DEPARTMENT for ENVIRONMENT, FOOD and RURAL AFFAIRS CSG 15 Research and Development Final Project Report (Not to be used for LINK projects) Two hard copies of this form should be returned to: Research Policy and International Division, Final Reports Unit DEFRA, Area 301 Cromwell House, Dean Stanley Street, London, SW1P 3JH. An electronic version should be e-mailed to [email protected] Project title The benthic ecology of the Western North Sea DEFRA project code AE1143 Contractor organisation CEFAS and location Remembrance Avenue Burnham-on-crouch Essex CM0 8HA Total DEFRA project costs £ 125436 Project start date 01/10/02 Project end date 31/12/04 Executive summary (maximum 2 sides A4) The main objective of this work is to provide a strategic evaluation of the status of the benthic communities of the western North Sea in relation to natural and anthropogenic influences, as a timely contribution to the DEFRA-led ‘State of the Seas’ assessment for UK waters, due for publication in 2005. This has been achieved through the generation of up-to- date information on the occurrences and densities of benthic species in the northern North Sea, by capitalising on sampling effort in 2001 by FRS, Aberdeen, accompanied by completion of a grid of benthic sampling stations off the English east coast, sampled (under NMMP auspices) by CEFAS, leading to coverage of the entire western North Sea. The outcome has particular benefit in providing a wider context for more localised appraisals of environmental quality status, and inter-relationships between assessment scales (both in space and time) were explored by reference to additional data sources, including those from established NMMP stations, and more site-specific surveys, such as those relating to disposal at sea and aggregate extraction. The generation of new data for coastal and offshore waters of the eastern UK has the additional and important benefit of contributing to an ongoing international evaluation of benthic community status in the North Sea, under ICES auspices, thereby providing a third (sea-wide) tier to the assessment of spatial pattern and the causative influences. DEFRA sponsorship of the proposal therefore had two complementary advantages, namely the servicing of a national need (the UK ‘State of the Seas’ report) and, through the provision of new data, further consolidation of a leading role for UK marine science in ongoing and future assessments of the quality status of the North Sea as a whole. Macrobenthic samples from 89 stations in the western North Sea were analysed for species occurrences, densities and biomass, in order to assess the current status of the western North Sea benthos. Evaluation of patterns against a suite of natural environmental factors identified sediment type and tidal current strength as the most influential in governing the distribution of contemporary species assemblages. CSG 15 (Rev. 6/02) 1 Project The benthic ecology of the Western North Sea DEFRA AE1143 title project code Data from the present study were also compared to those from the 1986 ICES North Sea benthos survey. Whilst there were subtle differences in species assemblages resulting mainly from an increase in the dominance of certain polychaete taxa, the species assemblages were seen to be similar between sampling occasions. The effects on benthic communities and sediments of anthropogenic influences such as those arising from oil and gas installations, aggregate extraction and dredged material disposal were not identifiable on the relatively coarse scale of the present sampling grid, indicating that, as might be expected, the consequences of these activities when considered on a case-by-case basis are much more localised. However, it may also be concluded that there is no evidence of a cumulative ‘footprint’ associated with concentrations of these activities, e.g., gas platforms and aggregate extraction sites off the English east coast. Similarly, there was no evidence of deleterious effects associated with demersal fishing activity, which operates on a much wider spatial scale. As with the other sources of anthropogenic activities investigated, the disposition and size of areas of relatively intense fishing effort are, individually, beyond the resolving power of the present survey design, and so this is not to imply the absence of any effects within the survey area. The outcome of the present study demonstrates the utility of periodic surveys to evaluate the broadscale status of the benthic communities of UK waters, especially in providing a wider context for the numerous ongoing environmental assessments conducted over smaller spatial scales. CSG 15 (Rev. 6/02) 2 Project The benthic ecology of the Western North Sea DEFRA AE1143 title project code Scientific report (maximum 20 sides A4) 1.0 Introduction During 2000-2002, 89 stations were sampled for the benthic macrofauna and sediments (thereafter referred to as “2000 survey”, Figure 1). CEFAS work involved the re-sampling of stations off the English east coast occupied in 1986 as part of the ICES North Sea Benthos Survey (Kunitzer et al., 1992). Samples at five of these stations were kindly contributed by the Senckenberg Institute, Germany. FRS work involved stratified random sampling of the northern and eastern North Sea as part of an EU project (MAFCONS). In 2002, DEFRA funded the work-up of these samples as a contribution both to the UK ‘State of the Seas’ report and to an international collaborative initiative to re-appraise the status of the North Sea benthos following an earlier (1986) survey, under ICES auspices. The present report relates to the first of these aims. CEFAS stations were sampled using a 0.1m2 Hamon grab or Day grab; Senckenberg Institute stations were sampled with a 0.1m2 Van Veen grab; FRS stations were sampled with a 0.25m2 box core. A 1 mm mesh sieve was used in the processing of all benthos samples. Sediment sub-samples collected by CEFAS and FRS were analysed for particle size. Additionally, sub-samples at CEFAS stations were analysed for % organic carbon and nitrogen content and the concentrations of a range of trace metals. Box core (FRS Aberdeen) Day grab (CEFAS) Hamon grab (CEFAS) Van Veen (Senckenberg Institute) 0 150 300 kilometres Figure 1. Locations of stations, principally in the western North Sea, sampled in the period 2000-2002 2.0 The Sedimentary Environment 2.1 Particle size All the sediments sampled in the 2000 survey were relatively coarse grained, with 90% containing < 10% silt/clay (< 63µm), and with most samples being predominantly sandy in nature. Gravelly sands and sandy gravels predominated in the south and east with the proportion of silt/clay increasing to the north (see Figure 2 for percentages of gravel, sand, silt/clay). This is consistent with the reported distribution of sediment types in the region and corresponds approximately to variations in bathymetry and tidal current velocities. The sources of sediment are varied and the present distribution has resulted from a complex interaction of modern processes (tides, waves and surges) with the effects of glaciations, changes in relative sea level, active sediment erosion, particularly of older Quaternary deposits, and relict features (Pantin, 1991; Basford et al., 1993; Nio et al, 1981; Irion and Zöllmer, 1999; Goldberg, 1973). CSG 15 (Rev. 6/02) 3 Project The benthic ecology of the Western North Sea DEFRA AE1143 title project code 0 100 200 % gravel kilometres % sand % silt/clay Figure 2. Percentage distributions of gravel, sand, silt/clay 2.2 Metals Trace metal concentrations in sediments were determined using ICP-MS following HF extraction. HF attacks the crystal lattice of alumino-silicate minerals and the resulting metal concentrations reflect both the mineralogy of the sediment and metals adsorbed onto particle surfaces (including the contaminant fraction). Contaminant concentrations in sediments often show an inverse correlation with particle size (finer sediments have a much greater surface area for adsorption). To some extent this can be addressed by analysing a defined size fraction. In the present study the silt-clay fraction (<63µm) was separated and analysed. Earlier studies used a variety of size fractionations (e.g. < 2mm (‘whole sediment’), < 63 µm, < 20µm, < 16 µm; < 2 µm; Rowlatt and Lovell, 1994; Whalley et al., 1999; Rowlatt, 1996; de Groot and Allersma, 1973; Basford et al., 1993; Irion, 1994). In addition, the metal concentration can be normalised against a non-contaminant element such as aluminium or lithium, to account for lithogenic variability. The relative merits of using Al and Li, which vary differently with the mineralogy, have been discussed by Loring (1990). He concluded that Li was more appropriate for use in relatively high latitude regions, such as the NW European Shelf. In the present study both Li and Al normalisation were used. The distribution patterns were not consistent. Higher concentrations of arsenic, cadmium, chromium, mercury, nickel, vanadium and zinc were observed in the northeast sector, although the extent was variable. Metal/Al ratios were compared with the published OSPAR background/reference concentrations (BRC; OSPAR, 1997) for Fe, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn (Table 1). Eighty percent of the samples were below or within the 1997 BRC range for Fe, Cr, Cu, Hg, and Ni. As and Cd were below or within range for fifty percent of the samples. Pb and Zn showed relatively high concentrations across the whole area. This is most likely to be an historical artefact of mining and industrial activity in northeast England in the previous century. Pb is also introduced into the North Sea as a result of atmospheric fallout (Förstner and Witmann, 1979), although there have been substantial reductions as a result of the phasing out of lead additives in petrol. The BRC's are being re-evaluated (Bignert et al., 2004), as more data become available, particularly to take account of regional variations due to differences in the background geochemistry, but these have not been finalised.