Pleustophyte

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Pleustophytes , floating plants or water floaters are an ecological group of macroscopic aquatic plants , or macrophytes, of still waters . These are freely swimming plant species that do not have roots in the water bed, but which do not belong to the (microscopic) phytoplankton (these are, rarely, called "planktophytes"). The pleustophytes floating on the surface of the water often form extensive floating blankets on nutrient-rich (eutrophic) inland waters, which are problematic and undesirable in the management of these waters.

Phytosociological form the Central European Wasserschweber widespread, mostly species-poor plant communities , which for the most common species, the duckweed ( Lemna are called Lemnetea).

Definition, demarcation and conceptual history

The term pleustophyte is derived from the Greek plein: sailing and phytos: plant. It was first introduced in 1896 by the botanist Carl Schroeter , the current definition goes back to the botanist Hans Luther in 1949. The Pleustophyten are the vegetable ingredient cohabitation of Pleustons . Together with the new clay , the microscopic community dependent on the surface membrane, and the plankton, they are often summarized under the term seston. A distinction is made in part: the mesopleustophytes, as plants that float rootlessly under water in the volume of water, such as the species of the genus horn leaf ( Ceratophyllum ), and the acropleustophytes (also acropleustophytes or natant pleustophytes) as species that swim freely on the water surface, this fine division but is not common practice. The floating leaf plants are related, but not belonging to them and form their own vegetation units ; these are aquatic plants rooted in the water bed, the leaves of which float on the water surface. While floating leaf plants are also found in rivers , floating plants are unable to withstand a current of water and are therefore largely restricted to still waters, but they can be particularly common in nutrient-rich oxbow lakes of rivers.

Pleustophytes have their distribution center in warm, tropical waters, in particular they are characteristic of South American wetlands such as the Pantanal. Almost worldwide and especially feared in reservoirs are the thick-stemmed water hyacinth ( Eichhornia crassipes ) and the water lettuce ( Pistia stratiotes ). Both species are used in the aquarium hobby and have thus been introduced worldwide. Millions of euros are spent annually to combat the water hyacinth blankets of tropical lakes, especially reservoirs.

Central European vegetation

The water floaters or pleustophytes of Central Europe form the class Lemnetea (minoris) in the plant-sociological system , named after the small duckweed ( Lemna minor ). The duckweed are the most common pleustophytes, all species belong to this group. Duckweed blankets are characteristic of nutrient-rich (eutrophic) to over-fertilized and excessively nutrient-supplied (hypertrophic) waters. Floating plant communities dominated by duckweed are grouped together to form the order Lemnetalia. Frequent companions of the species-poor societies are, besides the various duckweed species, the common swimming fern ( Salvinia natans ) and the great algae fern ( Azolla filiculoides ). Sometimes the star liver moss ( Riccia fluitans ) also forms floating blankets. Like the three-furrow duckweed ( Lemna trisulca ), the plants do not float up, but just below the surface of the water.

Much rarer than the duckweed ceilings are multi-layer water-floating societies, which, in addition to duckweed, also consist of larger pleustophytes. Characteristic species are the European frog bite ( Hydrocharis morsus-ranae ) and (in addition to duckweed of the genera Lemna and Spirodela ) floating in the open water, rough horn leaf ( Ceratophyllum demersum ) and misunderstood water tube ( Utricularia australis ). Normally rooting species such as water feathers ( Hottonia palustris ) and the half or fully submerged floating leaf plant crab claws ( Stratiotes aloides ) can also occur freely swimming and are regularly associated. The extremely rare water trap ( Aldrovanda vesiculosa ) also occurs in association. These multi-layered water float societies are usually grouped in their own order Hydrocharitetalia with the single association Hydrocharition (named after the frog bite Hydrocharis ), but some vegetation experts prefer the name Strationion, which is derived from the crab claws ( Stratiotes ). Together with the large spawning corridors of the nutrient-rich waters (in the plant-sociological system the association Magno-Potamogetonion), "natural eutrophic lakes with vegetation of the magnopotamion and hydrocharition type" are a protected habitat type (code number 3150) within the framework of the European nature reserve system Natura 2000 . In addition to their most characteristic habitat, the silting belt of warm, eutrophic lakes, they sometimes also occur in ponds, ponds or weed-rich drainage ditches, preferably in the lowlands.

Species of the small spawn dive corridors, i.e. submerged aquatic plants in the diving leaf zone , can often be associated.

Individual evidence

  1. ↑ Hans Luther : Proposal for a basic ecological classification of the hydrophytes. In: Acta Botanica Fennica. 44, 1949, pp. 1-15.
  2. ↑ Georg Toepfer: Historical dictionary of biology: history and theory of basic biological terms. Volume 1: Anatomy Wholeness. Springer-Verlag, 2016, ISBN 978-3-476-00439-0 , p. 314.
  3. ↑ Peter Englmaier: The macroflora of fresh water. In: Denisia. 33, 2014, pp. 313-345.
  4. ↑ Helmut Mühlberg: Growth forms of aquatic angiosperms (part 1). In: Schlechtendalia. 20 2010, pp. 5-20.
  5. ^ FD Por, CEF da Rocha: The Pleustal, a third limnic biochore and its neotropical center. In: Negotiations of the International Limnology Association. 26, 1998, pp. 1876-1881.
  6. ↑ Jean-Claude Felzines: Contribution au prodrome of végétations de France: les Lemnetea Minon Tüxen ex O. Boles & Masclans 1955. In: Journal de Botanique de la Societe Botanique de France. 59, 2012, pp. 189-240.
  7. ↑ E. Rennwald: directory and Red List of Plants companies in Germany. (= Series of publications on vegetation studies. 35). 2002.
  8. ↑ Ladislav Mucina, Helga Bültmann, Klaus Dierßen, Jean-Paul Theurillat, Thomas Raus, Andraz Carni, Katerina Sumberova, Wolfgang Willner, Jürgen Dengler, Rosario Gavilan Garcıa, Milan Chytry, Michal Hajek, Romeo Di Pietro, Dmytro Iakushenko, Jens Pallas, Fred JA Daniels, Erwin Bergmeier, Arnoldo Santos Guerra, Nikolai Ermakov, Milan Valachovic, Joop HJ Schaminee, Tatiana Lysenko, Yakiv P. Didukh, Sandro Pignatti, John S. Rodwell, Jorge Capelo, Heinrich E. Weber, Ayzik Solomeshch, Panayotis Dimopoulos , Carlos Aguiar, Stephan M. Hennekens, Lubomır Tich: Vegetation of Europe: hierarchical floristic classification system of vascular plant, bryophyte, lichen, and algal communities. In: Applied Vegetation Science. 19 (Supplement 1), 2016, pp. 3–264.
  9. ↑ Natural eutrophic lakes with magnopotamion or hydrocharition type vegetation. In: BfN Federal Office for Nature Conservation: The habitat types and species (protected objects) of the Habitats and Birds Protection Directive. Last change: December 16, 2011.
  10. ^ Frank Schwieger: Aquatic plants in flowing waters of the Lower Saxony Elbe region. Presentation and evaluation of floristic findings. (= NLWK Lower Saxony State Office for Water Management and Coastal Protection, series of publications. Volume 6). September 2002.
  11. ↑ Gerhard Wiegleb: The sociological connection of the 47 most common macrophytes of the waters of Central Europe. In: Vegetatio. 38 (3), 1978, pp. 165-174.