Executive Summary 
This document describes the framework (Sections 1-3) and implementation plans (Sections 4-8) 
for ecological effects research on aquatic stressors within the U.S. Environmental Protection 
Agency’s (EPA) National Health and Environmental Effects Research Laboratory (NHEERL). 
The ultimate goal of this research is to develop scientifically valid approaches for protecting and 
restoring the ecological integrity of aquatic ecosystems from the impacts of multiple aquatic 
stressors. The immediate focus is to develop and improve assessment methodologies, diagnostic 
capabilities, and ecological criteria to guide management options for 1) protection and restoration 
and 2) remediation efforts to meet designated uses. 
The context for this research is the common management goal of protecting aquatic systems to 
prevent degradation of habitat, loss of ecosystem function, and reduced biodiversity. To this end, 
environmental managers must be able to: 1) assess the condition of an aquatic resource and 
determine the degree of impairment, 2) diagnose the causes of impairment, 3) forecast the effects 
of changes in stressor levels, and 4) develop and implement remediation and maintenance 
strategies. Meeting the goals of effective management and protection of aquatic resources 
requires that multiple research elements be in place to provide the needed tools. This document 
provides a means to develop these tools. The research approach presents a generally linear 
sequence, although many research elements will be conducted simultaneously. 
The research herein focuses on the effects of aquatic stressors, including habitat alteration, 
nutrients, suspended and bedded sediments, and toxic chemicals. This approach is consistent 
with recent scientific consensus, recognizing that these stressors have the greatest potential for 
causing adverse effects to aquatic ecosystems. In the context of this effects research, the 
document also provides research that will develop diagnostic tools for a decision support system 
for resource managers. 
The importance of habitat quality and quantity for maintaining species is indisputable, but 
quantifying exactly how species depend on habitats is multi-faceted and complex. Research is 
needed to quantitatively link alterations in key habitats to provide the scientific basis to 
implement regulations and policies to protect fish, shellfish, and wildlife populations, and the 
ecosystems upon which they depend. To quantitatively assess effects over a range of foreseeable 
stressor conditions, stressor-response relationships need to be determined. These relationships 
provide fundamental information that helps to define response thresholds, or other patterns, and 
to improve aquatic life and aquatic dependent wildlife criteria. As stressor-response 
relationships are determined, research can be directed towards developing a "diagnostic tree" 
approach to list, analyze, and characterize the causes of impairment. EPA’s Stressor 
Identification Workgroup has developed such an approach. 
Another research need is to develop ecosystem classification approaches that allow for 
reasonable extrapolations of diagnostic approaches and stressor-response models. Classification 
is valuable for grouping ecosystems according to similar criteria and for spatially classifying 
ecosystems connected via stressor actions. Since little is known about scale relative to ecosystem 
classification, effects research also will provide guidance about the most appropriate scale for 
XIV 
