Elodea

Canadian Elodea (E. canadensis)

The aquatic plant genus Elodea ( Elodea; Syn: Anacharis, formerly also: Helodea ) belongs to the family of the frog bite plants ( Hydrocharitaceae ) and includes twelve species. Related species from the same plant family include crab claw and frog bite.

Description

Her green, pliable stems that are lively reception at a distance of a few millimeters, usually with three to four oblong leaves, can grow up to three meters long and are rooted in a body of water depending on the type. Elodea species are dioecious getrenntgeschlechtig ( dioecious ), so there are male and female plants.

Species in Central Europe

• Canadian Elodea ( Elodea canadensis Michx. )
• Narrow Elodea ( Elodea Nuttall ) ( Elodea nuttallii Planch. ( H.St. John ) )
• Argentine Elodea ( Elodea callitrichoides ( Rich. ) Casp. )

All these species are neophytes in Europe; they are originally from North America (E. canadensis, E. nuttallii ) or from South America ( E. callitrichoides ). Your establishment and spreading in Europe was favored by selective suspensions ( for example, by aquariums holder ) and supported among others by spreading beyond the shipping and waterfowl on.

At least the two North American species, which have in Europe comparable climatic conditions as in their home country, have been here since the mid-19th century (E. canadensis ) and in recent decades (E. nuttallii ) rapidly spread and are now one of the common species inventory many ponds, lakes and ditches.

Occurrence

The Elodea species thrive in summer warm, nutrient-rich, but not burdened excessively, standing or slow- flowing waters ( ponds, pools, congestion and lakes, ditches, rivers, etc.) with sandy- muddy bottoms. She makes her name then all honor by training quickly submerged dominance stocks, real " underwater forests ". While E. canadensis is all over Germany and beyond widespread for some time, E. nuttallii was towards the end of the 1980s only known regionally (especially in the northwest and in the Rhine area ), but has since come a long spread.

Reproduction and wintering

In Europe, only all-female plants are known, while it is also male plants are in North America.

In Europe, the plant is propagated exclusively by the Cancel and further growth of the brittle stems. Each separated fragment is now independent and autonomous and develops in a short time to a complete plant.

In autumn, the Waterweed forms Turionen, each consisting of a package of tightly packed leaves and leaf primordia. They grow in the following spring into new plants.

The "green ghost "

The poet Hermann Lons already wrote on October 9, 1910 at the Hanover Tageblatt on the Canadian Waterweed:

" There arose everywhere a terrible wailing and gnashing of teeth, because the day seemed not far distant, when all inland waters of Europe were filled to the brim with the herb, so that no ship go, no longer a man swimming, gründeln no longer duck and no fish could swim more (...). "

The strong and rapid, almost explosive growth and spreading ability of Elodea is known so long ago in Europe. Meanwhile, Elodea canadensis has declined again and barely still makes mass stocks. In contrast, Elodea nutallii caused increasing problems since the 1990s. Exemplary are the occurrences along the Ruhr in North Rhine -Westphalia, especially the reservoirs Hengsteysee, Harkortsee, Kemnade and to the Sauerland region Listertalsperre. There they hindered by their mass occurrence of water ( clogging of river power plants and locks), navigation, water sports and fishing. The competent Ruhrverband diminishes their stocks now regularly with its own Weed Harvester.

As an ecological interaction is to be noted that the spread of Elodea can be done at the expense of other, less competitive underwater plants of Potamogeton and Chara companies. Meanwhile appear in Central Europe Wasserpestarten but even among themselves to compete with the already- longer -established E. canadensis from the "younger" E. nuttallii is apparently displaced partially. The problem is the autumnal death of the plants whose excess quantity of biomass can lead to overturning of bodies of water. Meanwhile, many stocks, however, have stabilized at a more moderate level, partly because domestic nematodes feed on their buds, thereby limiting the growth. According to popular belief the plant is " every seven years to move on ."

As a positive feature of the strong photosynthetic activity is mentioned, which is easily viewable in sunlight based beaded rising air bubbles. Their comparatively high oxygen production rate, a marked upswing waters. The dense underwater forests fish and other aquatic animals provide shelter and nesting sites. The plant has a high nutritional value - the dry matter contains 18 % protein, 42 % starch and 2.5 % fat - which is why they used to be recommended even as cattle feed. The plant is even suitable according to the latest studies to decontaminate a surface water as it stores radioactive cobalt. Can be significantly reduced through a targeted removal of the plant, therefore, the cobalt content of a water body.

Elodea in the aquarium

Together with their South American relatives Egeria densa ( Elodea densa formerly ), which is a little stronger and has dense leaves, Elodea canadensis is a popular aquarium plant. It is in the attitude, no special demands on the water, but needs a lot of light. It can be easily propagated by planting cuttings.

Related species

In addition to the species of the genus Elodea are still more in Central Europe ( Germany ) to mention neophyte species from the family frog bite plants, some of which are also known as Elodea, but only rarely and sporadically occur:

• Dichtblättrige Elodea ( Egeria densa Planchon; Elodea densa Syn ( Planch. ) Casp. )
• Big change sheet Waterweed ( Lagarosiphon major ( Ridl. ) Moss )
• Reason nettle ( Hydrilla verticillata ( L. f ) Royle )
• Ordinary water screw ( Vallisneria spiralis L.)