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2000 Progress Report: The History of Anthropogenic Effects
EPA Grant Number: R825433C019Subproject: this is subproject number 019 , 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: The History of Anthropogenic Effects
Investigators: Richerson, Peter , Anderson, Daniel , Nelson, Douglas , Suchanek, Thomas
Institution: University of California - Davis
EPA Project Officer: Levinson, Barbara
Project Period: October 1, 1996 through September 30, 2000
Project Period Covered by this Report: October 1, 2000 through September 30, 2001
RFA: Exploratory Environmental Research Centers (1992)
Research Category: Center for Ecological Health Research , Targeted Research
Description:
Objective:To use sediment cores as tools in reconstructing the history of anthropogenic stresses on aquatic ecosystems and their watersheds. The core work supplements other historical investigations of watershed processes in the Clear Lake area including analysis of long-term data sets, documentary sources, and reanalysis of curated specimens.
Progress Summary:Project B.8 is closely tied to Projects B.1 (Fish as transporters/modifiers of Hg), Project B.3 (Wildlife bioaccumulation & effects), B.4 (Microbiology of Hg methylation in sediments), B.5 (Mercury and Iron Biogeochemistry) and B.6 (Water motions & material transport).
Signals deposited in sediment cores are extremely useful indicators of past processes within Clear Lake and other aquatic systems where deposition is relatively predictable. We have used relatively shallow sediment cores (200-300 cm deep) in Clear Lake to evaluate anthropogenic stressors that have affected this system over the past 200-300 yrs. The USGS raised some very deep cores (115m long, representing 450,000 years) during the 1970s and 80s for work on the long time scale, and the UC Davis Mercury Project raised some shallow cores (~1m, representing 50?75 years) during 1992 to investigate changes in sediment mercury since the last mining episode. In 1998 we collected and analyzed 2?3 meter length cores, which reflect the last 200?300 years of changes in the lake in order to assess the kinds of natural and anthropogenic stresses applied at various time frames since European colonization. Our initial hypothesis, derived from earlier historical work, was that the advent of heavy powered earthmoving equipment after W.W. I had multiple impacts on the lake and watershed. Open pit mining at Sulphur Bank, increased erosion due to road building and similar activities, and habitat destruction as a consequence of diking and filling activities were all made possible by the widespread use of this machinery beginning in the 1920s and early 1930s.
Some features of the five main cores we raised in 1998 are consistent with this hypothesis. Many sediment parameters change suddenly and substantially at a time depth that dates to about 1927 (dated using 210Pb activity), when open pit mining at Sulphur Bank, modern road-building, and larger scale diking and filling projects began. Total mercury in the cores jumped by a factor of 10, sediments became drier, nitrogen and organic matter contents became lower. Professor Mount's group has also demonstrated large changes in magnetic properties at the same horizon. We have estimated the rate of dry matter deposition before and after 1927, assuming that a small uptick in total Hg concentration in the cores signals the beginning of Hg mining at Sulphur Bank in 1973. Only one of the cores shows an increase in dry matter accumulation rates after 1927 according to this calculation. Pending the analysis of a larger sample of cores by Mount's group, we tentatively conclude that the earthmoving hypothesis is false.
We are currently investigating another hypothesis that may explain the changes in core characteristics after 1927. Acid mine drainage from Sulphur Bank carries large, but not yet accurately measured, amounts of sulfate and acidity into the lake. A conservative estimate suggests that acid mine drainage doubles to quadruples the sulfate loading to the lake. Sulfate concentrations dropped in the lake during the long drought of the late 1980s and early 1990s. At the same time, amounts of phosphorus cycling out of the sediments increased dramatically, while iron concentrations fell. Increased sulfate reduction in the sediments could well cause the changes we have observed in the sediments by increasing the amount of organic matter metabolized in the sediments. Sulfate diffuses to depths below which oxygen penetrates and hence supports oxidative microbial metabolism for some years after sediment burial. Our chemical modeling work suggests that the sulfide produced as a byproduct of sulfate reduction may reduce iron recycling from sediments. Iron is the limiting nutrient in Clear Lake, and the drop in its concentration led to a succession of years with relatively clear water, abundant macrophytes, and relatively small cyanobacterial blooms. These conditions resemble the scanty scientific accounts of the pre-1930 period that describe the lake as having abundant bottom growth. They are also consistent with oral histories of long-time residents collected in the 1960s. Attempts to test directly if cyanobacteria were less abundant before 1927 using pigment analysis has not proven practical. Pigments are highly degraded and are not suitable for quantitative analysis of cyanobacteria specific pigments. Interestingly, although the lake's phosphorus cycling regime has returned to pre-drought levels, cyanobacterial abundance remains low and macrophyte biomass high. Uncertainty about the dynamics of iron cycling currently limits our understanding of cyanobacterial bloom dynamics.
We have recently collected a new series of 250-300 cm deep cores (summer 2000), for several reasons. First, previous methyl mercury concentrations in buried core sections may not have been reported accurately because of an analytical artifact associated with the analytical procedure (distillation method) used to analyze for methyl mercury. This artifact problem has affected the entire scientific community throughout the world, but is especially problematic at Clear Lake because the high inorganic mercury content of the sediments enhances the analytical artifact. In fact, previously reported concentrations of methyl mercury in sediments may be as much as 95-98% artifact. We have collected a completely new series of five cores (one in the Upper Arm, one in the Lower Arm and three in the Oaks Arm) in order to obtain more accurate estimates of methyl mercury buried in Clear Lake sediments and within surficial sediments. Sediments from these core sections will be analyzed for methyl mercury using (1) the older distillation method and (2) a method that has been determined to be more accurate (extraction method), especially for conditions in which there is high inorganic mercury present. This will provide us with a more accurate estimate of methyl mercury concentrations and dynamics within sediments, and provide us with a correction factor that can be applied to all of the previous sediment samples that were analyzed using the former distillation method. Once these data are compiled, we will be able to provide a much more accurate representation of the deposition of methyl mercury before and after the Sulphur Bank Mercury Mine came into operation.
In addition to methyl mercury, we are also analyzing these recent sediment
cores for the following parameters: total mercury, arsenic (which is a contaminant
with increasing profile within USEPA and another contaminant discharged from
the Sulphur Bank Mercury Mine), grain size, total sulfur (for our sulfur budget),
total phosphorus, phosphorus species, total carbon and total N (for nutrient
loading), stable isotopes (
13C, 15N and 34S) for estimating changes in algal
communities over time), 210Pb (for dating shallow core sections to ca. 90 ybp),
possibly 14C (for dating deep cores sections), and possibly pesticides (especially
DDD, DDT and DDE) for evaluating the influence of the DDD additions to Clear
Lake during the late 1940s and 1950s. The total mercury, methyl mercury and
sulfur are especially critical for us to evaluate sulfate and mercury loading
into Clear Lake from the Sulphur Bank Mercury Mine. And, the dating techniques
will allow us to place these events into context with the various mining methods
(e.g. shaft versus open-pit) over the duration of activities at the mine site.
Lake sediments are the main loss term in the sulfur budget, and if sulfate loading
doubled, so should have sulfide deposition in sediments.
We are also working on a biogeochemical model of sediment processes to try to understand the impact of an increased sulfate load on nutrient cycling. If heavy equipment use was the cause of Clear Lake's historical changes, similar impacts are likely to have occurred throughout the region at about the same time. On the other hand, sulfate loading is a stress highly specific to watersheds with base metal mining, as are logging impacts in the Tahoe watershed. We would like to know if, at the regional scale, a few anthropogenic stressors like earthmoving dominate the impact on watersheds or whether a plethora of local, watershed specific, stressors are more important.
The answers to this question will have a major impact on how we monitor, study, and control anthropogenic stressors. For example, if local stressors are of dominant importance, technical resources and regulatory responsibility should perhaps be shifted towards smaller government units (cities and counties), whereas regional or super-regional commonalities suggest a relatively larger role for states and the federal government. At Clear Lake, the erosion of resources since Proposition 13 ended the ability of Lake County to fund its own monitoring and research efforts, and state agencies have largely failed to fill the gap. As a result, the County cannot really fulfill its management responsibilities for the lake. Even with generous support from CEHR, some problems of great interest to managers, such as the iron cycle, are not being addressed as vigorously as they should be.
Supplemental Keywords:Ecosystem Protection/Environmental Exposure & Risk, Toxics, Water, Geographic Area, Scientific Discipline, Waste, RFA, Ecosystem/Assessment/Indicators, Geology, Restoration, Aquatic Ecosystem Restoration, HAPS, Microbiology, Aquatic Ecosystems & Estuarine Research, Aquatic Ecosystem, Ecological Indicators, Environmental Engineering, Fate & Transport, mercury transport, Environmental Chemistry, Ecological Effects - Environmental Exposure & Risk, Ecosystem Protection, Environmental History, West Coast, 33/50, Monitoring/Modeling, Geochemistry, Engineering, lake ecosystem, anthropogenic stresses, ecosystem indicators, Clear Lake, mining, Sulphur Bank Mercury Mine, Clear Lake , sediment cores, mercury & mercury compounds, aquatic ecosystems, mercury, mercury loading, nutrients, anthropogenic stress, Mercury Compounds, transport
Progress and Final Reports:
1996 Progress Report
Original Abstract
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