Red List habitat classification > RL - Marine habitats > RLBAL - Baltic > BAL18 Infaunal communities of Baltic infralittoral coarse sediment

Infaunal communities of Baltic infralittoral coarse sediment

Quick facts

Red List habitat type code BAL18
Threat status
Europe Near Threatened
EU Near Threatened
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 coarse sediment according to the HELCOM HUB classification. No macrovegetation or epibenthic macrofauna is present however infaunal bivalves/polychaetes/crustaceans/echinoderms or insects may dominate, comprising at least 50% of the biomass. It is encountered in areas of high energy associated with currents or wave action. Five associated biotopes have been identified but not all occur in all the sub-basins. For example  ‘Baltic photic coarse sediment characterised by infaunal bivalve species’ (AA.I3L), has only been reported in the Baltic Proper, The Belt Sea and The Sound. Where the substrate is well sorted with medium to coarse sand, gravel or small shell fragments, often building small patches inside finer sediments, the large variety of interstitial space, may be inhabited by species of specialised fauna, such the polychaetes Ophelia limacina, O. rathkei and Travisia forbesii. In areas of poorly sorted substrate there may be a higher species diversity with none of the characateristic species clearly dominant but including bivalves such as Macoma calcarea, Mya truncata, Astarte spp., and Spisula spp.

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 habitatmay 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. Diversity, abundance and biomass of the dominant species and associated fauna are potential indicators of quality of this habitat.

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

Threat status

Synthesis of Red List assessment

There have been some declines in extent of this habitat, estimated to be more than 25% over the last 50 years in the case of the associated biotopes dominated by infaunal bivalves and polychaetes and at least 10% in a third associated biotope. Moderate to severe reductions of between10-15% of the habitat is also believed to have occurred in a similar period. The lack of quantitative data on extent, quality and trends over time means that accurate calculations of EOO and AOO are not possible at the present time. This Red List assessment has therefore been based on expert opinion.
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 two relevant Baltic biotopes (AA.I3L10 and AA.I3L11) as Near Threatened (A1). A third biotope AA.I3N3 was assessed as Least Concern (A1). The remaining three AA.I3N, AA.I3O and AA.I3P were not evaluated There is no additional data or information to update the assessment outcome past the HELCOM 2013 assessment. Given that there have been declines of more than 25% for much of this habitat, current expert opinion is therefore an assessment of Near Threatened for both the EU 28 and EU 28+.
Red List Category Red List Criteria
Near Threatened A1
Red List Category Red List Criteria
Near Threatened A1

Confidence in the assessment

Red List of habitat categories and criteria descriptions

Pressures and threats

  • Mining, extraction of materials and energy production
    • Mining and quarrying
    • Exploration and extraction of oil or gas
  • Biological resource use other than agriculture & forestry
    • Fishing and harvesting aquatic resources
    • Professional active fishing
    • Benthic or demersal trawling
    • Benthic dredging
  • 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
    • Siltation rate changes, dumping, depositing of dredged deposits
    • Dumping, depositing of dredged deposits
    • Other siltation rate changes

Habitat restoration potential


Trends in extent

Average current trend in quantity

Decreasing Decreasing
EU28 EU28+

Trends in quality

Average current trend in quality

Decreasing Decreasing
EU28 EU28+

Conservation and management needs

Restrictions or prohibition of bottom trawling and sediment extraction will protect this habitat along with activities that can improve oxygen conditions, for example by reducing the risk of eutrophication. A Baltic Sea wide biotope inventory and threat assessment would be a useful tool to guide conservation and management.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
  • Measures related to spatial planning
    • Establish protected areas/sites
  • Measures related to special resouce use
    • Regulating/Managing exploitation of natural resources on sea


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 Decreasing Decreasing
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

Not available

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
European Environment Agency (EEA)
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