Research Hydrologist
Email:
arstewar@usgs.gov
Office Phone:
650-329-4550
Fax:
650-329-4545
ORCID:
0000-0003-2918-546X
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Western North America is a region defined by extreme gradients in geomorphology and climate, which support a diverse array of ecological communities and natural resources. The region also has extreme gradients in mercury (Hg) contamination due to a broad distribution of inorganic Hg sources. These diverse Hg sources and a varied landscape create a unique and complex mosaic of ecological risk from Hg impairment associated with differential methylmercury (MeHg) production and bioaccumulation. Understanding the landscape-scale variation in the magnitude and relative importance of processes associated with Hg transport, methylation, and MeHg bioaccumulation requires a multidisciplinary synthesis that transcends small-scale...
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Robin Stewart's research is focused on identifying and understanding processes influencing the fate and bioavailability of selenium and mercury in food webs across a range of aquatic environments including estuaries, rivers, lakes and reservoirs.
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Estuaries provide critical habitat for a vast array of fish and wildlife but are also a nexus for core economic activities that mobilize and concentrate contaminants that can threaten aquatic species. Selenium (Se), an essential element and potent reproductive toxin, is enriched in parts of the San Francisco Estuary (SFE) to levels known to cause toxicity, yet the risk of Se to species that inhabit the SFE is not well understood. We quantified Se concentrations in muscle, liver, and ovary of the demersal cyprinid Sacramento Splittail from six regions in the SFE at three time points (fall 2010-11, spring 2017) to evaluate Se exposure risk. Here we report fish morphological attributes, total selenium concentrations...
Categories: Data;
Tags: Aquatic Biology,
Ecology,
Geochemistry,
Geography,
Geomorphology, All tags...
Hydrology,
Sacramento-San Joaquin Delta,
San Francisco Bay,
USGS Science Data Catalog (SDC),
Water Resources,
Wildlife Biology,
bioaccumulation,
biological monitoring,
cyprinid,
delta,
estuary,
exposure risk,
selenium, Fewer tags
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Birds (Clark’s grebe, Aechmophorus clarkii; Forster’s Tern, Sterna forsteri), fish (Peacock bass, Cichla temensis, Cichla monoculus; Pescada, Plagioscion squamosissimus) and earthworms were analyzed for selenium, total mercury, and methyl mercury concentration and mercury speciation. A Clark’s grebe was collected from Lake Berryessa (California, United States) in September 2012. A Forster’s Tern was collected from the San Francisco Bay Estuary (California, United States) in June 2018. Bird necropsies were performed at the U.S. Geological Survey (Dixon, CA) to obtain the following tissues: head feather, breast feather, brain, skeletal muscle, kidney, and liver. Fishes were collected in September 2018 from the Tapajós...
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Montana Fish, Wildlife, and Parks (MT FWP), in collaboration with the United States Geological Survey (USGS) Wyoming-Montana Water Science Center (WY-MT WSC), Montana Department of Environmental Quality (MDEQ), and the United States Environmental Protection Agency (USEPA) collected fish from the Koocanusa Reservoir in 2021 for tissue analysis. Fish tissue collected included muscle, eggs, liver, and whole body. Analysis of tissues included characterization of the concentration of selenium, mercury and methyl mercury, nitrogen and carbon stable isotopes, and vitamins A and E. The purpose of these analyses was to inform state and federal management agencies on transboundary coal mining impacts to downstream fish health.
Categories: Data;
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: Aquatic Biology,
Bioaccumulation,
Biota,
Columbia River Basin,
Environmental Health, All tags...
Koocanusa Reservoir,
Kootenai,
Kootenai River Basin,
Mercury,
Montana,
Selenium,
USGS Science Data Catalog (SDC),
United States,
Water Quality,
biota, Fewer tags
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