Effects of changing ocean regimes on deep-sea benthos on the Scottish continental shelf and slope

ATLAS work package 3 presentation at ATLAS 3rd General Assembly.

Time series of benthic samples collected at 2 sites (the Mingulay Reef Complex over the period 2003-2011, and the Scottish Hebrides continental slope over the period 1975-2012) are analysed as part of ATLAS Work Package 3. This analysis aims to measure the effects of interannual and multidecadal variability in water mass structure and ocean regimes, i.e. the North Atlantic Oscillation and Atlantic Multidecadal Oscillation, respectively, on deep-sea benthos biodiversity and biogeographic affinities. The Hebrides slope timeseries initiated in the 1970s provides an unparalleled insight into how longer-term ocean changes (Atlantic Multidecadal Oscillation) create species turnover.

In Mingulay Reef Complex, benthic samples have been collected from 88 stations using a Van Veen grab (over the years 2003, 2005, 2009, 2010 & 2011) accompanied by the collection of data on                                         geomorphology (depth, slope, aspect, rugosity, bathymetric position index) and hydrography (current speed). Over the last year 1) the sorting of Mingulay benthic samples from years 2009, 2010 and 2011 was completed, 2) the identification of specimens from Mingulay 2009 samples was completed to the lowest possible taxonomic level 3) and the identification of Mingulay specimens from years 2010 and 2011 was initiated. Work has already enriched our knowledge about Mingulay biodiversity since several new records of macrobenthos were recorded [e.g. the cnidarian Alcyonium digitatum Linnaeus, 1758, the polychaete Syllis armillaris (O.F. Müller, 1776), the bivalve Pododesmus squama (Gmelin, 1791), the amphipod Stenopleustes latipes (M. Sars, 1858), the ascidian Pyura tessellata (Forbes, 1848), among others] as well as a potentially new species to science (polychaete in the genus Pseudopotamilla, Family Sabellidae).

The availability of multidisciplinary data from the Mingulay Reef Complex creates a unique opportunity for investigating the role of hydrography and geomorphology in cold-water coral reef biodiversity and biogeography. Specifically, the analysis will unravel the relative importance of spatial vs temporal patterns in biodiversity as well as the possible role of interannual changes in oceanography (North Atlantic Oscillation).