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Like their reptilian cousins, birds also lack a diaphragm and thus rely on the intercostal and abdominal muscles to change the volume of the entire thoracoabdominal cavity. The active phase of respiration in birds is exhalation, which requires contracting of respiratory muscles, [11] while the relaxation of these muscles causes inhalation.
An aquatic system lacking dissolved oxygen (0% saturation) is termed anaerobic, reducing, or anoxic. In water, oxygen levels are approximately 7 ppm or 0.0007% in good quality water, but fluctuate. [5] Many organisms require hypoxic conditions. Oxygen is poisonous to anaerobic bacteria for example. [3]
The Citarum River (more correctly called the Tarum River, as the prefix "Ci" simply means "river") (Sundanese: Walungan Citarum) is the longest and largest river in West Java, Indonesia. [3] It is the third longest river in Java, after Bengawan Solo and Brantas. It plays an important role in the life of the people of West Java.
Water chemistry in river ecosystems varies depending on which dissolved solutes and gases are present in the water column of the stream. Specifically river water can include, apart from the water itself, [citation needed] dissolved inorganic matter and major ions (calcium, sodium, magnesium, potassium, bicarbonate, sulphide, chloride)
Decreased levels of dissolved oxygen (DO) is a major contributor to poor water quality. Not only do fish and most other aquatic animals need oxygen, aerobic bacteria help decompose organic matter. When oxygen concentrations become low, anoxic conditions may develop which can decrease the ability of the water body to support life.
The amount of dissolved oxygen in a water body is frequently the key substance in determining the extent and kinds of organic life in the water body. Fish need dissolved oxygen to survive, although their tolerance to low oxygen varies among species; in extreme cases of low oxygen, some fish even resort to air gulping. [ 25 ]
The model describes how dissolved oxygen (DO) decreases in a river or stream along a certain distance by degradation of biochemical oxygen demand (BOD). The equation was derived by H. W. Streeter, a sanitary engineer, and Earle B. Phelps , a consultant for the U.S. Public Health Service , in 1925, based on field data from the Ohio River .
A cubic meter of air contains about 275 grams of oxygen at STP. Fresh water hold less than 1/25th the oxygen content of air, the dissolved oxygen content being approximately 8 cm 3 /L compared to that of air which is 210 cm 3 /L. [4] Water is 777 times more dense than air and is 100 times more viscous. [4]