Infaunal communities on Baltic infralittoral shell gravel
|Red List habitat type||code BAL21|
|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 shell gravel according to the HELCOM HUB classification. The shell gravel fragments are coarse and well-sorted. This habitat is most often encountered in high energy exposure areas and is only found in the southern parts of the Baltic. Whilst macroscopic infauna are present, there is typically no macrovegetation or epibenthic macrofauna. Two associated biotopes have been identified: 'Baltic photic shell gravel characterised by mixed infaunal macrocommunity in coarse and well-sorted shells and shell fragments' (AA.E3X) and 'Baltic photic shell gravel characterized by mixed infaunal macrocommunity in fine sand-like shell fragments' (AA.E3Y). The benthic macroinfauna species vary as the interstitial spaces are smaller in the latter sand-like shell gravel substrate, enabling burrowing polychaetes and amphipods to build tunnels using the small grains.
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.
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 associated biotope AA.E3Y Baltic photic shell gravel characterised by mixed infaunal macrocommunity in fine sand-like shell fragments as Near Threatened (B1a(ii). The other associated biotope (AA.E3X) was not evaluated.
Expert opinion is that this habitat should be assessed as Endangered (B1aii, B3) for both the EU 28and EU 28+. This is because of the relatively restricted distribution of the shell gravel habitat combined with past and predicted future decline in abiotic environmental quality. It is important to note some shortcomings with the EOO and AOO calculations. The data used to calculate EOO and AOO was based on HELCOM mapping in 100 x 100 km2 cells of only one of the two associated biotopes. The full extent and area covered by the habitat could therefore be greater. Equally relevant is that HELCOM information has been converted to 10 x 10 km cells to derive AOO. As the habitat may not occur in all the cells mapped this figure could be an over estimate. The confidence in this assessment is therefore given as Low.
|Red List Category||Red List Criteria|
|Red List Category||Red List Criteria|
Confidence in the assessment
Pressures and threats
- Pollution to surface waters (limnic, terrestrial, marine & brackish)
- Nutrient enrichment (N, P, organic matter)
- Climate change
- Changes in abiotic conditions
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 wetland, freshwater and coastal habitats
- Restoring/Improving water quality
- Measures related to spatial planning
- Other marine-related measures
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||max 14,200||max 73||max 2,000||Based on presence in 100 x 100km grid squares therefore maximum potential EOO and AOO|
|EU28+||n/a||n/a||not present in EU28+ in the Baltic|
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).