Một hành tinh của chúng ta là nước. Ba phần tư bề mặt nước bao gồm ICT Làm cho lên hai-Thirds cho các Cơ quan của chúng tôi. Nó là như vậy quan trọng đối với cuộc sống chúng ta không thể sống ngày lò hơn mà không có nó. Nếu tất cả các trái đất nước-một gallon 325000000000000 Dự kiến Were-vắt vào một bình gallon và bạn đổ ra gì Đã không uống được (quá mặn, ô nhiễm hoặc đông lạnh) Bạn muốn Hãy để lại một giọt. Và Ngay cả đó Không Có thể đèo Mỹ chất lượng. | CHAPTER 7 Freshwater Ecology Ours is a water planet. Water covers three quarters of its surface makes up two-thirds of our bodies. It is so vital to life we can t live more than four days without it. If all the earth s water an estimated 325 trillion gallons were squeezed into a gallon jug and you poured off what was not drinkable too salty frozen or polluted you d be left with one drop. And even that might not pass . water quality NORMAL STREAM LIFE Normal stream life can be compared to that of a balanced aquarium. 96 That is nature continuously strives to provide clean healthy normal streams. This is accomplished by maintaining the stream s flora and fauna in a balanced state. Nature balances sfream life by maintaining both the number and the type of species present in any one part of the stream. Such balance ensures that there is never an overabundance of one species. Nature structures the stream environment so that plant and animal life is dependent upon the existence of others within the stream. Thus nature has structured an environment that provides for interdependence which leads to a balanced aquarium in a normal stream. FRESHWATER ECOLOGY To this point the fundamental concepts of ecology which are generally related to both terrestrial and freshwater habitats have been discussed. Before narrowing the focus to the topic of freshwater ecology and more particularly stream ecology and self-purification the two different ecosystems land and freshwater habitats will be contrasted. 95Narr J. Design for a Livable Planet. New York Harper Row p. 61 1990. 96ASTM. Manual on Water. Philadelphia American Society for Testing and Materials p. 86 1969. 73 Copyright 2001 by Technomic Publishing Company Inc. 74 FRESHWATER ECOLOGY The major difference between land and freshwater habitats is in the medium in which both exist. The land or terrestrial habitat is enveloped in a medium of air the atmosphere. The freshwater habitat on the other hand exists in
