Plankton ( Greek πλαγκτόν "the wandering", "the wandering") is the name for the totality of the organisms that live in free water ("floating", with little or no movement) and whose swimming direction is determined by the water currents. Individual organisms in plankton are called plankters . Organisms that can swim against currents, on the other hand, are called nectons .
The marine biologist Johannes Peter Müller can be considered the founder of systematic plankton research. He began scientific research on these organisms on the island of Helgoland in 1846 ; at that time he called the plankton buoyancy . Also of great importance is the Kiel marine scientist Victor Hensen , who in 1889 led the first scientific expedition that dealt only with plankton.
In 2013, the first atlas for marine plankton was published in a cooperation between ETH Zurich and the University of East Anglia . According to Meike Vogt , data from half a million measuring stations were evaluated, which was only possible through international cooperation.
Plankton is almost ubiquitous in bodies of water. However, due to the low availability of nutrients, most marine areas are considered ecological deserts. If there is an excess of nutrients in stagnant inland and running waters , the rapidly growing plant plankton ( e.g. algae ) can lead to what is known as tipping over .
Freshwater plankton is known as limnoplankton , seawater plankton as haliplankton or haloplankton .
For plankton, a prerequisite for survival is its ability to float (secured for example by water turbulence, locomotion or floating organs, water or gas storage). Contact with the ground usually leads to death.
According to systematic affiliation
Depending on the affiliation of planktonic organisms to one of the realms in the system of living beings, one differentiates:
- Mycoplankton (fungal plankton): There are representatives from the tribe of the egg mushrooms , from the class of the potty mushrooms and the yeast family
- Bacterioplankton (bacterial plankton): such as cocci and rods ( Bacillus , Escherichia , Vibrionen )
- Phytoplankton (vegetable plankton): diatoms (Bacillariophyta), green algae (Chlorophyceae), dinoflagellates (Dinoflagellata) etc.
- Zooplankton (animal plankton, which in comparison with the vegetal plankton represents the lower part of the plankton): various " protozoa " (single-celled animals such as acantharia , foraminifera ) and rotifers (rotifers), ciliates (ciliophora) as well as arrow worms , the larvae and also some adult ones (adult) copies of bristle worms , fish larvae , many crustaceans (Crustacea) and their larvae ( krill and other small crustaceans), some insect larvae , Stachelhäuterlarven (starfish, among others), mussel larvae , tunicates (tunicates) and their larvae etc.
Plankton come in all shapes and sizes. The spectrum ranges from planktonic viruses and phages, which were only discovered using electron microscopic methods at the end of the 1980s , to jellyfish several meters in size . A uniform classification according to size has not yet established itself. Plankton is widely classified based on the order of magnitude of its linear dimensions:
|designation||size||Organism groups (examples)|
|Picoplankton||0.2 µm - 2 µm||Bacterioplankton , the smallest phytoplankton|
|Nanoplankton, nannoplankton||2 µm - 20 µm||many phytoplankton, protozoa , largest bacterial plankton|
|Microplankton||20 µm - 200 µm||large phytoplankton and protozoa, small metazoa|
|Mesoplankton||0.2mm - 20mm||many metazoa, largest protozoa, phytoplankton colonies|
|Macroplankton||2 cm - 20 cm||largest phytoplankton colonies, large planktonic crustaceans (e.g. Euphausiidae )|
|Megaplankton, megaloplankton||> 20 cm||largest zooplankton (e.g. jellyfish)|
Other classifications are based on the methods with which plankton can be caught and examined: Plankton with a minimum size of 20–65 µm can be caught with the help of nets; it is also known as network plankton . The smallest plankton that can be extracted with such plankton nets is called microplankton . It can be examined with light microscopes . Zoo and phytoplankton up to a maximum size of fractions of a millimeter are counted here, with different maximum values being given, e.g. B. 0.2 mm or 0.5 mm. Some toxic microalgae from the dinoflagellates can multiply en masse and pose a threat to human health (→ algae bloom ).
In the case of nanoplankton with a size of a few micrometers, the water sample must be preserved by adding preservatives before the plankton is sedimented. The sedimented plankton can then be examined under the inverted microscope ( Utermöhl method ).
Picoplankton no longer sinks completely in the sedimentation chamber and is therefore not suitable for the Utermöhl method. Applied to filters with pores of 0.1 to 0.2 µm, it can be made visible with a fluorescence microscope after it has been colored . In the picoplankton there are mainly picozoa (only species Picomonas judraskeda ), which can make up up to 50 percent of the biomass in the nutrient-poor areas of cold coastal seas.
According to planktonic life stages
Species whose individuals spend their entire lives floating as plankton are part of the holoplankton . Some organisms, on the other hand, are only part of the plankton in certain stages of development ; this plankton is called meroplankton . These include B. floating eggs and larvae of fish or corals . Sessile animals living on the seabed are used in these pelagic stages for the distribution of the species.
Tychoplankton , also called pseudoplankton , consists of organisms that occur occasionally and in random life stages in plankton. These can be benthic organisms or organisms that have been washed in by water eddies. Some authors take the term tychoplankton wider and include meroplankton as well.
All planktonic organisms that do not photosynthesize but instead feed on other organisms are counted as zooplankton. A distinction is made between herbivorous and carnivorous species: herbivorous zooplankton include those species that feed directly on phytoplankton, zooplankton that feed on other zooplankton are referred to as carnivorous. These feeding relationships are linked to one another in the food web. The different types of zooplankton have widely varying reproduction and growth rates. As determining factors for the ecological niche occupied by a zooplankton species, their respective behavior as well as their respective geographical and vertical position in the sea could be identified.
The zooplankton plays an essential role as a food source for fish and many other marine life. Without the plankton of the arctic waters, the giant plankton-filtering baleen whales such as the blue whale or the fin whale lacked the basis of food. Copepods of the genus Calanus , together with krill, form huge amounts of animal biomass in plankton. Large areas of the sea are often discolored by the presence of plankton just below the surface of the water, giving fishermen clues about schools of fish that feed on zooplankton, such as herring and mackerel .
Single-cell diatoms make up the bulk of phytoplankton. The cells are surrounded by a two-part shell (theca) made of silica . According to various studies, the greatest amount of bound carbon is not bound in tropical forests , but in the plant plankton of the world's oceans .
Plankton is the basis of the marine and limnic food webs . The types listed below are some of the best-known representatives of this diet:
Plankton-like plastic parts
In the oceans driving waste from plastic so-called in recent decades by flow, weathering and other influences into smaller and smaller pieces, micro plastic decomposes. Some of these particles are similar in size, appearance and swimming behavior to plankton and mix with it, so that they are eaten by plankton filter feeders and can develop harmful effects. Microplastics are therefore sometimes referred to as plastic plankton , but they have also been discovered in the soil and drinking water.
- Manfred Klinkhardt: Plankton. In: Claus Schaefer, Torsten Schröer (Hrsg.): The large lexicon of aquaristics. Eugen Ulmer, Stuttgart 2004, ISBN 3-8001-7497-9 , p. 780.
- Jörg Ott : Oceanography. Second edition. UTB, Stuttgart 1996, ISBN 3-8252-1450-8 .
- Ecology. dtv-Atlas 1998
- Christian Sardet: Plankton: Wonders of the Drifting World. The University of Chicago Press, 2015. ISBN 978-0-226-18871-3 (print); ISBN 978-0-226-26534-6 (eBook)
- German: Plankton: The amazing microcosm of the oceans. Stuttgart, Verlag Eugen Ulmer, 2016. ISBN 978-3-8001-0398-0 .
- IDW press release 150 years of plankton research (1996)
- Reports from the Center for Marine and Climate Research ( Memento from May 22, 2011 in the Internet Archive ) - (PDF; 2.12 MB) Zooplankton in the North Sea: An overview of all research up to 2001
- plankton * net , Alfred Wegener Institute's online resource with taxonomic and ecological information on thousands of species of marine and limnic plankton
- Videos on plankton published by the Institute for Scientific Film . Provided in the AV portal of the technical information library .
- Manfred Klinkhardt: Plankton. 2004.
- Johannes Peter Müller first used this name in 1846 on the recommendation of Jacob Grimm .
- First atlas for marine plankton . Press release from ETH Zurich , July 17, 2013.
- ET Buitenhuis, M. Vogt , R. Moriarty, N. Bednaršek, SC Doney, K. Leblanc, C. Le Quéré, Y.-W. Luo, C. O'Brien, T. O'Brien, J. Peloquin, R. Schiebel, and C. Swan: MAREDAT: towards a world atlas of MARine Ecosystem DATa . In: Earth System Science Data 5, pp. 227-239, July 12, 2013, doi : 10.5194 / essd-5-227-2013 .
- Ulrich Sommer : Biological Oceanography . Springer, 2016, 6 marine communities 1: The plankton and necton, doi : 10.1007 / 978-3-662-50407-9 .
- Meinhard Simon: The bacterioplankton - giant and regulator in the marine metabolism . In: Gotthilf Hempel, Irmtraut Hempel, Siegrid Schiel (eds.): Fascination Marine Research . HM Hauschild, Bremen, ISBN 3-89757-310-5 , p. 73-74 .
- Ulrich Sommer : Planktology . Springer, Berlin Heidelberg 1994, ISBN 978-3-540-57676-1 , 2.1 size classes, doi : 10.1007 / 978-3-642-78804-8 .
- Lothar Kalbe: Limnic ecology . Vieweg + Teubner Verlag, Wiesbaden 1997, ISBN 3-663-10671-3 .
- Malte Elbrächter: Poisonous algae - algae poisons . In: Gotthilf Hempel, Irmtraut Hempel, Siegrid Schiel (eds.): Fascination Marine Research . HM Hauschild, Bremen, ISBN 3-89757-310-5 , p. 73-74 .
- Lars Edler, Malte Elbrächter: The Utermöhl method for quantitative phytoplankton analysis . In: Bengt Karlson, Caroline Cusack, Eileen Bresnan (Eds.): Microscopic and Molecular Methods for Quantitative Phytoplankton Analysis (= Manuals and Guides . No. 55 ). Intergovernmental Oceanographic Commission, 2010 ( noaa.gov [PDF; 4.2 MB ]).
- plankton. In: Spectrum Lexicon of Biology. Retrieved June 14, 2019 .
- Gustav-Adolf Pfaffenhöfer, Sigrid Schiel: The most important groups of zooplankton . In: Gotthilf Hempel, Irmtraut Hempel, Siegrid Schiel (eds.): Fascination Marine Research . HM Hauschild, Bremen 2006, ISBN 3-89757-310-5 , p. 95-98 .
- Michael J. Kennish: Ecology of Estuaries: Volume 2: Biological Aspects . CRC Press, 2019, pp. 4 .
- Matthias Schaefer: Dictionary of Ecology. 4th edition, Spektrum Akademischer Verlag, Heidelberg / Berlin 2003, ISBN 3-8274-0167-4 , p. 358.
- Lawrence Cahoon: Tychoplankton . In: Encyclopedia of Estuaries . August 2015, doi : 10.1007 / 978-94-017-8801-4_292 .
- Gustav Adolf Paffenhöfer: perception, feeding, fleeing - life marine zooplankton. In: Gotthilf Hempel, Ilka Hempel, Sigrid Schiel (eds.): Fascination Marine Research. Hauschild Verlag, Bremen 2006
- Keyword Calanus at Encyclopaedia Britannica online (accessed April 17, 2013).
- Algalita Marine Research Foundation: Plastic in the plankton ( Memento of 10 June 2006 at the Internet Archive ) - (English, accessed on May 28, 2010).