Water and the Effects on Living Things
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As humans, we often forget that we are sharing this
natural resource with many other organisms. Many of our activities
can change the quality of the water in a way that affects the health and
behaviour of other organisms. The addition of pollutants to a
river or lake tends to reduce the amount of oxygen available to
organisms in the water. There are at least two reasons why this
occurs. Effluents containing organic waste are broken down by bacteria
which require the use of oxygen. Secondly, some of the compounds
within the waste may change chemically if oxygen is present in the
water. As this process, known as oxidation, occurs the dissolved
oxygen concentration in the water decreases.
One way of determining water quality is to sample the types of organisms that are living in a specific area. As water quality changes, the types of organisms that live there will also change. Organisms that can tolerate lower quality water will be more evident as the intolerant organisms die off or move away.