Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 4

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

Wyszukiwano:
w słowach kluczowych:  sandy shore
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
A long wave run-up theory is applied to the modelling of wave-induced flow velocities, sediment transport rates and bottom changes in a swash zone. First, the properties of the water tongue motion and the resulting lithodynamic response are analysed theoretically. Next, an attempt is made to run the model for the natural conditions encountered on the southern Baltic Sea coast. The Lagrangian swash velocities are used to determine the Eulerian phase-resolved bed shear stresses with a momentum integral method, after which the motion of sand is described by the use of a two-layer model, comprising bedload and nearbed suspended load. Seabed evolution is then found from the spatial variability of the net sediment transport rates. The results presented are limited to cases of the small-amplitude waves that seem to be responsible for accretion on beaches.
On nine beaches and two transects in the surf zone along the Dutch coast the presence of benthic macrofauna was studied in relation to basic abiotic characteristics. According to Short’s classification system, Dutch beaches are mesotidal and dissipative (Ω = 8.6), and the RTR is low (1.52–1.27), which means that they are not tide-dominated. BSI ranged from 1.4 to 1.1 for the northern and western Dutch coasts respectively and had an overall value of 1.2. The rates of exposure of the beaches varied between 8 and 12, and are therefore regarded as sheltered to moderately exposed. The Dutch beaches display a geographical trend in beach types. Those of the Wadden Sea islands in the northern part of the Netherlands are dissipative, flat, fine-grained, and host high densities of many species of benthic macrofauna. The beaches along the western Dutch coast are less dissipative, steeper, with a higher mean grain size; the species diversity and abundance there are lower. Species diversity and abundance on the beaches increase from the high- to the low-water line. The maximum number of species was found between 0 and –1 m relative to the mean tidal level. The abundance peaks just above the mean tidal level, while the biomass reaches a maximum at the mean tidal level. Species diversity and abundance are low in the surf zone, but increase towards deeper water. Species numbers are high and the abundance is very high in the trough between the two bars. The relation between the diversity and abundance of macrobenthic species on the one hand, and the sediment composition, water column depth, and position between the bars on the other show a clear pattern of zonation for the beach, surf zone and near-shore: (1) a supralittoral zone with insects and air-breathing crustaceans, (2) a midshore zone, with intertidal species, (3) a lower shore zone, whose species extend into the shallow surf zone, and (4) a zone of sublittoral fauna in the trough between the two breaker bars within the surf zone.
Psammon habitats like freshwater sandy shores are the peculiar sites due to high fluctuation of physico-chemical conditions and due to the specific composition of the organisms communities distributed along the horizontal pattern related to the wave action. Taxonomic composition, numbers and biomass of phytopsammon were studied in hygroarenal (shore sand beach wetted by lake waves) of the small beach of the eutrophic Lake Mikołajskie (area 498 ha, max. depth 26 m) (Masurian Lake District, Poland). Samples were collected on one occasion (26 June 2003) from 30 sampling stations distributed parallel to lake shore along 10 m line at three different distances (sampling points A, B, C) from 0 to 60 cm from water line. The studies showed distinct horizontal distribution of psammon algae. Their numbers and biomass varied from 2.22 to 31.85 × 03 cm–3 of sand and from 0.49 to 4.69 μg cm–3 of sand, respectively. Mean numbers in all sampling distances were very similar, while the biomass increased with increasing distance from water line. Cyanoprokaryota, among which Oscillatoria spp. were most numerous species, dominated in the numbers, whereas Bacillariophycea (mainly Stephanodiscus hantzschii Grun. and Fragillaria spp.) constituted significant proportion of the total algae biomass. There were no significant correlations between abundance of algae and size fractions of sand. Among taxonomic groups, only the biomass of Cyanoprokaryota showed positive correlations with trophic parameters (TP, TN). The studies did not show any correlations between phytopsammon and the abundances of ciliates and rotifers, suggesting that different environmental factors as well as organisms of the higher trophic levels may play a decisive role in the development and horizontal distribution of algae in hygroarenal of the beach of the eutrophic lake.
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.