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Under Phytobenthos means the photoautotrophic growth of the aquatic soils ( seafloor ), with the exception of prokaryotic cyanobacteria . Animal species that have an autotrophic diet due to endosymbiotic algae, such as the polyps of corals, are not included.

The term phytobenthos is used for sea floors (marine habitats) as well as for standing and flowing inland waters (together limnic habitats). Often microphytobenthos (benthic microalgae ) is primarily meant, which consists of unicellular or cellular filaments and simple colonies or thalli-forming organisms classified as algae (many of the species are actually mixotrophic , they are often mobile and can, for example, after sediment relocation crawl back to the surface). Mostly the macroscopic or macroalgae ( called seaweed in the sea ) are also included. The inclusion of the higher aquatic plants belonging to the vascular plants (called macrophytes), however, is handled inconsistently. In limnic systems, both are treated separately from one another, especially in the applied context. Phytobenthos grows as growth ( periphyton ) on hard substrates (stones, shells of snails and mussels or other aquatic plants) and on soft substrates (sand and silt) alike, whereby rooting macrophytes depend on soft substrates, while the periphyton mostly on hard substrate is better developed and more species-rich is. In deep waters such as the sea or lakes, the phytobenthos is limited to the better exposed bank zone or littoral . The most important groups of marine phytobenthos are the Chlorophyceae , Rhodophyceae and Phaeophyceae , on soft substrates also representatives of the Bacillariophyta , especially the Bacillariophyceae (formerly: Pennales), in addition to the particularly important cyanobacteria. Many representatives of the soft substrate colonists are mobile and can withdraw deeper into the substrate in coastal habitats under unfavorable conditions. The only phytobenthos from macrophytes present in marine habitats are the seagrass meadows .

In limnic habitats, phytobenthos is predominant in rivers, as species floating in the water and belonging to the phytoplankton can hardly survive here because of the currents. Microphytobenthos also grows here as a periphyton, often as a component of biofilms that also include heterotrophic organisms such as bacteria or fungi.

As part of the evaluation procedure for the European Water Framework Directive , phytobenthos is one of the biological quality criteria for the ecological evaluation of running waters, and is therefore used as a bio-indicator . The standardized PHLIB assessment procedure was developed for the assessment. Within the scope of the indication, only the phytobenthos without the macrophytes and the diatoms, for which our own assessment procedures were developed, are considered here.

Literature and Sources

  • Klaus-Jürgen Götting, Ernst F. Kilian, Reinhard Schnetter: Introduction to marine biology. Part 1: Marine Organisms, Marine Biogeography. Viehweg, Braunschweig / Wiesbaden 1982, ISBN 3-528-07244-X , pp. 63-71, Das Phytobenthos.
  • M. Wilkinson: Phytobenthos. In: John H. Steele (Ed.): Encyclopaedia of Ocean Sciences: Marine Biology. Academic Press (Elsevier), London 2009, ISBN 978-0-08-096480-5 , pp. 140-146.
  • Rosemary J. Law: A review of the function and uses of, and factors affecting, stream phytobenthos. In: Freshwater Reviews. 4, 2011, pp. 135-166. doi: 10.1608 / FRJ-4.1.448
  • Jochen Schaumburg, Christine Schranz, Julia Foerster, Antje Gutowski, Gabriele Hofmann, Petra Meilinger, Susanne Schneider, Ursula Schmedtje: Ecological classification of macrophytes and phytobenthos for rivers in Germany according to the Water Framework Directive. In: Limnologica. 34, 2004, pp. 283-301.
  • PHILIB method: phytobenthos without diatoms. At, the information portal for evaluating surface water in accordance with the European Water Framework Directive.