Pool
A pond , also known as Lacke in Austria and Blänke in Northern Germany , is a still body of water that, limnologically, corresponds to a small pond , but can occasionally dry out. It belongs to the small bodies of water and thus to the small biotopes.
description
.jpg)
Pools are shallow and typically less than two inches deep. Due to the large surface area in relation to the water volume, they have an oxygen content of usually over 50% of saturation due to the diffusion of air into the water.
Ponds are naturally formed when the snowmelts in spring, when it rains heavily, when there is flooding or when groundwater escapes in depressions. Pools are mainly fed by rainwater . They therefore have a strongly fluctuating water level. You silt usually quickly. Ponds can dry up during the hot season due to high evaporation, ponds that temporarily dry out are counted as temporary bodies of water.
to form
Meadow pools have a high water temperature, which is always a little higher than in the air because of the heat given off by the subsoil. Forest pools are cooler and evaporate more slowly because the canopy of the trees shields most of the solar radiation. If it is a real spring , one speaks of a spring pool that surrounds the pool spring (Limnokren) from which the spring stream flows.
Blänke is the North German name for a pond. The word is derived from the adjective "blank" and comes from the shimmering surface of the water (compare " Blanker Hans "). Blänken are often ground or backwater horizons that come to light due to annual fluctuations, especially in lowlands.
The clear, humic acid- rich water of bog pools is usually very warm on the surface, but relatively cool at depths of one to two meters due to the shielding effect of the peat moss . The difference between day and night temperatures is also particularly pronounced. Bog pools are poor in species, they only accommodate living things that have been adapted to the properties of the bog water. In contrast to meadow pools, they hardly show any tendency to dry out or silt up and are also known as scour or bog eyes .
A special form is the salt varnish of semi-arid zones.
plants
One of the characteristics of a meadow pond is that it is continuously framed by rushes and other marsh plants , which is less the case with forest ponds due to the lack of light. Many pools only exist for a few weeks, so there are no real aquatic plants . The basic vegetation usually consists of grasses, which do not mind the temporary flooding. Because of the high water temperatures, many single and multi-cell algae live in the pond. High mountain ponds can be colored blood red by the eye animal Euglena sanguinea , which is why they are then referred to as blood lakes .
Animals
Since they are important as spawning waters , ponds are sometimes sealed with plastic sheeting or concrete. Not least for this reason, artificial pools are created in gardens or in nature. The yellow-bellied toad in particular prefers shallow, well-sunny pools. Fast growth, a high rate of reproduction and a short generation line characterize the animal world in the short-lived pond. The drying up of the ponds does not harm the adults , but sometimes the larvae of insects such as swimming beetles , water beetles , mosquitoes , mosquitoes , dragonflies and caddis flies . Other pond dwellers are better adapted to falling dry or freezing over. The hard-shelled eggs of some gill pods can lie in the dry for years, those of the amphipods for months if they are covered with soil. Some species can only develop after the eggs have gone through the dry state for some time. Many rotifers , roundworms , copepods, and mussel crabs can survive long periods of time in rigidity and become widespread in dust-dry mud.
literature
- Werner Nachtigall: Habitats. Central European landscapes and ecosystems. BLV, Munich 1986, ISBN 3-405-13254-1 .
- Wolfgang Engelhardt: What lives in pools, brooks and ponds? Franckh-Kosmos, Stuttgart 2008, ISBN 978-3-440-11373-8 .
