Polychaete abundance, biomass and diversity patterns at the Mid-Atlantic Ridge, North Atlantic Ocean

Mark A Shields,Raimundo Blanco-Perez

doi:10.1016/j.dsr2.2013.04.010

Abstract

Recent studies have revealed that the Mid-Atlantic Ridge (MAR) in the North Atlantic Ocean accounts for a large proportion of available bathyal soft-sediment habitat. When comparing the MAR to the continental margins of the North Atlantic, it is apparent that very little is known about the soft-sediment macrofaunal community associated with the MAR. In the present study, as part of the ECOMAR (Ecosystems of the Mid-Atlantic Ridge at the Sub-Polar Front and Charlie–Gibbs Fracture Zone) project, the polychaete component of the MAR macrofaunal community was investigated. A total of 751 polychaete specimens and 133 species were identified from megacorer samples collected at four MAR sites (48–54°N, depth: 2500–2800m) sampled during the RRS James Cook 48 cruise in the summer of 2010. Polychaetes were the most abundant member of the macrofaunal community, and there was no significant difference in polychaete abundance, biomass and diversity between any of the MAR sites. In addition, the MAR did not appear to provide a physical barrier to the distribution of bathyal polychaetes either side of the ridge.

Highlights

Our understanding of the diversity of deep-sea benthic communities is greatest at the continental margins, in particular in the North Atlantic Ocean (Rex and Etter, 2010)
Little is known about the macrofaunal community associated with mid ocean ridges (Bergstad et al, 2008; Shields et al, in press) and the present study provides an important insight into the polychaete community of the Mid-Atlantic Ridge (MAR)
Global estimates for bathyal macrofaunal abundance and biomass are predominately based on data compiled from the continental margins with very little data available from mid oceanic ridges (Wei et al, 2010b)

Summary

Introduction

Our understanding of the diversity of deep-sea benthic communities is greatest at the continental margins, in particular in the North Atlantic Ocean (Rex and Etter, 2010). Macrofaunal species diversity is known to reach its maximum at mid-slope depths (Carney et al, 1993) and species diversity is influenced by environmental parameters, such as primary productivity and food supply, bottom water oxygen, sediment heterogeneity and deep-sea currents (Levin et al, 2001). When investigating diversity patterns it can be beneficial to focus on a single taxonomic group (Rex et al, 1993) Polychaetes are often the most abundant and species rich members of deepsea macrofaunal communities (Fauchald and Jumars, 1979; Gage and Tyler, 1991; Grassle and Maciolek, 1992). Polychaetes are, an ideal component of the macrofaunal community for investigating abundance, biomass, diversify and feeding type patterns in relation to environmental parameters (Glover et al, 2001, 2002; Narayanaswamy et al, 2005)

Methods

Results

Discussion

Conclusion