Benthic polychaete diversity patterns and community structure in the Whittard Canyon system and adjacent slope (NE Atlantic)

Laetitia M Gunton,Lenka Neal,Andrew J Gooday,Brian J Bett,Adrian G Glover

doi:10.1016/j.dsr.2015.07.004

Laetitia M Gunton, Lenka Neal + Show 3 more

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https://doi.org/10.1016/j.dsr.2015.07.004

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Abstract

We examined deep-sea macrofaunal polychaete species assemblage composition, diversity and turnover in the Whittard Canyon system (NE Atlantic) using replicate megacore samples from three of the canyon branches and one site on the continental slope to the west of the canyon, all at ~3500m water depth. A total of 110 polychaete species were recorded. 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 west to east, the dominance of Paramphinome jeffreysii increased from 12.9% on the slope to 39.6% in the Eastern branch. Ordination of species composition revealed that the Central and Eastern branches were most similar, whereas the Western branch and slope sites were more distinct. High abundances of P. jeffreysii and Opheliidae sp. A characterised the Eastern branch of the canyon and may indicate an opportunistic response to a possible recent input of organic matter inside the canyon. Species richness and diversity indices were higher on the slope compared with inside the canyon, and the slope site had higher species evenness. Within the canyon, species diversity between branches was broadly similar. Despite depressed diversity within the canyon compared with the adjacent slope, the fact that 46 of the 99 polychaete species found in the Whittard Canyon were not present on the adjacent slope suggests that this feature may enhance the regional species pool. However, our sampling effort on the adjacent slope was insufficient to confirm this conclusion.

Highlights

Describing and understanding patterns of biodiversity on our planet is a fundamental aim in biology (Gaston, 2000)
The species composition of the polychaete assemblages differed between branches of the Whittard Canyon, in agreement with hypothesis 1
A, which made up 10% of the polychaete species in the Western branch but was not present in other canyon branches

Summary

Introduction

Describing and understanding patterns of biodiversity on our planet is a fundamental aim in biology (Gaston, 2000). A parabolic pattern of local diversity with water depth, with peaks at intermediate (i.e. mid to lower bathyal) depths and reduced diversity at upper bathyal and abyssal depths, is evident among some macrofaunal taxa, including polychaetes, in intensively studied areas of the North Atlantic (Rex, 1981; Rex, 1983; Etter and Grassle, 1992; Levin et al, 2001; Rex and Etter, 2010; Paterson and Lambshead, 1995) This pattern may not be a universal phenomenon across different taxa and deep-sea regions There is, no general agreement on whether alpha diversity is typically higher inside canyons (Vetter and Dayton, 1998, 1999; Vetter et al, 2010; De Leo et al, 2012) or higher on the adjacent slope outside canyons (Gage et al, 1995; Curdia et al, 2004; Garcia et al, 2007; Koho et al, 2007)

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