United States	EPA/600/F-18/329
Environmental Protection Agency
LINKING WATER QUALITY AND AQUATIC LIFE WITH
AQUATOX 3.2
AQUATOX is an ecosystem simulation model that predicts the environmental fate of pollutants,
such as excess nutrients and organic chemicals, and their effects on aquatic ecosystems, including
fish, invertebrates, and aquatic plants. AQUATOX has been used across the US and the world in a
wide variety of ecological risk assessments. EPA has released AQUATOX Release 3.2, which
extends the existing AQUATOX estuarine version to include improved capabilities for situations
encountered in the nearshore marine environment. In addition, the graphical user interface was
updated and modernized to add capabilities and to increase user-friendliness.
Background
One of the biggest challenges to protecting or
restoring our nation's waters is adequately
understanding the relationships between the
environment and the organisms that live there.
Ecosystems are complex, with natural
variations overtime, and multiple interactions
among components. The health of biological
communities in many water bodies is impaired,
but the causes of the impairment may not be
obvious due to numerous environmental
stressors. It is difficult to predict how the
aquatic community will respond to changes in
pollutants or environmental conditions using
simple methods of analysis, especially if those
methods address only one stressor at a time.
A complex simulation model like AQUATOX
may be more effective.
About AQUATOX
Simulation model for aquatic ecosystems and impacts on aquatic organisms
-	Streams, rivers, lakes, reservoirs, estuaries
-	Effects on algae, plants, invertebrates, and fish
Predicts responses of aquatic life to multiple stressors
-	Nutrients, organic loadings, sediments, organic chemicals, and temperature
-	Bioaccumulation of organic chemicals
Flexible and versatile
-	General or site-specific application
-	Can model just the species and scenarios you need to understand
-	Spatial options for linked segments and vertical stratification
-	Contains sophisticated uncertainty and sensitivity analysis tools
-	Includes many example studies and data libraries
PC-based, available at no cost on EPA web site
Open source software
User-friendly interface, with built-in Help files to lead users through required model input
CQ

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Applications
AQUATOX can be used to better understand the processes relating the chemical and physical
environment to the biological community. You can use AQUATOX to:
•	Develop and evaluate numeric nutrient targets based on desired biological endpoints.
•	Evaluate which of several stressors is causing observed biological impairment.
•	Predict effects of pesticides and other toxic substances on aquatic life.
•	Predict recovery of ecosystems with reduced nutrient loading.
•	Predict effects of land use on aquatic life by linking to watershed models.
•	Estimate time to recovery of fish tissues to safe levels after reducing pollutant loads.
AQUATOX links water quality to biological endpoints
Suspended sediment
(TSS, Sand/silt/clay)
Partitioning
Light extinction
Plants
Phytoplankton
Attached algae
Macrophytes
Organic
toxicant
Photosynthesis
Respiration
Oxygen
Ingestion
Animals
Invertebrates (spp)
Fish (spp)
Death
Detritus
(suspended, particulate,
dissolved, sedimented)
Ingestion
Settling, resuspension
Inorganic Sediment
What's New
AQUATOX Release 3.2 contains many new enhancements including:
•	Additional equations to model the physical complexity of oyster reefs and the marsh-
edge environment
•	The capability to model size-classes of oysters and crabs within the model
New invertebrate-modeling capabilities including allometric bioenergetics equations and
refuge from predation through burrowing
Reorganized animal guilds to better represent marine-biology conventions, the guilds
used by AQUATOX to characterize these state variables have been reorganized.
•	A modernized database management system that now uses SQLite databases
Capability to write all model inputs and outputs in ASCII format
•	Addition of a command-line version option, which allows users to execute and
manipulate the model using a DOS command prompt or batch file.
Additional information
Additional information on AQUATOX is available at https://www.epa.qov/ceam/aquatox You
may also contact Brenda Rashleigh in the EPA National Health and Environmental Effects
Laboratory at Rashleigh. Brenda@epa.gov or 401-782-3014.

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