Red List habitat classification > RL - Marine habitats > RLBAL - Baltic > BAL56 Epifaunal communities of Baltic upper circalittoral muddy sediment

Epifaunal communities of Baltic upper circalittoral muddy sediment

Quick facts

Red List habitat type code BAL56
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 aphotic zone where at least 90% of the substrate is  muddy sediment according to the HELCOM HUB classification. Sessile/semi-sessile epibenthic species cover at least 10% of the seabed and it is typically found below approximately 20 m in low to moderate energy exposure conditions. Six different biotopes associated with this habitat have been described. These are characterised by epibenthic bivalves, crustaceans, polychaetes and cnidarians, as well as biotopes with a mixed or sparse epibenthic community. Some of these biotopes have a restricted distribution in the Baltic e.g. those characterised by epibenthic polychaetes, or which have a sparse epibenthic macrocommunity which are only reported from The Belt Sea and The Sound. Aphotic muddy sediments characterised by epibenthic cnidarians are present in all the Baltic Sea sub-basins. 

Water movement is relatively limited in deep muddy areas and this creates a favourable environment for small tube-building amphipods such as Haploops spp. which can  be visible as a dense mat of tubes on the surface of the sediment. These are important feeding grounds for many species of fish including cod. Where seapens such as Virgularia mirabilis and Pennatula phosphorea dominate the epibenthos, for example in parts of the Kattegat trench and the Djupa Rännan trench, they also provide food and shelter for many other species, including commercially imporant fish. 

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 amount of sediment covering the hard surfaces and the diversity, abundance and biomass of associated fauna are potential quality indicators for this habitat.

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

Threat status

Synthesis of Red List assessment

There has been significant decline in quantity of some of the associated biotopes and the possibility of future decline in the most extenstive biotope (dominated by Mytilidae) has also been identified. Reductions in the density of the characteristic species (Modiolus and Haploops) are also an indication of decline in quality. Overall this habitat is considered to have declined in both quantity and quality 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 across the relevant biotopes. The outcomes were reviewed by Baltic experts to reach a final conclusion. HELCOM (2013) assessed AB.H1E1 and AB.H1K1 as Least Concern (A1) and AB.H1I12 as Endangered (A1). On the basis of these assessments and expert opinion, this habitat is assessed as Near Threatened for both the EU 28 and EU 28+, since there has been a significant decline in the area of some of the biotopes with the overall decline estimated to be between 25-30%.
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

  • 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
  • Climate change
    • Changes in abiotic conditions
    • Temperature changes (e.g. rise of temperature & extremes)

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

Bottom trawling restrictions in Öresund and Kattegat need to be enforced, so that any sporadic illegal trawling activities are stopped. In order to facilitate monitoring, Automatic Identification System (AIS) should become mandatory for all trawling fishing vessels. Bottom areas deeper than 20 m in Öresund should be protected from invasive fishing and other similar activities. The small area in Öresund where the Haploops spp. biotope occurs should be included in the Knähaken marine protected area south of the Helsingborg municipality border. Furthermore, the bottom areas around Ven island should be mapped and potentially protected. More generally, efforts to reduce eutrophication will benefit this habitat.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
  • Measures related to spatial planning
    • Other marine-related measures
    • Establish protected areas/sites
  • Measures related to hunting, taking and fishing and species management
    • Regulation/Management of fishery in marine and brackish systems
  • 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

The full list of characteristic species and genus are available above from the Summary. The species available in the EUNIS database are shown here.
Invertebrates Ophiura robusta
Invertebrates Pennatula phosphorea
Invertebrates Philomedes brenda
Invertebrates Virgularia mirabilis
Species scientific name English common name Species group
Ophiura robusta Invertebrates
Pennatula phosphorea Invertebrates
Philomedes brenda Invertebrates
Virgularia mirabilis Invertebrates

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
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