engleski

Diurnal Vertical Migration of Macrozooplankton in Karstic Lake Vrana (Croatia).

Diurnal vertical migrations of macrozooplankton species in lake Vrana were observed during summer stratification. Vrana is an oligotrophic, Mediterranean, karstic, monomictic lake, situated in the southwestern Croatia on the island of Cres, which mixes between November and April. The lake has the surface area of 5.75 km2, and a maximum depth of 75 m. It has been very poorly investigated, biologically, and it is used for drinking water supply. Diurnal vertical migrations of macrozooplankton were observed in a vertical profile from 1-40 m. There were five : macrozooplankton species in lake. Vrana: Daphnia longispina, Diaphanosoma brachyurum, Bosmina longirostris, Cyclops abyssorum and Megacyclops viridis. The spatial distribution of zooplankton is conditioned by the food supply and inter and intraspecies relations. Diurnal vertical migrations are regulated by complex of ecological parameters, (e.g., light) and endogenous rhythms. The extent of diurnal vertical migrations varied with the size of the animal and its reproductive state. The younger and smaller individuals were present in the surface layers of the metalimnion to 20 m depth, while the population nucleus of larger and older stages migrate deeper. The migration distance also varied by species. The lake fish population consists of: Scardinius eritrophtalmus hesperidicus , Leuciscus sp., Tinca tinca , and Esox lucius. Since S. eritrophtalmus hesperidicus is known to feed in its early stages primarily on zooplankton, diurnal vertical migrations were also induced by predators.

nije evidentirano

nije evidentirano