05A2
Underwater “meadows” of sea grasses
Relationships with habitat classifications. EUNIS: A5.53 Sublittoral sea grass beds, A2.613 Pontic [Zostera marina] and [Zostera noltii] meadows; PAL. CLASS.: 11.333 Pontic [Zostera] meadows; HD 92/43: 1110 Sandbanks which are slightly covered by sea water all the time.
Conservation status. BDA, BC, HD.
Category. Endangered [EN – A1, 2 E2 F2 G2 H2].
General characteristics. This habitat type encompasses monospecific or mixed communities of the sea grasses from the genera Zostera, Zannichellia, Potamogeton and Ruppia that develop on pure or muddy fine sand of shells and sandy mud at 0,5–5 (7) m depth. The salinity is normal or low. This habitat occurs in very quiet places protected from waves or in bays and estuaries with slow current. Generally the areas with Zostera marina are with high projective cover, 80–100% and 0,8–1 m height (at the estuary of Ropotamo River, up to 3 m), while the areas of Zostera noltii are with lower density, projective cover 20–60% and 0,1–0,4 m height. The sea grasses are edificators that create conditions for the development of diverse epiphytic algal flora and invertebrate fauna and serve as an environment for the growth of the larvae of various fish species and molluscs. They are very important for the geomorphology and ecology of the coastal ecosystems because they stabilize the sediment, contribute to the recycling of the biogenic elements and participate in the formation of the basis of the detritus trophic network.
Characteristic taxa.
- Plants: Algae – Rhodophyta: Laurencia obtusa; Phaeophyta: Ectocarpus siliculosus, Chlorophyta: Enteromorpha spp., Ulva rigida; Vascular plants: Potamogeton pectinatus, Ruppia maritima, Zannichellia palustris, Zostera marina, Z. noltii.
- Animals: Bivalvia: Tellina tenuis, Loripes lacteus, Lucinella divaricata, Solen marginatus, Abra ovata; Gastropoda – Hydrobiidae: Rissoa parva, Bittium reticulatum; Crustacea: Upogebia pusilla, Carcinus aestuari, Polybius vernalis, Rhithropanopeus harrisi, Palaemon adspersus, P. elegans; Actinopterygii: Zosterisessor ophiocephalus, Nerophis ophidion, Hippocampus guttulatus.
Distribution in Bulgaria. Black Sea, sandy and sandy-muddy bottom; 0–5 (7) m depth.
Conservation importance. Zostera marina (VU), Z. noltii (VU),Carcinus aestuarii (VU),Upogebia pusilla (EN), Nerophis ophidion (CR) are included in the Red Data Book of the Black Sea (1999) at regional level, while Zostera marina, Z. noltii,Carcinus aestuarii,andUpogebia pusilla are also in the list of species important for the Black Sea according to the Convention for the protection of the Black Sea from pollution. Zostera marina is also included in the Bern Convention.
Threats. The main threat for the habitat is the decreasing clarity of the seawater as a result of the eutrophication, hydro-engineering or digging in the coastal area causing suspension of the sediments. The reduced quantity of light that penetrates in the water causes the decrease in the depth at which the sea grasses can occur. Additionally the sea grasses are not tolerant to smothering by mud or other sediments. Their rhizomes and leaves can easily be damaged by passing motor boats, anchoring of marine vessels, digging or trampling. The increased growth of epiphytic algae as a result of the eutrophication also causes the disappearance of Zostera marina and Z. noltii.
Conservation measures taken. The habitat is in Annex № 1 of the Bulgarian Biodiversity Act and in sites of the European Ecological Network NATURA 2000.
Conservation measures needed. Purification of all waste waters that are poured in the Black Sea coastal area on the Bulgarian side including the removal of the nitrogen and phosphorus so that the eutrophication can be limited; correlation between the construction activities along the coast with the capacity of the purification stations; strict control on the illegal bottom trawling and digging; correlation between the hydro engineering activities and the coastal protection activities which cause suspension of sediments and accumulation of mud at the localities of the underwater "meadows". A main prerequisite for the conservation and restoration of the habitat is the development of a unified ecological network of protected marine areas that will provide for the connection between the different parts of the habitat and elaboration of management plans. Monitoring the area, degree of fragmentation, depth of distribution and percentage cover of the sea grasses is also needed
References. Dimitrova-Konaklieva 2000; Keremedchiev 2005; Marinov 1990; Petrova-Karadzhova 1982; Todorova et al. 2008.
Author: Valentina Todorova
