Biotopes and classification systems
Hierarchical levels of biological organisation (such as ecosystem) are widely used by scientists but also by decision-makers and managers. Limits of ecosystems are usually difficult to define and are often too large to be of a practical value. A relatively new way of defining sub-units in an ecosystem is based on the concept of the biotope. They can be mapped easily and changes in time in their distribution can be recorded. A recent definition of a biotope was used in the framework of the European programme Biomar-Life:
Definition of Biotope:
The physical habitat with its biological community; a term which refers to the combination of physical environment (habitat) and its distinctive assemblage of conspicuous species. So, a biotope combines the concepts of habitat and community for defining geographical units.
This is the common definition for Biotope, other definitions can be discussed in the article
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But, just the word habitat may be used in various ways:
Definition of Habitat:
1. The place where an organism is found – i.e. a wave-cut platform, as for example in the EU species and habitats Directive;
2. The area where a species is found, as used by biogeographers; or 3. The area where a species could potentially establish itself, as used by ecologists.This is the common definition for Habitat, other definitions can be discussed in the article
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Contents
Elaboration on definitions
In the definition of a biotope, a habitat is understood to be he place in which a plant or animal lives. It is defined for the marine environment according to geographical location, physiographic features and the physical and chemical environment (including salinity, wave exposure, strength of tidal streams, geology, biological zone, substratum, 'features' (e.g. crevices, overhangs, rockpools) and 'modifiers' (e.g. sand-scour, wave-surge, substratum mobility). The notion of ‘community’ also may vary depending on the authors. Data analysed with clustering and ordination techniques have been employed to define association of species in recognisable assemblages. Despite the fact that such groups are the product of statistical analysis, they are often misinterpreted as biological/ecological entities carrying out a recognised function in the ecosystem. In the working definition of a biotope, a community is identified as a group of organisms occurring in a particular environment, presumably interacting with each other and with the environment, and identifiable by means of ecological survey from other groups. A community is normally considered as a biotic element of a biotope. Biotopes help solving the problem of scale in relying on the definition of boundaries which correspond to physical discontinuities along ecological gradients. They summarise not only the type of underlying habitat, and thus the niche created, but also the dominant and structuring biological elements; hence their description does not need to contain all species in a community.
History of the term
The term “biotope” was introduced by a German scientist, F. Dahl in 1908 as an addition to the concept of ‘biocenosis” earlier formulated by K. Möbius (1877)Cite error: Closing </ref> missing for <ref> tag. In France, the Zones Nationales d'Intérêt Scientifique, Faunistique et Floristique (ZNIEFF) have been developed. Such systems are at the basis to a Europe wide classification system put in palace by the European Union (EU) and the Oslo & Paris Commission (OSPARin the early 2000s.
The accuracy level of characterization of biotic features in biotopes varies in different classification systems. Thus in the Red list of marine a coastal biotopes complexes of the Baltic Sea, Belt Sea and Kattegat prepared by HELCOM experts, the hierarchical principle is applied:
- Substratum is the main characteristic;
- Further, its location is considered – if it is located within the euphotic zone or outside it;
- And finally, for the euphotic zone biotopes, the presence and abundance (many, few, none) of macrophytes is determined.
Species composition or even their life form (perennial, annual, filamentous) is not defined more precisely. The presence or absence of animals is not taken into consideration, in exception of special types of biotopes – i.e. the mussel bed. The biotical features, which characterize sea floor structures formed by macrozoobenthos activities, are not applied either. The system needs to be further detailed and elaborated.
Perspectives in the use of biotopes
The use of biotopes may lead to a better interpretation of the heterogeneity of the ecosystem (in terms of the relative abundance of the various structural components) and its complexity (in terms of relationships between components). The biotope concept can be adapted to fit in a system approach to the ecology of coastal marine ecosystems. Such aspects include the consideration of:
- biotopes as components of the ecosystem and structuring aspects of dominant organisms,
- the spatial scale of biotopes in relation to their physical boundaries and their individual characteristics,
- the temporal scale relating to the changes to the distribution of biotopes within the ecosystem over time,
- connections between biotopes within the ecosystem demonstrating processes and functions,
- constraints (natural or anthropogenic disturbances) on the ecosystem behaviour and how biotopes translate such changes.
The concept of the biotope links with other levels of biodiversity in the ecosystem and integrates its various functions Possible further research at biotope and lower hierarchical levels include the modelling of relationships between biotopes in relation to the overall behaviour of the ecosystem. The quantification of fluxes between various compartments, at biotope level and lower, is another avenue to explore in relation to the use of photography and GIS (Geographical Information System). Applications to management could lead to interesting socio-economic considerations (i.e. the sustainable exploitation of natural resources or the search for new fisheries).
References
Further Reading
- Olenin S. & Ducrotoy J.P. 2005. The concept of biotope in marine ecology and coastal management. Marine Pollution Bulletin, 53, 1-4: 20-29.
See also
External links
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