Phosphates are present in many natural waters, such as lakes and streams. Phosphates are essential to aquatic plant growth, but too much phosphate can lead to the growth of algae and results in an algae bloom. Too much algae can cause a decrease in the amount in dissolved oxygen in the water. Oxygen in water is affected in many different ways by phosphates Phosphorus is usually present in natural waters as phosphate (Mc welsh and Raintree, 1998). Phosphates are present in fertilizers and laundry detergents and can enter the water from agricultural runoff, industrial waste, and sewage discharge (Out water, 1996). Phosphates, like nitrates, are plant nutrients (Phosphates, 1997).

When too much phosphate enters a water, plant growth flourishes (Phosphates). Phosphates also stimulate the growth of algae which can result in an algae bloom (World Book Encyclopedia, 1999)... Algae blooms are easily recognized as layers of green slime, and can eventually cover the water's surface. As the plants and algae grow, they choke out other organisms. These large plant populations produce oxygen in the upper layers of the water but when the plants die and fall to the bottom, they are decomposed by bacteria which use a lot of the dissolved oxygen in the lower layers (Phosphates). Bodies of water with high levels of phosphates usually have high biological oxygen demand (BOD) levels due to the bacteria consuming the organic plant waste and subsequent low dissolved oxygen levels (Hooper, 1998).

The addition of large quantities of phosphates to waterways accelerates algae and plant growth in natural waters (Hooper), enhancing eutrophication and depleting the water body of oxygen. This can lead to fish kills and the degradation of habitat with loss Boyington 5 of species. Large mats of algae can form and in severe cases can completely cover small lakes. Dying plants and algae will create phosphates while decaying, as a result, water can become putrid from decaying organic matter (World Book Encyclopedia).

When the concentration of phosphates rises above 100 mg / liter the coagulation processes in drinking water treatment plants may be adversely affected (World Book Encyclopedia). Manmade sources of phosphate include human sewage, agricultural run-off from crops, sewage from animal feedlots, pulp and paper industry, vegetable and fruit processing, chemical and fertilizer manufacturing, and detergents. Dissolved oxygen is one of the best indicators of the health of a water ecosystem. Dissolved oxygen can range from 0-18 parts per million (ppm), but most natural water systems require 5-6 parts per million to support a diverse population (Phosphates). Dissolved oxygen levels change and vary according to the time of day, the weather and the temperature. If yearly comparisons are made on dissolved oxygen levels, they should be done at the same time of day, during the same season and on a day with a temperature variation of only 10 degrees Celsius from the previous reading (Phosphates).

A decrease in the dissolved oxygen levels is usually an indication of an influx of some type of organic pollutant (Phosphates). When too much phosphorus becomes available, plants grow rapidly. Phosphates that enter a stream may cause algae to multiply and grow quickly, this may result in an algae bloom (Phosphates). Algae blooms are thick layers of green slime that cover the surface of ponds or slow moving streams. Algae blooms are harmful to most aquatic organisms. They cause a decrease in the dissolved oxygen levels of the water.

They Boyington 6 prevent waves and the surface of the water from coming into contact with the air which provides the main source of oxygen for the water (Hooper). Their dark color absorbs more heat energy from sunlight causing the water temperature to rise. Warm water holds less oxygen than cold and it causes the metabolic rate of aquatic organisms to increase. In addition, the algae which grow rapidly near the surface block sunlight to plants that live on the bottom causing them to die.

Plants which grow fast die fast and sink to the bottom. Dead plant material is decomposed by bacteria increasing the BOD (Hooper). All of these factors combine to cause oxygen levels in the water to decrease rapidly. This can result in a fish kill and the death of many organisms. Algae blooms are indicators of cultural eutrophication (Phosphates). Eutrophication refers to the aging of a lake or other body of water (Phosphates).

Cultural eutrophication occurs when nutrients (such as nitrates and phosphates) are added from agricultural runoff, sewage, detergents or other sources such as golf courses or lawns. Advanced stages of cultural eutrophication can be detected by an unmistakable 'rotten egg's mell. Phosphorous has a great effect on the dissolved oxygen levels in natural waters. Phosphates mostly act as nutrients for plants, and helps them to grow, but too much phosphorous can cause a production of algae blooms. The production of algae blooms can cause in decrease in dissolved oxygen levels. Algae blooms can cause the deaths of many fish in rivers because of a decrease of dissolved oxygen..