Éditeur(s) : Inter-research
Résumé : Mixed beds of Ophiocomina nigra and Ophiothrix fragilis (Echinodermata, Ophiuroidea) are usually predominated by O. fragilis and are reported to be stable over time. The Bay of Brest (Brittany, France) is a highly productive ecosystem where both species co-occur in the main central part. Using a geostatistical approach, we tested for changes in O. nigra and O. fragilis density and total biomass patterns between 1987 and 2011. Our results highlighted an increase in O. nigra population size and the induction of a spatial shift of the co-occurring O. fragilis. O. nigra increased similar to 5 times in density and covered almost all the study area, while its density-dependent biomass increased similar to 3 times (22 t km(-2), ash-free dry mass) between 1987 and 2011. Overall, the O. fragilis population decreased in density by similar to 30%, but its total biomass did not change over time. The current distribution pattern revealed a clear spatial exclusion of O. fragilis from the central part of the study area toward the southern part, overlapping beds of dead slipper limpet Crepidula fornicata, which were formerly considered to be the dominant suspension-feeder species in the bay. The success of O. nigra colonization is linked to its biological and functional traits, as well as deep changes in food supply over the studied period. Ecological consequences of such a large change in the benthic compartment of the bay are explored in the light of associated changes in environmental patterns.
Marine Ecology-progress Series (0171-8630) (Inter-research), 2012 , Vol. 460 , P. 79-90

Droits : 2012 Inter-Research
http://archimer.ifremer.fr/doc/00090/20136/17782.pdf
DOI:10.3354/meps09784
http://archimer.ifremer.fr/doc/00090/20136/

Résumé : Ifremer launched and coordinated the development of a strategy for the REBENT network (REseau BENThique) in 2000 to monitor the aftermath of the "Erika" oil spill in December 1999. Its aim is to provide consistent baseline knowledge about coastal benthic habitats and constitute a monitoring tool to detect changes at various scales over time and space. Sector-based seabed habitat mapping in shallow water (< 50 m deep), is currently being conducted throughout Brittany's coastal waters through a combination of geoacoustic marine systems and ground-truthing using biological grab sampling and seabed observations. Sedimentological and biological results on Glenan area emphasize a great diversity of subtidal habitats and marine species recognized. Sidescan imagery accentuates the complexity of the communities structure in a marine environment distinguished by strong and regulary roughness of the sea. Maerl biocenose is present at the nord-east of the archipelago. Progressively it gives way to mud sediment colonized by Amphiura filiformis and Haploops in the deeper channel. To the west and the south, substratum types are more coarse, occasionally mobiles, composed of essentially sand community with Nephtys and gravelly sand community with Branchiostoma lanceolatum.
Le Rebent (Réseau benthique), initié en 2000 à la suite de la catastrophe de l'Erika, a pour objectif de suivre les habitats benthiques côtiers et de détecter les changements à différentes échelles de temps et d'espace. L'approche sectorielle dans les petits fonds (< 50 m) des côtes bretonnes combine, des moyens de prospection acoustique, afin de délimiter les principaux types de substrats, avec des prélèvements et des observations biologiques pour caractériser les peuplements macrobenthiques. Les résultats des analyses sédimentologiques et faunistiques montrent autour de l'archipel des Glénan, une grande diversité d'habitats et d'espèces reconnues. L'imagerie acoustique fait ressortir la complexité de leur structuration dans un environnement marin soumis à de fortes et régulières périodes d'agitation. La biocénose de maërl occupe le nord-est de l'archipel. Elle laisse place progressivement aux sédiments envasés à Amphiura filiformis et aux vases à Haploops dans le fond du chenal. A l'ouest et au sud, les subtrats sont plus grossiers, essentiellement sableux à Nephtys et sablo-graveleux à Branchiostoma lanceolatum, épisodiquement mobiles.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2006/rapport-2301.pdf
http://archimer.ifremer.fr/doc/2006/sup-2301.pdf
http://archimer.ifremer.fr/doc/00000/2301/