823F04001
United States Environmental
Protection Agency
FACT SHEET
Office of Water
4304T
EPA-823-F-04-001
January 2004
AQUATOX (RELEASE 2): MODELING
ENVIRONMENTAL FATE AND ECOLOGICAL
EFFECTS IN AQUATIC ECOSYSTEMS
SUMMARY
The U.S. Environmental Protection Agency announces the availability of an enhanced version of the
freshwater ecosystem simulation model AQUATOX which predicts the fate of various pollutants, such as
nutrients and organic chemicals, and their effects on the ecosystem, including fish, invertebrates, and
aquatic plants. AQUATOX is a valuable tool for ecohgists, biologists, water quality modelers, andanyone
involved in performing ecological risk assessments for aquatic ecosystems. Release 2 has enhanced
scientific capabilities and analytical tools to more completely simulate and understand aquatic ecosystems.
It also features improvements that make the model easier to use.
BACKGROUND
One of the biggest challenges to protecting or restoring our
Nation's waters is to adequately understand the relationships
between the chemical and physical environment and the
organisms that live there.' Ecosystems are complex, with
seasonal and annual variations and multiple interactions
among species. The biological communities in many water
bodies are impaired, but the causes of the impairment may
not be obvious in the face of numerous environmental
stressors. It is difficult to predict how the aquatic community
will respond to changes in pollutants or environmental
conditions with simple methods of analysis, especially if the
methods address a single stressor at a time. A complex
simulation model may be required.
ABOUT AQUATOX RELEASE 2
AQUATOX is a PC-based ecosystem model that predicts the fate of nutrients and organic chemicals in
water bodies as well as their direct and indirect effects on the resident organisms. Most water quality
models predict only concentrations of pollutants in water: they do not project effects of pollutants on
organisms. AQUATOX simulates multiple environmental stressors (including nutrients, organic loadings
and chemicals, and temperature) and their effects on the algal, macrophyte, invertebrate, and fish
communities. Therefore, AQUATOX can help identify and understand the cause and effect relationships
between chemical water quality, the physical environment, and aquatic life. AQUATOX can represent a
variety of aquatic ecosystems, including vertically stratified lakes, reservoirs and ponds, and rivers and
streams. Release 2 has many new features, including:
Enhanced scientific capabilities
more complete ecosystem representation
improved stream simulation (habitat differentiation and simulation of inorganic sediments)
more realistic simulation of fish
• increased number of organic toxicants (up to 20) that can be modeled simultaneously
enhanced uncertainty analysis capabilities
new linkage to BASINS 3.1 - EPA's CIS-based watershed modeling system
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How AQUATOX Represents Ecosystems
Enhanced user friendliness
new study setup Wizard
context-sensitive Help files
expanded data libraries
improved graphing capabilities
MANY ENVIRONMENTAL ISSUES
CAN BE ADDRESSED WITH AQUATOX
AQUATOX can be used in a myriad of ways to
address water management issues and programs
(water quality criteria and standards, Total
Maximum Daily Loads, and ecological risk
assessment). AQUATOX should be considered
when the user needs to understand the processes
relating the chemical and physical environment to
the biological community. A sample of the types of
analyses that can be addressed includes:
Ecological understanding and problem analysis
Evaluate which of several stressors is causing observed biological impairment. For example: Are
nuisance levels of attached algae in streams controlled primarily by nutrients, sediments, grazing
by snails, or flow conditions?
Predict effects of pesticides and other toxic substances on aquatic life. For example: Will sublethal
concentrations eventually cause game fish to disappear? Will reduction of one group of organisms
reduce the food supply for other, more beneficial species, or lead to increases in nuisance species?
Evaluate potential ecosystem responses to invasive species
• Explore how changes in land use or agricultural practices in a watershed might affect aquatic life,
by using the new linkage to BASINS
Environmental Management
Compare differences in biological responses to control alternatives
Develop targets for nutrients in lakes and reservoirs with nuisance algal blooms
Estimate time to recovery offish or invertebrate communities after reducing pollutant loads
• Calculate bioaccumulation factors for organic toxic chemicals
* Estimate how long before tissue levels of toxic organ ics in fish will return to safe levels following
removal of contaminated sediments
WHO WILL WAIST TO USE AQUATOX?
AQUATOX is a valuable tool for ecologists. biologists, water quality modelers, and anyone involved in
performing ecological risk assessments for aquatic ecosystems.
How to Get More Information
You can download AQUATOX Release 2 and accompanying documentation at fhttp://www.epa.qov/water-
science/models/aquatox/V You will be able to get the CD and hard copy soon from the National Service Center for
Environmental Publications (NSCEP) at 1-800-490-9198 or by email to ncepimal@one.net or from the Water
Resources Center at 202-566-1729. You may also contact Marjorie Coombs Wellman, Office of Science and
Technology, U.S. EPA, 1200 Pennsylvania Ave., NW (4305T), Washington, DC, 20460 (telephone: 202-566-0407,
or email: wellman. mariorief5>epa .gov)
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