07A3

A. Marine habitats

Infralittoral rocks and other hard substrates

Relationships with habitat classifications. EUNIS: A3. Infralittoral rock and other hard substrata; Pal. class.: 11.24 Sublittoral rocky seabeds and kelp forests; HD 92/43: 1170 Reefs.

Conservation status. BDA, BC, HD.

Category. Vulnerable [VU – A1, 2 D2 E2 G1 H1].

General characteristics. The habitat covers the massive rocky bottom and stones in the shallow sub-littoral zone between 0,5–25 m depth and supports communities of photophilic brown algae, red and green macroalgae and/or overgrowing fauna. The habitat has various subtypes. The phytocoenoses dominated by brown algae belonging to the genus Cystoseira live in pure, rough waters, with high level of transparency. The communities of the red algae Corallina officinalis are typical for the upper horizons of the infralittoral in quiet or rough waters also with high level of transparency. The soft mergel and limestone are inhabited by stone-burrowing mussels Pholas dactylus, Petricola lithophaga and Barnea candida. The banks of Ostrea edulis on the rocky seabed represent another typical subtype of the habitat. Dense covers of Mytilus galloprovincialis are typical for places with higher levels of organic influx and lower transparency. Mytilus galloprovincialis is a competing dominant for the existing space and can replace other species by overgrowing them. The species is an active filter feeder, feeding on bacteria, phytoplankton, detritus and dissolved organic substances. The release of the sexual products of the black mussel in the water brings a considerable quantity of organic carbon and probably eggs and larvae are a significant food resource for the zooplankton and some fish larvae. A diverse flora of green algae (Enteromorpha intestinalis, Ulva rigida, Briopsis plumosa, Cladophora vagabunda) and red algae (Ceramium rubrum, Porphyra leucosticta) is often observed among or on the black mussels. The rare species Lepidochitona cinerea is a typical phytophag. Other phytophags are the polychaetes Platynereis dumerilii, Perinereis cultrifera, and the snail Gibbula divaricata. The marine sponges Halichondria panicea, Dysidea fragilis and Petrosia dura, attached on the stones and sometimes on the shells of the black mussels, also play an important role in the community. Typical inhabitants of the rocky bottom are the small black mussel Mytilaster lineatus, the common sea anemone Actinia equina and the barnacle Balanus improvisus, as well as the epibionts colonizing the surface of the black mussel – the hydroids Obelia spp, Campanularia spp., the bryozoans Membranipora membranacea and Lepralia pallasiana and the colonial ascidian Botryllus schlosseri. Polychaetes from the fam. Serpulidae– Pomatoceros triqueter, Janua pagenstecheri and the alien invader Ficopomatus enigmaticus are typical for the rocks. Decapod crabs occur regularly in these habitats as well as the invasive alien snail Rapana venosa – all they are carnivores feeding on the blue mussel.

Characteristic taxa.

Distribution in Bulgaria. In the shelf zone along the whole Bulgarian Black Sea coast, at 0,5-25 m depth.

Conservation importance. Species included in the annexes of the Bulgarian Biodiversity Act and the Red Book of the Black Sea (1999) occur: Aidablennius sphinx, Chromogobius quadrivittatus, Coryphoblennius galerita, Cystoseira barbata, C. crinita, Dictiota dichotoma, Diplodus annularis, Eriphia verrucosa, Gobius cobitis, Halichondria panicea, Mesogobius batrachocephalus, Neogobius ratan, Ostrea edulis,Pachygrapsus marmoratus, Pilumnus hirtellus,Salaria pavo, Scorpaena porcus, Symphodus ocellatus, S. tinca, Syngnatus tenuirostris, Xantho poressa.

Threats. Existing threats are the industrial and chemical pollution and deposition of solid waste in the coastal waters.  The building of embankments and tourism activities (yacht ports) in the coastal area causes changes in the hydrological and hydro-chemical regime and deterioration of the habitat. The petrol spills are a potential threat. The habitat is influenced by the invasion and massive development of Rapana venosa at the end of 1950s. Despite its active industrial exploitation in the recent years its numerical strength is still high.

Conservation measures taken. The habitat is included in Annex №1 of the national Biodiversity Act and parts of its localities are within the borders of Kaliakra Strict Nature Reserve and in sites of the European Ecological Network NATURA 2000.

Conservation measures needed. Establishment of a network of marine sites that will ensure connectivity between the separate parts of the habitat; elaboration and implementation of management plans for the already existing protected marine sites; such plan is lacking even for Kaliakra Strict Nature Reserve – the only reserve that includes marine territory; investigation into the changes of the state, composition and structure of the living communities; periodical assessment of the conservation status of the characteristic taxa according to the contemporary IUCN criteria and categories.

References. Dimitrova-Konaklieva 2000; Georgiev 1964; Karapetkova & Zhivkov 2006; Kiseleva 1981; Marinov 1990; Palazov & Stanchev 2006; Sivkov & Sivkova 2004; Stoyanov et al. 1963; Vassilev & Pehlivanov 2005; Zhivkov et al. 2005.

Authors: Valentina Todorova, Marina Panayotova


Infralittoral rocks and other hard substrates (distribution map)