Ecosystem Consequences of Eurasian Watermilfoil (Myriophyllum Sspicatum) Invasion in Lake Tahoe, California-Nevada

EPA Grant Number: U915658
Title: Ecosystem Consequences of Eurasian Watermilfoil (Myriophyllum Sspicatum) Invasion in Lake Tahoe, California-Nevada
Investigators: Walter, Katey M.
Institution: University of California - Davis
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 1999 through January 1, 2003
Project Amount: $94,876
RFA: STAR Graduate Fellowships (1999) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems


The overall objective of this research project is to determine ecosystem effects of the invasion of Eurasian watermilfoil (Myriophyllum spicatum) in Lake Tahoe. The specific objectives of this research project study are to: (1) monitor the occurrence and spread of M. spicatum around Lake Tahoe; (2) estimate the potential for infestation of new areas around the lake; (3) determine whether M. spicatum threatens lake water quality by enhancing the growth of algae; (4) quantify phosphorus transfer between sediments, water, and algae via M. spicatum; and (5) compare the effects of a native aquatic plant (Elodea sp.) and M. spicatum on lake water quality.


To monitor the occurrence of M. spicatum atin Lake Tahoe, aerial and boat surveys have been completed annually since 1995 (originally by the U.S. Department of Agriculture/Agricultural Research ServiceUSDA/ARS). Underwater benchmarks have been established using SCUBA to monitor changes in plant community, sediment chemistry, and water quality. A reciprocal transplant experiment was completed to investigate the potential for spread of M. spicatum around the lake. Monthly in situ surveys were completed at four sites around the lake to test the hypothesis that M. spicatum alters water chemistry by pumping phosphorus from sediments to the water column. Phosphorus transfer through M. spicatum and Elodea sp. was quantified through a series of laboratory experiments using 32P-PO4. Additional bioassays were conducted with 14C to test the hypothesis that M. spicatum enhances the growth of algae, thereby reducing water quality.

Supplemental Keywords:

fellowship, Eurasian watermilfoil, Lake Tahoe, Myriophyllum spicatum, phosphorus, water quality., RFA, Scientific Discipline, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, State, Aquatic Ecosystem, Environmental Monitoring, Ecological Risk Assessment, Ecology and Ecosystems, aquatic plants, algal blooms, habitat fragmentation, bidoveristy, aquatic ecosystems, bioassay, environmental stress, invasive species, phosphorus, water quality, California (CA)

Progress and Final Reports:

  • 1999
  • 2000
  • 2001
  • Final