AA.H1B4, AA.I1B4, AA.J1B4 and AA.M1B4 (NT)

Summary Estimated observations of the biotope AA.H1B4, AA.I1B4, AA.J1B4 and AA.M1B4 were collected from the Baltic Sea area by expert judgements for HELCOM Red List of biotopes, habitats and biotope complexes. Description Baltic photic muddy or coarse sediment, sand or mixed substrate dominated by Charales The HELCOM Red List of Baltic Sea underwater biotopes, habitats and biotope complexes (2013) is an updated and improved version of the Red List assessment of marine and coastal biotopes and biotope complexes published in 1998. The classification of the report follows the proposed International Union for Conservation of Nature (IUCN) criteria and assessment principals but with some modifications for the Baltic Sea.Altogether, the HELCOM Underwater Biotope and habitat classification (HELCOM HUB) includes 209 biotopes of which 59 were red-listed. Many of the red-listed biotopes are located in deep areas of the Baltic Sea due to oxygen-free nature as well as in the southwestern Baltic Sea due to the salinity restricted distribution of species in certain biotope. The HELCOM assessment relies heavily on expert judgment and inference, and the questionnaire data represents the estimated presence-absence data not in-situ measured data. This must be taken in account when observing the map presentation. The biotopes are shown on the map using the EEA 100 km grid. This dataset displays estimated presence of AA.H1B4, AA.I1B4, AA.J1B4 andAA.M1B4according to HELCOM RED LIST assessment experts:The Charales biotopes are distributed along the whole Baltic Sea coastline. The biotope covers largeareas in the comparatively large, shallow and sheltered erman Bodden areas, the Polish and LithuanianLagoons, the Latvian Bay ofRiga and Estonian, and along the coasts of Finland and Sweden especially inflads. The higher the salinities, the higher the diversity of the biotope withrespect to accompanyingplant species and inhabiting invertebrate and fishcommunities. The diversity of Charales and relatedgenera can howeverincrease with decreasing salinity, as the charophytes are brackish andfreshwatermacrophytes. The distribution map indicates the area in the 100 x100 km grid where biotope is knownto occur.AA.H1B4, AA.I1B4, AA.J1B4 andAA.M1B4have been placed in the Red List classification to the category of Near Threatened (NT) biotopes. (Data (expert judgements) collected in HELCOM RED LIST project, released in May 2013)