Red List habitat classification > RL - Marine habitats > RLBAL - Baltic > BAL39 Infaunal communities in Baltic infralittoral muddy sediment - bivalves

Infaunal communities in Baltic infralittoral muddy sediment - bivalves

Quick facts

Red List habitat type	code BAL39
Threat status
Europe	Near Threatened
EU	Near Threatened
Relation to	Annex I habitat types (EU Habitats Directive)
Source	European Red List habitat factsheet
	European Red List of habitats reports
	European Red List of habitats (Excel table)

Summary

This is a Baltic Sea benthic habitat in the photic zone where at least 90% of the substrate is muddy sediment according to the HELCOM HUB classification. Sessile/semi-sessile epibenthic macrofauna are absent and infaunal bivalves dominate the biomass at depths of below approximately 20 m. It is a habitat that is present in conditions of low to moderate exposure to wave action and currents.

Three associated biotopes with different dominant species of bivalves (at least 50% of the infaunal bivalves) and slightly different distributions have been identified. ‘Baltic aphotic muddy sediment dominated by Baltic tellin (Macoma balthica)’ (AB.H3L1) is commonly found all parts of the Baltic Sea. ‘Baltic aphotic muddy sediment dominated by ocean quahog (Arctica islandica)’ (AB.H3L3) can only be found in the southwestern parts in the Belt Sea where the salinity is > 15 psu and has an optimum depth range of between 25 and 80 m. ‘Baltic aphotic muddy sediment dominated by Astarte spp.’ (AB.H3L5) is only found in areas where the near bottom water exhibits a salinity range between 10 and 15 psu, a temperature between 3 and 8^oC and relatively good oxygen conditions. It is encountered in the southern and western Baltic Sea, in the southern Baltic Proper, in the Belt Sea and the Sound. As an arctic-boreal species, Astarte borealis appears in these Baltic biotopes at its southern limit.

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. Diversity, abundance and biomass of fauna are potential indicators of quality.

Characteristic species

For full habitat description, please download the habitat factsheet.

Threat status

Synthesis of Red List assessment

The presence of this habitat type in the Baltic is well established and the occurrence of some of the biotopes has been mapped, but there is a lack of comprehensive quantitative data on the area covered. There have been declines in the extent of two of the four associated biotopes with overall decline is considered to be more than 25%. There have also been some declines in quality of this habitat in the Belt Sea (more than 10% in for A.islandica dominated areas).
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 AA.H3L1 and AA.H3L8 as LC(A1). AA.H3L3 and AA.H3L8 were assessed as NT(A1). Given the severity of decline of some of the associated biotopes over the last 50 years, the current expert opinion is that this habitat should be assessed as Near Threatened (A1).

EU
Red List Category	Red List Criteria
Near Threatened	A1

Europe
Red List Category	Red List Criteria
Near Threatened	A1

Confidence in the assessment

low

Red List of habitat categories and criteria descriptions

European Red List of Habitats categories

Based on Scientific Foundations for an IUCN Red List of Ecosystems

European Red List of Habitats criteria

Reduction in quantity (area of distribution)	A	A1 Present decline (over last 50 years) A2a Future decline (over the next 50 years) A2b Future/present decline (over a 50-year period inclunding present and future) A3 Historic decline
Restricted geographic distribution	B	B1 Restricted Extent of Occurrence (EOO) B2 Restricted Area of Occupancy (AOO) B3 Present at few locations
Reduction in abiotic quality	C	C/D1 Reduction in quality over the last 50 years C/D2 Reduction in quality in the future or in a period including present and future C/D3 Historic reduction in quality
Reduction in biotic quality	D
Quantitative analysis of probability of collapse	E

From Scientific Foundations for an IUCN Red List of Ecosystems

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

Pollution to surface waters (limnic, terrestrial, marine & brackish)
Nutrient enrichment (N, P, organic matter)

Natural System modifications

Siltation rate changes, dumping, depositing of dredged deposits

Climate change

Changes in abiotic conditions
Temperature changes (e.g. rise of temperature & extremes)
Changes in biotic conditions
Habitat shifting and alteration

Habitat restoration potential

The most threatened biotopes, those dominated by ocean quahog (Arctica islandica) and Unionidae are characterised by species with a slow growth rate and a life span >>50 years so natural recovery times to re-establish communities with mixed age populations of this species are likely to be substantial.
Adult individuals of Arctica islandica can tolerate periods of anoxia by burrowing deeper into the sediment and remaining inactive. The larvae settling on the surface and younger specimens have not got this potential. Astarte borealis is resistant to anoxic conditions, however recurring and long lasting anoxia is fatal

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

All actions that reduce the level of eutrophication in the Baltic Sea will benefit this habitat.These actions include measures to reduce the diffuse run off of nutrients from agriculture and tackling point source pollution by installation of waste water treatment plants. Some consecutive years when the oxygen level remains at a good level is needed for the recruitment to be successful.

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
Legal protection of habitats and species

Measures related to hunting, taking and fishing and species management

Regulation/Management of fishery in marine and brackish systems

Distribution

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	Unknown	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

Legal status

Relation to other habitat types mentioned in legal instruments

Legal text	Annex	Name in legal text	Code in legal text	Habitat type relationship	More information
Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora - consolidated version 01/01/2007	Annex I: natural habitat types of community interest whose conservation requires the designation of special areas of conservation	Estuaries	1130	Overlap	http://ec.europa.eu/environm...rective/index_en.htm
Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora - consolidated version 01/01/2007	Annex I: natural habitat types of community interest whose conservation requires the designation of special areas of conservation	Coastal lagoons	1150	Overlap
Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora - consolidated version 01/01/2007	Annex I: natural habitat types of community interest whose conservation requires the designation of special areas of conservation	Large shallow inlets and bays	1160	Overlap
Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora - consolidated version 01/01/2007	Annex I: natural habitat types of community interest whose conservation requires the designation of special areas of conservation	Boreal Baltic narrow inlets	1650	Overlap

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Infaunal communities in Baltic infralittoral muddy sediment - bivalves

Quick facts

Summary

Threat status

Synthesis of Red List assessment

Confidence in the assessment

European Red List of Habitats categories

European Red List of Habitats criteria

Pressures and threats

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

Distribution

Geographic occurrence and trends

Extent of Occurrence, Area of Occupancy and habitat area

Characteristic species

Legal status

Relation to other habitat types mentioned in legal instruments

Vegetation types

Relation to vegetation types (syntaxa)

Other classifications