1180 - Structures sous-marines causées par des émissions de gaz

Submarine structures made by leaking gases

Liste hiérarchisée et descriptifs des habitats d'intérêt communautaire de la directive "Habitats"

Description

Submarine structures consist of sandstone slabs, pavements, and pillars up to 4 m high, formed by aggregation of carbonate cement resulting from microbial oxidation of gas emissions, mainly methane. The formations are interspersed with gas vents that intermittently release gas. The methane most likely originates from the microbial decomposition of fossil plant materials.
The first type of submarine structures is known as “bubbling reefs”. These formations support a zonation of diverse benthic communities consisting of algae and/or invertebrate specialists of hard marine substrates different to that of the surrounding habitat. Animals seeking shelter in the numerous caves further enhance the biodiversity. A variety of sublittoral topographic features are included in this habitat such as: overhangs, vertical pillars and stratified leaf-like structures with numerous caves. The second type are carbonate structures within “pockmarks”. “Pockmarks” are depressions in soft sediment seabed areas, up to 45 m deep and a few hundred meters wide. Not all pockmarks are formed by leaking gases and of those formed by leaking gases, many do not contain substantial carbonate structures and are therefore not included in this habitat. Benthic communities consist of invertebrate specialists of hard marine substrata and are different from the surrounding (usually) muddy habitat. The diversity of the infauna community in the muddy slope surrounding the “pockmark” may also be high.

Espèces caractéristiques

Plants: "Bubbling reefs" - If the structure is within the photic zone, marine macroalgae may be present such as Laminariales, other foliose and filamentous brown and red algae. "Pockmarks" - Usually none
Animals: "Bubbling reefs" - A large diversity of invertebrates such as Porifera, Anthozoa, Polychaeta, Gastropoda, Decapoda, Echinodermata as well as numerous fish species are present. Especially the polychaete Polycirrus norwegicus and the bivalve Kellia suborbicularis are associated species of the "bubbling reefs". "Pockmarks" - Invertebrate specialists of hard substrate including Hydrozoa, Anthozoa, Ophiuroidea and Gastropoda. In the soft sediment surrounding the pockmark Nematodae, Polychaeta and Crustacea are present.

Correspondances avec la classification du Paléarctique

11.24

Correspondances avec d'autres classifications

HELCOM classification: All subtypes under "Bubbling reefs (2.10)"
EUNIS: Relevant types under A5.71 Seeps and vents in sublittoral sediments.

Remarques

"Bubbling reefs" can be found in association with the habitat types "sandbanks, which are covered by sea water all the time (1110)" and "reefs (1170)".

Informations du Manuel d'interprétation EUR 15/2

Structures sous-marines spectaculaires complexes, formées de blocs et de colonnes pouvant atteindre 4 mètres de haut. Elles résultent de l'agrégation de grains de sable par un ciment carbonaté se formant sous l'action de l'oxydation microbienne d'émissions de gaz, principalement du méthane. Ce méthane provient vraisemblablement de la décomposition de dépôts végétaux fossiles et s'échappe de manière intermittente des formations par les nombreux orifices qui les parsèment. Ces formations abritent un écosystème très diversifié, composé d'espèces richement colorées.
 
Animales: Porifera- Cliona celata; Anthozoa- Metridium senile, Tealia felina, Alcyonium digitatum; Polychaeta- Pomatoceros triqueter, Dodocaceria concharum;. Gastropoda- Cingula striata, Alvania punctura, Rissoa albella, R. parva; Decapoda- Porcellana longicornis, Cancer pagurus; Echinodermata- Ophiotrix fragilis.

Bibliographie

 Conseil de l'Union européenne, 2013. Directive 2013/17/UE du Conseil du 13 mai 2013 portant adaptation de certaines directives dans le domaine de l'environnement, du fait de l'adhésion de la République de Croatie. Annexes. Partie B Protection de la nature. Journal officiel de l'Union européenne, L 158 du 10/06/2013, p. : 195-203. (Source)

 European Commission, 2013. Interpretation manual of European Union habitats. EUR 28. European Commission, DG Environment, 144 p. (Source)

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Hovland M. & Judd A.G. (1988). Seabed Pockmarks and seepages: Impact on Geology, Biology and the Marine Environment. Graham & Trotman, London. 245pp.

Jensen, P. et al. (1992). "Bubbling reefs" in the Kattegat: submarine landscapes of carbonatecemented rocks support a diverse ecosystem at methane seeps. Mar. Ecol. Prog. Ser., vol. 83:103-112.

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Jørgensen, N.O. et al (1989). Holocene methane-derived dolomite-cemented sandstone pillars from Kattegat, Denmark. Mar. Geol., vol. 88: 71-81.

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