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Laetitia Gunton, National Oceanography Centre, Southampton, UK
Andrew Gooday, National Oceanography Centre, Southampton, UK
Adrian G. Glover, Natural History Museum of London, UK
Brian J. Bett, National Oceanography Centre, Southampton, UK
Neal L, National Oceanography Centre, Southampton, UK
Helena Wiklund, Natural History Museum of London, UK
Benthic Polychaete Assemblage Patterns in the Whittard Canyon System

Deep-sea macrofaunal polychaete species assemblage characteristics were examined in the Whittard Canyon system (NE Atlantic). Replicate Megacore samples were collected, from three canyon branches and one site on the continental slope to the west of the canyon (~ 3500 m water depth).

A total of 110 polychaete species were morphologically identified. Paramphinome jeffreysii was the most abundant species (2326 ind m-2) followed by Aurospio sp. B (646 ind m-2), Opheliidae sp. A (393 ind m-2), Prionospio sp. I (380 ind m-2), and Ophelina abranchiata (227 ind m-2). Species composition varied significantly across all sites. From east to west, the dominance of Paramphinome jeffreysii decreased from 39.6 % in the Eastern branch to 12.9 % on the slope.  Environmental variables depth and clay % best explained patterns in species composition. Species diversity between branches inside the canyon was roughly similar. Richness and diversity indices were higher on the slope compared with inside the canyon. Forty-six of the ninety-nine polychaete species found in the Whittard Canyon were not present on the adjacent slope site, suggesting that the canyon may increase beta diversity and enhance the regional species pool.

Additional polychaetes were collected for a preliminary molecular analysis (CO1 and 16S genes) from the shallower parts (~ 1000 m) of the canyon and nearby Goban Spur to the northwest of the canyon. A total of 109 sequences were obtained from 139 specimens. This resulted in the identification of 33 polychaete species, of which 5 could be assigned Latin binomial names based on phylogenetic analyses. Only two of these species (P.jeffreysii, Aurospio dibranchiata) occurred at the deeper (3500 m) sites, suggesting that polychaete assemblages in the shallower regions of the canyon are different from the deeper assemblages. However, more samples from shallower regions would be needed to confirm this conclusion.

This study highlights the variability of polychaete assemblages within the soft-sediment habitat of a submarine canyon. This variation probably reflects the dynamic environmental conditions, which are influenced by the topographic profiles of individual canyon branches.

Theme 3: Biological patterns in submarine canyons: role of scale and heterogeneity
Oral Presentation
biodiversity, polychaeta, Whittard Canyon, DNA barcoding