water saprobity factor

Among the biological methods of analyzing surface waters, saprobiological analysis occupies one of the main places. Progressive pollution of the aquatic environment prompted scientists in the last century to compare the flora and fauna of polluted and uncontaminated water bodies, and to identify the role of hydrobionts in the transformation of a variety of substances entering into internal and external water bodies with human waste. The deterioration of water quality in many water bodies and streams has put researchers in the task of developing systems for assessing the degree of pollution by biological indicators.

Classification of water saprobity

Limnosaprobes group of waters

  • The polysaprobic zone or polysaprobic waters from the chemical position are characterized by a very low oxygen content and high concentrations of dissolved carbon dioxide and high molecular weight easily decomposed organic substances - proteins, carbohydrates. In these waters, the processes of decomposition of organic matter with the formation of sulphurous iron in bottom sediments and hydrogen sulphide are proceeding intensely. The population of polysaprobic zones has insignificant species richness, but some species can reach a huge density. Aerophilic organisms are completely absent. Colorless flagellates and bacteria are especially common here.
  • The α-mesosaprobic waters are characterized by vigorous self-purification. In the processes of purifying water from organic pollution, green plants that release oxygen during photosynthesis actively participate. Among the latter there are some blue-green, diatom and green algae. Here already fish can live, not demanding to the oxygen regime.
  • β-mesosupportive waters. The processes of self-purification are less intense than in a-mesosaprobic. They are dominated by oxidative processes, often oversaturated with oxygen, are dominated by such protein mineralization products as ammonium compounds, nitrates and nitrites. In these waters are diverse animal and plant organisms, among the latter - diatoms, blue-green and green.
  • Oligosaprobic waters are represented, for example, by practically pure waters of large lakes. If such waters have occurred by mineralization from contaminated water, then they are characterized by almost complete mineralization of organic compounds to inorganic components. The content of organic compounds, as a rule, does not exceed 1 mg / l. Many oligosaprobic waters are rich in gold and dinophyte.
  • Xenosaprobes are waters of pure mountain streams, small glacial rivers, key outlets depleted of biota and containing minimal amounts of mineral compounds and traces of organic substances.

The boundary between two groups of waters: the last zone of limnosaprobic waters (polysaprobic) - and the first zone of eusaprobic, from the point of view of the oxygen regime, is the boundary between aerobic and anaerobic conditions.

Eusaprobe group of waters

  • The isosaprobic area is characterized from the biological point of view by the predominance of the protozoans, with the concomitance of colorless flagellates and bacteria. Green organisms are practically absent. Anaerobic conditions are observed
  • The metasaprobic zone is characterized by the predominance of colorless flagellates. A large number of bacteria are noted. Conditions are anaerobic, many hydrogen sulphide.
  • The hypersaprobic zone is a zone of predominance of bacteria, fungi, other organisms are completely absent.
  • The ultrasuprobic zone is lifeless and characterizes the most concentrated waste fluids

Trans-saprobe waters

These are drains or natural waters, to which the notion of saprobity is not applicable

  • Antisaprobic waters are industrial wastewater containing toxic substances of an organic and inorganic nature.
  • Radioactive water - water contaminated with radioactive substances.
  • Cryptosuprobic waters are characterized by suppression of saprobity (ie processes of decomposition of organic compounds) by physical factors of the medium (high or low temperature), etc.

Definition of saprobity

In accordance with the division of all waters into saprobity zones among the population of water bodies, there are indicator or demonstration species that characterize certain zones of saprobity:

  1. Organisms of heavily polluted waters - polysaprobes or polysaprobionts;
  2. Organisms of moderately polluted waters - mesosaprobes or mesosaprobionts;
  3. Organisms of slightly polluted waters - oligosaprobes or oligosaprobionts;
  4. Organisms of perfectly pure natural waters - xenosaprobes or xenosaprobionts.

In the system of saprobiological analysis there are specially developed lists of indicator organisms with indication of their belonging to a certain zone of saprobity.

The method of calculating the average saprobity of the biocenosis according to Knepp.

To apply this method, the results of qualitative and quantitative treatment of various communities of hydrobionts are needed. Fill the list of species with an indication of their abundance on a seven-point scale.

Then, the scores of the oligosaprobic and ß-mesosaprobic zones and the scores of the a-mesosaprobic and polysaprobic zones are summarized, and a graph is constructed that reflects the ratio of the sums of scores of all saprobity zones along the river cross-section.

As a result of the connection of the corresponding points by straight lines, a figure consisting of 4 parts is obtained, which shows the ratio of the saprobity indicator types at each station.

In addition to visual assessment with assignment of abundance scores, specific values ​​of abundance and biomass of indicator species in the sample are used as values. The index of saprobity in the xenosaprobic zone is 0-0.5; In the oligosaprobic zone 0.5-1.5 (pure water); In the in-mesosaprobic - 1.51-2.50 (water of moderate pollution), a-mesosaprobic - 2.51-3.50 (heavily polluted), polysaprobic zone 3.51-4.50 (very heavily polluted). The conclusion about the level of water pollution at the alignment is made on a six-point scale.

From biological methods, the most widely used system for assessing the state of water according to the index of capacity (trophy-saprobity). The capacity indicates the adaptability of hydrobionts to various influences, thanks to the existence of physiological and biological mechanisms developed in phylogeny.

The degree of water pollution, adequate to the availability of correspondingly existing hydrobionts-indicators, is determined on the basis of experimental and field studies.

A promising system for monitoring the state of aquatic ecosystems is the assessment of the level of accumulation of various substances in organisms of hydrobionts.

The most promising objects for assessing the state of water and ecosystems, in our opinion, are algae - the primary and very informative link of the trophic chain. In addition, unlike other groups of hydrobionts, algae occur almost everywhere, where there is water.

When the content of organic substances in the water changes, the species composition of the algae changes and, as a rule, their abundance, that is, the species that definitely react to changes in environmental conditions are indicator species.