From: http://www.savethebay.cbf.org/resources/facts/nutrients.htm
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Nutrients, primarily nitrogen and phosphorus, are essential for the growth of all living organisms in the Chesapeake Bay; however, too many nutrients degrade the Bay’s water quality.
Excess nutrients, also called, nutrient pollution, are perhaps the most serious pollution problem for the Bay. Too many nutrients are harmful to the Bay’s health because they cause organisms such as algae to grow to abundance.
At its healthiest in the early 1600s, the watershed mainly comprised of forested buffers, wetlands, and resources lands (open space and farmland),) that absorbed and filtered nutrients.
According to CBF’s State of the Bay Report, the Chesapeake Bay of the 1600s had an estimated health index of 100.
In 2001, the State of the Bay Report rates the Bay a 27 out 100; forested buffers at 54; wetlands at 42; and resources lands at 30.
Farms, factories, cities, and suburbs have replaced much of these natural filters.
As land use patterns change and the watershed’s population grows, the amount of nutrients entering the Bay’s waters increases tremendously.
Each year, roughly 331 million pounds of nitrogen and 20 million pounds of phosphorus reach the Chesapeake Bay, although reduction goals have been set at 230 million pounds of nitrogen and 16 million pounds of phosphorus.
The combination of increasing our loadings of nutrients to the Bay and decreasing our natural buffers has resulted in too many nutrients in the Bay’s system.
Nutrients come from natural sources such as decaying organic matter in forests and wetlands.
The majority of nutrients, however, comes from human impacts, such as sewage treatment plants, large-scale animal operations, agriculture, vehicle exhaust, septic systems, runoff from roadways, development, residential and commercial lawn fertilizers, power plants and air deposition from factories.
The number one source of nutrient pollution in the Bay watershed is runoff from agriculture, which contributes 40 percent of the nitrogen and 50 percent of the phosphorus entering the Chesapeake Bay.
In Maryland, chicken production plays a big role in agricultural nutrient loads to the Bay: 300 million chickens are produced annually in Maryland, producing about 720 million pounds of manure. Chickens outnumber people approximately 1,000 to 1 on Maryland’s Eastern Shore.
In the Shenandoah and Potomac watersheds, corporate poultry operations produce more waste than hog, cattle, or dairy farms and up to 150 percent more of the nutrient pollution generated by human waste in the same area. In addition, poultry waste creates four times more nitrogen and 24 times more phosphorous than hog waste in Virginia.
As a direct result of all of this polluted runoff, the Bay’s waters have become overfertilized, or eutrophic¾simply put, too much nitrogen and phosphorus are entering the watershed.
Excess nutrients fuel the explosive growth of floating plant life, called algae, that clouds the water and blocks out light needed by the underwater grasses.
When the algae die, they sink to the bottom where their decomposition consumes oxygen. Some deep channels can become so low in oxygen that they can no longer support aquatic life.
Another consequence of too many nutrients phosphorus in our waters is the threat of Pfiesteria piscicida, a microscopic organism that has likely existed in the Bay for thousands of years.
In 1998, a team of physicians and health experts from the University of Maryland and Johns Hopkins University medical schools determined that people heavily exposed to Pfiesteria can develop severe difficulties in learning and concentrating.
The scientists also found that people with high exposure to Pfiesteria complained of neuropsychological symptoms, including new or increased forgetfulness, headaches, and skin lesions or burning sensation when their skin comes in contact with water.
Studies indicate that Pfiesteria becomes more prevalent in part because of poor water quality associated with excessive nutrients. (NOTE: Current evidence indicates that there is no risk from eating seafood from Pfiesteria infected waters. No scientific or anecdotal evidence links the consumption of seafood to any Pfiesteria-like symptoms or any other illness.)
Solutions also include upgrading sewage treatment plants, proper operation of septic systems, using nitrogen removal technologies on septic systems decreased, and decreasing fertilizer applications to lawns.
We can also reduce nutrient loads by conserving energy, which will result in fewer demands on power plants that emit nitrogen, and driving less to reduce vehicle emissions that also contribute to airborne nitrogen loads.
Important natural filters such as forests, oysters, wetlands, and underwater grasses need to be protected and restored. Maryland alone has lost more than 75 percent of its wetlands, 98 percent of its oysters, about 90 percent of grasses, and nearly 50 percent of forest buffers.
We must reduce the amount of nutrient runoff from agricultural sources and promote effective use of nutrient management plans. These practices include testing soil for nutrient content, careful application of fertilizer and manure to meet but not exceed the crops’ nutrient requirements, barnyard runoff and soil erosion controls, and other site-specific measures. Many of these practices benefit farmers as well as the environment by conserving the farm’s soil.
Other methods for reducing runoff from agriculture include planting cover crops, proper storage and composting of manure, and other alternative uses (conversion to energy and pelletizing) of the excess manure.
Revised 12/01