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At least 415 records · Page 23Linked to original sources

Legacy of the fumigant 1,2-dibromo-3-chloropropane (DBCP) in California groundwater

The fumigant pesticide 1,2-dibromo-3-chloropropane (DBCP) was widely used in California agriculture during the 1960s and 1970s before being banned in 1979. Despite this ban, DBCP continues to contaminate groundwater due to its persistence and mobility. This study evaluates the distribution, historical trends, and projected persistence of DBCP in California using data from over 13,000 public supply wells and additional domestic, irrigation, and observation wells (1980-2022). Since 2010, DBCP has been detected in 9% of public supply wells statewide, with higher frequencies in the San Joaquin Valley (21%) and upper Santa Ana River watershed (13%), where DBCP use was most prevalent. Approximately 70% of wells had decreasing concentration trends, whereas increases were more common in deeper wells, indicating downward vertical migration of the DBCP front. Groundwater age estimates show that recharge timing aligns with the 1960s–1970s loading period, enabling reconstruction of peak inputs and providing a basis for age based modeling. To estimate future persistence, we applied a one dimensional advection–dispersion model that simulates long term declines in peak concentrations based on groundwater age, historical loading, and a 38 year degradation half life. Model projections suggest that concentrations above the maximum contaminant level may persist in a declining number of wells until approximately 2080 (range: 2048–2109), with longer persistence in the San Joaquin Valley. The simplified modeling framework, based on age distributions typical of wells capturing peak concentrations, can provide practical regional scale assessment of non-point source contaminants where long-term monitoring exists. This study highlights how the legacy of DBCP contamination will likely affect California's groundwater resources throughout the 21st century.

California

Bifenthrin causes trophic cascades and alters insect emergence in mesocosms: implication for small streams

Direct and indirect ecological effects of the widely used insecticide bifenthrin on stream ecosystems are largely unknown. To investigate such effects, a manipulative experiment was conducted in stream mesocosms that were colonized by aquatic insect communities and exposed to bifenthrin-contaminated sediment; implications for natural streams were interpreted through comparison of mesocosm results to a survey of 100 Midwestern streams, USA. In the mesocosm experiment, direct effects of bifenthrin exposure included reduced larval macroinvertebrate abundance, richness, and biomass at concentrations (EC50s ranged 197.6 – 233.5 ng bifenthrin/ g organic carbon) previously thought safe for aquatic life. Indirect effects included a trophic cascade in which periphyton abundance increased after macroinvertebrate scrapers decreased. Adult emergence dynamics and corresponding terrestrial subsidies were altered at all bifenthrin concentrations tested. Extrapolating these results to the Midwestern stream assessment suggests pervasive ecological effects, with altered emergence dynamics likely in 40% of streams and a trophic cascade in 7% of streams. This study provides new evidence that a common pyrethroid might alter aquatic and terrestrial ecosystem function at the regional scale.

Environmental Science & Technology

Science information to support Missouri River Scaphirhynchus albus (pallid sturgeon) effects analysis

The Missouri River Pallid Sturgeon Effects Analysis (EA) was commissioned by the U.S. Army Corps of Engineers to develop a foundation of understanding of how pallid sturgeon ( Scaphirhynchus albus ) population dynamics are linked to management actions in the Missouri River. The EA consists of several steps: (1) development of comprehensive, conceptual ecological models illustrating pallid sturgeon population dynamics and links to management actions and other drivers; (2) compilation and assessment of available scientific literature, databases, and models; (3) development of predictive, quantitative models to explore the system dynamics and population responses to management actions; and (4) analysis and assessment of effects of system operations and actions on species’ habitats and populations. This report addresses the second objective, compilation and assessment of relevant information. Scientific information on pallid sturgeon and its environment has grown substantially during the last decade. Presently available (2015) information indicates that stocked sturgeon are surviving and growing, and that wild and hatchery sturgeon are spawning in the wild. However, natural recruitment to age-1 and older has not been detected since systematic sampling began in 2005. Population models indicate the sensitivity of population growth to certain demographic variables, in particular early-life stage survival and perhaps adult fecundity. This report documents the existing population models for the pallid sturgeon, and the substantial quantities of information developed through the Pallid Sturgeon Population Assessment Program (PSPAP), the Habitat Assessment and Monitoring Program (HAMP), the Comprehensive Sturgeon Research Project (CSRP), range-wide genetics databases, and related research studies. The reference database compiled for the EA consists of over 190 peer-reviewed documents specifically related to pallid sturgeon and over 12,000 references on the Missouri River system and related species. Notwithstanding the large quantity of information available, the EA faces challenges in synthesizing the information into useful, quantitative models. In particular, critical demographic parameters for population models remain uncertain and the functional relationships between the two main categories of physical management action—changes in flow regime and reengineering channel form—and pallid sturgeon survival responses are obscure. In addition, there is an overarching uncertainty about how physical management actions interact with propagation management actions in view of evolving understanding of genetic structuring of the pallid sturgeon population. Synthesis efforts are also challenged by the fragmentation of information sources among projects and agencies; one objective of this report is to facilitate future assessments by providing documentation of what information is available and where.

Iowa, Kansas, Missouri, Montana, Nebraska, North D

Incorporating life history diversity in an integrated population model to inform viability analysis

Life history diversity can significantly affect population dynamics and effects of management actions. For instance, variation in individual responses to environmental variability can reduce extirpation risk to populations, as the portfolio effect dampens temporal variability in abundance. Moreover, differences in habitat use may cause individuals to respond differently to habitat management and climate variability. To explore the role of life history diversity in population trajectories, population models need to incorporate within-population variation. Integrated population modeling (IPM) is a population modeling approach that offers several advantages for sharing information and propagating uncertainty across datasets. In this study, we developed an IPM for an endangered population of Chinook salmon ( Oncorhynchus tshawytscha ) in the Wenatchee River, Washington, USA, that accounts for diversity in juvenile life histories, spawning location, and return age. Our analysis revealed that diversity in the age of juvenile emigration from natal streams had a portfolio effect, resulting in a 20% reduction in year-to-year variability in adult abundance in population projections. Our population viability analysis suggests that management interventions may be necessary to meet recovery goals, and our model should be useful for simulating the outcomes of proposed actions.

Washington

Uptake, tissue distribution, and metabolism of malachite green in the channel catfish (Ictalurus punctatus)

The disposition of malachite green was determined in channel catfish ( Ictalurus punctatus ) after intravascular dosing (0.8 mg . Kg -1 ) or waterborne exposure (0.8 mg . L -1 for 1 h). After intravascular dosing, mean plasma concentrations of the parent compound exhibited a triphasic decline with a terminal elimination half-life of 6.2 h. Malachite green was rapidly absorbed and concentrated in the tissues during waterborne exposure. The rate of accumulation was directly related to pH of the exposure water. After waterborne exposure, elimination of the parent compound from plasma also was triphasic with a terminal half-life of 4.7 h. In muscle, the half-life of the parent compound was approximately 67 h. Malachite green and its metabolites were widely distributed in all tissues. In fish exposed to C-14-labeled malachite green, total drug equivalent concentrations were highest in abdominal fat and lowest in plasma. Malachite green was rapidly and extensively metabolized to its reduced form, leucomalachite green, which was slowly eliminated from the tissues. Leucomalachite green is an appropriate target analyte for monitoring exposure of channel catfish to this drug.

Canadian Journal of Fisheries and Aquatic Sciences

A closed recirculated sea-water system

Study of a virus disease in the chinook salmon (Oncorhynchus tshawytscha ) necessitated the use of a marine environment to study the long range effects of the disease and to complete the life cycle of its etiologic agent. A closed recirculated sea-water system was designed for use under experimental laboratory conditions so that controlled studies of the disease could be made. As others may wish to do marine environment studies in the laboratory, the design and operation of our system are presented. Other systems currently in use have been described by Chin (1959), DeWitt and Salo (1960), McCrimmon and Berst (1966), and the authors of collected papers edited by Clark and Clark (1964). Preparatory to the design and construction of the system in use in this laboratory, visits were made to marine systems in use at the University of Washington's College of Fisheries, Seattle, -washington, and Friday Harbor Laboratory, San Juan Island, Washington; the Washington State Department of Fisheries' Point whitney Shellfish Laboratory, Brinnon, Washington; Humboldt State College, Arcata, California; and the Steinhart Aquarium of the California Academy of Science, San Francisco, California.

Progressive Fish-Culturist

Walter Rowe Courtenay, Jr. (1933–2014)

WALTER R. COURTENAY, JR., ichthyologist and retired professor, Florida Atlantic University, Boca Raton, Florida, died in Gainesville, Florida, on 30 January 2014 at age 80. Walt was born in Neenah, Wisconsin, on 6 November 1933, son of Walter and Emily Courtenay. Walt's interest in fish began at a young age as evidenced by a childhood diary in which at 13 years of age he wrote about his first catch—a two-and-a-half pound “pike” from Lake Winnebago. When Walt turned ten, the family moved from Wisconsin to Nashville, Tennessee, the move precipitated by his father accepting a position as pastor of the First Presbyterian Church. During those early days in Nashville, Walt's father would take summers off and travel to Michigan to teach at Camp Miniwanca along the shore of Lake Michigan where father and son honed their angling skills. It was also at that time Walt's father had definite views on what his son should be doing in adult life—in Walt's case it was to become a medical doctor. However, his Woods Hole internship in marine biology and oceanography toward the end of his undergraduate years was a transformative experience for him so much so that he abandoned all ideas of becoming a medical doctor and instead specialized in ichthyology and oceanography. Apart from the inherent interest and opportunities Woods Hole opened to him, being back at the shore of a large body of water, in this case the Atlantic Ocean, was far more interesting than sitting in lectures on organic chemistry. With that, Walt completed his B.A. degree at Vanderbilt University in 1956. In 1960 while in graduate school in Miami, Walt met and married Francine Saporito, and over the next several years had two children, Walter III and Catherine. He went on to receive his M.S. in 1961 from The Rosenstiel School of Marine and Atmospheric Science at the University of Miami on the systematics of the genus Haemulon (grunts) and his Ph.D. degree in 1965 working under his advisor C. Richard “Dick” Robins, also at Miami, with his dissertation entitled “Atlantic Fishes of the Genus Rypticus (Grammistidae): Systematics and Osteology.” Dick and wife Catherine Robins, also a fellow biologist, thought of him as a great friend to have. They fondly recalled that those of us who knew Walt in his early grad student days valued his sense of humor and unmistakable laugh, much of which was directed at bureaucratic foolishness and pomposity. However, he also had a very serious side when it came to justice and responsibility.

Copeia

Estimating drivers and identifying uncertainties in smallmouth bass population dynamics in an invaded river network

Smallmouth bass ( Micropterus dolomieu ) is an important recreational sportfish and destructive non-native species when introduced into freshwater habitats. There is therefore a need to understand the drivers of, and uncertainties in, smallmouth bass population dynamics for various management objectives. We combined long-term smallmouth bass catch-effort and early life history data from a non-native population in the Green River sub-basin of the upper Colorado River to develop a demographic model that links interannual variability in environmental conditions to recruitment in three river reaches. We used the model to quantify how hydrology, river temperature, and exploitation drive smallmouth bass population dynamics. Early life stages were influenced by timing of hatching and discharge. Dispersal of age-0 fish and density-dependent dynamics were identified as primary sources of uncertainty. Determining the true nature of density-dependent dynamics is important, as the impact of exploitation-based management actions is dependent on the strengths of any density-dependent feedbacks. Our model provides a framework to predict smallmouth bass population responses to future climate conditions, reservoir operations, and exploitation levels.

Utah

Ecological and socioeconomic factors associated with the human burden of environmentally mediated pathogens: A global analysis

Background Billions of people living in poverty are at risk of environmentally mediated infectious diseases—that is, pathogens with environmental reservoirs that affect disease persistence and control and where environmental control of pathogens can reduce human risk. The complex ecology of these diseases creates a global health problem not easily solved with medical treatment alone. Methods We quantified the current global disease burden caused by environmentally mediated infectious diseases and used a structural equation model to explore environmental and socioeconomic factors associated with the human burden of environmentally mediated pathogens across all countries. Findings We found that around 80% (455 of 560) of WHO-tracked pathogen species known to infect humans are environmentally mediated, causing about 40% (129 488 of 359 341 disability-adjusted life years) of contemporary infectious disease burden (global loss of 130 million years of healthy life annually). The majority of this environmentally mediated disease burden occurs in tropical countries, and the poorest countries carry the highest burdens across all latitudes. We found weak associations between disease burden and biodiversity or agricultural land use at the global scale. In contrast, the proportion of people with rural poor livelihoods in a country was a strong proximate indicator of environmentally mediated infectious disease burden. Political stability and wealth were associated with improved sanitation, better health care, and lower proportions of rural poverty, indirectly resulting in lower burdens of environmentally mediated infections. Rarely, environmentally mediated pathogens can evolve into global pandemics (eg, HIV, COVID-19) affecting even the wealthiest communities. Interpretation The high and uneven burden of environmentally mediated infections highlights the need for innovative social and ecological interventions to complement biomedical advances in the pursuit of global health and sustainability goals. Funding Bill & Melinda Gates Foundation, National Institutes of Health, National Science Foundation, Alfred P. Sloan Foundation, National Institute for Mathematical and Biological Synthesis, Stanford University, and the US Defense Advanced Research Projects Agency.

The Lancet Planetary Health

Long-term isolation of a highly mobile seabird on the Galapagos

The Galapagos Islands are renowned for their high degree of endemism. Marine taxa inhabiting the archipelago might be expected to be an exception, because of their utilization of pelagic habitats—the dispersal barrier for terrestrial taxa—as foraging grounds. Magnificent frigatebirds ( Fregata magnificens ) have a highly vagile lifestyle and wide geographical distribution around the South and Central American coasts. Given the potentially high levels of gene flow among populations, the species provides a good test of the effectiveness of the Galapagos ecosystem in isolating populations of highly dispersive marine species. We studied patterns of genetic (mitochondrial DNA, microsatellites and nuclear introns) and morphological variation across the distribution of magnificent frigatebirds. Concordant with predictions from life-history traits, we found signatures of extensive gene flow over most of the range, even across the Isthmus of Panama, which is a major barrier to gene flow in other tropical seabirds. In contrast, individuals from the Galapagos were strongly differentiated from all conspecifics, and have probably been isolated for several hundred thousand years. Our finding is a powerful testimony to the evolutionary uniqueness of the taxa inhabiting the Galapagos archipelago and its associated marine ecosystems.

Galapagos Islands

Why are the PCB concentrations of salmonine individuals from the same lake so highly variable?

An individual-based model (IBM) was applied to the Lake Michigan rainbow trout ( Oncorhynchus mykiss ) population, with the objectives of explaining the observed variation in growth and in polychlorinated biphenyl (PCB) concentration within the population. When variation in prey PCB concentration was incorporated into the model, variability in PCB concentration among individual rainbow trout was fully explained by the IBM. Although number of spawnings and number of years spent in a stream prior to first entering the lake were factors in determining growth, these life history characteristics appeared to have only a minor impact on PCB accumulation rate in rainbow trout. The IBM application to the rainbow trout population was compared with an application to the Lake Michigan lake trout ( Salvelinus namaycush ) population. Modeling results indicated that the lower observed PCB concentrations in rainbow trout compared with lake trout were chiefly due to greater longevity in lake trout. The IBM simulations identified gross growth efficiency, assimilation efficiency of PCBs from food, and diet as other important sources of variability in salmonine PCB concentrations.

Canadian Journal of Fisheries and Aquatic Sciences

Ecological interfaces between land and flowing water: Themes and trends in riparian research and management

This paper provides an overview of past, present and future themes for research and management of riparian zones, often relating to papers within this Wetlands Special Feature. Riparian research expanded in the United States around 1980 with themes that recognized (1) damage from excessive livestock, or (2) damage from river damming and diversion, and (3) the beneficial capacity of riparian buffers to intercept and assimilate nutrients and other water contaminants. Research expanded globally in the 1990s, with themes including (4) plant life history requirements and (5) reliance on fluvial geomorphic dynamics that enable riparian rejuvenation. Resource managers recognized that riparian areas provide (6) rich wildlife habitats (7) along with valued ecosystem services, (8) which encouraged conservation and restoration initiatives, (9) including environmental flow regimes. Floodplains are (10) vulnerable to invasive plants and management has included biocontrol such as for Tamarix in the American Southwest. Into the twenty-first century, (11) climate change is advancing, and riparian ecosystems may be especially impacted due to the compound challenges from increasing water demand and declining summer flows. As an emerging opportunity, (12) while reservoirs submerge floodplain vegetation, reservoir deltas may support compensatory riparian wetlands. (13) Studies increasingly utilize remote sensing tools including satellite imagery, LiDAR and unmanned aircraft systems, and (14) the coordination of large data sets invites digital ecology, including artificial intelligence and machine learning. Since riparian zones are centres for human activities, (15) there are opportunities for citizen science, social media and internet applications, which will increasingly democratize riparian research and management.

Wetlands

The confluences of ideas leading to, and the flow of ideas emerging from, individual-based modeling of riverine fishes

In this review article, we trace the history of events leading to the development of individual-based models (IBMs) to represent aquatic organisms in rivers and streams. As a metaphor, we present this history as a series of confluences between individual scientists (tributaries) sharing ideas. We describe contributions of these models to science and management. One iconic feature of river IBMs is the linkage between flow and the physical habitat experienced by individual animals, and the first model that focused on this linkage is briefly described. We continue by reviewing the contributions of riverine IBMs to eight broad areas of scientific inquiry. The first four areas include research to understand 1) the effects of flow regimes on fish populations, 2) species interactions (e.g., size-mediated competition and predation), 3) fish movement and habitat selection, and 4) contaminant and water quality impacts on populations. Next, we review research using IBMs 5) to guide conservation biology of imperiled taxa through population viability analysis, including research 6) to understand river fragmentation by dams and reconnection, 7) to understand genetic outcomes for riverine metapopulations, and 8) to anticipate the future effects of temperature and climate change. This rich body of literature has contributed to both theoretical insights (e.g., about animal behavior and life history) and applied insights (e.g., population-level effects of flow regimes, temperature, and the effects of hydropower and other industries that share rivers with aquatic biota). We finish by exploring promising branches that lie ahead in the braided, downstream channel that represents future river modeling research.

Ecological Modelling

Habitat evaluation using GIS a case study applied to the San Joaquin Kit Fox

Concern over the fate of plant and animal species throughout the world has accelerated over recent decades. Habitat loss is considered the main culprit in reducing many species' abundance and range, leading to numerous efforts to plan and manage habitat preservation. Our work uses Geographic Information Systems (GIS) data and modeling to define a spatially explicit analysis of habitat value, using the San Joaquin Kit Fox (Vulpes macrotis mutica) of California (USA) as an example. Over the last 30 years, many field studies and surveys have enhanced our knowledge of the life history, behavior, and needs of the kit fox, which has been proposed as an umbrella or indicator species for grassland habitat in the San Joaquin Valley of California. There has yet been no attempt to convert much of this field knowledge into a model of spatial habitat value useful for planning purposes. This is a significant omission given the importance and visibility of the imperiled kit fox and increasing trends toward spatially explicit modeling and planning. In this paper we apply data from northern California to derive a small-cell GIS raster of habitat value for the kit fox that incorporates both intrinsic habitat quality and neighborhood context, as well the effects of barriers such as roads. Such a product is a useful basis for assessing the presence and amounts of good (and poor) quality habitat and for eventually constructing GIS representations of viable animal territories that could be included in future reserves. ?? 2001 Elsevier Science B.V.

Landscape and Urban Planning

Persistence of native riverine fishes downstream from two hydropower dams with contrasting operations

Identifying hydropower dam operations that lessen detrimental effects on downstream fauna could inform conservation strategies for native fishes. We compared occurrence of native fishes in 20 shoal habitats downstream from two differently operated hydropower dams in the Coosa River system, Georgia, USA. Species richness averaged 7 and 11, respectively, in surveys downstream from (1) a hydropeaking dam and (2) a dam with a re-regulation structure that stabilized downstream flows. In contrast, surveys in two nearby reference communities averaged 19 and 24 species. Species persisting downstream from the dams tended toward water-column orientation, larger body size, longer life-span, and greater prevalence in tributary stream collections, compared with missing or rarely captured species. We observed no evidence of recovery toward reference conditions when operations were paused for 28 months at the hydropeaking dam. Our observations suggest that (1) strongly contrasting dam operations can result in similar alterations to native fish assemblages, potentially reflecting effects of thermal alteration by hypolimnetic water release, and (2) periodic dispersal from tributary streams may enhance fish persistence in flow-altered rivers.

Canadian Journal of Fisheries and Aquatic Sciences

A 107-year-old coral from Florida Bay: barometer of natural and man- induced catastrophes?

The 107-yr growth history of a massive coral Solenastrea bournoni from Florida Bay was reconstructed with X-ray imagery from a single 4 in. diameter (10 cm) core that penetrated the exact epicenter of the 95.3 cm high colony. Growth increments totalled 952.9 mm, averaging 8.9 mm/yr over the life of the coral. Growth rate trends in the Florida Bay coral were compared to those in a Montastraea annularis of similar age from a nearby patch reef on the Atlantic Ocean side of the Florida Keys. It was concluded that growth rate, at least in these specimens, is a questionable indicator of past hurricanes and freezes. There does appear to be, however, a possible cause-and-effect relationship between major man-induced environmental perturbations and a prolonged reduction in growth rate in each coral's growth record. -from Authors

Bulletin of Marine Science

An estimate of hydrothermal fluid residence times and vent chimney growth rates based on 210Pb Pb ratios and mineralogic studies of sulfides dredged from the Juan de Fuca Ridge

The 210 PbPb ratios across two sulfide samples dredged from the Juan de Fuca Ridge are used to estimate the growth rate of the sulfide material and the residence time of the hydrothermal fluid within the oceanic crust from the onset of basalt alteration. 210 Pb is added to the hydrothermal fluid by two processes: (1) high-temperature alteration of basalt and (2) if the residence time of the fluid is on the order of the 22.3-year half-life of 210 Pb, by in-situ growth from 222 Rn ( Krishnaswami and Turekian, 1982 ). Stable lead is derived only from the alteration of basalt. The 210 Pb/Pb ratio across one sample was ∼ 0.5 dpm/10 −6 g Pb, and across the other it was ∼ 0.4 dpm/10 −6 g Pb. These values are quite close to the 238 UP/b ratios of basalts from the area, suggesting that the residence time of the hydrothermal fluid from the onset of basalt alteration is appreciably less than the mean life of 210 Pb, i.e., the time required for ingrowth from the radon. An apparent growth rate of 1.2 cm/yr is derived from the slope of the 210 Pb/Pb curve for one of the samples. This is consistent with its mineralogy and texture which suggest an accretionary pattern of development. There is no obvious sequential growth pattern, and virtually no gradient in 210 Pb/Pb across the second sample. This is consistent with alteration of the original 210 Pb/Pb distribution by extensive remobilization reactions which are inferred from the mineralogic and textural relationships of the sample.

Earth and Planetary Science Letters

Life history, genetics, range expansion and new frontiers of the lionfish (Pterois volitans, Perciformes: Pteroidae) in Latin America

Pterois volitans (lionfish) is a midsize predatory fish commonly found in waters of the western Pacific and Indian Ocean. The species was first documented in Dania Beach, Florida (northwestern Caribbean) in 1985. Since that time the species has expanded its range rapidly to the Northwestern Atlantic Ocean, Gulf of Mexico, and Caribbean Sea. Since its introduction P. volitans has changed community structure and biodiversity of Caribbean reef communities and other coastal tropical ecosystems. Continuous introductions (accidental or intentional), limited natural predators, naïve-range prey behavior, high predation rates on competitors, continuous reproduction, and an extended period of larval dispersal have been the keys for successful invasion and rapid range extension of P. volitans . This invasion has become so severe that it has been recognized as one of the world’s top conservation issues. Here, we review the life history, behavior, and historical and contemporary genetic patterns that facilitate expansion and the colonization process. A greater understanding of lionfish biology, ecology, and the changes related to its present condition as a super-invader could improve current and future management strategies and new detection and response methodologies. We also examine new invasion frontiers that this species has the potential to colonize such as the eastern Pacific. This information will provide managers, the scientific community, and the civil society better tools for eradication, control and management of future invasions of this and other invasive species.

Caribbean Sea, Latin America