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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.
A new USGS study estimates total nitrogen (N) and total phosphorus (P) yields from catchments throughout the Mississippi/Atchafalaya River Basin, which drains about 41% of the conterminous U.S. Results could assist nutrient reduction strategies.
A new study successfully predicts when mixtures of the toxins produced by these blooms in Kabetogama Lake, Voyageurs National Park, will exceed drinking-water guidelines.
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".
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.
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.
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.
U.S. Environmental Protection Agency
Natural Resources Conservation Service
Nutrients can come from many areas, but mostly they are associated with runoff from agricultural applications. Here are a few studies that relate to nutrients.
Below are data or web applications related to USGS research on nutrients.
Below are a few videos and images related to nutrients and eutrophication.
Follow the links below to USGS publications on nutrients and the quality of our nation's waters.
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.
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.
There are numerous software packages scientists use to investigate water quality and pollution transport. Here are a few examples of applications USGS uses.
RSPARROW, now available on the USGS GitLab repository, provides the first open-source version of the USGS SPARROW water-quality model
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.
See what is newsworthy concerning water-quality in the Nation's lakes and rivers.
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.
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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...
Highest concentrations found in Iowa, Minnesota and Illinois.
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The Water Environment Federation (WEF) and the Northeast Midwest Institute invite you to a briefing by the USGS National Water-Quality Assessment...