Ecological Thresholds and Responses of Stream Benthic Communities to Heavy Metals

EPA Grant Number: R832441
Title: Ecological Thresholds and Responses of Stream Benthic Communities to Heavy Metals
Investigators: Clements, William , Noon, Barry , Wang, Haonan
Institution: Colorado State University
EPA Project Officer: Packard, Benjamin H
Project Period: July 31, 2005 through December 30, 2007 (Extended to December 30, 2008)
Project Amount: $295,760
RFA: Exploratory Research: Understanding Ecological Thresholds In Aquatic Systems Through Retrospective Analysis (2004) RFA Text |  Recipients Lists
Research Category: Aquatic Ecosystems , Water


This project will identify and validate threshold responses of stream ecosystems to anthropogenic disturbance. We hypothesize that the location of ecological thresholds along a well defined stressor gradient will vary among state variables and will be influenced by local (reach-scale) and landscape level environmental drivers.


We will integrate results of stream microcosm experiments and spatially extensive surveys of 79 Colorado streams to locate ecological thresholds along gradients of heavy metal contamination. Using a variety of parametric and nonparametric statistical procedures, we will quantify the influence of environmental drivers on ecological thresholds and test the hypothesis that thresholds vary among watersheds. We will validate and assess the ecological relevance of these thresholds using (1) results of a long-term (15 year) survey of the Arkansas River, a metal polluted stream in central Colorado undergoing remediation; and (2) a spatially extensive survey of 19 streams in the same region.

Expected Results:

The most significant expected result from this research will be the identification of ecological thresholds for a suite of state variables across several levels fo biological organization. We expect that these state variables will likely show different statistical distributions. Therefore, we will make specific recommendations concerning the applicability of several parametric and nonparametric approaches for locating thresholds. We predict that the location of thresholds along stressor gradients will vary among state variables and will be infuenced by reach-scale and landscape level environmental drivers. We will also assess the ecological significance of these thresholds and provide water resource managers with guidelines regarding the effectiveness of different levels of remediation.

Publications and Presentations:

Publications have been submitted on this project: View all 45 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 32 journal articles for this project

Supplemental Keywords:

streams, ecological thresholds, statistical modeling, heavy metals, resilience, Rocky Mountains,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, POLLUTANTS/TOXICS, Aquatic Ecosystems & Estuarine Research, Chemicals, Aquatic Ecosystem, Environmental Monitoring, Ecology and Ecosystems, Ecological Risk Assessment, anthropogenic stress, estuarine research, ecological thresholds, anthropogenic impact, ecosystem indicators, modeling ecosystem change, stream habitat, benthic indicators, aquatic ecosystems, water quality, ecosystem stress, riverine ecosystems, trophic interactions, aquatic ecosystem restoration, ecosystem response, environmental history

Progress and Final Reports:

  • 2006 Progress Report
  • 2007 Progress Report
  • 2008 Progress Report
  • Final Report