Wildlife Bioaccumulation and Effects

EPA Grant Number: R825433C014
Subproject: this is subproject number 014 , established and managed by the Center Director under grant R825433
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EERC - Center for Ecological Health Research (Cal Davis)
Center Director: Rolston, Dennis E.
Title: Wildlife Bioaccumulation and Effects
Investigators: Anderson, Daniel
Institution: University of California - Davis
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1996 through September 30, 2000
RFA: Exploratory Environmental Research Centers (1992) RFA Text |  Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research


To better understand the current effects of mercury contamination on Clear Lake avifauna and to reconstruct the past exposures of birds to the multiple stresses of chlorinated hydrocarbons and mercury.


Past work on avifauna at Clear Lake has developed an excellent picture of the current exposure of fish-eating birds to chlorinated hydrocarbons and mercury. Effects of current population significance in the species studied are not as clear. The species receiving our most intense investigation have been osprey (Pandion haliaetus) and western/Clarke's grebes (Aechmophorus occidentalis and A. clarkii). Osprey virtually disappeared from Clear Lake in the chlorinated hydrocarbon application era, and the decline of western grebes was the basis for several classic papers on food chain accumulation of chlorinated hydrocarbons and their population consequences. Osprey have steadily increased from 13-25 successful nests each year on Clear Lake, fledging rates are consistently above maintenance reproduction, and Clear Lake breeding populations were at their highest recorded level in 2000. 1999 marked the first year known at Clear Lake with successful bald eagle (Haliaeetus leucocephalus) reproduction (two nests produced two young each). Western grebes are also abundant on Clear Lake, but are mostly breeding at very low rates, despite apparently good body condition. In three years of our long-term study (10 years), reproduction has been successful. But in other years, severe disturbances by humans have been the most frequent cause of nest abandonment. In 1997, most of the 400 or so grebe nests at Clear Lake were completely obliterated by weed control operators; but in 1998 after resolution of the disturance issue, grebes at Clear Lake performed as well as those at our comparison site, Eagle Lake. In 1998, grebe populations at both lakes were high and reproducing at normal rates (0.54 young/adult versus 0.55 young/adult).

In 1999, most of the western grebe breeding effort was, however, again disturbed-out, this time by chronic disturbances from bass fishermen, with associated predation of eggs by crows, night herons, and otters. All this was mostly due to low and decreasing water levels in 1999, which left grebe nests vulnerable to ground predators and even trampling by cattle. In contrast, the year 2000 marked the most successful and largest grebe populations at Clear Lake since studies began ten years ago; and the osprey nesting population was at an all time high, as well. In comparison to western grebes at control Klamath and Eagle Lakes, grebes at Clear Lake have been shown to have significantly higher mercury burdens, but this cannot be related to sometimes poor reproductive status, due mainly to the overriding effects of disturbances in recent years and the extreme variability seen from area-to-area and from year-to-year. Analyses of historical grebe wing-feathers collected from the DDD-era (archived in our collections) indicated elevated mercury levels (previously unknown and unreported) in historical specimens (1992 levels were about half of those collected in the late 1960s). DDT derivatives such as DDD body-burdens have fallen dramatically from levels in the 1960s and 70s, 1-2 orders of magnitude. Mercury tissue and feather levels from 1998 and 1999 samples (analyses not yet complete) will be compared with residues from earlier in the study to determine if mean mercury levels have continued to decline since the most recent mine site remediation in 1992. After 1994, a three-year, statistically significant, running relationship between increasing reproductive success and distance from the Sulfur Bank mine site broke down and has remained so through 2000. Histological analyses of tissue samples from grebes collected in 1998 compared to those collected in 1992 are also currently in progress.

Expected Results:

Once the breeding colony at Clear Lake is receiving full agency protection from disturbances, it will be possible to more closely observe and study specific potential reproductive problems in this known-contaminated population. Work in 2001 will concentrate on better understanding the current effects of mercury contamination at Clear Lake by incubating in the laboratory a sample of eggs to test for mercury relationships to nesting success and upon establishing a critical level in grebe eggs for evaluating future reproduction. Investigators expect to build a sample base to further reconstruct the past exposures of birds to the multiple stresses of chlorinated hydrocarbons and mercury, combined with other ecological stressors in the system.

We will also continue to obtain current and historical specimens of grebes from other areas in their geographic range to define geographical populations from their current and historical elemental feather profiles, including mercury. Experimental studies of caged birds and mammals fed foods collected at different lakes will be used in the future to investigate the dynamics of acquisition and depuration, and the possible effects of mercury on the ontogeny and growth of young grebes.

Supplemental Keywords:

watershed, aquatic ecosystem restoration, Clear Lake, bioaccumulation, mercury, birds, osprey, chlorinated hydrocarbons., RFA, Scientific Discipline, Water, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, Ecology, Aquatic Ecosystems & Estuarine Research, Water & Watershed, mercury transport, Aquatic Ecosystem, Environmental Monitoring, Ecology and Ecosystems, Aquatic Ecosystem Restoration, Watersheds, eutrophication, wetlands, nutrient loading, migratory birds, watershed management, nutrients, nutrient flux, restoration strategies, Clear Lake, esturarine eutrophication, organochlorides, fish consumption, lakes, ecological recovery, wetland restoration, watershed influences, diagnostic indicators, nutrient stress, algal blooms, aquatic ecosystems, environmental stress, environmental rehabilitation, lake ecosysyems, mercury contamination in fish, wildlife bioaccumulation, riparian ecosystem integrity, riparian habitat, bioaccumulation, lake ecosystems

Progress and Final Reports:

  • 1997
  • 1998
  • 1999
  • Final Report

  • Main Center Abstract and Reports:

    R825433    EERC - Center for Ecological Health Research (Cal Davis)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R825433C001 Potential for Long-Term Degradation of Wetland Water Quality Due to Natural Discharge of Polluted Groundwater
    R825433C002 Sacramento River Watershed
    R825433C003 Endocrine Disruption in Fish and Birds
    R825433C004 Biomarkers of Exposure and Deleterious Effect: A Laboratory and Field Investigation
    R825433C005 Fish Developmental Toxicity/Recruitment
    R825433C006 Resolving Multiple Stressors by Biochemical Indicator Patterns and their Linkages to Adverse Effects on Benthic Invertebrate Patterns
    R825433C007 Environmental Chemistry of Bioavailability in Sediments and Water Column
    R825433C008 Reproduction of Birds and mammals in a terrestrial-aquatic interface
    R825433C009 Modeling Ecosystems Under Combined Stress
    R825433C010 Mercury Uptake by Fish
    R825433C011 Clear Lake Watershed
    R825433C012 The Role of Fishes as Transporters of Mercury
    R825433C013 Wetlands Restoration
    R825433C014 Wildlife Bioaccumulation and Effects
    R825433C015 Microbiology of Mercury Methylation in Sediments
    R825433C016 Hg and Fe Biogeochemistry
    R825433C017 Water Motions and Material Transport
    R825433C018 Economic Impacts of Multiple Stresses
    R825433C019 The History of Anthropogenic Effects
    R825433C020 Wetland Restoration
    R825433C021 Sierra Nevada Watershed Project
    R825433C022 Regional Transport of Air Pollutants and Exposure of Sierra Nevada Forests to Ozone
    R825433C023 Biomarkers of Ozone Damage to Sierra Nevada Vegetation
    R825433C024 Effects of Air Pollution on Water Quality: Emission of MTBE and Other Pollutants From Motorized Watercraft
    R825433C025 Regional Movement of Toxics
    R825433C026 Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley
    R825433C027 Source Load Modeling for Sediment in Mountainous Watersheds
    R825433C028 Stress of Increased Sediment Loading on Lake and Stream Function
    R825433C029 Watershed Response to Natural and Anthropogenic Stress: Lake Tahoe Nutrient Budget
    R825433C030 Mercury Distribution and Cycling in Sierra Nevada Waterbodies
    R825433C031 Pre-contact Forest Structure
    R825433C032 Identification and distribution of pest complexes in relation to late seral/old growth forest structure in the Lake Tahoe watershed
    R825433C033 Subalpine Marsh Plant Communities as Early Indicators of Ecosystem Stress
    R825433C034 Regional Hydrogeology and Contaminant Transport in a Sierra Nevada Ecosystem
    R825433C035 Border Rivers Watershed
    R825433C036 Toxicity Studies
    R825433C037 Watershed Assessment
    R825433C038 Microbiological Processes in Sediments
    R825433C039 Analytical and Biomarkers Core
    R825433C040 Organic Analysis
    R825433C041 Inorganic Analysis
    R825433C042 Immunoassay and Serum Markers
    R825433C043 Sensitive Biomarkers to Detect Biochemical Changes Indicating Multiple Stresses Including Chemically Induced Stresses
    R825433C044 Molecular, Cellular and Animal Biomarkers of Exposure and Effect
    R825433C045 Microbial Community Assays
    R825433C046 Cumulative and Integrative Biochemical Indicators
    R825433C047 Mercury and Iron Biogeochemistry
    R825433C048 Transport and Fate Core
    R825433C049 Role of Hydrogeologic Processes in Alpine Ecosystem Health
    R825433C050 Regional Hydrologic Modeling With Emphasis on Watershed-Scale Environmental Stresses
    R825433C051 Development of Pollutant Fate and Transport Models for Use in Terrestrial Ecosystem Exposure Assessment
    R825433C052 Pesticide Transport in Subsurface and Surface Water Systems
    R825433C053 Currents in Clear Lake
    R825433C054 Data Integration and Decision Support Core
    R825433C055 Spatial Patterns and Biodiversity
    R825433C056 Modeling Transport in Aquatic Systems
    R825433C057 Spatial and Temporal Trends in Water Quality
    R825433C058 Time Series Analysis and Modeling Ecological Risk
    R825433C059 WWW/Outreach
    R825433C060 Economic Effects of Multiple Stresses
    R825433C061 Effects of Nutrients on Algal Growth
    R825433C062 Nutrient Loading
    R825433C063 Subalpine Wetlands as Early Indicators of Ecosystem Stress
    R825433C064 Chlorinated Hydrocarbons
    R825433C065 Sierra Ozone Studies
    R825433C066 Assessment of Multiple Stresses on Soil Microbial Communities
    R825433C067 Terrestrial - Agriculture
    R825433C069 Molecular Epidemiology Core
    R825433C070 Serum Markers of Environmental Stress
    R825433C071 Development of Sensitive Biomarkers Based on Chemically Induced Changes in Expressions of Oncogenes
    R825433C072 Molecular Monitoring of Microbial Populations
    R825433C073 Aquatic - Rivers and Estuaries
    R825433C074 Border Rivers - Toxicity Studies