06A2
Submerged macrophytic communities in hypersaline water bodies
Relationships with habitat classifications. EUNIS: A2.614 Ruppia maritima on lower shore sediment; PAL. CLASS.: 11.412 Mediterraneo-Pontic marine tassel weed communities; HD 92/43: 1150 *Coastal lagoons.
Conservation status. BDA, HD.
Category. Critically endangered [CR – A1, 2 C3 D3 E3 F2 G1 H3 L2].
General characteristics. These are relatively small, coastal, hyperhaline water bodies with clay-muddy bottoms and banks. They occur along the north and south Black Sea coasts – Shablenska Tuzla, Nanevska Tuzla and Balchishka Tuzla (eastwards from Balchik) localities, Atanasovsko and Pomoriisko lakes. The water bodies are firths or lagoons by origin – with the exception only of Atanasovsko lake whose northern part has firth origin while the southern part is a typical lagoon. The depth of these water bodies is from 0,5 m to 2,0–2,5 m. They are separated from the sea by sandy strips that sometimes are overcome by the sea waves – mainly in autumn and winter, when their salinity decreases as a result of the inflow of the seawater. The salinity of these water bodies also decreases in spring as a result of the influx of rainwater. In summer and autumn the salinity increases due to strong evaporation and can reach up to 90 ‰ and sometimes even up to 120 ‰ compared to the normal salinity of the sea water (approx. 35–36 ‰). Usually, the beds of these water bodies are covered by black hydrosulphuric mud rich in organic substances. As a result of the high salinity of these water bodies they contain no vegetation or, communities belonging to the classes Ruppietea maritimae, Potametea, Zosteretea, Phragmitetea can develop. Sometimes, submerged habitats (underwater “meadows”) can develop with Ruppia maritima (Balchishka Tuzla locality, Nanevska Tuzla locality and Pomoriisko lake) or Zannichellia palustris (Pomoriisko lake) as the most frequently occurring species. In some places, phytocoenoses can develop on the banks of the lakes, with Juncus maritimus, Lemna gibba, Phragmites australis, Scirpus lacustris (= Schoenoplectus lacustris), Scirpus triqueter (= Schoenoplectus triqueter), Typha angustifolia, and T. latifolia. Groups of Iris pseudacorus also can occur. In winter-spring period massive development of blue-green algae from the genera Enteromorpha, Cladophora, Ulotrix etc. can be observed on the shells of the dead molluscs. In summer, abundant blue-green algae belonging to the genera Lyngbya, Oscillatoria, Phormidium, etc. can develop on the bottom of the lakes. The unicellular green algae Dunaliella salina is typical for such hypersaline water bodies. Representatives of Bacillariophyta, Dinophyta, Chlorophyta and Cryptophyta also participate in the composition of the phytoplankton. The zooplankton consists mainly of brackish water species which have high biological plasticity. Representatives of the orders Calanoida, and Cyclopoida and class Rotatoria, etc. can be recorded. Molluscs play the most significant role in the formation of the zoobenthos. Representatives of Insecta, Polychaeta, Oligochaeta, Crustacea, etc. can also be found. The ostracod (Cyprideis torosa), appears in all hyperhaline water bodies and is very specific for them. The high salinity and shallow depths of the hyperhaline lakes are the main reason why its ichthyofauna is not rich in species. Their permanent inhabitants are European flounder (Platichthys flesus luscus) and Knipowitschia caucasica. Sometimes Atherina boyeri, Mugil cephalus, Liza aurata and Liza saliens enter these lakes to feed their generations.
Characteristic taxa.
- Vascular plants: Juncus maritimus, Lemna gibba, Phragmites australis, Ruppia maritima, Scirpus lacustris, S. triqueter, Typha angustifolia, T. latifolia, Zannichellia palustris.
- Animals: Invertebrates – Syndesmia ovata, Cardium edule, Cyprideis torosa; Vertebrates – Platichthys flesus luscus, Knipowitschia caucasica, Atherina boyeri, Mugil cephalus, Liza aurata, L. saliens.
Distribution in Bulgaria. Black Sea coast: Shablenska Tuzla (northwards from Shabla), Nanevska Tuzla (Tauk Liman near vacation complex Russalka), Balchishka Tuzla (eastwards from Balchik) localities, Atanasovsko and Pomoriisko lakes.
Conservation importance. Unique habitats for Bulgaria. Very important for the biodiversity conservation and protection of important bird areas. Some of them are wetlands of international importance according to the Ramsar Convention (Atanasovsko lake) and CORINE Biotopes (Atanasovsko and Pomoriisko lakes).
Threats. Main threat for these habitats is the constant and uncontrolled visits of people with different purposes: collection of the saline crab for bait for fishermen, poaching, etc. Other negative factors are the roads that pass in close proximity to the habitats, waste pollution and draining, noise pollution, possible construction of wind-power parks, and restitution of the land around them.
Conservation measures taken. The habitat is included in Annex № 1 of BDA and is of conservation priority. Atanasovsko lake is a Managed Nature Reserve and Pomoriisko lake is a Protected Site. Both lakes are CORINE sites. All localities are in sites of the European Ecological Network NATURA 2000 in Bulgaria.
Conservation measures needed. Prevention of building of wind power parks, transport infrastructure and vacation complexes in close proximity to the habitat; decrease in anthropogenic pressures and strict control on the visits of people in the habitats.
References. Ganchev et al. 1971; Konaklieva & Vasilev 1997; Vasilev 1994; Vasilev & Mitrofanova 1998.
Authors: Vladimir Valchev, Vassil Vassilev, Valeri Georgiev
