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“saprobity”
saprobity
The degree to which the decomposition of organic material is occurring in an aquatic environment.
The saprobity system is based on the observation that in the course of the self-purification process a body of water shows distinct zones of decreasing pollution (or improved water quality); these zones are termed polysaprobic (gross pollution), alpha-mesosaprobic, beta-mesosaprobic, and oligosaprobic; the latter may be divided into alpha- and beta- oligosaprobic.
Each zone is characterized by a particular content of oxygen, organic matter, products of septic decay, and products of mineralization. Biologically, each zone affords optimal conditions for certain species and communities of organisms, the so-called "indicator" organisms.
- Polysaprobic zone, heavy pollution with sewage or other organic materials, mass development of bacteria that are involved in decomposition processes, a high rate of oxygen consumption, and a high production of ammonia and hydrogen sulfide.
- Alpha-mesosaprobic zone, vigorous oxidation processes, increased dissolved oxygen though oxygen consumption is still high, no hydrogen sulfide production, oxidation of ammonia starts.
- Beta-mesosaprobic zone, much dissolved oxygen, low oxygen consumption, mineralization of organic materials, and large amounts of the end-products of mineralization; for example, nitrates.
- Oligosaprobic zone, all mineralization processes have been completed, the dissolved oxygen content is high and oxygen consumption nearly zero; the beta-oligosaprobic level is characterized by rather moderate variety of species and low bioactivity, while the alpha-oligosaprobic level is characterized by a comparatively large variety of species and high bioactivity.
The particular saprobity zones may be characterized as follows: