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Estuaries

NATURA 2000 Code: 1130

Definition:

Coastal inlets of rivers which are still influenced by brackish water (with recognizable adaptations by plants and animals) and are subject to tidal influence (North Sea only), comprising biocoenoses of the open water, the estuarine bed, and the shoreline. As opposed to the habitat type &quotLarge shallow inlets and bays" there is a water throughflow with substantial freshwater influence. The riparian vegetation (riparian tall herbaceous perennial vegetation, plant communities comprised of annuals, saltmarshes, estuarine woodlands) forms an ecological unit with estuaries. This habitat type is a landscape complex which can be comprised of a variety of biotopes.

The EU Commission has pointed out that in delimiting such sites the entire estuary (as a hydrological unit) shall be included.


Notes on habitat mapping:

Estuaries are taken to comprise all parts of the river estuaries and lower reaches of rivers which are subject to regular tidal and sea water influence. North Sea estuaries also include the parts of the river mouths which are in the freshwater zone and subject to the tide (freshwater tidal mudflats, limit: mean high water tide). Apart from the river itself (incl. possible navigable channels) these include all shoreline sites influence by the tide, such as sands, reed and large sedge swamps, herbaceous perennial vegetation, estuarine woodlands, and sites which emerge at mean low water tide. In the estuarine area the relevant habitat types  rivers with muddy banks with Chenopodion rubri p.p. and Bidention p.p. vegetation (3270),  hydrophilous tall herb fringe communities (6430) and  alluvial forests (91E0 and 91F0, the special case of the  riparian mixed forests) are thus integrated into the habitat type 'estuary'. Elevated areas within the river (e.g. islands) which are not covered by the mean high water tide should be excluded. In the Baltic Bodden landscape, estuaries are differentiated from the Large shallow inlets and bays and the Coastal lagoons on the basis of the prevailing hydrological and chemical conditions. To assign a site to Estuaries, the influence of the watercourse must predominate. On the seaward side sites are defined by the freshwater influence. However, as this is difficult to determine precisely, a pragmatic approach is generally taken to delimitation based on an imaginary line running between those landmarks reaching furthest out into the sea. Estuaries are distinguished from the  coastal lagoons (1150) and the  large shallow inlets and bays (1160) by their continuous throughflow of freshwater.


Last Change: 19/01/2012

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