Скачать или смотреть EPA Perspective on Nutrient Pollution

For more: http://www.extension.org/67798 Although nutrients, nitrogen and phosphorus in particular, are essential for aquatic life, too many nutrients can create significant problems for our nation's lakes, streams, and coastal waters. Nutrient pollution can degrade habitat for fish and wildlife, render water bodies unsafe for swimming and other forms of contact recreation, create a public health concern for drinking water supplies, decrease property values, and negatively impact local economies. According to national statistics, more than 45% of streams have medium to high levels of nutrients, approximately four million lake acres have been identified as threatened or impaired, and approximately 78% of assessed coastal areas exhibit signs of eutrophication.