The deep seabed environment of the UK continental margin - integration and interpretation of geological and biological data

Abstract

Until recently the seafloor environment of the continental slope west of Shetland was relatively unknown, particularly with regards to its biology but also the general seabed environment. Since the AFEN (Atlantic Frontier Environmental Network) survey, using sidescan sonar, seabed photography and seabed sampling in 1996 in order to establish an environmental baseline for this region, the ‘Atlantic Frontier’, the knowledge and understanding of the environment has greatly increased. Two main layers, a warm-, upper layer overlying a cold-, deeper layer, within the hydrography (Turrell et al., 1999) and the macrofauna (Bett, 2000a, 2001a; Narayanaswamy, 2001) but little is known about the megafaunal distributions.

In this study, a total of 19 photographic stations have been used with 18 stations from the AFEN sampling programme carried out in 1996 (Bett, 1997) and one station (M200) from a Department of Trade and Industry (DTI) survey in 2000 (Bett, 2001b).  The processing and analysis of these photographs resulted in a total of 4537 photographs covering approximately 87,760 m² of the seabed.  The main aim of the study was to analyse this extensive collection of photographic material with the key objectives being the integration of biological and geological data to further the understanding of the seabed sedimentary environment and develop an overview of the biological communities that inhabit the continental slope west of Shetland.

The results presented illustrate a complex sedimentary environment with a number of sediment zones present as well as a current regime with strong currents flowing towards the northeast on the upper continental slope, while relatively weaker currents flowing towards the south-southwest are found at depth within the Faroe-Shetland channel.  In addition, two large-scale patterns and a number of local-scale patterns have been identified within the megafaunal distribution.  The variations in the megafaunal distributions show a division of the fauna into a two-layer system as well as some bathymetric variations along the continental slope west of Shetland.  Within these two regional systems there are a number of local-scale features including the iceberg plough mark zone, the ‘sponge-belt’ and a novel discovery on a sand contourite at the bottom of the continental slope. 

The division of the megafauna into two layers with a boundary at approximately 600 m appear to reflect the distribution of the water masses within the Faroe-Shetland Channel with a warm-, upper layer overlying a cold-, lower layer.  Two of the main bathymetric trends are the increase in megafaunal density with depth along the continental slope and the decrease in species diversity with depth, the latter a result indicating that the suggested generalisation that the deep sea has uniformly high species diversity may be too simplistic.

More information

Identifiers

Catalogue record

Export record

ASCII CitationAtomBibTeXData Cite XMLDublin CoreDublin CoreEP3 XMLEndNoteHTML CitationHTML CitationHTML ListJSONMETSMODSMPEG-21 DIDLOpenURL ContextObjectOpenURL ContextObject in SpanRDF+N-TriplesRDF+N3RDF+XMLRIOXX2 XMLReferReference ManagerSimple Metadata