nitrogen (δ¹⁵N) and carbon (δ¹³C) in benthic organic matter (BOM) as proxies for isotope ratios of filter feeding bivalves in lakes and estuaries, which can be used as indicators but are harder to sample and often spatially sparse, and (2) evaluated if stable isotope ratios in benthic organic matter could be used to assess impacts from anthropogenic land development of watersheds. The δ¹⁵N in BOM isolated from surficial sediment (δ¹⁵N_BOM) was significantly correlated with δ¹⁵N in filter feeding unionid mussels (Elliptio complanata, δ¹⁵N_UN) from lakes and with hard-shell clams (Mercenaria mercenaria, δ¹⁵N_MM) from estuaries. In lakes, δ¹³C_BOM was significantly correlated with δ¹³C_UN, but δ¹³C_BOM was not significantly correlated with δ¹³C_MM in estuaries. Values of δ¹⁵N_BOM and δ¹⁵N_UN were significantly and positively correlated with increasing amounts of impervious surface, urban land cover, and human populations in watersheds surrounding lakes. In estuaries, δ¹⁵N_BOM was only significantly and positively correlated with greater percent impervious surface in the watersheds. Correlations of δ¹³C_BOM in lakes and estuaries, δ¹³C_UN, and δ¹³C_MM with land use and human population were mostly non-significant or weak. Overall, these results show that δ¹⁵N_BOM can serve as a proxy for δ¹⁵N of filter feeding bivalves in lakes and estuaries and is useful for assessing anthropogenic impacts on aquatic systems and resources. Our study area was limited in size, but our results support further studies to test the application of this sediment stable isotope-based technique for assessing and ranking aquatic resources across broad geographical areas. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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18 pages, 1992 KiB

Open AccessArticle

A Vegetation Assessment of the Kearl Treatment Wetland following Exposure to Oil Sands Process-Affected Water

by Alexander M. Cancelli, Andrea K. Borkenhagen and Asfaw Bekele

Water 2022, 14(22), 3686; https://0-doi-org.brum.beds.ac.uk/10.3390/w14223686 - 15 Nov 2022

Cited by 1 | Viewed by 2004

Abstract

Treatment wetlands have emerged as a potential option for the treatment of oil sands process-affected water (OSPW). The long-term viability of these treatment systems relies, in part, on the health and productivity of wetland vegetation. The aim of this study is to investigate the physiological and community-level effects on wetland vegetation at the Kearl Treatment Wetland (KTW) following exposure to different OSPW sources. Annual vegetation assessments were performed during 2016–2021 to monitor species composition, total percent cover, species richness, species morphology (plant stem density, leaf length, and leaf width), and plant vigor in the KTW. Cattail was found to dominate the deep-water zones whereas water sedge was found to dominate the shallow-water zones of the wetland. Species richness in the KTW decreased with time which is typical of constructed wetlands receiving industrial effluents. No changes in plant stem density of cattails or water sedge were observed; however, leaf length decreased from 2019 to 2021, and leaf width decreased from 2020 to 2021. Plant vigor ratings increased in the KTW each year suggesting that the vegetation does not show any major signs of phytotoxicity from OSPW exposure. These results demonstrate the complex dynamics and resiliency of the vegetative community in treatment wetlands, but continued efforts to monitor plant uptake and accumulation are needed to fully assess the phytotoxic effects of OSPW exposure. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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24 pages, 5353 KiB

Open AccessFeature PaperArticle

Developing Indicators of Nutrient Pollution in Streams Using 16S rRNA Gene Metabarcoding of Periphyton-Associated Bacteria

by Erik M. Pilgrim, Nathan J. Smucker, Huiyun Wu, John Martinson, Christopher T. Nietch, Marirosa Molina, John A. Darling and Brent R. Johnson

Water 2022, 14(15), 2361; https://0-doi-org.brum.beds.ac.uk/10.3390/w14152361 - 30 Jul 2022

Cited by 1 | Viewed by 2338

Abstract

Indicators based on nutrient-biota relationships in streams can inform water quality restoration and protection programs. Bacterial assemblages could be particularly useful indicators of nutrient effects because they are species-rich, important contributors to ecosystem processes in streams, and responsive to rapidly changing conditions. Here, we sampled 25 streams weekly (12–14 times each) and used 16S rRNA gene metabarcoding of periphyton-associated bacteria to quantify the effects of total phosphorus (TP) and total nitrogen (TN). Threshold indicator taxa analysis identified assemblage-level changes and amplicon sequence variants (ASVs) that increased or decreased with increasing TP and TN concentrations (i.e., low P, high P, low N, and high N ASVs). Boosted regression trees confirmed that relative abundances of gene sequence reads for these four indicator groups were associated with nutrient concentrations. Gradient forest analysis complemented these results by using multiple predictors and random forest models for each ASV to identify portions of TP and TN gradients at which the greatest changes in assemblage structure occurred. Synthesized statistical results showed bacterial assemblage structure began changing at 24 µg TP/L with the greatest changes occurring from 110 to 195 µg/L. Changes in the bacterial assemblages associated with TN gradually occurred from 275 to 855 µg/L. Taxonomic and phylogenetic analyses showed that low nutrient ASVs were commonly Firmicutes, Verrucomicrobiota, Flavobacteriales, and Caulobacterales, Pseudomonadales, and Rhodobacterales of Proteobacteria, whereas other groups, such as Chitinophagales of Bacteroidota, and Burkholderiales, Rhizobiales, Sphingomonadales, and Steroidobacterales of Proteobacteria comprised the high nutrient ASVs. Overall, the responses of bacterial ASV indicators in this study highlight the utility of metabarcoding periphyton-associated bacteria for quantifying biotic responses to nutrient inputs in streams. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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23 pages, 6179 KiB

Open AccessFeature PaperArticle

Development of a Risk Characterization Tool for Harmful Cyanobacteria Blooms on the Ohio River

by Christopher T. Nietch, Leslie Gains-Germain, James Lazorchak, Scott P. Keely, Gregory Youngstrom, Emilee M. Urichich, Brian Astifan, Abram DaSilva and Heather Mayfield

Water 2022, 14(4), 644; https://0-doi-org.brum.beds.ac.uk/10.3390/w14040644 - 18 Feb 2022

Cited by 4 | Viewed by 3021

Abstract

A data-driven approach to characterizing the risk of cyanobacteria-based harmful algal blooms (cyanoHABs) was undertaken for the Ohio River. Twenty-five years of river discharge data were used to develop Bayesian regression models that are currently applicable to 20 sites spread-out along the entire 1579 km of the river’s length. Two site-level prediction models were developed based on the antecedent flow conditions of the two blooms that occurred on the river in 2015 and 2019: one predicts if the current year will have a bloom (the occurrence model), and another predicts bloom persistence (the persistence model). Predictors for both models were based on time-lagged average flow exceedances and a site’s characteristic residence time under low flow conditions. Model results are presented in terms of probabilities of occurrence or persistence with uncertainty. Although the occurrence of the 2019 bloom was well predicted with the modeling approach, the limited number of events constrained formal model validation. However, as a measure of performance, leave-one-out cross validation returned low misclassification rates, suggesting that future years with flow time series like the previous bloom years will be correctly predicted and characterized for persistence potential. The prediction probabilities are served in real time as a component of a risk characterization tool/web application. In addition to presenting the model’s results, the tool was designed with visualization options for studying water quality trends among eight river sites currently collecting data that could be associated with or indicative of bloom conditions. The tool is made accessible to river water quality professionals to support risk communication to stakeholders, as well as serving as a real-time water data monitoring utility. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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21 pages, 2209 KiB

Open AccessArticle

Assessing the Impacts of Chloride and Sulfate Ions on Macroinvertebrate Communities in Ohio Streams

by Robert Miltner

Water 2021, 13(13), 1815; https://0-doi-org.brum.beds.ac.uk/10.3390/w13131815 - 30 Jun 2021

Cited by 8 | Viewed by 3085

Abstract

Salinization of freshwaters is a growing concern, especially in urban catchments. Existing aquatic life criteria for chloride (230 mg/L; a US standard) or total dissolved solids (1500 mg/L; specific to Ohio) do not protect sensitive species, and standards for sulfate have yet to be promulgated on the national level. To help identify water quality thresholds for protection and restoration, species sensitivity distributions were compiled for chloride and sulfate based on field observations of macroinvertebrate communities co-located with water quality samples obtained from rivers and streams throughout Ohio. Additionally, attainment of biological benchmarks for macroinvertebrate communities found in headwater streams were modeled against chloride and sulfate using Bayesian logistic regression. The hazard concentration based on statewide data for chloride was 52 mg/L. The hazard concentration for sulfate based on data from the Western Allegheny Plateau ecoregion was 152 mg/L. The median effect levels from logistic regression for chloride and sulfate varied by ecoregion. Mayfly taxa were disproportionately represented in taxa comprising the lower 5th percentile of the species sensitivity distributions for chloride. However, logistic regression models of individual taxa response (as presence/absence) revealed that some taxa considered sensitive to pollution in general were highly tolerant of chloride. For 166 taxa showing directional response to chloride, 91 decreased and 75 increased. For the 97 individual taxa showing directional responses to sulfate, 81 decreased. Of the 16 taxa showing an increase, 6 are considered tolerant of pollution, 9 facultative and 1 moderately intolerant, the latter being taxa in the dipteran family Tipulidae. The hazard concentrations are useful as protective thresholds for existing high-quality waters. The logistic regression model of attainment can be used to inform management goals conditional on site-specific information. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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20 pages, 624 KiB

Open AccessFeature PaperArticle

A Novel Thin-Film Technique to Improve Accuracy of Fluorescence-Based Estimates for Periphytic Biofilms

by Leon Katona, Yvonne Vadeboncoeur, Christopher T. Nietch and Katie Hossler

Water 2021, 13(11), 1464; https://0-doi-org.brum.beds.ac.uk/10.3390/w13111464 - 23 May 2021

Viewed by 1876

Abstract

Recent studies suggest that photophysiological parameters for intact substrates with depth (e.g., periphytic biofilms, microphytobenthos) are overestimated by pulse-amplitude modulated (PAM) fluorometry. This overestimation results from depth-integration effects, following the activation of deeper photosynthesizing layers by an attenuated light signal. To mitigate this error, we propose a novel slide-based thin-film technique in which fluorescence is measured on a vertically representative subsample of the biofilm, spread evenly on a microscope slide. We compared bias and precision for photosynthetic parameters estimated through conventional PAM fluorometry on intact biofilms and through our novel slide-based technique, both theoretically and empirically. Numerical simulations confirmed the consistent overestimation of key parameters for intact biofilms, with relative errors up to 145%, compared to, at most, 52% on thin films. Paired empirical observations likewise demonstrated that estimates based on intact biofilms were consistently higher (up to 248%,

p < 0.001

) than estimates from thin films. Numerical simulation suggested greater precision with the slide-based technique for homogeneous biofilms, but potentially less precision for heterogeneous biofilms with improper subsampling. Our empirical comparison, however, demonstrated some improvement in precision with the slide-based technique (e.g., the coefficient of variation for the maximum electron transport rate was reduced 30%,

p = 0.009

). We recommend the use of the slide-based technique, particularly for biofilms that are thick or have small light attenuation coefficients. Care should be taken, however, to obtain vertically representative subsamples of the biofilm for measurement. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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16 pages, 2770 KiB

Open AccessArticle

Physiological, Developmental, and Biomarker Responses of Zebrafish Embryos to Sub-Lethal Exposure of Bendiocarb

by Gyöngyi Gazsi, Zsolt Czimmerer, Bence Ivánovics, Izabella Roberta Berta, Béla Urbányi, Zsolt Csenki-Bakos and András Ács

Water 2021, 13(2), 204; https://0-doi-org.brum.beds.ac.uk/10.3390/w13020204 - 16 Jan 2021

Cited by 11 | Viewed by 2784

Abstract

Bendiocarb is a broad-spectrum insecticide recommended for malaria control by the World Health Organization (WHO). Still, bendiocarb poses a toxic risk to populations of nontargeted aquatic organisms. Thus, our study was aimed to evaluate the sub-lethal effects of bendiocarb exposure on zebrafish (Danio rerio) embryos by assessing of physiological, developmental, and biochemical parameters. Bendiocarb-induced adverse effects on embryonic development, larval growth, heart rate, changes in phase II detoxifying enzyme glutathione-S-transferase (GST) activity, oxidative stress-related enzyme activities (superoxide dismutase (SOD), catalase (CAT)), and the damage-linked biomarker lipid peroxidation (LPO) in early life stage zebrafish were investigated. Our results highlight that the selected nonlethal concentrations (96 h median lethal concentration in this study was 32.52 mg/L⁻¹) of bendiocarb inflicted adverse effects resulting in embryo deformities (96 h EC₅₀ = 2.30 mg L⁻¹), reduced body- and notochord length (above 0.75 and 0.39 mg L⁻¹ bendiocarb concentrations at 96 hpf, respectively), oxidative stress, and altered heart rate (above 0.4 mg L⁻¹ at 48 hpf) in the studied model system. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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21 pages, 5318 KiB

Open AccessArticle

Characterization of Antibiotic Resistance and Metal Homeostasis Genes in Midwest USA Agricultural Sediments

by Michael R. Brooker, William A. Arnold, Jill F. Kerrigan, Timothy M. LaPara, Jonathan D. Witter and Paula J. Mouser

Water 2020, 12(9), 2476; https://0-doi-org.brum.beds.ac.uk/10.3390/w12092476 - 04 Sep 2020

Cited by 2 | Viewed by 2079

Abstract

Microbial antibiotic resistance is a naturally occurring phenomenon that has grown in part with the use of antibiotics in agricultural operation. There are also known connections between genes for metal homeostasis and antibiotic resistance, and either antibiotics or metals may select for both kinds of genes. Antibiotics, metals, and their associated genes have the potential to enter agricultural drainage channels and migrate to downstream locations through receiving water bodies. A relatively new agricultural best management practice—the two-stage channel design—functions by sequestering sediments and dissolved constituents as they flow through agricultural ditches from surface runoff and tile drainage discharge. Sedimentation in agricultural watersheds may entrap aggregate pollutants including antibiotics, metals, and associated resistance genes before transport into the drainage system. Here, we characterized the abundance and diversity of 22 antibiotic resistance and metal homeostasis genes in three two-stage channels that had self-developed in an area dominated by agricultural land use. Additionally, we analyzed the sediments for 17 antibiotics and nine metals that could affect the selection of these genes. In these rural systems that drain into Lake Erie, the abundance of antibiotic resistance and metal homeostasis genes were on the lower end of ranges (e.g., <10⁶ gene copies g⁻¹ of intI1) reported in other riverine and lake systems, with only five genes—intI1, aacA, mexB, cadA, and merA—differing significantly between sites. The diversity of antibiotic resistance and metal homeostasis genes for these sediment samples were largely similar to other human impacted environments. Few antibiotics were detected in two stage channel sediments, with concentrations below the quantifiable limits (<0.02–34.5 µg kg⁻¹ soil) in most cases. Likewise, metals were present at what could be considered background concentrations. Despite serving as important drainage channel features in a region dominated by agricultural land use, results serve as an important baseline reference against which other monitoring studies can be compared to assess the perturbation of antibiotics and metals on agricultural channel sediments. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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21 pages, 2574 KiB

Open AccessArticle

Drivers of Benthic Macroinvertebrate Assemblages in Equatorial Alpine Rivers of the Rwenzoris (Uganda)

by Peace S.L. Musonge, Pieter Boets, Koen Lock and Peter L.M. Goethals

Water 2020, 12(6), 1668; https://0-doi-org.brum.beds.ac.uk/10.3390/w12061668 - 11 Jun 2020

Cited by 15 | Viewed by 3690

Abstract

The Sub-Saharan alpine freshwater biodiversity is currently impacted by human settlements, climate change, agriculture, and mining activities. Because of the limited biodiversity studies in the region, a better understanding is needed of the important environmental variables affecting macroinvertebrate assemblages. In this paper, macroinvertebrate diversity responses to 18 environmental variables were studied at 30 sites along unique Rwenzori rivers at the equator in Uganda. We hypothesized that anthropogenic disturbance and local environmental variables affect macroinvertebrate diversity, irrespective of altitudinal gradients. Based on altitude and climate, the sites were subdivided into three altitude groups consisting of 10 sites each: upstream (US) 1400–1600 m.a.s.l.; midstream (MS) 1091–1399 m.a.s.l., and downstream (DS) 900–1090 m.a.s.l. A total of 44 macroinvertebrate families and 1623 individuals were identified. The macroinvertebrate diversity patterns were influenced by temperature, altitude, and latitude. Regression analysis revealed that temperature and nickel, were negative predictors of taxa richness. Nickel, which is released by mining activity, is detrimental to aquatic communities in Sub-Saharan alpine ecosystems. Significant longitudinal variation in macroinvertebrate diversity was observed between the sites, which were also affected by mineral and temperature gradients. Our study highlights the need for long-term monitoring in this region to detect and reduce the threats to river biodiversity from anthropogenic activity. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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14 pages, 728 KiB

Open AccessArticle

Uptake of Sulfate from Ambient Water by Freshwater Animals

by Michael B. Griffith, James M. Lazorchak and Herman Haring

Water 2020, 12(5), 1496; https://0-doi-org.brum.beds.ac.uk/10.3390/w12051496 - 23 May 2020

Cited by 3 | Viewed by 2553

Abstract

To better understand how the sulfate (SO₄²⁻) anion may contribute to the adverse effects associated with elevated ionic strength or salinity in freshwaters, we measured the uptake and efflux of SO₄²⁻ in four freshwater species: the fathead minnow (Pimephales promelas, Teleostei: Cyprinidae), paper pondshell (Utterbackia imbecillis, Bivalvia: Unionidae), red swamp crayfish (Procambarus clarkii, Crustacea: Cambaridae), and two-lined mayfly (Hexagenia bilineata, Insecta: Ephemeridae). Using δ(³⁴S/³²S) stable isotope ratios and the concentrations of S and SO₄²⁻, we measured the SO₄²⁻ influx rate (J_in), net flux (J_net), and efflux rate (J_out) during a 24 h exposure period. For all four species, the means of J_in for SO₄²⁻ were positive, and J_in was significantly greater than 0 at both target SO₄²⁻ concentrations in the fish and mollusk and at the lower SO₄²⁻ concentration in the crayfish. The means of J_out and J_net were much more variable than those for J_in, but several species by target SO₄²⁻ concentration combinations for J_out and J_net, were negative, which suggests the net excretion of SO₄²⁻ by the animals. The results of our experiments suggest a greater regulation of SO₄²⁻ in freshwater animals than has been previously reported. Full article

(This article belongs to the Special Issue Applied Ecology Research for Water Quality Management)

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