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223 results on '"Mahler, Barbara J."'

22. Ecological consequences of neonicotinoid mixtures in streams

Author

Schmidt, Travis S., primary, Miller, Janet L., additional, Mahler, Barbara J., additional, Van Metre, Peter C., additional, Nowell, Lisa H., additional, Sandstrom, Mark W., additional, Carlisle, Daren M., additional, Moran, Patrick W., additional, and Bradley, Paul M., additional

Published
2022
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27. Common insecticide disrupts aquatic communities: A mesocosm-to-field ecological risk assessment of fipronil and its degradates in U.S. streams

Author

Miller, Janet L., Schmidt, Travis S., Van Metre, Peter C., Mahler, Barbara J., Sandstrom, Mark W., Nowell, Lisa H., Carlisle, Daren M., and Moran, Patrick W.

Subjects
Multidisciplinary, Ecology, 010504 meteorology & atmospheric sciences, Aquatic ecosystem, Environmental Studies, SciAdv r-articles, STREAMS, 010501 environmental sciences, 01 natural sciences, Mesocosm, chemistry.chemical_compound, chemistry, Benthic zone, Environmental chemistry, Environmental science, Ecological risk, Trophic cascade, Research Articles, Fipronil, Research Article, 0105 earth and related environmental sciences, Invertebrate
Abstract

Study shows that a common insecticide frequently detected in U.S. streams is more toxic than previously thought., Insecticides in streams are increasingly a global concern, yet information on safe concentrations for aquatic ecosystems is sparse. In a 30-day mesocosm experiment exposing native benthic aquatic invertebrates to the common insecticide fipronil and four degradates, fipronil compounds caused altered emergence and trophic cascades. Effect concentrations eliciting a 50% response (EC50) were developed for fipronil and its sulfide, sulfone, and desulfinyl degradates; taxa were insensitive to fipronil amide. Hazard concentrations for 5% of affected species derived from up to 15 mesocosm EC50 values were used to convert fipronil compound concentrations in field samples to the sum of toxic units (∑TUFipronils). Mean ∑TUFipronils exceeded 1 (indicating toxicity) in 16% of streams sampled from five regional studies. The Species at Risk invertebrate metric was negatively associated with ∑TUFipronils in four of five regions sampled. This ecological risk assessment indicates that low concentrations of fipronil compounds degrade stream communities in multiple regions of the United States.

Published
2020
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33. Urban sprawl leaves its PAH signature

Author

Van Metre, Peter C., Mahler, Barbara J., and Furlong, Edward T.

Subjects
Polycyclic aromatic hydrocarbons -- Research, Lakes, Reservoirs, Sediments (Geology), Water pollution -- Research, Environmental issues, Science and technology
Abstract

The increasing amounts of polycyclic aromatic hydrocarbons in lake and reservoir sediments may be caused by the growth of automobile emissions encouraged by urban sprawl.

Published
2000

34. DNA-labeled clay: a sensitive new method for tracing particle transport

Author

Mahler, Barbara J., Winkler, Matthew, Bennett, Philip, and Hillis, David M.

Subjects
Clay -- Research, Sedimentation and deposition -- Research, Colloids -- Research, DNA -- Usage, Earth sciences
Abstract

The behavior of mobile colloids and sediment in most natural environments remains poorly understood, in part because characteristics of existing sediment tracers limit their widespread use. Here we describe the development of a new approach that uses a DNA-labeled montmorillonite clay as a highly sensitive and selective sediment tracer that can potentially characterize sediment and colloid transport in a wide variety of environments, including marine, wetland, ground-water, and atmospheric systems. Characteristics of DNA in natural systems render it unsuitable as an aqueous tracer but admirably suited as a label for tracing particulates. The DNA-labeled-clay approach, using techniques developed from molecular biology, has extremely low detection limits, very specific detection, and a virtually infinite number of tracer signatures. Furthermore, DNA-labeled clay has the same physical characteristics as the particles it is designed to trace, it is environmentally benign, and it can be relatively inexpensively produced and detected. Our initial results show that short (500 base pair) strands of synthetically produced DNA reversibly adsorb to both Na-montmorillonite and powdered silica surfaces via a magnesium bridge. The DNA-montmorillonite surface complexes are stable in calcium-bicarbonate spring waters for periods of up to 18 days and only slowly desorb to the aqueous phase, whereas the silica surface complex is stable only in distilled water. Both materials readily release the adsorbed DNA in dilute EDTA solutions for amplification by the polymerase chain reaction (PCR) and quantification. The stability of the DNA-labeled clay complex suggests that this material would be appropriate for use as an extremely sensitive sediment tracer for flow periods of as long as 2 weeks, and possibly longer.

Published
1998

35. Lanthanide-labeled clay: a new method for tracing sediment transport in karst

Author

Mahler, Barbara J., Bennett, Philip C., and Zimmerman, Mitch

Subjects
Aquifers -- Research, Rare earth metals -- Research, Water, Underground -- Research, Sediment transport -- Research, Particles -- Research, Earth sciences, Research
Abstract

Introduction Sediment and sediment surfaces are a fundamental control on the transport and fate of organic contaminants. In porous media aquifers, sediments retard contaminant transport because of sorption and partitioning [...]

Published
1998

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