Subject: Water Pollution from Organisms

I want to ask you how small animals such as fish contribute to water pollution?

    All organsims "pollute", in the sense that they excrete waste materials from their bodies to the surrounding environment. What is "waste" for one organism can be essential to another. Think for instance of the CO2 humans and other respiring organisms produce as waste from buring carbohydrates with oxygen. This CO2 is essential for plants, who combine it with energy from the sun to make carbohydrates, thus producing O2 as waste. In this case, life itself has evolved into a synergistic system where one group's waste is another's essential ingredient and vice versa.
    Most animals and fish contribute waste to their environments that are essentially the same as human waste (fecal matter laden with bacteria and reduced compounds). If the population of an environment exceeded the capability of the environment to neutralize or at least tolerate those wastes, certain organisms will begin to die. This limit is known as the "carrying capacity" of the environment. In general, nature is wise enough to not naturally reach this limit in most instances, such that most systems can self regulate themselves and avoid reaching this limit.
    There are examples of indivividual organisms that can excrete specific polutants or toxins into an environment, usually as a defense mechanism. There are also plenty of examples of organisms that can detoxify and store polutants from an environment in their bodies, making the overall environment "safer" (until the organism dies, at which point some toxins can be re-released to the environment).

Dr. Ken Rubin, Assistant Professor
Department of Geology and Geophysics
University of Hawaii, Honolulu HI 96822

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