Red List habitat classification > RL - Marine habitats > RLBAL - Baltic > BAL3 Aquatic moss communities on Baltic infralittoral rock and mixed substrata (predominantly hard)

Aquatic moss communities on Baltic infralittoral rock and mixed substrata (predominantly hard)

Quick facts

Red List habitat type code BAL3
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)


This is a Baltic Sea benthic habitat in the photic zone where at least 90% of the substrate is rock, boulders or stones according to the HELCOM HUB classification, or mixed (predominantly hard) substrates where the percentage of rock is lower but between 10- 90%. Perennial mosses cover at least 10% of the seabed and more than other perennial attached erect groups. In some places the mosses form extensive underwater meadows which provide shelter and food for benthic animals. The habitat typically occurs where the salinity is <5 psu and usually from depths of 1-7m. Whilst more common in exposed areas, it does occur under other conditions of exposure to wave action and currents. 

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.Depth range, biodiversity and the amount of epiphytic ephemeral filamentous algae are potential indicators of quality.

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

Threat status

Synthesis of Red List assessment

This habitat is limited to areas of low salinity in the Gulf of Bothnia and Gulf of Finland but there are no quantitative data on its geographical extent or on any changes in quality in recent or historic periods of time. Expert opinion is that there has been less than a 25% decline in extent over the last 50 years.
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 acrossthe relevant biotopes. The outcomes were reviewed by Baltic experts to reach a final conclusion. HELCOM (2013) assessed the two relevant Baltic biotopes (AA.A1D and AA.M1D) to be of Least Concern (based on criterion A1). With no additional information on changes in extent or quality of this habitat the current expert opinion is an assessment of Least Concern in both the EU 28 and EU 28+
Red List Category Red List Criteria
Least Concern -
Red List Category Red List Criteria
Least Concern -

Confidence in the assessment

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)
  • Natural System modifications
    • Human induced changes in hydraulic conditions
    • Siltation rate changes, dumping, depositing of dredged deposits
    • Other human induced changes in hydraulic conditions

Habitat restoration potential


Trends in extent

Average current trend in quantity

Unknown Unknown
EU28 EU28+

Trends in quality

Average current trend in quality

Unknown Unknown
EU28 EU28+

Conservation and management needs

There is limited information on conservation and management measures specifically relating to this habitat but they could be expected to include those which reduce the risks of eutrophication and increase water clarity.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality


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)
Gulf of Bothnia Present Unknown Unknown Unknown
Gulf of Finland

Extent of Occurrence, Area of Occupancy and habitat area

Extent of Occurrence (EOO) (Km2) Area of Occupancy (AOO) Current estimated Total Area Comment
EU28 Unknown Unknown Unknown There is insufficient quantitative data to make an accurate estimate of EOO and AOO.
EU28+ Unknown Unknown There is insufficient quantitative data to make an accurate estimate 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

Not available

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
European Environment Agency (EEA)
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