Rola przyborów wody w wynoszeniu i nanoszeniu fauny bentonicznej środowisk związanych z rzeką

Kajak, Zdzisław

doi:ISSN 0424-7205

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Tytuł: Rola przyborów wody w wynoszeniu i nanoszeniu fauny bentonicznej środowisk związanych z rzeką

Abstrakt:

Material for the present work was collected in 1955 from two shallow sections (stations I and II) of the branch cut off from the Vistula (called the Konfederatka), and from the adjacent branch of the river, and from environments above sandbanks in the Vistula. Benthic material was collected by means of tubular sampler, with a collecting surface of 10 sq. cm. Collection was made every few days or even daily, during periods of sudden changes in water level, and in other periods every two weeks, in series of 10 samples. Several samples of syrton were also collected (a sample consisted of collection made over a period of 5 minutes by means of an apparatus having a collecting surface of 120 sq.cm).In the above environments considerable rises in water level completely wash away the stratum of mud and the fauna inhabiting it. The numbers of Tendipedidae during a high water period (19.7.; 12-20.8.) are very small (fig. l); these consist mainly of forms which burrow in the sand, or become covered with it. During. the period of a fall in the water level, or even of complete cessation of flooding, Tendipedidae appeared in large numbers, developing on the site probably from eggs deposited by the imagines. Syrton fauna plays a very small part here. (Very frequent sampling in the Konfederatka pool during a period of rise in waterr level - fig. l - excludes the possibility of overlooking the settlement of syrton fauna., and later of its selection). The following facts bear witness to this:1. The number of Tendipedidae did not as a rule increase until the occurrence of a period of weak flow of water, or even when this had completely ceased (fig. 1). When the flow is weak, as is shown by syrton material, the numbers of in-borne fauna are negligible, and cannot therefore cause the appearance of benthos in large numbers.2. Appearance of benthos in large numbers was as a rule observed from approximately 7-17 days after a layer of mud had settled. If the benthos fauna derived from syrton, it might be expected that it would settle on the bottom earlier, as being heavier than the mud particles in suspension.3. Of the benthic Tendipedidae occurring in large numbers, young individuals either predominated, or appeared to the exclusion of all others. The organisms carried by the river, originating from various environments, would undoubtedly have a more varied age structure.4. The species composition of the syrton differed distinctly from that of the developing benthos.5. In the various environments, soon after the flow has taken place, the species composition and quantitative ratios of the species differ considerably. Where the fauna is mechanically introduced by the rise in water level, a greater similarity should be expected.

Bibliografia:

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