Nutrient Loading

EPA Grant Number: R825433C062
Subproject: this is subproject number 062 , 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: Nutrient Loading
Investigators: Goldman, Charles R.
Institution: University of California - Davis
EPA Project Officer: Packard, Benjamin H
Project Period: June 30, 1995 through June 30, 1998
RFA: Exploratory Environmental Research Centers (1992) RFA Text |  Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research


Increased sediment loading to Sierra Nevada lakes is the direct result of multiple stress in the watershed. Given that these aquatic ecosystems are typically high in clarity and are characterized by mesotrophic-oligotrophic production, accelerated sediment loading contributes to reduced lake water quality and aquatic habitat, e.g. eutrophication, decreased water clarity, decrease in deepwater oxygen levels, change in biodiversity, modification of chemical properties of the lake, etc. Using Lake Tahoe as a model, the Investigators goals in this section of the research were to directly characterize the organic and inorganic features of the lake's suspended particulate matter, relate changes in each of these fractions to historical and current optical conditions, and evaluate characteristics of sediment loading from the watershed. This research is a direct extension of the sediment transport modeling in other projects.

Following the documented shift toward increasing phosphorus limitation in Lake Tahoe since the early 1980s, watershed erosion, with its contributions to sediment and nutrient loading, has become a more critical issue in land-use and environmental planning. The objectives include providing greater detail concerning natural watershed characteristics and environmental stresses such as forest health, nature of land use, road construction rates, erosion control measures and natural geomorphology, which have direct impacts on nutrient loading, algal growth and water clarity.


A preliminary analysis of the historic Secchi depth and chlorophyll data by the Tahoe Research Group suggests that inorganic SPM may be playing a role in the long-term variability of clarity. Although monitoring data on sediment loading from the major watersheds exists through the Lake Tahoe Interagency Monitoring Program, an analyses of this information, in light of the changing optical properties of the lake has not been done. Given that the Lake has lost nearly 50 feet of its unique clarity during the past 30 years (average rate of 1.5 feet or 0.5 meters per year) and if rate continues, its extraordinary transparency will be gone in another 30 years, it is critical that the investigators more completely understand the factors which regulate its optical characteristics. As discussed earlier in this section, clarity in aquatic systems is an ecosystem response variable which integrates the impacts of multiple stress. Further clarity is a property of lakes which is simple and appreciated by the public at large. It is, in fact, a matter of state policy to maintain Lake Tahoe's remarkable transparency.

Statistical analysis on existing time series data. These analyses will be performed to determine the quantitative relationship between Secchi depth and, inorganic SPM and phytoplankton. The first step is to decompose the series with a novel application of principal component analysis. The next step is to explore the relation between the several amplitude time series for Secchi depth and time series for variables that are postulated to underlay Secchi variability. In this case, we will be examining the historical record of watershed runoff and of algal fluorescence as causal factors. Using these and similar techniques, we expect to be able to uncover the separate effects of inorganic SPM and phytoplankton on water clarity and predict future change.
Direct measurement and characterization of inorganic SPM. Water column sampling will allow investigators to more directly distinguish the nature of total SPM and its influence on the lake's photic environment. The vertical light extinction can be separated into three components: K8, the contribution of all suspended matter, Kp, pigments dissolved in water, and Ka, attributable to water alone. Ks, can further be divided into: Kchl, those related to algal chlorophyll, K., the non-chlorophyll related organic matter, and Ki, the inorganic suspensoids. According to theory, if the dry weight of the suspensoid is determined, along with carbon:chlorophyll regressions which statistically isolates the nonchlorophyll related carbon, then estimates of the various components can be achieved. This will allow us to separate biological and non-biologic components of light transmission.

Individual samples will be collected at 10-meter intervals to a depth of 50 m, the maximum Secchi depth at various locations throughout the year. Each sample will be analyzed for the following biogeochemical constituents: particulate carbon, nitrogen and phosphorus, total seston (dry weight), chlorophyll and phaeophytin, zooplankton, individual soil elements (using PIXE analyses), Secchi depth and profiles of photosynthetically active radiation (PAR), upwelling and downwelling irradiance, and backscattering. The use of PIXE or photon induced x-ray emission analysis will allow us to distinguish specific elements, such as Ti, Al and others, which serve as geochemical markers for inorganic SPM.

Analyses of Long-Term Stream/Watershed Sediment Loading Data. Monitoring of stream loading has been continuous since 1980, and includes flow, suspended sediment, soluble and total nitrogen and phosphorus, iron, temperature, and ionic content. These are taken on 45-60 dates each year, for each tributary, with emphasis on sampling during periods of high flow and eventrelated runoff. The tributaries were selected as representative of various watershed characteristics in the Basin. Since the watersheds have a unique composition of natural geology, geomorphic features, precipitation, amount and type of urbanization and land disturbance, and population size and distribution, our objective is to determine the most important factors which regulate sediment and nutrient loading from each.

Expected Results:

The influence of inorganic SPM on the photic environment of the lake will be investigated using two complimentary approaches; (1) analysis of existing time series data, and (2) direct measurement and characterization of inorganic SPM. In addition, investigators will (3) analyze the relationship between long-term, suspended sediment and nutrient data from the 15 Tahoe Research Group data bases, and geomorphic, hydrologic and anthropogenic characteristics of the 8-10 distinct watersheds which are monitored.

Supplemental Keywords:

Aquatic ecosystem, California, environmental assessment, biodiversity, algal blooms, nutrients, Lake Tahoe, watersheds, eutophication, ecosystem modeling, land use., RFA, Scientific Discipline, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Aquatic Ecosystems & Estuarine Research, Ecosystem/Assessment/Indicators, Ecosystem Protection, Oceanography, Aquatic Ecosystem, Ecological Effects - Environmental Exposure & Risk, Ecological Risk Assessment, Ecology and Ecosystems, West Coast, Ecological Indicators, eutrophication, nutrient loading, phosphorus, aquatic ecosystems, Lake Tahoe

Progress and Final Reports:

  • 1995
  • 1996 Progress Report
  • Final

  • 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