Large-scale faunal characterisation of marine benthic sedimentary habitats around the UK Christopher R.S. Barrio Froján ⁎, Stefan G. Bolam, Jacqueline D. Eggleton, Claire Mason The centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk, NR33 0HT, UK abstract article info Article history: Received 26 July 2011 Received in revised form 23 January 2012 Accepted 11 February 2012 Available online 19 February 2012 Keywords: Macrofauna Benthos United Kingdom Large-scale We present the findings of a large-scale study designed to characterise the benthic faunal assemblages inhabiting soft sedimentary habitats surrounding the British Isles. The number, variety and spatial variability of the organ- isms encountered are presented and analysed using a suite of standard univariate and multivariate analytical techniques. Triplicate grab sampling at 155 stations arranged in a grid pattern yielded over 68,000 organisms, representing 1123 taxa. Observed variations in faunal assemblage composition were driven predominantly by differences in environmental conditions, such as mean sediment particle size, stratification and tidal stress. Con- sequently, a similar faunal assemblage occurred wherever the same combination of environmental conditions were present. Despite the high level of variability of the various assemblage metrics observed between sampling stations, some trends in the data could be detected. Most assemblage metrics decreased in value with increasing latitude. Most diversity indices increased at greater depths, yet abundance and biomass decreased with depth. Mean abundance and biomass values per station were higher in the English Channel and in parts of the Irish and North Seas than elsewhere. The number, richness, diversity and evenness of taxa were higher in the South and West than in the North and East. Similarly, assemblage structure was most dissimilar between these two areas, each area harbouring a distinct macrofaunal community. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Assemblages of marine sediment-dwelling organisms (i.e. the benthos) have been the subject of many ecological studies as they are able to adapt to changes in the environment. Because the structure of these assemblages strongly depends on—and readily responds to changes in—a range of biotic and environmental factors, they are considered highly suitable for the evaluation of environmental quality, especially as any observed changes in the assemblage may be directly traceable to natural or anthropogenic environmental variations (Gray, 1981; Gray et al., 1990; Pearson and Rosenberg, 1978; Warwick and Clarke, 1991). Consequently, benthic organisms have become an impor- tant tool in marine environmental monitoring, where they are routinely used as ‘indicators’ of various environmental characteristics. In addition to their utility as environmental quality indicators, benthic organisms are equally valuable as purveyors of ecosystem functions (Beaumont and Tinch, 2003; Kremen, 2005; Solan et al., 2008). Such functions include the production of oxygen and biomass, recycling of waste material and the sequestration of harmful substances. Only recent- ly has the importance of these functions been fully appreciated, as the possibility and consequences of their failure following irreparable damage by human activities becomes apparent (Edwards and Abivardi, 1998; Lovejoy, 1997; McVittie and Moran, 2008; Tilman, 2000). In the quest to better understand the mechanisms that underpin the effective and efficient running of ecosystem functions, benthic assemblages have been the subject of innumerable studies whose aim has been to charac- terise and map the various components that constitute them. Knowledge of how and why assemblages vary in space and over time is the first step towards attaining such understanding. Despite the wealth of studies that have contributed towards our awareness of the range of organisms that inhabit the seabed around the UK (including those recently compiled by Somerfield et al. (2009) at a pan-European scale), there remains a distinct lack of an overarching study conducted specifically to create a contemporary reference point of information on the diversity and spatial distribution of benthic organisms inhabiting the whole of the UK's territorial waters. Given their important role in maintaining ecosystem functions and their established status as effective indicators for the evaluation of the envi- ronmental consequences of human activities, the absence of such broad-scale information limits our capability to assess, understand and therefore effectively and holistically manage our seas. The present investigation seeks to overcome this apparent gap in our knowledge by systematically characterising the diversity and distribution of benthic animals (the macro-infauna or macrofauna) around most of the UK's territorial waters. In doing so, it will also provide a national environmental context into which all of the other important smaller- scale studies can be placed (e.g., Emu, 2009; James et al., 2010; Limpenny et al., 2011; Mackie et al., 2006; Tappin et al., 2011). Journal of Sea Research 69 (2012) 53–65 ⁎ Corresponding author. E-mail address: christopher.barrio@cefas.co.uk (C.R.S. Barrio Froján). 1385-1101/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.seares.2012.02.005 Contents lists available at SciVerse ScienceDirect Journal of Sea Research journal homepage: www.elsevier.com/locate/seares