The Chesapeake Bay: Problems

Nutrients???

• What Are Nutrients: The two main nutrients in the bay, nitrogen and phosphorus, are naturally found in water, soil, and air. Not only do nitrogen and phosphorus in fertilizer aid the growth of agricultural crops, but also both nutrients are vital to the growth of plants within the Bay and rivers.
  

• Nitrogen And Phsosphorous In The Ecosystem: Nitrogen, which is essential to the production of plant and animal tissue, is mainly used by plants and animals to get protein. Nitrogen enters the ecosystem in several chemical forms and also occurs in other dissolved or particulate forms, such as tissues of living and dead organisms. Some bacteria and blue-green algae can extract nitrogen gas from the atmosphere and transform it into organic nitrogen compounds. This process, called nitrogen fixation, cycles nitrogen between organic and inorganic components. Other bacteria, as a part of their normal metabolism, release nitrogen gas back into the atmosphere. Phosphorus, which occurs in dissolved organic and non-organic forms, is another key nutrient in the Bay's ecosystem. Phhosphorus is a vital component in the process of photosynthesis. It is also essential to cellular growth and reproduction for organisms such as phytoplankton and bacteria. Phosphates, the inorganic form are preferred, but organisms will use other forms of phosphorus if needed. When in the presence of oxygen, high concentrations of phosphates in the water will combine with floating particles. These particles eventually settle to the bottom of the Bay and are temporarily removed from the cycling process.

• Nutrients Becoming Pollution: Although nutrients are essential to all plant life, an excess of these same nutrients can be harmful. Too many nutrients is called "Nutrient Pollution". Nutrients have always existed in the Bay, but never at this amount. When the Bay was surrounded primarily by forest and wetlands, very little nitrogen and phosphorus ran off the land into the water. Most of it was absorbed or held in place by the natural vegetation. Today, becuase of development, many of the forests and wetlands has been replaced by farms, cities, and suburbs. As the use of the land has changed and the watershed's population has grown, the amount of nutrients entering the Bay's water has increased tremendously and rapidly. Excess amounts of phosphorus and nitrogen cause Algae "Blooms" which block sunlight. These blooms become so dense that they reduce the amount of sunlight available to the SAV. Without sufficent light, plants cannot photosynthesize and produce the food they need to sunlight. Algae may also grow directly on the surface of SAV. Unconsumed algae will ultimately sink and be decomposed by bacteria in a process that depletes bottom waters of oxygen. Like humans, most aquatic species require oxygen. When oxygen in deep water is depleted, fish and other species will die unless they move to other areas of suitable condition.

• Sources Of Nutrients***: The main causes of the Bay's poor water quality and aquatic habitat loss are elevated levels of two nutrients, nitrogen and phosphorous. These nutrients occur naturally in soil, animal waste, plant material, and even the atmosphere. In addition to these natural sources, sewage treatment plants, industries, vehicle exhaust, acid rain, and runoff from agricultural, residential and urban areas contribute nutrients to the Chesapeake Bay and its rivers. Virtually all individuals and industries in the watershed, and some even beyond the watershed, contribute the nutrients that ultimately reach the Bay. In the Bay region, excess nutrients are supplied to the system through two sources: point and nonpoint sources.
  • Point Source - A source of pollution that can be attributed to a specific physical location; an identifiable, end of pipe "point". The vast majority of point source discharges for nutrients are from wastewater treatment plants, although some come from industries.
  • Nonpoint Source - A diffuse source of pollution that cannot be attributed to a clearly identifiable, specific physical location or a defined discharge channel. This includes the nutrients that runoff the ground from any land use - croplands, feedlots, lawns, parking lots, streets, forests, etc. - and enter waterways. It also includes nutrients that enter through air pollution, through the groundwater, or from septic systems.

  Recent observations indicate that:

  • Nutrients from septic systems are increasing throughout the watershed as development spreads farther into the countryside, beyond the reach of sewer systems.
  • Stormwater runoff from urban and suburban areas is increasing as more land is developed.
  • Nitrogen from wastewater treatment plants is declining in rivers where biological nutrient removal (BNR) technology is being used. It is increasing in other rivers.
  • Phosphorus from sewage treatment plants has declined sharply, in large part because of the phosphate detergent ban.
  • Among the major land use categories, urban and suburban lands contribute, per acre, the largest amount of nutrients to the Bay when septic and wastewater treatment plant discharges are factored in.
  • Runoff from farms is generally declining as farmers adopt nutrient management and runoff control techniques, and because the overall amount of farmland is declining.