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USGS2022

Next-generation lampricides: A three-stage process to develop improved control tools for invasive sea lamprey

Successful integrated management of the invasive predatory sea lamprey ( Petromyzon marinus ) in the Laurentian Great Lakes of North America is owed largely to the long history of beneficial use of two lampricides: 3-trifluoromethyl-4-nitrophenol (TFM) and 2′,5-dichloro-4′-nitrosalicylanilide (niclosamide). Ensuring continued successful sea lamprey control necessitates consideration of possible next-generation lampricides to supplement or replace current lampricides. This review identifies fifteen hallmarks of success for current lampricides to be used as design criteria in a search for next-generation lampricides. A three-stage research approach is outlined. Targeted research using omics, computer modelling, and high-throughput technology to define molecular mechanisms and high probability molecular targets for sea lamprey selective toxic action is crucial to prioritizing chemical candidates. Targeted delivery or identifying synergists to existing or new lampricides can provide increased efficiency and reduced environmental impact. Ultimate development of next-generation lampricides will rely on traditional toxicity testing methodologies to ensure safety and regulatory compliance.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2013

Agricultural sources of contaminants of emerging concern and adverse health effects on freshwater fish

Agricultural contaminants of emerging concern (CECs) are generally thought of as certain classes of chemicals associated with animal feeding and production facilities. Veterinary pharmaceuticals used in animal food production systems represent one of the largest groups of CECs. In our review, we discuss the extensive increase in use of antibiotics in animal feeding operations (AFOs) around the world. AFOs are a major consumer of antibiotics and other veterinary pharmaceuticals and over the past decade there has been growing information on the occurrence, release, and fate of CECs from animal food production operations, including the application of pharmaceutical-containing manure to agricultural fields and releases from waste lagoons. Concentrations of CECs in surface and ground water in proximity to AFOs correspond to their presence in the AFO wastes. In many cases, the environmental concentrations of agriculturally-derived CECs are below toxicity thresholds. Hormones and hormone replacement compounds are a notable exception, where chemical concentrations near AFOs can exceed concentrations known to cause adverse effects on endocrine-related functions in fish. In addition, some agricultural pesticides, once thought to be safe to non-target organisms, have demonstrated endocrine-related effects that may pose threats to fish populations in agricultural regions. That is, we have pesticides with emerging concerns, thus, the concern is emerging and not necessarily the chemical. In this light, one must consider certain agricultural pesticides to be included in the list of CECs. Even though agricultural pesticides are routinely evaluated in regulatory testing schemes which have been used for decades, the potential hazards of some pesticides have only recently been emerging. Emerging concerns of pesticides in fish include interference with hormone signaling pathways; additive (or more than additive) effects from pesticide mixtures; and adverse population-level effects at concentrations below predicted toxicity thresholds. Consequently, there is a need to evaluate the environmental concerns related to pesticide exposures to fish populations based on current biological and toxicological techniques. This presentation reviews some of the agricultural chemicals that have emerged as contaminants of concern and potentially threaten fish populations in agricultural watersheds.

Conference Paper↗

USGS2010

Microbial oxidation of arsenite in a subarctic environment: diversity of arsenite oxidase genes and identification of a psychrotolerant arsenite oxidiser

Arsenic is toxic to most living cells. The two soluble inorganic forms of arsenic are arsenite (+3) and arsenate (+5), with arsenite the more toxic. Prokaryotic metabolism of arsenic has been reported in both thermal and moderate environments and has been shown to be involved in the redox cycling of arsenic. No arsenic metabolism (either dissimilatory arsenate reduction or arsenite oxidation) has ever been reported in cold environments (i.e. < 10°C). Results : Our study site is located 512 kilometres south of the Arctic Circle in the Northwest Territories, Canada in an inactive gold mine which contains mine waste water in excess of 50 mM arsenic. Several thousand tonnes of arsenic trioxide dust are stored in underground chambers and microbial biofilms grow on the chamber walls below seepage points rich in arsenite-containing solutions. We compared the arsenite oxidisers in two subsamples (which differed in arsenite concentration) collected from one biofilm. 'Species' (sequence) richness did not differ between subsamples, but the relative importance of the three identifiable clades did. An arsenite-oxidising bacterium (designated GM1) was isolated, and was shown to oxidise arsenite in the early exponential growth phase and to grow at a broad range of temperatures (4-25°C). Its arsenite oxidase was constitutively expressed and functioned over a broad temperature range. Conclusions : The diversity of arsenite oxidisers does not significantly differ from two subsamples of a microbial biofilm that vary in arsenite concentrations. GM1 is the first psychrotolerant arsenite oxidiser to be isolated with the ability to grow below 10°C. This ability to grow at low temperatures could be harnessed for arsenic bioremediation in moderate to cold climates.

BMC Microbiology↗

USGS2009

White phosphorus at Eagle River Flats, Alaska: A case history of waterfowl mortality

White phosphorus has a limited distribution in the environment because it only occurs where it has been directly used by humans. It is not transported aerially for any distance and, due to its density, has a limited ability to disperse through water. Therefore, it is not a contaminant of broad-scale concern. However, where it does occur, it can cause substantial mortality or critically injure populations of waterfowl. This chronic harm includes impaired liver and kidney functioning, decreased respiratory efficiency, increased susceptibility to predation, loss of body mass, general weakening and malaise, and curtailment of reproductive functioning. Lethal effects occur around 3---4 mg/kg or approximately 3-6 ingested particles; sublethal effects can occur with ingestion of as little as a single particle. The impact of P4 on waterfowl populations nesting around ERF has never been estimated. Even if direct mortality on ERF could be estimated accurately in ducks, the delayed toxicity of P4 in swans (and presumably other species that use small grit size) and the potential for swans to fly away after ingesting a lethal dose of P4 could greatly underestimate the overall mortality. Inhibition of laying, reduced fertility and hatchability, and teratogenesis in hens ingesting even a small amount of P4 could potentially have, an effect on populations greater than that exhibited by direct mortality. Predators such as bald eagles and gulls are also at risk due to the toxicity of pelletized, dissolved, and assimilated P4 in prey organisms. Although the U.S. Army stopped using P4 in wetlands in 1993 and remediation efforts have been underway since 1995, waterfowl mortality is expected to continue for several more years. Because Eagle River Flats is only one of several sites where P4 has been found in wetland conditions, further biological investigation is warranted at these other sites.

Book chapter↗

USGS2010

Ecotoxicology of organic contaminants to amphibians

The effects of organic contaminants on amphibians are poorly known but of considerable interest. These contaminants include the highly toxic dioxins and furans as well as PCBs, PAHs and organochlorine pesticides. Although these compounds may have lower acute toxicity than dioxins and furans, they have been implicated in several problems associated with genotoxicity, endocrine disruption, malformations and reduced growth. There is evidence that amphibian tadpoles bioaccumulate these organic compounds and may have biological concentrating factors ranging in the hundreds. This chapter reviews what is known about the effects and concentrations of organic contaminants in amphibians and provides recommendations for further research

Book chapter↗

USGS2007

Impacts of waste from concentrated animal feeding operations on water quality

Waste from agricultural livestock operations has been a long-standing concern with respect to contamination of water resources, particularly in terms of nutrient pollution. However, the recent growth of concentrated animal feeding operations (CAFOs) presents a greater risk to water quality because of both the increased volume of waste and to contaminants that may be present (e.g., antibiotics and other veterinary drugs) that may have both environmental and public health importance. Based on available data, generally accepted livestock waste management practices do not adequately or effectively protect water resources from contamination with excessive nutrients, microbial pathogens, and pharmaceuticals present in the waste. Impacts on surface water sources and wildlife have been documented in many agricultural areas in the United States. Potential impacts on human and environmental health from long-term inadvertent exposure to water contaminated with pharmaceuticals and other compounds are a growing public concern. This workgroup, which is part of the Conference on Environmental Health Impacts of Concentrated Animal Feeding Operations: Anticipating Hazards-Searching for Solutions, identified needs for rigorous ecosystem monitoring in the vicinity of CAFOs and for improved characterization of major toxicants affecting the environment and human health. Last, there is a need to promote and enforce best practices to minimize inputs of nutrients and toxicants from CAFOs into freshwater and marine ecosystems.

Environmental Health Perspectives↗

USGS2015

Geochemical legacies and the future health of cities: A tale of two neurotoxins in urban soils

The past and future of cities are inextricably linked, a linkage that can be seen clearly in the long-term impacts of urban geochemical legacies. As loci of population as well as the means of employment and industry to support these populations, cities have a long history of co-locating contaminating practices and people, sometimes with negative implications for human health. Working at the intersection between environmental processes, communities, and human health is critical to grapple with environmental legacies and to support healthy, sustainable, and growing urban populations. An emerging area of environmental health research is to understand the impacts of chronic exposures and exposure mixtures—these impacts are poorly studied, yet may pose a significant threat to population health. Acute exposure to lead (Pb), a powerful neurotoxin to which children are particularly susceptible, has largely been eliminated in the U.S. and other countries through policy-based restrictions on leaded gasoline and lead-based paints. But the legacy of these sources remains in the form of surface soil Pb contamination, a common problem in cities and one that has only recently emerged as a widespread chronic exposure mechanism in cities. Some urban soils are also contaminated with another neurotoxin, mercury (Hg). The greatest human exposure to Hg is through fish consumption, so eating fish caught in urban areas presents risks for toxic Hg exposure. The potential double impact of chronic exposure to these two neurotoxins is pronounced in cities. Overall, there is a paradigmatic shift from reaction to and remediation of acute exposures towards a more nuanced understanding of the dynamic cycling of persistent environmental contaminants with resultant widespread and chronic exposure of inner-city dwellers, leading to chronic toxic illness and disability at substantial human and social cost.

Indiana↗

USGS2022

Assembling a safe and effective toolbox for integrated flea control and plague mitigation: Fipronil experiments with prairie dogs

Background Plague, a widely distributed zoonotic disease of mammalian hosts and flea vectors, poses a significant risk to ecosystems throughout much of Earth. Conservation biologists use insecticides for flea control and plague mitigation. Here, we evaluate the use of an insecticide grain bait, laced with 0.005% fipronil (FIP) by weight, with black-tailed prairie dogs (BTPDs, Cynomys ludovicianus ). We consider safety measures, flea control, BTPD body condition, BTPD survival, efficacy of plague mitigation, and the speed of FIP grain application vs. infusing BTPD burrows with insecticide dusts. We also explore conservation implications for endangered black-footed ferrets ( Mustela nigripes ), which are specialized predators of Cynomys . Principal findings During 5- and 10-day laboratory trials in Colorado, USA, 2016–2017, FIP grain had no detectable acute toxic effect on 20 BTPDs that readily consumed the grain. During field experiments in South Dakota, USA, 2016–2020, FIP grain suppressed fleas on BTPDs for at least 12 months and up to 24 months in many cases; short-term flea control on a few sites was poor for unknown reasons. In an area of South Dakota where plague circulation appeared low or absent, FIP grain had no detectable effect, positive or negative, on BTPD survival. Experimental results suggest FIP grain may have improved BTPD body condition (mass:foot) and reproduction (juveniles:adults). During a 2019 plague epizootic in Colorado, BTPDs on 238 ha habitat were protected by FIP grain, whereas BTPDs were nearly eliminated on non-treated habitat. Applications of FIP grain were 2–4 times faster than dusting BTPD burrows. Significance Deltamethrin dust is the most commonly used insecticide for plague mitigation on Cynomys colonies. Fleas on BTPD colonies exhibit the ability to evolve resistance to deltamethrin after repeated annual treatments. Thus, more tools are needed. Accumulating data show orally-delivered FIP is safe and usually effective for flea control with BTPDs, though potential acute toxic effects cannot be ruled out. With continued study and refinement, FIP might be used in rotation with, or even replace deltamethrin, and serve an important role in Cynomys and black-footed ferret conservation. More broadly, our stepwise approach to research on FIP may function as a template or guide for evaluations of insecticides in the context of wildlife conservation.

South Dakota↗

USGS2025

Neonicotinoid exposure causes behavioral impairment and delayed mortality of the federally threatened American burying beetle, Nicrophorus americanus

Among the most immediate drivers of American burying beetle ( Nicrophorus americanus Olivier) declines, nontarget toxicity to pesticides is poorly understood. Acute, episodic exposure to neonicotinoid insecticides at environmentally relevant concentrations is linked to negative impacts on beneficial terrestrial insect taxa. Beyond mortality, behavioral indicators of toxicity are often better suited to assess sublethal effects of residual concentrations in the environment. First, Nicrophorus spp. congeners were used to generate and identify a low-dose exposure rate (lethal dose 10%; LD10) from an acute, 24-hour exposure and the concentration-series was confirmed by LC–MS/MS. Next, we evaluated the effects of single and repeated low-dose (LD10 = 58.9 ng/beetle) imidacloprid exposure on N . americanus behavior (10 minutes post-dose) and mortality (10 days post-dose). Behavior parameters were analyzed using EthoVision-XT. Control N . americanus were significantly less mobile, demonstrating death-feigning, an anti-predator behavior. Single LD10 dosed N . americanus were hyperactive, traveling over 4 times farther (total distance; p = 0.03) and faster (mean velocity; p = 0.02) than controls. Single and repeated LD10 dosed N . americanus extended their wings without taking flight and flipped on their backs. All control N . americanus survived 10 days post-dose; single LD10 and repeated LD10 exhibited 30% and 50% mortality, respectively. A single LD10 exposure event was sufficient to significantly elicit greater movement and high predation risk behaviors, whereas repeated LD10 exposure did not worsen behavioral impairment but increased mortality over time. Collectively, generalized linear mixed effects models indicated that distance traveled, velocity, and extended wings were significant predictors of mortality. Recently reclassified, the federally threatened N . americanus may be at greater risk to insecticide exposure than previously thought and vulnerable to episodic, low-dose neonicotinoid exposure.

Nebraska, Oklahoma↗

USGS1993

A receptor binding assay applied to monitoring the neurotoxicity of parathion to Peromyscus after oral exposure

Many naturally occurring toxins, as well as pesticides, metals, and other compounds that occur in our environment from anthropogenic activities, stimulate or antagonize neuro-receptors to produce acute and/or chronic toxicities. Recent advances in laboratory instrumentation and the availability of a variety of radiolabeled ligands and type-specific drugs for numerous receptors make it possible to easily screen large numbers of samples and detect changes in sensitivity and density of receptor types and subtypes. A receptor binding assay for examining the chronic dietary toxicity of parathion will be used as a model to describe the methodology.

Book chapter↗

USGS2012

A perspective on modern pesticides, pelagic fish declines, and unknown ecological resilience in highly managed ecosystems

Pesticides applied on land are commonly transported by runoff or spray drift to aquatic ecosystems, where they are potentially toxic to fishes and other nontarget organisms. Pesticides add to and interact with other stressors of ecosystem processes, including surface-water diversions, losses of spawning and rearing habitats, nonnative species, and harmful algal blooms. Assessing the cumulative effects of pesticides on species or ecological functions has been difficult for historical, legal, conceptual, and practical reasons. To explore these challenges, we examine current-use (modern) pesticides and their potential connections to the abundances of fishes in the San Francisco Estuary (California). Declines in delta smelt (Hypomesus transpacificus), Chinook salmon (Oncorhynchus tshawytscha), and other species have triggered mandatory and expensive management actions in the urbanizing estuary and agriculturally productive Central Valley. Our inferences are transferable to other situations in which toxics may drive changes in ecological status and trends.

California↗

USGS2005

Xenobiotics: Chapter 15

While a number of compounds have been reported as toxic to amphibians, until recently, there have been conspicuously few ecotoxicological studies concerning amphibians. Studies are now focusing on the effects of xenobiotics on amphibians, an interest likely stimulated by widespread reports of amphibian declines. It has been speculated that chemical contamination may be partially to blame for some documented amphibian declines, by disrupting growth, reproduction, and behavior. However, evidence that xenobiotics are directly to blame for population declines is sparse because environmental concentrations are typically not great enough to generate direct mortality. Although the effects of environmental contaminants on the amphibian immune system are currently unknown, it is possible that exposure to stressors such as organic pollutants (which enter ecosystems in the form of pesticides) may depress immune system function, thus allowing greater susceptibility to fungal infections. This chapter discusses toxicity testing for xenobiotics and presents the results of a study that has focused on the subtle effects of sublethal concentrations of the chemical carbaryl on tadpoles.

Book chapter↗

USGS2017

Pharmaceuticals and personal care products (PPCPs) are ecological disrupting compounds (EcoDC)

Pharmaceuticals and personal care products (PPCPs) are ubiquitous in freshwater ecosystems worldwide and are recognized as contaminants of concern. Currently, contaminants of concern are classified for their persistence, bioaccumulation, and toxicity (PBT criteria). PPCPs are not classified as persistent organic pollutants (POPs), although some PPCPs share characteristics similar to POPs. For example, PPCPs are known to be pseudopersistent due to constant discharge into the environment, often at low concentrations. At commonly reported environmental concentrations, PPCPs are rarely toxic, but the ability of these compounds to disrupt ecological processes and functions in freshwater ecosystems is often overlooked. Herein we briefly summarize recent studies highlighting the potential ecological effects of PPCPs, including effects on key ecological processes (e.g. primary productivity and community respiration), and we propose that appropriate screening for harmful effects of PPCPs in surface waters should be expanded to include Ecologically Disrupting Compounds (EcoDC) in addition to the established PBT criteria.

Elementa: Science of the Anthropocene↗

USGS1948

New compounds for the control of bacterial gill disease

BACTERIAL GILL DISEASE, a common epizootic among hatchery fish, can be controlled by copper sulphate dips, as stated by Davis (1945), or by prolonged treatments with Roccal, as noted by Fish (1947). The use of copper sulphate is not without danger because of variation in toxicity according to the hardness of the particular water supply; also, the toxicity and efficacy of Roccal have varied considerably in different lots. Neither copper sulphate nor Roccal will cure in one treatcent a well-established epizootic of bacterial gill disease. For these reasons, a series of new disinfectants has been tested in the laboratory in an attempt to find a more effective cure and preventive for bacterial Eill disease. One of these tested, pyridylmercuric acetate, was suggested by Wan Horn and Katz (1946).

Progressive Fish-Culturist↗

USGS1970

Experimental control of Columnaris sisease with a new Nitrofuran drug, P-7138

P-7138 is a new, broad-spectrum, vinylogous, nitrofuran chemotherapeutic that was developed specifically for treating fish diseases. Although it can be added to the diet of fish, therapeutic tissue levels can be obtained in eels (Anguilla japonica) and goldfish (Carassius auratur) by absorption of the drug directly from the water. Moreover, the drug is eliminated from the tissues within hours and shows a low level of toxicity (Shimizu and Takase 1967). The purpose of the present study was to deterime 910 the efficacy of P-7138 in controlling an experimentally induced Chrondrococcus columnaris infection, 920 the absorption and elimination rates, and 930 the degree of acute and chronic toxicity to coho salmon (Oncorhynchus kitutch).

Progressive Fish-Culturist↗

USGS1970

An obscure disease of rainbow trout

An annul mortality among Rainbow Trout (Salmo gairdneri) has plagued the Shelton Hatchery of the Washington State Department of Game for the last several years. No infectious agent could be isolated from the moribund fish, but histopathologica1 changes in the liver of 1-month-old fish suggested the presence of a toxic substance. Scoliosis in 3-month-old fish suggested a possible deficiency in vitamin C. With this background in mind, we designed studies to determine the nature and source of possible toxicants and the role of vitamin C deficiency in the etiology of this disease.

Progressive Fish-Culturist↗

USGS1996

Prevention of zebra mussel infestation and dispersal during aquaculture operations

The zebra mussel Dreissena polymorpha , an exotic invasive species, poses a major threat to North American fish management programs and the aquaculture industry. Fish hatcheries may become infected with zebra mussels from a variety of sources, including the water supply, fish shipments, boats, and equipment. The hatcheries could then serve as agents for the overland dispersal of zebra mussels into stocked waters and to other fish hatcheries. We evaluated the effectiveness and safety of aquaculture chemicals for use in controlling zebra mussels in fish hatcheries and preventing dispersal of veligers during fish transport. Chemicals were evaluated for use in fish transport and as disinfectants for ponds and equipment. Standardized static toxicity tests were conducted with representative species of warmwater, coolwater, and coldwater fishes and with larval (3‐d‐old veligers), early juvenile (settling larvae), and adult zebra mussels. Chemical concentrations and exposure durations were based on recommended treatment levels for fish, eggs, and ponds. Recommended treatment levels were also exceeded, if necessary, to establish lethal levels for zebra mussels of different developmental stages. Our results indicate that some chemicals currently in use in hatcheries may be effective for controlling zebra mussels in various operations. Chloride salts were the safest and most effective therapeutants tested for use in fish transport. The toxicity of chloride salts to fish varied among species and with temperature: only one treatment regime (sodium chloride at 10,000 mg/L) was safe to all fish species that we tested, but it was only effective on veliger and settler stages of the zebra mussel. Effective disinfectants were benzalkonium chloride for use on equipment and rotenone for use in ponds after fish are harvested. The regulatory status of the identified chemicals is discussed as well as several nonchemical control alternatives.

Progressive Fish-Culturist↗

USGS1956

Lignasan for bacterial gill disease

Bacterial gill disease plagues salmon and trout in many hatcheries: some infections are sporadic, but others are continual. An inexpensive, easily applied, stable, safe chemical would be highly advantageous for treatment. The use of Roccal as a 1-hour treatment for bacterial gill disease (Fish 1947) was developed at the Leavenworth (Washington) Station of the Fish and Wildlife Service in 1942 and was quite successful. Since then, Roccal has been used extensively; but because of variability in composition, its efficacy is not consistent (Rucker et al. 1949). The objection to the variability of Roccal was overcome by using another compound, pyridylmercuric acetate, which was suggested by Van Horn and Katz (1946) as having some therapeutic therapy. Pyridylmercuric acetate was tested experimentally at the Leavenworth Station and was found to be very effective for bacterial gill disease. This compound had highly differential toxicities for bacteria and fish but was quite expensive (Rucker 1948, Burrows and Palmer 1949, Snieszko 1949). Another objection to pyridylmercuric acedate was its toxicity to rainbow trout—not to other species of trout or to salmon—at the concentration necessary to control the bacteria (Seaman 1950, Rodgers et al. 1951, Bryant 1951, Foster and Olson 1951).

Progressive Fish-Culturist↗