The following information is from the Field Manual for Water Quality Monitoring - An Environmental Education Program for School  by Mitchell and Stapp and is the foundation for GREEN'S Educational Model.

Phosphorous is usually present in natural waters as phosphate. Organic phosphate is a part of living plants and animals, their by-products, and their remains.  Phosphorus is an essential element for life. It is a plant nutrient needed for growth, and a fundamental element in the metabolic reactions of plants and animals. In most waters, phosphorus functions as a "growth-limiting" factor because it is usually present in very low concentrations.  Algae and larger aquatic plants rapidly take up any unattached or "free" phosphorus, in the form of inorganic phosphates. Because algae only require small amounts of phosphorus to live, excess phosphorus causes extensive algal growth called "blooms." Algal blooms are a classic symptom of cultural eutrophication.  Most of the eutrophication occurring today is human caused.  

Sources of Phosphorus

Phosphorus comes from several sources: human wastes, animal wastes, industrial wastes, and human disturbance of the land and its vegetation. Sewage from wastewater treatment plants and septic tanks is one source of phosphorus in rivers.  Animal waste containing phosphorus sometimes finds its way into rivers and lakes in the runoff from feedlots and barnyards. Soil erosion can also contribute phosphorus to rivers. The removal of natural vegetation for farming or construction, for example, exposes soil to the eroding action of rain and melting snow. Soil particles washed into waterways contribute more phosphorus and fertilizers used for crops, lawns, and home gardens usually contain phosphorus. When used in excess, much of the phosphorus in these fertilizers eventually finds its way into lakes and rivers. Draining swamps and marshes for farmland or shopping malls releases nutrients like phosphorus that have remained dormant in years of accumulated organic deposits. Also, drained wetlands no longer function as filters of silt and phosphorus, allowing more runoff and phosphorus to enter waterways.

Impacts of Cultural Eutrophication

Shallow lakes and impounded river reaches, where the water is shallow and very slow moving, are most vulnerable to the effects of cultural eutrophication. Phosphorus stimulates the growth of rooted aquatic vegetation. These plants, in turn, draw phosphorus previously locked within bottom sediments and release it into the water, causing further eutrophication. Eventually, the entire lake or river stretch may fill with aquatic vegetation. The first symptom of cultural eutrophication is an algal bloom that colors the water a pea soup green. As eutrophication increases, algal blooms become more frequent. Aquatic plants that normally grow in shallow waters become very dense. Swimming and boating may become impossible. The advanced stages of cultural eutrophication can produce anaerobic conditions In which oxygen in the water is completely depleted. These conditions usually occur near the bottom of a lake or impounded river stretch, and produce gases like hydrogen sulfide, unmistakable for its rotten egg smell.

Changes in Aquatic Life

As with other types of water pollution, cultural eutrophication causes a shift in aquatic life to a fewer number of pollution intolerant species. The many different species that exist in clean water are replaced by a fewer number of species that can tolerate low dissolved oxygen levels - carp, midge larvae, sewage worms (Tubifex), and others. For example, waters that once supported bass, walleye, pike, and bluegill may only be able to support carp under eutrophic conditions.

Reversing the Effects of Cultural Eutrophication

Aquatic ecosystems have the capacity to recover if the opportunity is provided by:
1. Reducing our use of lawn fertilizers (particularly inorganic forms) that drain into waterways
2. Encouraging better farming practices: low till farming to reduce soil erosion; soil testing to match the amount of fertilizer applied to soil needs, thus preventing excess fertilizer from finding its way into waterways; building storage or collecting areas around cattle feedlots, so that phosphorus containing manure is not carried away with surface runoff
3. Preserving natural vegetation whenever possible, particularly near shorelines, preserving wetlands to absorb nutrients and maintain water levels; enacting strict ordinances to prevent soil erosion
4. Supporting measures (including taxes) to improve phosphorus removal by wastewater treatment plants and septic systems; treating storm sewer wastes if necessary; encouraging homeowners along lakes and streams to invest in community sewer systems; and
5. Requiring particular industries to pre-treat their wastes before sending it to a wastewater treatment plant. Can you think of any other actions that would prevent or reduce the effects of eutrophication?

Sampling Procedure

It is important that glassware used for measuring total phosphate be "acid washed"; that is, soaked in dilute HCl and then rinsed thoroughly with distilled water. Please wear protective gloves when handling this glassware. WARNING; never wash this glassware with phosphorus containing detergents.

Phosphate testing kits are available from scientific supply companies such as Lamotte or Hach (see materials).  Follow their directions completely to obtain your results.

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