Potamal

The potamal ( altgr. ποταμός, river ) is a technical term limnology and hydrology of the lower reaches of a river (ie, the river habitat ) and is divided into epi-, meta- and Hypopotamal. The cohabitation of potamal is the Potamon.

Above the potamal is the Rhithral (Bach region ) and the Krenal (source region).

The habitat of the region is divided potamal fishing legally after living there Leitfischarten. The Epipotamal corresponds to the barbel region, the Metapotamal the Brachsenregion and the Hypopotamals ( mouth area into the sea ) of the ruffe flounder region.

The annual amplitude of water temperature is around 20 ° C.

In Epipotamal water depth and turbidity are relatively low, so that a variety can develop at submerged, so mostly submerged aquatic plants. These are here naturally more often than in Rhithral because rivers by the higher water level width receive more light than streams. ( Makrophytenreiche streams can therefore usually only develop when the riparian woodlands have been cleared. ) Potamalarten Typical are the large pond weeds of the genus Potamogeton, Potamogeton nodosus especially, Potamogeton lucens and Potamogeton perfoliatus. Other typical species are yellow water lily (Nuphar lutea), Simple bur-reed ( Sparganium emersum f fluitans ), arrowhead ( Sagittaria sagittifolia var vallisnerifolia ), water crowfoot (Ranunculus sect. Batrachium, as a collective species Ranunculus aquatilis agg. ). This vegetation structures are absent in the subsequent Metapotamal and Hypopotamal largely. These river sections are similar to many standing waters, dominated by phytoplankton.

In potamal fewer species of flow- adapted invertebrates ( benthic invertebrates ) than in Rhitral. Many of the species living here but are highly specialized and are exclusively found in large rivers. Due to the ( historical and current ) pollution of most major rivers, many of these species are threatened with extinction. A number of typical species of the potamal are:

• Mussels: mussels of the genus Unio River: Unio crassus, U. pictorum, U. Tumidus
• Snails: water snails of the genus Viviparus and Theodoxus
• Crustaceans: flow amphipod ( Gammarus roeseli )
• Dragonflies: River Virgin of the genus gomphus: Common Clubtail ( gomphus vulgatissimus ), Asian Clubtail ( gomphus flavipes )
• Ephemera: Ephoron virgo, Heptagenia longicauda, Oligoneuriella rhenana, Palingenia longicauda, Potamanthus luteus, Prosopistoma pennigerum
• Stoneflies: Isogenus nubecula, Marthamea vitripennis
• Caddisflies: Brachycentrus subnubilus, Hydropsyche bulgaromanorum

These types are only exemplary of the species spectrum of potamal. Some of them are now extinct in Germany or threatened with extinction. At least one German Trichoptera of potamal, Hydropsyche tobiasi is, obviously, as a species extinct (worldwide). It is only from museum specimens collected in the Middle Rhine, known. Some others have recovered in recent decades due to improved water quality, eg the Virgin River.

Some typical Potamalarten are conspicuous by mass flights. It is the synchronized hatching of millions of individuals of a section of river at the same time, similar to dense fog and can literally block out the sun. Such phenomena are then reported in the daily press. Mass - slip phenomena are known from historical accounts. Some of the dead falling insects were so numerous that they were fed to the pigs. Early and mid- 20th century they were known because of the biological obliteration of many Central European rivers only from Eastern and Southeastern Europe :; since some years back from Central Europe ( Danube and tributaries, Rhine). Known for mass shelter some species of mayflies ( Ephoron virgo) and caddisflies ( Hydropsyche contubernalis, Brachycentrus subnubilus ). The mayfly Palingenia longicauda was called because of their mass flights in the Hungarian Danube tributary Tisza ( Tisza ) " Theißblüte ". In addition to the specialized Potamalarten live in potamal a large number of species with distribution focus in Bach underruns ( Hyporithral ), also types of stagnant water and freshwater ubiquitous.

Typical of the potamal today is still a very large number of animal species that have been introduced by humans ( invasive species ). Shall be considered as possible reasons for this:

• By the strong water pollution of the past, many rivers were nearly uninhabited, so that all newly arriving species had good career prospects
• By the construction of canals through traditional watersheds of time ( eg the Rhine -Main- Danube Canal ) had many kinds of new distribution channels
• Modern transport mechanisms procrastinate species over long distances. Aquatic organisms are attached to ships or transported in ballast water. Some species are kept in aquariums or are abducted attached to aquatic plants.

The macrozoobenthos of the Middle Rhine was at times more than 90 % of the individuals share and about 30 % of the species from invasive species.

Typical and potamal widespread today neozoische types are, for example:

• The mussel species of the genus Corbicula ( clams ) and the zebra mussel ( Dreissena polymorpha ).
• The New Zealand mud snail ( Potamopyrgus antipodarum )
• The gill worm ( Branchiura sowerbii )
• Mud crabs of the genus Corophium, particularly Corophium curvispinum
• Big Dikerogammarus ( Dikerogammarus villosus ) and other gammarids ( Gammarus tigrinus eg, Echinogammarus spp., Obesogammarus spp.)
• The American crayfish ( Orconectes limosus ).
• The Chinese mitten crab ( Eriocheir sinensis)

Typical mammal species of otter and beaver are Potamon. Typically as breeding birds are Uferschwalben - they nest in steep, eroded by the water's edge breakage - and sandpipers.