Final Report: 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


The objectives of this wildlife bioaccumulation project were to: (1) establish residue and exposure patterns of mercury (Hg) in breeding, high-trophic-level fish-eating birds of the Clear Lake ecosystem (osprey and Western/Clark's grebes); (2) relate this and other ecological factors in the system to demographic performance; (3) document potential changes associated with an overall trend of decline in both organochlorine and Hg residues and a one time remediation event at the Hg pollution site, a Hg mine; and (4) develop nonlethal tissue sampling techniques that are minimal in disturbance effect to our study species, and that can easily be used to obtain specimens in the future. We conducted studies each year from 1992 through 2002, and we continue this work at present.

Summary/Accomplishments (Outputs/Outcomes):

Early in the study period (1992 through about 1995), local exposures to Hg in both osprey and grebes were shown to be among the highest in the lakes of California. The U.S. Environmental Protection Agency (EPA) assessed Hg levels in another independent study during that same period. Our data indicated generally the same results as EPA's data, except that nesting subpopulations of osprey nearest the mine site were at greater risk than those that were more distant, and that some grebes in the local population also had residues high enough to predict some effects. Several hematological biomarkers of the Hg effect were shown to be present in the early phases of the study as well. Western/Clark's grebe population performance was impaired throughout the study period, most importantly by factors related to human disturbance events: weed control operations in the nesting areas, recreational activities disturbing nesting and swimming grebes, and undesirable water level fluctuations associated with water management activities. Historical analysis indicated that residues of both Hg and organochlorines had declined significantly from the mid-1950s and early 1960s, and continued to decline through the study period. By the early 2000s, feather Hg residues in both osprey and grebes had declined to levels comparable to those from our uncontaminated comparison sites. A significant improvement in both osprey and grebe reproductive rates occurred in the period after local mine site remediation (1996-2003).

We found that effective management for both osprey and grebes can help "overcome" the potential negative population effects brought about by contaminants. Over the study period, osprey breeding populations at Clear Lake steadily increased from about 8 active pairs to almost 30, and reproductive rates throughout the study period were above maintenance levels. The situation for grebes was more complicated, but when managers controlled for disturbances, successful nesting performance increased to levels equivalent to those from our comparison populations at Eagle Lake, an uncontaminated site.

We recommend further historical analysis of contaminants, as well as continued monitoring of osprey and grebe nesting populations at Clear Lake and comparison sites in California to confirm whether Hg residues will continue to decline or will increase again as local conditions (related to acid mine drainage and increasing sediment loading) potentially change. We also recommend genetic studies that would define the relationships of the local Clear Lake nesting population of Western/Clark's grebes to the overall grebe metapopulation of western North America.

The following activities were accomplished:

• Early on in our studies, we identified Clear Lake as California's lake of highest Hg contamination with regards to "top" avian piscivores (osprey and Western/Clark's grebes) in the food web. This result was necessary to justify the initiation of long-term demographic studies to document the possible long-term effects of Hg contamination on local populations of breeding avian piscivores in the system. We also characterized several routine physiological biomarkers of effect in grebes from this system; these markers were necessary for documentation purposes after remediation.

• First utilized for field evaluations, our x-ray fluorescence and particle induced x-ray emission nondestructive analytical techniques for feather analysis in birds eliminate the need for lethal or disturbing techniques in residue evaluations. Because this study was supported only minimally by funds for analytical chemistry, we had to find more efficient and cheaper techniques to evaluate Hg exposure in birds. We developed a feather-sampling procedure whereby we also could obtain tissue samples that easily could be stored and archived for possible future reference and use in further research.

• We identified several biomarkers of Hg contamination in Clear Lake piscivores. Again, because of a low budget, it was necessary for us to obtain biomarkers of Hg effects through routine veterinary evaluations. We utilized standard veterinary hematological techniques to meet this end. These markers will be useful to other researchers studying Hg contamination effects in Clear Lake piscivores.

• As part of a historical analysis, we documented large declines of both organochlorine and Hg contamination in indicator species, representing Clear Lake avifauna over a three-decade period that included cessation of organochlorine use, closing of the Hg mine, and a period of additional mine site remediation. All aspects of our study, from demographic observations through residue monitoring, indicated that various actions by regulating agencies may have had observable effects on important ecological endpoints—in this case, top-level avian fish eaters. This information will aid regulating agencies in making further decisions about resource management at Clear Lake.

• We demonstrated consistent, year-to-year residual effects of the long past organochlorine residue, p,p'-dichlorodiphenyldichloroethane (DDE) (a persistent metabolite of dichlorodiphenyltrichloroethane [DDT]) on eggshells in Western/Clark's grebes, some three decades after cessation of use. This result was an offshoot of our studies on organochlorines when we tested the biomarker, eggshell thinning, as a possible product of DDE contamination (the originating insecticide, DDT, was not used for three decades before our study). This information will be important to other researchers because it shows that we still have important "legacy chemicals" remaining in the system from use in decades past.

• We documented a significant decline in Hg residues in osprey and grebe feathers, a change to normal in several biomarkers of the Hg effect, and significant improvements in demographic performance of both species throughout the study period (1992-2002). These changes, in part, resulted from a long-term trend of declining Hg residues and a single mine site remediation event in the early 1990s. All indications from our monitoring program were that several endpoints of negative effect from Hg contamination were lessened by active agency management activities. This finding reinforces management agencies’ essential role in ensuring ecosystem health.

• We significantly stimulated local conservation efforts at Clear Lake for the two indicator species, osprey and grebes, used in this study. Because of the many additional factors affecting demographic performances of both our study species in the Clear Lake ecosystem, we identified elements that could be managed or controlled to further enhance these breeding populations. Our efforts may compensate for small negative effects brought about by potential contaminants in the ecosystem, and will be of interest to those continuing conservation efforts in the area.

• Our work compelled California to develop a statewide management plan for the general conservation of Western/Clark's grebes. When studying contaminants in a system, one cannot help but identify additional ecological factors in a suite of multiple stressors. Thus, we developed a strong working relationship with managers and conservationists from various agencies, who then developed a management plan for grebes throughout California and integrated our results into an overall waterbird management plan for the western United States. This plan—a joint venture of the Colonial Waterbird Management Plan initiated by the U.S. Department of the Interior—has only recently received funding. The state management plan outcome was a direct result of our project.

Supplemental Keywords:

ecosystem, ecosystem protection, environmental exposure and risk, geographic area, international cooperation, water, terrestrial ecosystems, aquatic ecosystem, aquatic ecosystem restoration, aquatic ecosystems and estuarine research, biochemistry, ecological effects, ecological indicators, ecological monitoring, ecology and ecosystems, environmental chemistry, restoration, state, water and watershed, watershed, watershed development, watershed land use, watershed management, watershed modeling, watershed restoration, watershed sustainability, agricultural watershed, exploratory research environmental biology, California, CA, Clear Lake, Lake Tahoe, anthropogenic effects, aquatic habitat, biogeochemical cycling, ecological assessment, ecology assessment models, ecosystem monitoring, ecosystem response, ecosystem stress, environmental stress, environmental stress indicators, fish habitat, hydrologic modeling, hydrology, integrated watershed model, lake ecosystems, lakes, land use, nutrient dynamics, nutrient flux, water management options, water quality, wetlands., 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, wetlands, eutrophication, watershed management, nutrient loading, migratory birds, nutrients, nutrient flux, fish consumption, organochlorides, restoration strategies, esturarine eutrophication, Clear Lake, diagnostic indicators, lakes, nutrient stress, watershed influences, ecological recovery, algal blooms, wetland restoration, aquatic ecosystems, environmental stress, lake ecosysyems, environmental rehabilitation, mercury contamination in fish, wildlife bioaccumulation, riparian habitat, riparian ecosystem integrity, bioaccumulation, lake ecosystems

Relevant Websites: Exit

Progress and Final Reports:

Original Abstract
  • 1997
  • 1998
  • 1999

  • 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