Infaunal communities in Baltic upper circalittoral coarse sediment and shell gravel not dominated by bivalves

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. Four associated biotopes have been described characterised by mixed infaunal macrocommunities with substrates ranging from coarse and well sorted shells and shell fragments (AB.E3X) to fine shell fragments (AB.E3Y), and also areas where the substrate is predominantly coarse and the biotope characterised by infaunal polychaetes (AB.I3M) or infaunal crustaceans (AB.I3N). In the latter case a sub-habitat identified by a large representation of Bathyporeia pilosa, which constitutes at least 50% of the biomass of the infaunal crustacean has also been described.

The habitat occurs in high energy areas, typically below 20m and for the coase sediments more usually below 30m. The community composition of macroinfauna is presumed to be different in the sand like shell gravel sand compared to coarser shell gravel of mainly semi-intact shells. These substrates support many different animals including non-burrowing animals but where the interstitial space is smaller burrowing polychaetes and amphipods can build tunnels using the small grains. The biotopes on shell gravel have a restricted distribution in the Baltic, especially where the substrate is comprised of  fine sand-like shell fragments as this has only been reported from The Belt 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

Confidence in the assessment

Pressures and threats