Coral habitats in submarine canyons of the Bay of Biscay: distribution, ecology and vulnerability = Habitats coralliens dans les canyons sous-marins du Golfe de Gascogne: distribution, écologie et vulnérabilité
van den Beld, I. (2017). Coral habitats in submarine canyons of the Bay of Biscay: distribution, ecology and vulnerability = Habitats coralliens dans les canyons sous-marins du Golfe de Gascogne: distribution, écologie et vulnérabilité. PhD Thesis. Université de Bretagne Occidentale: Brest. 260 + annexes pp.
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| Available in | Author |
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Document type: Dissertation
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| Keyword |
Topographic features > Submarine features > Submarine canyons
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| Author keywords |
cold-water corals; Lophelia and Madrepora reefs; coral gardens, coral habitats; diversity; associated megafaunal community; marine litter; Bay of Biscay; anthropogenic impact; vulnerable |
| Abstract |
Cold-water coral (CWC) habitats formed by colonial scleractinians, gorgonians, antipatharians and sea pens are biodiversity and biomass hotspots that provide important functions, such as shelter and feeding grounds, to other organisms. But, they are also vulnerable to human activities, because they are long-lived, grow slowly and have a low resistance. CWC habitat development, due to their steep topography, complex hydrodynamics and substrate heterogeneity. In the Bay of Biscay, which margin is incised by hundreds of canyons, CWCs are known to exist since the late 19th century, but their distribution, and three locations between adjacent canyons were visited with an ROV and a towed camera system during 46 dives on 7 cruises. Images were analyzed for CWC habitats using the CoralFISH classification system. In these habitats, corals, associated fauna were identified and substrate cover measured. Litter was identified in 15 out of 24 canyons.Eleven coral habitats constructed by 62 coral morphotypes were observed in the canyons of the Bay of Biscay hosting 191 associated megafaunal morphotypes, including 160 unique morphotypes. The distribution patterns at regional and local scales could be linked to hydrodynamics and sedimentary regimes. Substrate type was an important driver for coral and associated faunal assemblages, distinguishing biogenic, hard substrate and soft substrate habitats. Coral assemblages were similar between biogenic and hard substrate habitats, but the associated fauna was more abundant and diverse on biogenic habitats. The alpha, beta and gamma diversity were surprisingly high on soft substrates, equals or exceeding that of biogenic habitats.Marine litter was abundant and was mainly composed of plastic items and fishing gear. Litter could co-occur with CWCs and impact them: litter and most CWC habitats were observed at similar water depths and were more abundant in areas with a seafloor relief created by biological or geological features. Observations of coral reefs on steeper areas in the canyons and coral debris on flatter areas on the interfluve / upper slope. Natura 2000 is a naturally occurring coral habitat on the southern part of the island. |
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