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Richesse et biodiversité en mer mégatidale: communautés sublittorales rocheuses de la région Trebeurden-Ploumanac'h (Nord Bretagne, France) = Richness and biodiversity in megatidal sea: subtidal rocky communities in Trebeurden-Ploumanac'h area (north Brittany, France)
Castric-Fey, A. (1996). Richesse et biodiversité en mer mégatidale: communautés sublittorales rocheuses de la région Trebeurden-Ploumanac'h (Nord Bretagne, France) = Richness and biodiversity in megatidal sea: subtidal rocky communities in Trebeurden-Ploumanac'h area (north Brittany, France). Cah. Biol. Mar. 37(1): 7-31
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723, more
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    Marine

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  • Castric-Fey, A.

Abstract
    Investigations on the influence of strong currents on the subtidal epifaunal communities was undertaken through a diving survey on the rocky seabed off Trebeurden and Ploumanac'h. Tidal currents, in this area, are between 2-3.5 knots. Data on the abundance of species are treated statistically (Principal Component Analysis). The areas of Trebeurden and Ploumanac'h appear quite different. The Trebeurden area is dominated by wave action and a moderate current allows sedimentation of coarse sand on the surrounding of rocks. This zone shows rich epibiosis, with active suspension feeders, mainly ascidians and bryozoans, dominating. The following assemblages are described: the sandy ascidians mat facies, the turf bryozoans "fur" facies and the Distomus-Polycarpa facies. In the Ploumanac'h area, which is under the influence of strong currents, the flora is luxuriant, particularly in the channel separating the Sept-iles and the mainland whilst the animal biomass is generally less important and the passive suspension feeders are, in proportion, less abundant than in the Trebeurden area. The specific richness is maximal in the vicinity of Trebeurden-Triagoz. Biomasses show high values (average total biomass 12.7 kg.m super(-2) wet weight) indicating the beneficial influence of moderate to strong currents on the flora and fauna, and perhaps the effect of a reduced grazing pressure by urchins which are scarce in these two areas.

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