| Summary: | Coastal lagoons are unique habitats of high ecological value, and they are included in the priority habitats of the EU Habitats Directive. The vegetation covering the bottoms and shores provide invertebrates, fish and birds with food and protection. Pike and perch amongst other fish species are dependent on the underwater vegetation for their recruitment. These habitats are threatened by the ongoing eutrophication of the Baltic Sea and by physical disturbance such as dredging, marine constructions and boat traffic. Stoneworts (Charales) are a group of macroalgae which are sensitive to changes in the water quality and have been recognised as useful bioindicators. Some of them are rare, red-listed species. On assignment by the Government of Åland Islands, a mapping of the vegetation in shallow, brackish-water bays with a potential presence of stoneworts was carried out. The methods used were snorkelling, raking and aquascope. Between July and September 2008, 26 bays in the municipalities of Saltvik, Sund and Föglö, Åland Islands were visited. All species along transects were identified and the percent cover of each species was determined. Water samples were analysed for salinity, pH and turbidity and the type of bottom substrate was assessed. In total, 45 species of macroalgae and plants were encountered. Several of the mapped bays have a high coverage of vegetation and high species diversity. In fifteen of the bays, larger meadows of stoneworts were identified; the most common species of stoneworts was Chara aspera. The red-listed species Chara horrida and the rare C. connivens were found in the bays where they had been identified in 2005. Additionally, C. horrida was found at a new locality; in the bay of Fjärd, Föglö. Possible findings of C. connivens were made in the bays of Mockoviken and Skeppshusviken. Bays of special interest for conservation are Inre verkviken, Skeppshusviken, Gloet, Glohålet,, Fjärd and Lökholmsfjärden.
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