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Red List of European Habitats Habitat code & name AA.J1Q - Baltic photic sand characterized by stable aggregations of unattached perennial vegetation Author and Date HELCOM RED LIST Biotope Expert Team, November 2013. Relationship to EUNIS The biotope does not correspond directly to any EUNIS (2004) level 4 habitats due to structural differences the classification systems. The closest correspondence in EUNIS is to subhabitats of ‘Sublittoral macrophyte-dominated sediment’ (A5.5). Habitat description Baltic bottoms in the photic zone with at least 90% coverage of sand. Sand has less than 20% of mud/silt/clay fraction (<63 µm), and the proportion of sand (grain size 0.063–2 mm) exceeds 70% of the combined gravel and sand fraction. Stable aggregations of unattached perennial vegetation covers at least 10%, while perennial attached erect groups cover less than 10% of the bottom. The biotope is rare, but can be found in most of the Baltic Sea area where the salinity is <10 or 5 psu (depending on the area), the exposure is moderate to sheltered and the seabed is level over wide areas within the photic zone. Three sub-biotopes with different dominant species of vegetation can be identified. ‘Baltic photic sand dominated by stable aggregations of unattached Fucus spp. (typical form)’ (AA.J1Q1) can be identified where the biovolume of Fucus spp. (typical form) constitutes at least 50% of the biovolume. This sub-biotope is encountered down to a depth of 5 meters. ‘Baltic photic sand dominated by stable aggregations of unattached Fucus spp. (dwarf form)’ (AA.J1Q2) can be identified where the biovolume of a specific morphological dwarf form of Fucus spp. constitutes at least 50% of the total biovolume of the unattached perennial vegetation. This sub-habitat is the only one of the five sub-habitats which has been classified as endangered (EN; A1) in the HELCOM Red List Assessment in 2013. This specific morphology of the Fucus spp. dwarf form lacks bladders and holdfasts; it is regularly dichotomous branched with branches of similar length resulting in a fanshaped appearance of the thalli. The single plants can be loosely anchored in the sediment with its lower, dark brownish parts. The thalli are very fragile, break very easily into pieces and thus generate new thalli (Bauch 1954). Under more exposed conditions plants form a ball-shaped form, able to roll over the sea bottom (Bauch 1954). The Fucus dwarf forms coexist with attached F. vesiculosus, unattached Furcellaria lumbricalis, higher plants like Ruppia spp., Zannichellia palustris, Stukenia pectinatus, Zostera spp. and several charophytes. The biotope exists in lower mesohaline salinities (7–10 psu) and moderately exposed to very sheltered conditions. It forms a characteristic biotope of shallow bays and lagoons between 0.25 and 2.5 m (Overbeck 1965). The unattached thalli can cover the sediment up to about 10 cm height and thus form a threedimensional habitat comparable to the interstitial space in coarse sediments. Epifauna is seldom attached to the Fucus dwarf form, but in between the loose lying thalli mobile gastropods, amphipods and insects look for shelter and food (von Oertzen 1968). However, if abundances of the unattached form are very high, the sediment below becomes deoxygenated and the associated infauna below the Fucus layer may die. Presently this biotope is only known to occur in Sweden and Germany. In Germany it exists only in very few coastal lagoons with low to moderate eutrophication pressures and salinities of around 7–10 psu. ‘Baltic photic sand dominated by stable aggregations of unattached Furcellaria lumbricalis’ (AA.J1Q3) can be identified where the biovolume of Furcellaria lumbricalis constitutes at least 50% of the biovolume. This sub-biotope is encountered down to a depth of 10 meters. Characteristic species Fucus spp., Furcellaria lumbricalis Indicators of quality Depending on the sub-habitat: - ‘Baltic photic muddy sediment dominated by stable aggregations of unattached Fucus spp. (typical form)’ (AA.H1Q1): density of unattached Fucus spp. (normal form). ‘Baltic photic muddy sediment dominated by stable aggregations of unattached Fucus spp. (dwarf form)’ (AA.H1Q2): density of unattached Fucus spp. (dwarf form). ‘Baltic photic muddy sediment dominated by stable aggregations of unattached Furcellaria lumbricalis’ (AA.H1Q3): Lower limit of Furcellaria belt, amount of epiphytic algae, and density of Furcellaria. Relationships with other schemes Annex 1 relationships The relationship between HUB biotopes and Annex 1 habitats has not yet been mapped by HELCOM. MAES relationships Marine - Marine inlets and transitional waters Marine - Coastal MSFD relationships Shallow sublittoral sand EUSeaMap relationships Shallow sands IUCN ecosystem relationships 9.4 Sublittoral Sandy Other relationships Level 5 of the HELCOM HUB classification (2013). This habitat has three sub-habitats on HUB level 6; ‘Baltic photic sand dominated by stable aggregations of unattached Fucus spp. (typical form)’ (AA.J1Q1) ‘Baltic photic sand dominated by stable aggregations of unattached Fucus spp. (dwarf form)’ (AA.J1Q2) ‘Baltic photic sand dominated by stable aggregations of unattached Furcellaria lumbricalis’ (AA.J1Q3) Photograph Please see the end of the document for a picture on the sub-habitat ‘Baltic photic sand dominated by stable aggregations of unattached Fucus spp. (dwarf form)’ (AA.J1Q2). Countries list To be inserted when data sheets completed. Regional Sea Baltic Sea Baltic Proper Belt Sea Gulf of Bothnia Gulf of Finland Gulf of Riga The Sound Map This will be inserted by NatureBureau based on the Regional Sea information above. References HELCOM Website 1 http://helcom.fi/baltic-sea-trends/biodiversity/helcom-hub/hub/aa-j1q HELCOM website 2 http://helcom.fi/Red%20List%20of%20biotopes%20habitats%20and%20biotope%20complexe/HELCOM% 20Red%20List%20AA.M1Q2,%20AA.H1Q2.%20AA.J1Q2,%20AA.J1Q2.pdf Unattached ball-shaped Fucus dwarf form on sandy substrate (left) and fan-shaped of different size on sandy bottom (right) (Photo: Karin Fürhaupter, MariLim GmbH)