11A4
Sublittoral mussel beds on sediments
Relationships with habitat classifications. EUNIS: A5.62 Sublittoral mussel beds on sediment; Pal. Class.: 11.254 Mussel beds; HD 92/43: 1170 Reefs.
Conservation status. BDA, BC, HD.
Category. Vulnerable [VU – A1, 2 D1 G2 H2 I L3].
General characteristics. Mytilus galloprovincialis forms specific mussel beds on different sediments varying from coarse shelly sand and muddy sand to mud. The banks are long and narrow and are transverse to the prevailing currents. The black mussel is an important structural species – edificator of the habitat whose populations form biogenic reefs and provide a solid substrate, stabilize the surface of the sediment and modify it into organic-rich “Mytilus mud”. The habitat plays a key ecological role for the functioning and resilience of the marine ecosystem as a whole due to the strong bio-filtrating capacity of the black mussels, hence transforming the primary production into a secondary one. In the same time the mussel beds provide substrate for a diverse epifauna (sponges, hydrozoans, sea anemones, bryozoans, ascidians, polychaetes). They are the food source for the carnivores (Veined rapa whelk, decapods, bottom fishes) and deposit-feeders (polychaetes), as well as suitable places for the reproduction and growth of numerous organisms, some of which are important fishing species (turbot, European flounder, Veined rapa whelk). The species composition of the accompanying fauna is variable and depends on the sediment matrix and depth.
Characteristic taxa.
- Animals: Anthozoa: Actinithoe clavata; Polychaeta: Aonides paucibranchiata, Aricidea claudiae, Capitella capitata, C. minima, Eumida sanguinea, Glycera alba, Hediste diversicolor, Heteromastus filiformis, Nephtys hombergii, Nereiphylla rubiginosa, Pectinaria koreni, Polycirrus jubatus, Polydora spp., Pomatoceros triqueter; Gastropoda: Rapana venosa; Crustacea: Ampelisca diadema, Apseudes acutifrons, Athanas nitescens, Balanus improvisus, Caprella acanthifera, Corophium runcicorne, Crangon crangon, Cumella limicola, Iphinoe elisae, Microdeutopus gryllotalpa, Pilumnus hirtellus, Pisidia longicornis, Polybius vernalis, Upogebia pusilla; Holothurioidea: Leptosynapta inhaerens,Elasmobranchii – Dasyatis pastinaca, Raja clavata, Squalus acanthias; Actinopterygii – Acipenser gueldenstaedti, A. stellatus, Chelindonichthys lucernus, Gobius niger, Huso huso, Mesogobius batrachocephalus, Neogobius melanostomus, Pomatoschistus minutus, Psetta maxima, Uranoscopus scaber.
Distribution in Bulgaria. Black Sea, shell sand, muddy sand and muddy sea bottom, 10–70 m depth.
Conservation importance. Many animals of national and international conservation value have been registered: Acipenser gueldenstaedti, A. nudiventris,A. stellatus,A. sturio, Huso huso, Raja clavata, Squalus acanthias. Acipenser gueldenstaedti,A. stellatus, Apseudes acutifrons, Chelindonichthys lucernus, Mesogobius batrachocephalus, Pilumnus hirtellus,Pomatoschistus minutus, Upogebia pusilla, Uranoscopus scaber are included in the Black Sea Red Data Book (1999).
Threats. Anthropogenic eutrophication of the Black Sea that has caused “blooms” of the phytoplankton and hypoxia/anoxia in the bottom water layers that lead to the mass mortability of black mussels, arthropods and bottom fishes in the habitat. The invasive species Rapana venosa has caused a significant decrease in the natural resources of the blue mussel along the Bulgarian Black Sea coast in the 1970s. . A strong distructive factor for the mussel banks is the bottom trawling. Industrial and chemical pollution also is a threat for the habitat. A threat is also the construction of fuel and gas pipelines through the areas of this habitat or in close proximity to them.
Conservation measures taken. The habitat is included in Annex № 1 of the national Biodiversity Act. Bottom trawling is forbidden by the Law on fishing and aquacultures.
Conservation measures needed. Inclusion of the habitat in the European Ecological Network NATURA 2000 in Bulgaria. The definition of quotas for the turbot fishing, control on the fishing intensity, and strict control on the use of forbidden fishing devices (bottom trawls) is obligatory. Investigation on the changes of the state, composition and structure of the living communities as well as periodic assessment of the conservation status of the characteristic taxa according to the contemporary IUCN criteria and categories are needed.
References. Georgiev 1964; Kaneva-Abadzhieva 1967; Karapetkova & Zhivkov 2006; Konsulova et al. 2001; Marinov 1977; Panayotova et al. 2006; Stoyanov et al. 1963; Vassilev & Pehlivanov 2005; Zhivkov et al. 2005.
Authors: Valentina Todorova, Marina Panayotova
