Nutrients and Eutrophication
Featured Study: Nitrate Loads to Gulf of Mexico Not Decreasing
Nitrate loads entering the Gulf of Mexico have not changed despite reductions at local scales, reports a new USGS study.
Learn MoreUpdated SPARROW mappers now available!
Access new interactive SPARROW mappers for estimating flow and nutrient and sediment yields in streams and rivers across the U.S. Updated base year, improved resolution! Learn more here.
Try the Mappers!Science Center Objects
Like people, plants need nutrients, but too much of a good thing can be a problem. Nutrients, such as nitrogen and phosphorus, occur naturally, but most of the nutrients in our waterways come from human activities and sources—fertilizers, wastewater, automobile exhaust, animal waste. The USGS investigates the source, transport, and fate of nutrients and their impacts on the world around us.
BACKGROUND
Nutrients are essential for plant growth, but the overabundance of nutrients in water can have many harmful health and environmental effects. An overabundance of nutrients—primarily nitrogen and phosphorus—in water starts a process called eutrophication. Algae feed on the nutrients, growing, spreading, and turning the water green. Algae blooms can smell bad, block sunlight, and even release toxins in some cases. When the algae die, they are decomposed by bacteria—this process consumes the oxygen dissolved in the water and needed by fish and other aquatic life to "breathe". If enough oxygen is removed, the water can become hypoxic, where there is not enough oxygen to sustain life, creating a "dead zone".
A scientist collects water-quality sample to better understand the role of nutrients in the overabundance of duckweed and algae.
Too much nitrogen and phosphorus in water can lead to an overgrowth of free-floating plants such as duckweed and filamentous algae, resulting in dense layers of scum on the surface of the water. This can damage aquatic plants, fish, and other lake organisms by depriving them of the oxygen and sunlight they need to survive. (Credit: James Fischer)
WHAT ARE NUTRIENTS?
Nutrients are chemical elements found in the food that plants and animals need to grow and survive. Although there are many kinds of nutrients, two of the most important and abundant are nitrogen and phosphorus. Nitrogen and phosphorus occur in a variety of forms, or species, and the species present can change as they move between the air, water, and soil.
- AMMONIA (NH3) and AMMONIUM (NH4+) are among the primary forms of nitrogen in natural waters. Ammonia can be toxic to fish. It is also soluble in water and relatively unstable in most environments. Ammonia is easily transformed into nitrate (NO3-) in waters that contain sufficient dissolved oxygen or into nitrogen gas in waters that have no dissolved oxygen.
- NITRATE (NO3-) is another primary form of nitrogen in lakes and streams. Nitrate is verysoluble in water and is stable over a wide range of environmental conditions. It is readily transported in groundwater and streams. An excessive amount of nitrate in drinking water can cause health problems.
- PHOSPHATES (containing PO43−) are the most common form of phosphorus in natural waters. Phosphates are only moderately soluble and, compared to nitrate, are not very mobile in soils and groundwater. Phosphates tend to remain attached to soil particles, but erosion can transport considerable amounts of phosphate to streams and lakes.
Learn more about nutrients in our Nation's surface water and groundwater.
USGS Circular 1350
WHAT HAPPENS WHEN THERE ARE EXCESSIVE NUTRIENTS?
Eutrophication is a natural process that results from accumulation of nutrients in lakes or other bodies of water. Algae that feed on nutrients grow into unsightly scum on the water surface, decreasing recreational value and clogging water-intake pipes. Decaying mats of dead algae can produce foul tastes and odors in the water; their decay by bacteria consumes dissolved oxygen from the water, sometimes causing fish kills. Human activities can accelerate eutrophication by increasing the rate at which nutrients enter the water. Algal growth is usually limited by the available supply of either phosphate or nitrate, and we say that a water body is nitrogen limited if the ratio of nitrogen species to phosphorus species (N:P) is low, or is phosphorus limited if N:P is high.
Harmful algal blooms (HABs) are can be caused by many different types of algae in freshwater ecosystems, and can be triggered by nutrient enrichment. The most frequent and severe blooms typically are caused by cyanobacteria, the only known freshwater algae with the potential for production of toxins potent enough to harm human health. CyanoHABs can threaten human and aquatic ecosystem health. Economic damages related to cyanoHABs include the loss of recreational revenue, decreased property values, and increased drinking-water treatment costs.
Harmful algal blooms turn water in Milford Lake, Kansas, emerald green. (Credit: Jennifer Graham, USGS)
RELATED USGS RESEARCH
The USGS works extensively across the country on a variety of aspects related to nutrients and eutrophication. Explore the related projects tab for some examples or click the links below.
- Agriculture and the Quality of the Nation's Waters
- Regional Stream Quality Assessments
- SPARROW modeling: Estimating nutrient, sediment, and dissolved solids transport
- Harmful Algal Blooms
- Effects of Nutrient Enrichment on Stream Ecosystems
- Nutrient Loading for the Mississippi River and Subbasins
- Water-Quality Benchmarks, Including Nutrient Criteria
ADDITIONAL RESOURCES
U.S. Environmental Protection Agency
Natural Resources Conservation Service
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Date published: March 2, 2019Status: ActiveAgriculture and the Quality of the Nation's Waters
Intensive studies by the USGS National Water-Quality Assessment (NAWQA) Project in agricultural areas provide insight into how agricultural activities have altered the natural flow of water and the way that agricultural chemicals enter streams and aquifers, and in particular how nutrients affect algal and invertebrate communities in agricultural streams.
Contacts: Paul D Capel, Mark D MunnAttribution: Water Resources
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Date published: March 4, 2019Status: ActiveSPARROW modeling: Estimating nutrient, sediment, and dissolved solids transport
SPARROW (SPAtially Referenced Regression On Watershed attributes) models estimate the amount of a contaminant transported from inland watersheds to larger water bodies by linking monitoring data with information on watershed characteristics and contaminant sources. Interactive, online SPARROW mapping tools allow for easy access to explore relations between human activities, natural processes...
Contacts: David A Saad, Stephen D Preston -
Date published: March 2, 2019Status: ActiveGroundwater/Surface-Water Interaction
Water and the chemicals it contains are constantly being exchanged between the land surface and the subsurface. Surface water seeps into the ground and recharges the underlying aquifer—groundwater discharges to the surface and supplies the stream with baseflow. USGS Integrated Watershed Studies assess these exchanges and their effect on surface-water and groundwater quality and quantity.
Contacts: Paul D CapelAttribution: Water Resources, National Water Quality Program -
Date published: March 2, 2019Status: ActiveAgricultural Contaminants
About 40 percent of the land in the United States is used for agriculture, and agriculture supplies a major part of the our food, feed, and fiber needs. Agricultural chemicals move into and through every component of the hydrologic system, including air, soil, soil water, streams, wetlands, and groundwater.
Attribution: Water Resources -
Date published: March 1, 2019Status: ActiveWater-Quality Benchmarks for Contaminants
How does the water quality measure up? It all depends on what the water will be used for and what contaminants are of interest. Water-quality benchmarks are designed to protect drinking water, recreation, aquatic life, and wildlife. Here you’ll find links to some of the most widely used sets of water, sediment, and fish tissue benchmarks and general guidance about their interpretation.
Contacts: Lisa NowellAttribution: Water Resources -
Date published: February 28, 2019Status: ActiveRegional Stream Quality Assessment (RSQA)
The goals of the Regional Stream Quality Assessment (RSQA) are to characterize multiple water-quality factors that are stressors to aquatic life (contaminants, nutrients, sediment, and streamflow alteration) and to develop a better understanding of the relation of these stressors to ecological conditions in streams throughout the region.
Attribution: Water Resources -
Date published: September 17, 2018Status: ActiveNWQP Research on Harmful Algal Blooms (HABs)
Harmful algal blooms (HABs) are caused by a complex set of physical, chemical, biological, hydrological, and meteorological conditions. Many unanswered questions remain about occurrence, environmental triggers for toxicity, and the ability to predict the timing, duration, and toxicity of HABs.
Contacts: Jennifer L Graham, Ph.D.Attribution: Water Resources, National Water Quality Program -
Date published: June 5, 2018Status: CompletedPhosphorus and Water
Nutrients, such as nitrogen and phosphorus, are essential for plant and animal growth and nourishment, but the overabundance of certain nutrients in water can cause a number of adverse health and ecological effects.
Contacts: Ask USGS -
Date published: May 21, 2018Status: CompletedNitrogen and Water
Nutrients, such as nitrogen and phosphorus, are essential for plant and animal growth and nourishment, but the overabundance of certain nutrients in water can cause several adverse health and ecological effects.
Contacts: Ask USGS -
Date published: March 10, 2017Status: ActiveBiological Response to Nutrients
Eutrophication, or excess nutrients in streams, is typically one of the top reasons that a stream is listed as impaired on the 303(d) list as part of the Clean Water Act.
Contacts: Jeffrey Frey -
Date published: August 9, 2016Status: ActiveExcess Nutrients
USGS scientists have gained a better understanding of the nutrient supply and how nutrients affect habitat quality, algal productivity, and food-web dynamics in the Bay-Delta.
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Year Published: 2018Understanding the influence of nutrients on stream ecosystems in agricultural landscapes
Sustaining the quality of the Nation’s water resources and the health of our diverse ecosystems depends on the availability of sound water-resources data and information to develop effective, science-based policies. Effective management of water resources also brings more certainty and efficiency to important economic sectors. Taken together,...
Munn, Mark D.; Frey, Jeffrey W.; Tesoriero, Anthony J.; Black, Robert W.; Duff, John H.; Lee, Kathy E.; Maret, Terry R.; Mebane, Christopher A.; Waite, Ian R.; Zelt, Ronald B.Attribution: Water, Ohio-Kentucky-Indiana Water Science Center, Water Resources, National Water Quality Program, United States of America, Water Science SchoolView CitationMunn, M.D., Frey, J.W., Tesoriero, A.J., Black, R.W., Duff, J.H., Lee, Kathy, Maret, T.R., Mebane, C.A., Waite, I.R., and Zelt, R.B., 2018, Understanding the influence of nutrients on stream ecosystems in agricultural landscapes: U.S. Geological Survey Circular 1437, 80 p., https://doi.org/10.3133/cir1437.
Network controls on mean and variance of nitrate loads from the Mississippi River to the Gulf of Mexico
Excessive nitrate loading to the Gulf of Mexico (GoM) has caused widespread hypoxia over many decades. Despite recent reductions in nitrate loads observed at local scales, decreases in nitrate loading from the MRB to the GoM have been small (1.58 % during 2002-2012) with a low level of analytical confidence in this trend. This work seeks to...
Crawford, John T.; Stets, Edward G.; Sprague, Lori A. Response of nitrogen loading to the Chesapeake Bay to source reduction and land use change scenarios: A SPARROW‐informed analysis
In response to concerns regarding the health of streams and receiving waters, the United States Environmental Protection Agency established a total maximum daily load for nitrogen in the Chesapeake Bay watershed for which practices must be in place by 2025 resulting in an expected 25% reduction in load from 2009 levels. The response of total...
Miller, Matthew; Capel, Paul D.; Garcia, Ana M.; Ator, Scott W. Phosphorus and nitrogen transport in the binational Great Lakes Basin estimated using SPARROW watershed models
Eutrophication problems in the Great Lakes are caused by excessive nutrient inputs (primarily phosphorus, P, and nitrogen, N) from various sources throughout its basin. In developing protection and restoration plans, it is important to know where and from what sources the nutrients originate. As part of a binational effort, Midcontinent SPARROW (...
Robertson, Dale M.; Saad, David A.; Benoy, Glenn A.; Vouk, Ivana; Schwarz, Gregory E.; Laitta, Michael T Drinking water quality in the glacial aquifer system, northern USA
Groundwater supplies 50% of drinking water worldwide, but compromised water quality from anthropogenic and geogenic contaminants can limit usage of groundwater as a drinking water source. Groundwater quality in the glacial aquifer system, USA (GLAC), is presented in the context of a hydrogeologic framework that divides the study area into 17...
Erickson, Melinda L.; Yager, Richard M.; Kauffman, Leon J.; Wilson, John T. Monitoring the Riverine Pulse: Applying high-frequency nitrate data to advance integrative understanding of biogeochemical and hydrological processes
Widespread deployment of sensors that measure river nitrate (NO3-) concentrations has led to many recent publications in water resources journals including review papers focused on data quality assurance, improved load calculations, and better nutrient management. The principal objective of this paper is to review and synthesize studies of high-...
Burns, Douglas A.; Pellerin, Brian A.; Miller, Matthew P.; Capel, Paul; Tesoriero, Anthony J.; Duncan, Jonathan M.
Annual wastewater nutrient data preparation and load estimation using the Point Source Load Estimation Tool (PSLoadEsT)
The Point-Source Load Estimation Tool (PSLoadEsT) provides a user-friendly interface for generating reproducible load calculations for point source dischargers while managing common data challenges including duplicates, incompatible input tables, and incomplete or missing nutrient concentration or effluent flow data. Maintaining a consistent...
Gorman Sanisaca, Lillian E.; Skinner, Kenneth D.; Maupin, Molly A.
Point-source nutrient loads to streams of the conterminous United States, 2012
Total nitrogen and phosphorous loads were estimated for 5,430 major point-source facilities (all types) and 11,537 minor wastewater treatment facilities discharging to streams in the conterminous United States during 2012. Facilities classified as a major discharger are typically a facility that discharges greater than one million gallons of water...
Skinner, Kenneth D.; Maupin, Molly A. Recent trends in nutrient and sediment loading to coastal areas of the conterminous U.S.: Insights and global context
Coastal areas in the U.S. and worldwide have experienced massive population and land use changes contributing to significant degradation of coastal ecosystems. Excess nutrient pollution causes coastal ecosystem degradation, and both regulatory and management efforts have targeted reducing nutrient and sediment loading to coastal rivers. Decadal...
Oelsner, Gretchen P.; Stets, Edward G.
Catchment-level estimates of nitrogen and phosphorus agricultural use from commercial fertilizer sales for the conterminous United States, 2012
Nutrient inputs from commercial agricultural fertilizer, particularly nitrogen and phosphorus, are important factors contributing to the degradation of surface-water quality and the alteration of aquatic ecosystems. Despite this importance, information about the application of fertilizer to agricultural land is not available in a consistent manner...
Stewart, Jana S.; Schwarz, Gregory E.; Brakebill, John W.; Preston, Stephen D. Effects of urban multi-stressors on three stream biotic assemblages
During 2014, the U.S. Geological Survey (USGS) National Water-Quality Assessment(NAWQA) project assessed stream quality in 75 streams across an urban disturbance gradient within the Piedmont ecoregion of southeastern United States. Our objectives were to identify primary instream stressors affecting algal, macroinvertebrate...
Waite, Ian R.; Munn, Mark D.; Moran, Patrick W.; Konrad, Christopher P.; Nowell, Lisa H.; Meador, Michael R.; Van Metre, Peter C.; Carlisle, Daren M. Linking the agricultural landscape of the Midwest to stream health with structural equation modeling
Multiple physical and chemical stressors can simultaneously affect the biological condition of streams. To better understand the complex interactions of land-use practices, water quality, and ecological integrity of streams, the U.S. Geological Survey National Water Quality Assessment Project is conducting regional-scale assessments of stream...
Schmidt, Travis S.; Van Metre, Peter C.; Carlisle, Daren M. Water-quality trends in US rivers: Exploring effects from streamflow trends and changes in watershed management
We present a conceptual model that explores the relationship of streamflow trends to 15 water-quality parameters at 370 sites across the contiguous United States (US). Our analytical framework uses discrete water-quality data, daily streamflow records, and a statistical model to estimate water-quality trends between...
Murphy, Jennifer C.; Sprague, Lori A.-
Date published: September 1, 2017NWIS Mapper
This mapper provides access to over 1.5 million sites contained in the USGS National Water Information System (NWIS), including sites where surface-water, groundwater, springs, and atmospheric data has been collected.
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Date published: January 1, 2017County-Level Estimates of Nitrogen and Phosphorus from Commercial Fertilizer for the Conterminous United States, 1987-2012
This data set contains county-level estimates of nitrogen and phosphorus from fertilizer, for both farm and nonfarm uses, for the conterminous United States, for 1987 through 2012. State-level farm and nonfarm nitrogen and phosphorus were derived from the Association of American Plant Food Control Officials (AAPFCO) commercial fertilizer sales data. State estimates were then allocated to the...
Attribution: Water Resources, National Water Quality Program -
Date published: April 6, 2016Great Lakes SPARROW Mapper, 2002
This mapper displays SPARROW nutrient load and yield data specifically for U.S. tributaries to the Great Lakes. The results are based on the SPARROW models developed for the Great Lakes, Ohio, Upper Mississippi, Red River Basins (MRB3). Modeling results can be exported as an Excel spreadsheet or a geospatial dataset.
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Date published: April 5, 2016Mississippi/Atchafalaya River Basin (MARB) SPARROW Mapper, 2002
The mapper displays SPARROW nutrient load and yield data and the importance of various nutrient sources for the MARB, given nutrient inputs similar to 2002. Rankings can be shown by major watershed, state, HUC8, tributary, and catchment. Nutrient data can be explored using maps and interactive graphs and tables. Modeling results can be exported as an Excel spreadsheet or a geospatial dataset...
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Date published: October 3, 2019RSPARROW
RSPARROW, now available on the USGS GitLab repository, provides the first open-source version of the USGS SPARROW water-quality model
Attribution: Water Resources, National Water Quality Program -
Date published: January 25, 2018
SPARROW modeling: Estimating contaminant transport
What’s New: A new version of the SPARROW code is being developed in the R programming language. The advantage of R is that it is non-proprietary and does not require a license or software cost. The R – SPARROW code is now being completed and should be available early in CY18. Stay Tuned.
Attribution: Oregon Water Science Center
Agriculture - A River Runs Through It - Video
Agriculture - A River Runs Through It - Video
Nutrients in the Nation's Streams and Groundwater
Nutrient sources in both agricultural and urban areas contribute to elevated nutrient concentrations in streams and groundwater across the nation. A new USGS study shows that, despite efforts to control nutrient sources and transport, concentrations of nutrients that can damage aquatic ecosystems and affect drinking water have remained the same or increased in many streams
...Too Much of a Good Thing: Increasing Nitrogen Deposition in Lakes
Increasing nitrogen emissions from motor vehicles, energy production, and agriculture are being deposited in lakes throughout the world, directly affecting lake biology and associated food webs. Alpine lake ecosystems are especially vulnerable to this deposition. USGS scientist Jill Baron, co-author of two new studies on how increased nitrogen pollution can affect lake
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Date published: August 8, 2019What's In Your Stream? Get Online to Find Out!
A new update to an online interactive tool for learning about pesticides, nutrients, and overall stream health in major regions of the U.S. is available from the U.S. Geological Survey’s Regional Stream Quality Assessment.
Attribution: Water Resources, National Water Quality Program
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Date published: January 22, 2020Nitrate loads entering the Gulf of Mexico have not changed despite reductions at local scales
Reducing delivery of nitrate to the Gulf of Mexico is critical to decreasing the size of the “dead zone”—an area of hypoxia, or low dissolved oxygen—in Louisiana coastal waters. A new USGS study reports that larger, more widespread decreases in nitrate loading to the Gulf are needed to achieve the target levels of a 25% reduction by...
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Date published: August 8, 2019Contaminants present in many parts of the Glacial aquifer system
Are you one of 30 million Americans whose drinking-water supply relies on groundwater from the glacial aquifer system? A new USGS study assesses the quality of untreated groundwater from this critical water resource, which underlies parts of 25 northern U.S. states.
Attribution: Water Resources, National Water Quality Program -
Date published: June 6, 2016Rainfall Following Drought Linked to Historic Nitrate Levels in Some Midwest Streams in 2013
Highest concentrations found in Iowa, Minnesota and Illinois.
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Date published: October 28, 2015U.S. Rivers Show Few Signs of Improvement from Historic Nitrate Increases
During 1945 to 1980, nitrate levels in large U.S. rivers increased up to fivefold in intensively managed agricultural areas of the Midwest, according to a new U.S. Geological Survey study. In recent decades, nitrate changes have been smaller and levels have remained high in most of the rivers studied.
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Date published: April 8, 2014
Media Advisory: Congressional Briefing on Nutrients and Pesticides in the Nation’s Rivers and Streams
The Water Environment Federation (WEF) and the Northeast Midwest Institute invite you to a briefing by the USGS National Water-Quality Assessment Program (NAWQA) on findings of trends in nutrients and pesticides in the Nation's streams and rivers.
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Date published: October 25, 2011Media Advisory: Briefing on New Science to Identify Sources of Excessive Nutrients in Rivers and Estuaries
The USGS will demonstrate a new and innovative online decision support system used to identify sources of nutrients to downstream waters, such as the Gulf of Mexico, Long Island Sound and others. The decision support system provides access to six newly-developed regional models that describe how rivers receive and transport nutrients to sensitive waters.