Vertical hike
In hydrology , limnology and oceanology , vertical migration is the migration of aquatic organisms across the vertical profile of a body of water - as a specific special form of migration of individuals and populations that occur in the three-dimensional habitat of water.
Light-dependent ( phototrophic ) microorganisms ( algae , planktons ) as well as rotifers , copepods and some mosquito larvae migrate daily through the thermal layers of the water, from the lowest, coldest layer to the uppermost, warm layer and vice versa. Since there are no thermal stratifications in winter and spring due to the seasonal temperature equalization, this behavior can only be observed in summer. The Volvox alga can cover a height difference of up to 18 m.
The form of migration varies depending on the species. This can be limited to the uppermost, heated and strongly agitated layer ( epilimnion ) of stagnant water or the lowest, only slightly agitated layer ( hypolimnion ) - or it can be from epilimnion to hypolimnion. The main reason for the hikes is the changing intensity of the incoming sunlight during the day .
Some fish, e.g. B. Lanternfish , make a day-long vertical hike all year round. In addition to the behavior already mentioned, this behavior is also known from larvae of the tufted mosquito and daphnia .
Individual evidence
- ↑ Ulrich Sommer : Algae, Jellyfish Water Flea - The World of Plankton ; Springer-Verlag 1996; Page 65-68; ISBN 3540603077