Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 17

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The greatest development of bivalves in the Goczałkowice Reservoir occurred at the turn of the 1960s. In 1983 and 1992 detailed investigations of the exposed bottom of the reservoir were conducted. In 1983, in the north-eastern zone of the reservoir 2.23 individuals with a biomass of 26.9 per 1 m2 were recorded, while in the south-eastern zone there were 0.77 individuals with a biomass of 20.2 g per m2 . In 1992, in the north-eastern zone of the reservoir there were 1.68 individuals with a biomass of 37.6 g per m2. The population of bivalves, when compared with that in the year 1983, had diminished there by about 30%.
On the basis of data from many years an increase was found in the degree of mineralization and fertility of the water of the River Vistula. Quantitative and qualitative changes in the bottom macrofauna against the background of changing physico-chemical conditions of the River Vistula were shown by a constant increase in the share of larvae of Chironomidae and Oligochaeta and a decrease in that of Ephemeroptera and Plecoptera.
The present work gives the characteristics of the bottom macrofauna against the background of the changing chemical composition and pollution of the water of the Vistula in a section of about 45 km of its upper course. A fairly rich and differentiated bottom macrofauna was found. The variability in bottom macrofauna throughout the area was the result of changes in the environmental conditions, while the increase in water fertility and pollution corresponded to the rising numbers of Chironomidae and the appearance and increasing numbers of Oligochaeta.
A tendency to an increase in electrolytes and nutrients (mineral nitrogen and total phosphorus) was found. The bottom macrofauna was not affected by human activity in the period from 1955 to 1982, when the degree of eutrophication was small. From 1983 the effect of human activity was revealed in both qualitative and quantitative changes in the composition of the macrofauna.
In 1992, there took place in the Goczałkowice Reservoir intensive water blooms caused by blue-green algae with the domination of Aphanizomenon flos-aquae. They led to the dying out of the bottom macrofauna (Chironomidae, Oligochaeta, Ceratopogonidae larvae) and other animals connected with the bottom (Decapoda, Bivalvia). It is assumed that this event was due to the toxic effect of the metabolites of the blue-green algae.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.