Infaunal communities in Baltic upper circalittoral coarse sediment and shell gravel dominated by bivalves
|Red List habitat type||code BAL46|
|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 upper circalittoral where at least 90% of the substrate is coarse sediment or shell gravel according to the HELCOM HUB classification. The substrate is usually poorly sorted with different proportions of gravel, coarse or medium sand, but may also contain finer sediment fractions. Macrovegetation and epibenthic macrofauna are generally absent and the biomass is typically dominated by infaunal bivalves. This habitat occurs in high energy exposure areas and two associated biotopes with different dominant species of macrofauna (at least 50% of the biomass) have been described.
‘Baltic aphotic coarse sediment dominated by multiple infaunal bivalve species: Macoma calcarea, Mya truncata, Astarte spp., Spisula spp.’ (AB.I3L10) is mainly restricted to small patches between hard substrates on ridges formed by lag sediment and till (e.g. Fehmarnbelt) in the photic and aphotic zone. It supports a high species diversity and high biomass and only occurs in areas where the salinity exceeds 18 psu as all characteristic bivalve species are eumarine. For this reason it has only been reported from the Kiel Bight to Isle of Fehmarn, and occasionally present from Mecklenburg Bight to the Darss Sill.
‘Baltic aphotic coarse sediment dominated by multiple infaunal polychaete species including Ophelia spp.’ (AB.I3L11) is an associated biotope where biomass of bivalves still dominates but due to the large variety of interstitial space there is a specialised infauna, e.g., the polychaetes Ophelia limacina, O. rathkei and Travisia forbesii. This biotope is restricted to the Belt Sea (sandbanks) and parts of the ‘submerged belt’ of the Arkona Basin in the south-western Baltic Sea.
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 havebeen 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
Synthesis of Red List assessment
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 two biotopes AB.I3L10 and AB.I3L11 as Near Threatened (A1).
Current expert opinion is that this habitat should be assessed as Vulnerable under Criterion B for both the EU 28 and EU 28+ because of its restricted distribution and predicted continuing decline although, because it is present in very few 'locations' (defined by the extent of the main threats), it could also be considered Endangered. This assessment should be reviewed when more detailed mapping of the extent of this habitat has been undertaken because the EOO and AOO calculations used to apply Criterion B are based on data derived from a general mapping exercise.
|Red List Category||Red List Criteria|
|Red List Category||Red List Criteria|
Confidence in the assessment
Pressures and threats
- Biological resource use other than agriculture & forestry
- Fishing and harvesting aquatic resources
- Professional active fishing
- Benthic or demersal trawling
- Benthic dredging
- 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
- Siltation rate changes, dumping, depositing of dredged deposits
- Dumping, depositing of dredged deposits
Habitat restoration potential
Trends in extent
Average current trend in quantity
Trends in quality
Average current trend in quality
Conservation and management needs
List of conservation and management needs
- Measures related to spatial planning
- Establish protected areas/sites
- Measures related to special resouce use
- Regulating/Managing exploitation of natural resources on sea
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)|
Extent of Occurrence, Area of Occupancy and habitat area
|Extent of Occurrence (EOO) (Km2)||Area of Occupancy (AOO)||Current estimated Total Area||Comment|
|EU28||49,150||199||Unknown||Based on presence in 100 x 100km grid squares therefore maximum potential EOO and AOO|
|EU28+||199||Unknown||This habitat is only present in the EU28|
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).
|Species scientific name||English common name||Species group|