Communities on Baltic circalittoral clay and other hard substrata
Quick facts
| Red List habitat type | code BAL44 |
|---|---|
| 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) |
Summary
This is a Baltic Sea benthic habitat in the aphotic zone with at least 90% coverage of hard clay, marlstonerock, ferromanganese concretions and/or peat according to the HELCOM HUB classification. Hard clay substrates are known to occur mostly in high energy environments. Marlstone rock habitats have only been reported in the Baltic proper, Belt Sea and The Sound, and Ferromanganese concretions in the Baltic Proper, Gulf of Bothnia, Gulf of Finland and Gulf of Riga.
Sessile/semisessile epibenthic bivalves cover of at least 10% of the seabed and no perennial attached erect group has more than 10% coverage in this habitat. In some cases there may be no macrofauna but two associated biotopes with different dominant species of macrofauna have been identified: ‘Baltic aphotic hard clay dominated by Mytilidae’ (AB.B1E1) and ‘Baltic aphotic hard clay dominated by Astarte spp.’ (AB.B1E4). The latter is characterised by species preferring cold and saline water with Astarte spp. often making up between 70–90% of the total biomass.The near bottom water exhibits a salinity range between 10 and 15 psu, a temperature between 3 and 8°C and relatively good oxygen conditions. For ecological purposes, hard clay can be considered to be a hard substrate. Very few macrofauna species have the capacity to burrow into the substrate.
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 the dominant species and associated fauna are potential indicators of quality of this habitat.
species and associated fauna are potential indicators of quality of this habitat
Threat status
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 three relevant Baltic associated biotopes (AB.B1E1, AB.C and AB.F) as Least Concern (A1), and Baltic aphotic hard clay dominated by Astarte spp. (AB.B1E4) was assessed as Endangered (B2c(ii)). Three other biotopes were not evaluated.
Due to general rarity of areas dominated by Astarte spp. and no evidence of a significant decrease in quantity over the last 50 years for areas dominated by Mytilidae, this habitat has been assessed as Least Concern for both the EU 28 and EU 28+.
| EU | |
| Red List Category | Red List Criteria |
| Least Concern | - |
| Europe | |
| Red List Category | Red List Criteria |
| Least Concern | - |
Confidence in the assessment
Pressures and threats
- Mining, extraction of materials and energy production
- Mining and quarrying
- Pollution
- Pollution to surface waters (limnic, terrestrial, marine & brackish)
- Nutrient enrichment (N, P, organic matter)
- Natural System modifications
- Human induced changes in hydraulic conditions
- Removal of sediments (mud...)
- Extraction of sea-floor and subsoil minerals (e.g. sand, gravel, rock, oil, gas)
- Climate change
- Changes in abiotic conditions
- Temperature changes (e.g. rise of temperature & extremes)
- Flooding and rising precipitations
Habitat restoration potential
Trends in extent |
|
Average current trend in quantity |
|
Decreasing  |
Decreasing |
| EU28 | EU28+ |
Trends in quality |
|
Average current trend in quality |
|
Unknown  |
Unknown |
| EU28 | EU28+ |
Conservation and management needs
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 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
Distribution
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 | 86,343 | Unknown | 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 | >50 | 86,343 | The area estimate for this habitat has been derived from a synthesis of EUNIS seabed habitat geospatial information for the European Seas but is recognised as being an underestimate. |
| EU28+ | >50 | 86,343 | The area estimate for this habitat has been derived from a synthesis of EUNIS seabed habitat geospatial information for the European Seas but is recognised as being an underestimate. |
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).
