Geology topics

Thomas H. Suchanek

Publications and source records attributed to Thomas H. Suchanek.

7 recordsLinked to original sources

USGS2014

Mercury in birds of San Francisco Bay-Delta, California: trophic pathways, bioaccumulation, and ecotoxicological risk to avian reproduction

San Francisco Bay Estuary in northern California has a legacy of mercury contamination, which could reduce the health and reproductive success of waterbirds in the estuary. The goal of this study was to use an integrated field and laboratory approach to evaluate the risks of mercury exposure to birds in the estuary. We examined mercury bioaccumulation, and other contaminants of concern, in five waterbird species that depend heavily on San Francisco Bay Estuary for foraging and breeding habitat: American avocets ( Recurvirostra americana ), black-necked stilts ( Himantopus mexicanus ), Forster’s terns ( Sterna forsteri ), Caspian terns ( Hydroprogne caspia ), and surf scoters ( Melanitta perspicillata ). These species have different foraging habitats and diets that represent three distinct foraging guilds within the estuary’s food web. In this report, we provide an integrated synthesis of the primary findings from this study and results are synthesized from 54 peer-reviewed publications generated to date with other unpublished results.

California↗

USGS2012

The Palmyra Atoll Research Consortium

Palmyra Atoll in the tropical Pacific is the site of some exciting work by scientists from a diverse collection of research institutions. The Palmyra Atoll Research Consortium (PARC) fosters collaborative multi- and inter-disciplinary research by U.S. Department of the Interior (DOI) agencies (USGS and U.S. Fish and Wildlife Service–USFWS), academic institutions (for example, Stanford University, University of California, and Victoria University of Wellington in New Zealand) and non-governmental organizations (for example, American Museum of Natural History and The Nature Conservancy) on the terrestrial and marine ecosystems at Palmyra Atoll. USGS has been a member of PARC since its inception in 2004. Palmyra functions as a living laboratory. It is a low-lying coral atoll located about 1,800 kilometers south/southwest of Hawaii near the equator in the central Pacific Ocean (latitude 5°53'N, longitude 162°05'W). Palmyra Atoll and nearby Kingman Reef are U.S. territories and represent the northern atolls/reefs of the U.S. Line Islands. Palmyra also is one of the nine sovereign territories of the United States commonly referred to as the U.S. Pacific Remote Island Areas (PRIAs) that straddle the equator (fig. 1). Palmyra Atoll and nearby Kingman Reef also were included as part of the seven territories that comprise the Pacific Remote Islands Marine National Monument set aside by President Bush in 2009 (Proclamation 8336), which includes the same territories as the PRIAS, except Rose Atoll and Midway Atoll.

Palmyra Atoll↗

USGS2010

Mercury assessment and monitoring protocol for the Bear Creek Watershed, Colusa County, California

This report summarizes the known information on the occurrence and distribution of mercury (Hg) in physical/chemical and biological matrices within the Bear Creek watershed. Based on these data, a matrix-specific monitoring protocol for the evaluation of the effectiveness of activities designed to remediate Hg contamination in the Bear Creek watershed is presented. The monitoring protocol documents procedures for collecting and processing water, sediment, and biota for estimation of total Hg (TotHg) and monomethyl mercury (MMeHg) in the Bear Creek watershed. The concurrent sampling of TotHg and MMeHg in biota as well as water and sediment from 10 monitoring sites is designed to assess the relative bioavailability of Hg released from Hg sources in the watershed and identify environments conducive to Hg methylation. These protocols are designed to assist landowners, land managers, water quality regulators, and scientists in determining whether specific restoration/mitigation actions lead to significant progress toward achieving water quality goals to reduce Hg in Bear and Sulphur Creeks.

California↗

USGS2008

Changes in fish diets and food web mercury bioaccumulation induced by an invasive planktivorous fish

The invasion, boom, collapse, and reestablishment of a population of the planktivorous threadfin shad in Clear Lake, California, USA, were documented over a 20-year period, as were the effects of changing shad populations on diet and mercury (Hg) bioaccumulation in nearshore fishes. Threadfin shad competitively displaced other planktivorous fish in the lake, such as inland silversides, young-of-year (YOY) largemouth bass, and YOY bluegill, by reducing zooplankton abundance. As a result, all three species shifted from a diet that was dominated by zooplankton to one that was almost entirely zoobenthos. Stable carbon isotopes corroborated this pattern with each species becoming enriched in δ 13 C, which is elevated in benthic vs. pelagic organisms. Concomitant with these changes, Hg concentrations increased by ∼50% in all three species. In contrast, obligate benthivores such as prickly sculpin showed no relationship between diet or δ 13 C and the presence of threadfin shad, suggesting that effects of the shad were not strongly linked to the benthic fish community. There were also no changes in Hg concentrations of prickly sculpin. The temporary extirpation of threadfin shad from the lake resulted in zooplankton densities, foraging patterns, isotope ratios, and Hg concentrations in pelagic fishes returning to pre-shad values. These results indicate that even transient perturbations of the structure of freshwater food webs can result in significant alterations in the bioaccumulation of Hg and that food webs in lakes can be highly resilient.

Ecological Applications↗

USGS2007

Mercury concentrations and space use of pre-breeding American avocets and black-necked stilts in San Francisco Bay

We examined factors influencing mercury concentrations in pre-breeding American avocets ( Recurvirostra americana ) and black-necked stilts ( Himantopus mexicanus ), the two most abundant breeding shorebirds in San Francisco Bay, California. We tested the effects of species, site, sex, year, and date on total mercury concentrations in blood of pre-breeding adult birds and used radio telemetry to determine space use and sites of dietary mercury exposure. We collected blood from 373 avocets and 157 stilts from February to April in 2005 and 2006, radio-marked and tracked 115 avocets and 94 stilts, and obtained 2393 avocet and 1928 stilt telemetry locations. Capture site was the most important factor influencing mercury concentrations in birds, followed by species and sex. Mercury concentrations were higher in stilts (geometric mean: 1.09 μg g − 1 wet weight [ww]) than in avocets (0.25 μg g − 1 ww) and males (stilts: 1.32 μg g − 1 ww; avocets: 0.32 μg g − 1 ww) had higher levels than females (stilts: 1.15 μg g − 1 ww; avocets: 0.21 μg g − 1 ww). Mercury concentrations were highest for both species at the southern end of San Francisco Bay, especially in salt pond A8 (stilts: 3.31 μg g − 1 ww; avocets: 0.58 μg g − 1 ww). Radio telemetry data showed that birds had strong fidelity to their capture site. Avocets primarily used salt ponds, tidal marshes, tidal flats, and managed marshes, whereas stilts mainly used salt ponds, managed marshes, and tidal marshes. Our results suggest that variation in blood mercury concentrations among sites was attributed to differences in foraging areas, and species differences in habitat use and foraging strategies may increase mercury exposure in stilts more than avocets.

Science of the Total Environment↗

USGS2004

Mercury and Methylmercury concentrations and loads in Cache Creek Basin, California, January 2000 through May 2001

Concentrations and mass loads of total mercury and methylmercury in streams draining abandoned mercury mines and near geothermal discharge in Cache Creek Basin, California, were measured during a 17-month period from January 2000 through May 2001. Rainfall and runoff averages during the study period were lower than long-term averages. Mass loads of mercury and methylmercury from upstream sources to downstream receiving waters, such as San Francisco Bay, were generally the highest during or after winter rainfall events. During the study period, mass loads of mercury and methylmercury from geothermal sources tended to be greater than those from abandoned mining areas because of a lack of large precipitation events capable of mobilizing significant amounts of either mercury-laden sediment or dissolved mercury and methylmercury from mine waste. Streambed sediments of Cache Creek are a source of mercury and methylmercury to downstream receiving bodies of water such as the Delta of the San Joaquin and Sacramento Rivers. Much of the mercury in these sediments was deposited over the last 150 years by erosion and stream discharge from abandoned mines or by continuous discharges from geothermal areas. Several geochemical constituents were useful as natural tracers for mining and geothermal areas. These constituents included aqueous concentrations of boron, chloride, lithium, and sulfate, and the stable isotopes of hydrogen and oxygen in water. Stable isotopes of water in areas draining geothermal discharges were enriched with more oxygen-18 relative to oxygen-16 than meteoric waters, whereas the enrichment by stable isotopes of water from much of the runoff from abandoned mines was similar to that of meteoric water. Geochemical signatures from stable isotopes and trace-element concentrations may be useful as tracers of total mercury or methylmercury from specific locations; however, mercury and methylmercury are not conservatively transported. A distinct mixing trend of trace elements and stable isotopes of hydrogen and oxygen from geothermal waters was apparent in Sulphur Creek and lower Bear Creek (tributaries to Cache Creek), but the signals are lost upon mixing with Cache Creek because of dilution.

Scientific Investigations Report↗

USGS2004

Summary and Synthesis of Mercury Studies in the Cache Creek Watershed, California, 2000-01

This report summarizes the principal findings of the Cache Creek, California, components of a project funded by the CALFED Bay?Delta Program entitled 'An Assessment of Ecological and Human Health Impacts of Mercury in the Bay?Delta Watershed.' A companion report summarizes the key findings of other components of the project based in the San Francisco Bay and the Delta of the Sacramento and San Joaquin Rivers. These summary documents present the more important findings of the various studies in a format intended for a wide audience. For more in-depth, scientific presentation and discussion of the research, a series of detailed technical reports of the integrated mercury studies is available at the following website: .

Water-Resources Investigations Report↗