Final answer:
Biochemical Oxygen Demand (BOD) measures the oxygen used by aerobic bacteria to decompose organic waste in water. Low BOD suggests clean water, while high BOD indicates pollution and low dissolved oxygen levels, which can affect aquatic life.
Step-by-step explanation:
Biochemical Oxygen Demand (BOD) is a critical measure used to quantify the amount of dissolved oxygen required by aerobic bacteria to decompose organic matter in a water sample. When there is excessive decaying organic matter, such as that from sewage, grass, and leaves, it can become a significant pollutant. This is because the decomposition process consumes the dissolved oxygen that aquatic organisms, such as fish and insects, depend on for cellular respiration.
A low BOD indicates an unpolluted water body, like a turbulent river that has plenty of opportunity to mix with atmospheric oxygen, supporting organisms like trout. On the other hand, a high BOD suggests a polluted water body, often seen in stagnant lakes with little aeration and high input from organic waste like sewage runoff. Such environments typically have dissolved oxygen levels under 5 ppm (parts per million), leading to the dominance of species that can tolerate low oxygen levels, such as carp and catfish.
Understanding BOD is essential for the management of water quality as it impacts both human health and the ecosystem. In ecosystem dynamics, the presence of oxygen-demanding waste can have significant consequences, demonstrating the importance of BOD as an environmental indicator.