Red List habitat classification > RL - Marine habitats > RLBAL - Baltic > BAL37 Emergent vegetation communities on Baltic infralittoral muddy sediment

Emergent vegetation communities on Baltic infralittoral muddy sediment

Quick facts

Red List habitat type code BAL37
Threat status
Europe Least Concern
EU Least Concern
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)

Summary

This is a Baltic Sea benthic habitat in the photic zone where at least 90% of the substrate is muddy sediment according to the HELCOM HUB classification. Emergent vegetation covers at least 10% of the seabed and exceeds that of any other perennial attached erect groups. The habitat requires a salinity of less than 6 psu for the associated communities to develop and is encountered in sheltered areas down to a depth of 2 meters.  Two associated biotopes with different dominant plant species have been identified. The common reed (Phragmites australis) forms the characteristic biotope in water depths of up to 2m and in moderately exposed conditions, whereas sedges such as Schoenoplectus spp., and Bolbaschoenus maritimus are generally present in more sheltered and shallower waters in areas of low to moderate salinity.

In the Baltic Sea, sedges form large biotopes in shallow areas typically in estuaries and inlets. It can be found in very sheltered lagoons and in some estuaries around the whole Baltic Sea, but occurs mainly in the north along the Swedish and Finnish coasts of the Bothninan Bay and Gulf of Finland.  The species diversity is usually high because of the large variety and abundance of associated fish and birds. The benthic fauna consists mainly of soft-sediment invertebrates, such as polychaetes, crustaceans, bivalves and insect larvae. These shallow sheltered areas are of high biological productivity in a brackish environment. They form important breeding, resting, and feeding sites for water birds. The muddy substrate biotope dominated by the common reed (Phragmites australis) often occurs in the immediate vicinity of the biotope dominated by sedges and the two biotopes can form a mosaic.  Nutrient levels play a part in affecting the balance between the two biotopes with reed dominated areas favoured by conditions of eutrophication.

Indicators of quality

Both biotic and abiotic indicators have been used to describe marine habitat quality. These include: the presence of characteristic species as well as those which are sensitive to the pressures the habitat may face; water quality parameters; levels of exposure to particular pressure, and more integrated indices which describe habitat structure and function, such as trophic index, or successional stages of development in habitats that have a natural cycle of change over time. There are no commonly agreed indicators of quality for this habitat, although particular parameters may have been set in certain situations e.g. protected features within Natura 2000 sites, where reference values have been determined and applied on a location-specific basis. The overall quality and continued occurrence of this habitat is, however, largely dependent on the presence of the emergent plant species which create the biogenic structural complexity on which the characteristic associated communities depend. The density and the maintenance of a viable population of these species is a key indicator of habitat quality, together with the visual evidence of presence or absence of physical damage. In the case of this habitat the situation is further complicated because the reed dominated biotope is favoured by the deterioration of the sedge dominated biotope under conditions of eutrophication.

Characteristic species
For full habitat description, please download the habitat factsheet.

Threat status

Synthesis of Red List assessment

Cycles of change have been evident in this habitat in some areas. In Matsalu Bay, Estonia, for example there was expansive growth of the reed beds in the middle of the last century followed by a decrease in the last 20 years. In the Gulf of Bothnia the habitat has steadily increased, due to the expansion of reed (while sedges have declined).The expansion has been attributed to a combination of natural processes such as the shoreline advance due to neotectonic land uplift and human activities, both indirect and direct from dredging and eutrophication. In recent decades enlargement has stopped and there are signs of deterioration, attributed to a combination of sea level rise and an increased storminess which is believed to have inhibited reed growth and therefore resulted in decline in some areas exposed to wave action. Changes in the dominant species have also taken place with reeds being able to outcompete the sedges in less muddy areas.
The overall assessment for this EUNIS level 4 habitat has been based on the HELCOM (2013) assessments for the associated HELCOM HUB biotopes. Draft assessments were derived using a weighted approach whereby the HELCOM assessment outcomes were assigned a score. This was averaged across the relevant biotopes. The outcomes were reviewed by Baltic experts to reach a final conclusion. HELCOM (2013) assessed AA.H1A1 as Least Concern (A1) and AA.H1A2 as Near Threatened (A1). The overall assessment for this habitat type, based on expert opinion is Least Concern for both the EU 28 and EU 28+ as the area dominated by Phragmites (AA.H1A1) is large and not threatened in any way.
EU
Red List Category Red List Criteria
Least Concern -
Europe
Red List Category Red List Criteria
Least Concern -

Confidence in the assessment

low
Red List of habitat categories and criteria descriptions

Pressures and threats

  • Pollution
    • Pollution to surface waters (limnic, terrestrial, marine & brackish)
    • Nutrient enrichment (N, P, organic matter)
    • Input of contaminants (synthetic substances, non-synthetic substances, radionuclides) - diffuse sources, point sources, acute events
  • Natural System modifications
    • Human induced changes in hydraulic conditions
    • Estuarine and coastal dredging
    • Modification of hydrographic functioning, general
    • Dykes, embankments, artificial beaches, general
  • Climate change
    • Changes in abiotic conditions
    • Wave exposure changes
    • Sea-level changes
    • Changes in biotic conditions
    • Habitat shifting and alteration

Habitat restoration potential

Phragmites is a pioneer species and a strong competitor therefore there is considered to be a good capacity for recovery at least for the reed dominated biotope.

Trends in extent

Average current trend in quantity

Increasing Increasing
EU28 EU28+

Trends in quality

Average current trend in quality

Stable Stable
EU28 EU28+

Conservation and management needs

One of the main solutions to stop and reverse degradation of the estuaries is a general protection of this natural habitat type by law. Further, programmes and measures are needed to maintain or restore natural conditions along the whole course of the rivers, which e.g. allow natural erosion and temporary flooding of river banks. A drastic reduction of nutrient and pollution loads in the catchment area of rivers with estuaries would help to improve the environmental situation of the whole Baltic marine area and this habitat.
In some areas, there is an active programme of reed removal to encourage re-establishement of the sedge dominated biotopes. Improvements in water quality are also beneficial although it should be noted that whereas increased eutrophication leads to reed replacing sedges, a later decrease in eutrophication does not necessarily facilitate a process where sedges come back.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
    • Restoring/Improving the hydrological regime
  • Measures related to marine habitats
    • Other marine-related measures
  • Measures related to spatial planning
    • Establish protected areas/sites

Distribution

For each habitat a distribution map was produced from a wide variety of sources indicating known and potential occurrences of the habitat in 10x10 km grids within Europe. Occurrences in grid cells were given in two classes: actual distribution from relatively reliable sources (surveys, expert knowledge), and potential distribution based on models or less reliable indicators. Please download the fact sheet to see the map.

Geographic occurrence and trends

Seas Present or presence uncertain Current area of habitat (Km2) Recent trend in quantity (last 50 years) Recent trend in quality (last 50 years)
Baltic Proper Present Unknown Stable Increasing
Belt Sea
Gulf of Bothnia
Gulf of Finland
Gulf of Riga
The Sound

Extent of Occurrence, Area of Occupancy and habitat area

Extent of Occurrence (EOO) (Km2) Area of Occupancy (AOO) Current estimated Total Area Comment
EU28 >50,000 Unknown Unknown This habitat is present in all the Baltic sub-basins however there is insufficient information for accurate calculation of EOO and AOO.
EU28+ Unknown Unknown This habitat is present in all the Baltic sub-basins however there is insufficient information for accurate calculation of EOO and AOO.
AOO = the area occupied by a habitat measured in number of 10x10 km grid cells.
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).

Characteristic species

The full list of characteristic species and genus are available above from the Summary. The species available in the EUNIS database are shown here.
Flowering Plants Phragmites australis
Species scientific name English common name Species group
Phragmites australis Flowering Plants

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
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