Bathymetrical distribution and size structure of cold-water coral populations in the Cap de Creus and Lacaze-Duthiers canyons (northwestern Mediterranean)

[摘要] Submarine canyons are known as one of the seafloor morphological featureswhere living cold-water coral (CWC) communities develop in the MediterraneanSea. We investigated the CWC community of the two westernmost submarinecanyons of the Gulf of Lions canyon system: the Cap de Creus Canyon (CCC)and Lacaze-Duthiers Canyon (LDC). Coral associations have been studiedthrough video material recorded by means of a manned submersible and aremotely operated vehicle. Video transects have been conducted and analyzedin order to obtain information on (1) coral bathymetric distribution anddensity patterns, (2) size structure of coral populations, and (3) coralcolony position with respect to the substrate. Madrepora oculata was the most abundant CWC inboth canyons, while Lophelia pertusa and Dendrophyllia cornigera mostly occurred as isolated colonies or in smallpatches. An important exception was detected in a vertical cliff in LDCwhere a large L. pertusa framework was documented. This is the first record of such anextended L. pertusa framework in the Mediterranean Sea. In both canyons coralpopulations were dominated by medium and large colonies, but the frequentpresence of small-sized colonies also indicate active recruitment. Thepredominant coral orientation (90° and 135°) is probably driven by the current regime as well as by the sediment loadtransported by the current flows. In general, no clear differences wereobserved in the abundance and in the size structure of the CWC populationsbetween CCC and LDC, despite large differences in particulate matter betweencanyons.

[学科分类] 地球化学与岩石