PLANKTON (grech, planktos wandering) — set of the various organisms inhabiting sea and fresh-water reservoirs. Overwhelming part II. present to a bacterium (bakterioplankton), one-celled seaweed (phytoplankton) and various backboneless animals (zooplankton). Conditionally by the sizes P. divide into nanno-plankton (organisms less than 50 microns in size), microplankton (50 — 1000 microns), mesoplankton (from 0,5 to 10 mm), macroplankton (from 10 to 40 mm) and megaloplankton — marine animals, hl. obr. sifonofor, jellyfishes (coelenterates) and pirozoma (chordates) which size is measured by meters.
Items of fresh-water reservoirs make hl. obr. diatomic and blue-green seaweed, protozoa, rotifers, Copepoda and vetvistousy Crustacea. Sea phytoplankton is presented by diatomic, flagellar, blue-green seaweed and kokkolitoforida, and zooplankton — radiolarias, foraminifera, infusorians, Crustacea (Copepoda, rakushkovy, evfauziyevy, fresh-water shrimps, etc.), shchetinkochelyusty, coelenterates, appendikulyariya (chordates), salpam (chordate), some mollusks and some other organisms. Sea tropical and subtropical P. on species composition is much more various than P. Arctic, subarctic and midlatitudes. Quantity P. (biomass) and its species composition in reservoirs change depending on a season. Seasonal fluctuations of quantity are least of all expressed in a tropical zone; in a zone of a temperate climate two maxima in P.'s development (spring and autumn) and a winter minimum are observed usually. Seasonal fluctuations in P.'s number are quite often connected with life cycles of planktonts (ontogenetic migrations). P. sites of the seas where there is a raising of deep waters to a surface, on joints of cold and warm currents, and also in mouths of the rivers that is connected with inflow of the biogenic substances which are taken out by the rivers are richest. Quantity of G1. it is possible to increase artificially — by introduction of fertilizer.
The item — the main source of organic matter in reservoirs. Phytoplanktonts synthesize organic matter in process photosynthesis (see) from the carbon dioxide gas dissolved in water and mineral salts, using for this purpose energy of the Sun. Phytoplankton serves as food for herbivorous zooplankton which, in turn, «predatory» zooplankton eats. Phyto - and zooplankton many fishes and even such large animals as whales eat. Certain representatives of oceanic P. are used in food of the person (e.g., shrimps, a krill, etc.).
The died-off planktonts, falling by a bottom, are exposed to bacterial decomposition, enriching at the same time water and ground deposits with biogenic elements.
Extent of development of P. can serve as an indicator of impurity of fresh-water reservoirs organic matters that the dignity is used in practice. - epid, service. Snowballing of some types of P. (e.g., blue-green seaweed) in drinking reservoirs promotes a contamination of water intaking filters, products of their disintegration can poison water etc. Nek-ry planktonts serve as intermediate owners of parasites of the person and animals. E.g., Cyclops-trennuus Diatomus gracilis, etc. are intermediate owners of different types of a tape-worm, and Cyclops coronatus, S. of viridis intermediate owners of a parasitic worm. Nek-ry types of nematodes, trematodes, etc. can lead temporarily planktonic life. Separate species of coelenterates animals, napr, fizaliya, a jellyfish-krestovichok, etc., belong to poisonous animal (see).
Plankton in the medicolegal relation. P.'s detection in liquids and body tissues is one of objective proofs of a drowning death. At the same time the greatest value has P. of a plant origin, first of all diatomic seaweed — diatoms (see. Seaweed ). Diatoms are surrounded with the armor consisting of inorganic compounds, most often of silicon. The Kremnezemovy armor is poorly subject to influence of the high temperatures concentrated to - t and alkalis and does not change at putrefactive processes in a corpse, in Krom, as a rule, there are no all other signs characterizing a drowning death.
At capture of objects of a research from corpses in cases of suspicion to death from drowning it is necessary to observe careful precautionary measures to exclude an accidental possibility of entering of P. from the outside. For this purpose all tools and dishes before use should be washed and rinsed with carefully distilled water.
Due to the wide spread occurance of P. (in the closed reservoirs, snow, polar ices, even in dust and water vapors near open reservoirs) P.'s detection only in lungs cannot serve in the nature as the proof of a drowning death yet. Each reservoir is inhabited by certain types of P. therefore for P.'s identification for expert diagnosis of drowning from different levels of a reservoir from which the corpse is taken take away a certain amount of water (1 — 2 l). . It is the most reasonable to direct blood, a liver, marrow and the unimpaired kidney to a research; gross weight of objects shall make not less than 200 g. Conservation of objects any substances is not allowed.
For P.'s detection a row a lab is offered. techniques. The greatest practical application was received by a method, at Krom objects of a research destroy strong mineral to-tami, and ostatg after centrifuging study under a microscope and photograph. The microphoto is the document confirming reliability of results of the conducted research.
It is necessary to consider that in the studied objects so-called pseudo-plankton — grains of sand, grains of starch and other inclusions having with the true Item nothing in common can be found. Detection of pseudo-plankton is not the proof of drowning.
Bibliography: Beklemishev K. V. The ecology and biogeography pelagiat, M., 1969; Biology of the Pacific Ocean, Plankton, under the editorship of V. G. Bogorov, t. 7, book 1, M., 1967; Vinogradov M. E. Vertical distribution of oceanic zooplankton, M., 1968; The Diatomic analysis, under the editorship of A. N. Krishtofovich, book 1 — 3, M., 1949 — 1950; To and with e of l of e in I. A. Plankton of the seas and continental reservoirs, t. 1, D., 1969; it, Plankton of continental reservoirs, p.1 — 2, L., 1979; Skopin I. V. and And with and f e in and N. I. Detection of plankton in internals as the proof of drowning, in book: Vopr, court. - medical examinations, under the editorship of M. I. Avdeev, century 2, page 232, M., 1955.
M. V. Geptner, D. N. Zasukhin; Yu. L. Melnikov of Loans. - medical).