Related Experiment Video
Updated: Jun 21, 2026
05:04
Visualization of Productivity Zones Based on Nitrogen Mass Balance Model in Narragansett Bay, Rhode Island
Published on: July 14, 2023
Ecosystem modeling applied to nutrient criteria development in rivers.
James N Carleton1, Richard A Park, Jonathan S Clough
1U.S. Environmental Protection Agency, Washington, DC 20460, USA. carleton.jim@epa.gov
Environmental Management
|July 29, 2009
Summary
Determining nutrient impairment thresholds in rivers is challenging. This study used the AQUATOX model, identifying 0.1 mg/l total phosphorus as a key threshold to prevent algal blooms and excessive periphyton.
Area of Science:
- Environmental Science
- Ecosystem Modeling
- Aquatic Ecology
Background:
- Quantifying nutrient impairment thresholds in lotic systems is complex.
- US States and Tribes require water quality criteria for ecosystem protection.
- Excessive nutrient enrichment poses a significant threat to riverine ecosystems.
Purpose of the Study:
- To explore the utility of the AQUATOX ecosystem model for identifying biological impairment thresholds.
- To investigate simulated biological responses to nutrient and sediment load reductions.
- To propose a method for developing water quality criteria for lotic systems.
Main Methods:
- Utilized the AQUATOX ecosystem model to simulate biological responses.
- Selected key biological indexes: sestonic cyanobacterial biomass and benthic chlorophyll a.
- Analyzed responses to concurrent reductions in phosphorus, nitrogen, and suspended sediment in a river.
Main Results:
- Biological indexes showed strong responses to phosphorus and suspended sediment changes.
- Nitrogen concentration changes had a less pronounced effect on the selected indexes.
- A total phosphorus concentration of 0.1 mg/l was identified as a threshold for preventing algal blooms and excessive periphyton.
Conclusions:
- The AQUATOX model can effectively evaluate the impacts of nutrient and sediment reductions.
- A total phosphorus concentration of 0.1 mg/l is proposed as a hypothetical water quality criterion.
- This modeling approach can aid in balancing multiple management objectives for nutrient criteria development.
Related Concept Videos
01:30Microbial Wastewater Treatment
Microbial communities in aquatic ecosystems play a key role in the natural breakdown of contaminants introduced through domestic and industrial effluents. Acting as biological catalysts, these microbes change and mineralize a wide range of organic and inorganic pollutants under different redox conditions.In oxygen-rich surface waters, aerobic heterotrophs lead organic matter breakdown, using oxygen as the terminal electron acceptor to efficiently oxidize substrates to carbon dioxide and water.
01:24Freshwater Microbial Ecology
Freshwater systems such as streams, rivers, and lakes exhibit distinct physical and biological characteristics that influence their microbial communities. These environments are broadly categorized into lotic systems—those with flowing waters like streams and most rivers—and lentic systems, which include still or slow-moving waters such as lakes, ponds, and marshes.In lentic systems, phytoplankton drive primary production, generating autochthonous organic carbon. In contrast, lotic systems...
01:30Typical Model Studies
Fluid mechanics model studies often utilize scaled-down systems to predict fluid behavior in full-scale environments, such as river flows, dam spillways, and structures interacting with open surfaces. Maintaining Froude number similarity in river models is crucial, as it replicates surface flow features like wave patterns and velocities.
01:30Environmental Applications of Microorganisms
Microorganisms play a pivotal role in maintaining ecosystem balance by recycling essential elements such as carbon, nitrogen, and phosphorus, as well as supporting processes like bioremediation, wastewater treatment, and biofuel production.Microbes in Elemental CyclesIn the carbon cycle, microorganisms decompose organic matter, releasing carbon dioxide via aerobic respiration. This carbon dioxide is subsequently used by photosynthetic organisms to synthesize organic compounds, closing the...
01:17What is an Ecosystem?
Overview
01:26Pharmacokinetic Models: Comparison and Selection Criterion
Physiological and compartmental models are valuable tools used in studying biological systems. These models rely on differential equations to maintain mass balance within the system, ensuring an accurate representation of the dynamic processes at play.
Physiological models take a detailed approach by considering specific molecular processes. They can predict drug distribution, metabolism, and elimination changes, providing a comprehensive understanding of how drugs interact with the body.
Physiological models take a detailed approach by considering specific molecular processes. They can predict drug distribution, metabolism, and elimination changes, providing a comprehensive understanding of how drugs interact with the body.