Research Projects 
The research projects proposed here establish a conceptual framework to guide implementation 
of diagnostics, provide case studies to develop and test methods and models for both single-and 
multiple-stressor scenarios, assess the likelihood of multiple stressor interactions, and establish 
the structure for a decision-support system. Opportunities for interlaboratory collaboration on 
this research are shown in Appendix 2. 
Project Title 1. Conceptual Model Development and Information Management Framework 
Project Coordination and Resources (6.5 FTEs: FY02: AED, GED, MED [total = 6.0]; FY03: 
MED-0.25, AED-0.25 [total = 0.5]) 
Objectives 
The goal of this project is to support the problem formulation stage in diagnostics (EPA 1996). 
The main objective is to develop conceptual models describing stressor-response relationships 
within ecosystems, including potential interactions among multiple stressors across all scales 
relevant to setting a protective TMDL (EPA 1996). These conceptual models will then provide 
the basis for creating a national database on nontoxic aquatic stressor-response relationships and 
for improving information management systems in support of 303(d) assessment activities. 
Scientific Approach 
Conceptual model development will focus on the effects of habitat alteration, nutrients, 
suspended and bedded sediments, and toxic chemicals on appropriate endpoints (individuals, 
populations, communities, ecosystems) across spatial scales (habitats, water body, watershed, 
region) relevant to setting a protective TMDL. This research will be coordinated across all of the 
Ecology Divisions and across all five research areas (Sections 4-7). Priorities for refining 
conceptual models for single and multiple stressors at the habitat scale will be established by 
examining the relative frequency of stressor X or stressor combination X, ,Xj... with habitat type 
Y combinations in the OW 303(d) listing database (EPA 2001, 
http://www.epa.gov/owow/tmdl/trcksvs.htiTih . A determination of impairment may be controlled 
by different factors as the scale of impact gets larger. Therefore, conceptual models will examine 
the cross-scale interactions (habitat <=> water-body <=> watershed <=>region) that must be 
understood to determine the appropriate scale at which a protective TMDL must be established. 
In addition, the interactions among predominant stressors will be included as appropriate, based 
on expected mechanisms of action. Conceptual models will be developed through one or more 
cross-divisional workshops. 
Two types of information management frameworks will be developed in support of the 303(d) 
listing process and diagnosis of the causes of impairments. First, a framework for supplying 
existing geospatial information for the problem formulation stage will be established. To 
identify potential causes of impairment, this framework will build upon database networks 
currently under development or refinement by OW, including geospatial databases incorporated 
within the Better Assessment Science Interacting Point and Nonpoint Source (BASINS) 
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