Red List habitat classification > RL - Marine habitats > RLBAL - Baltic > BAL14 Annual algae communities on Baltic infralittoral coarse sediment

Annual algae communities on Baltic infralittoral coarse sediment

Quick facts

Red List habitat type code BAL14
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 benthic habitat is distributed in the photic zone with at least 90% coverage of coarse sediment. Coarse sediment has less than 20% of mud/silt/clay fraction (<63 µm), and the proportion of gravel and pebbles (grain size 2–63 mm) exceeds 30% of the combined gravel and sand fraction according to the HELCOM HUB classification. Annual algae cover at least 10% of the bottom, while all other epibenthic biotic structures like perennial algae, rooted plants or blue mussels cover less than 10%. The habitat is present in the full salinity range of the Baltic Sea and is more common in exposed areas, mainly within the surf zone, in which wave energy prevents the establishment of either perennial vegetation or blue mussels.

One associated biotope has been identified: ‘Baltic photic coarse sediment dominated by Chorda filum and/or Halosiphon tomentosus’ (AA.I1S2). This is encountered in the Baltic Sea up to the Quark, and is identified by a large representation of Chorda filum and/or Halosiphon tomentosus, at least 50% of the biovolume of annual algae. 

Indicators of quality: 

The ratio of annual to perennial epibenthic components is used in several countries to describe habitat quality. As such the area of the habitat itself or the biomass of the corresponding species is used as an indicator for quality.In this particular case the lowest area or biomass is a sign of high quality as only in very high exposure levels should annual algae dominate. In all other circumstances perennials (Fucus) should dominate except where there is a low salinity (below 3 psu) as perennial algae growth does not generally occur under such conditions.

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

Threat status

Synthesis of Red List assessment

This habitat is present in all the sub-basins of the Baltic and is particularly common in areas with reduced salinity and/or high wave exposure. Site records and distribution maps are available for some of the characteristic species but there are no quantitative data on extent and area of the habitat. Expert opinion is that the extent is believed to have changed by less than 10% over the past 50 years and that there have been moderate changes in quality in some parts of the Baltic (<10%). No significant changes in extent or quality are envisaged for the near future.
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 the relevant Baltic biotope (AA.I1S2) as Least Concern (A1). With no additional information on changes in extent or quality of this habitat, the current expert opinion is an assessment of Least Concern for 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

  • No threats or pressures
    • No threats or pressures

Habitat restoration potential

As the dominant species of this habitat are annual species, often known as opportunists with short life cycles, recovery can be very fast (1-2 years) even after strong declines.

Trends in extent

Average current trend in quantity

Stable Stable
EU28 EU28+

Trends in quality

Average current trend in quality

Stable Stable
EU28 EU28+

Conservation and management needs

No conservation and management measures specific to this habitat have been identified.

List of conservation and management needs

  • No measures
    • No measure known / impossible to carry out specific measures


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 Stable
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 742,934 455 Unknown This habitat is present in all the Baltic sub-basins.
EU28+ >50 Unknown This habitat is present in all the Baltic sub-basins
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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1050 Copenhagen K
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