Implications of dredging induced changes in sediment particle size composition for the structure and function of marine benthic macrofaunal communities K.M. Cooper a,⇑ , M. Curtis a , W.M.R. Wan Hussin b,c , C.R.S. Barrio Froján a , E.C. Defew b , V. Nye a , D.M. Paterson b a The Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Suffolk NR33 OHT, UK b Sediment Ecology Research Group, Scottish Oceans Institute, School of Biology, University of St Andrews, St Andrews, Fife KY16 8LB, UK c Fakulti Agroteknologi dan Sains Makanan, Universiti Malaysia Terengganu, Mengabang Telipot, 21030 Kuala Terengganu, Malaysia article info Keywords: Sediment Marine aggregate extraction Physical impacts Biological impacts Function abstract A meta-analysis approach was used to assess the effect of dredging induced changes in sediment compo- sition, under different conditions of natural physical disturbance, for the structure and function of marine benthic macrofaunal communities. Results showed the sensitivity of macrofaunal communities increased as both the proportion of gravel increased and the level of natural physical disturbance decreased. These findings may be explained by the close association of certain taxa with the gravel fraction, and the influ- ence of natural physical disturbance which, as it increases, tends to restrict the colonisation by these spe- cies. We conclude that maintaining the gravel content of surface sediments after dredging and, where practicable, locating extraction sites in areas of higher natural disturbance will minimise the potential for long-term negative impacts on the macrofauna. Crown Copyright Ó 2011 Published by Elsevier Ltd. All rights reserved. 1. Introduction Marine aggregate dredging has the potential to lead to changes in the composition of seabed sediment habitats (Sarda et al., 2000; van Dalfsen et al., 2000). These changes can occur in four ways. Firstly, as a result of sediment screening, whereby unwanted sed- iment fractions (usually sands) are returned to the seabed (Hitch- cock and Drucker, 1996; Newell et al., 1998, 2004). Secondly, as a result of the ‘infilling’ of dredge depressions and furrows with fine sediments (Dickson and Lee, 1972; Kenny et al., 1998; Boyd et al., 2002). Thirdly, as a result of ‘overspill’, where fine sediments, in suspension, are lost through chutes in the side of the dredger hold as the cargo is loaded (Newell et al., 1998). Fourthly, as a result of the exposure of underlying sediments which are different in nature to the original substrata (Kenny and Rees, 1996; Cooper et al., 2007). Material rejected by screening and overspill may also accu- mulate outside the boundaries of the extraction site, depending on local hydrodynamic conditions (Poiner and Kennedy, 1984; Hitch- cock and Drucker, 1996; Newell et al., 2004; Cooper et al., 2006). Changes in sediment composition can have implications for res- ident and recolonising fauna, resulting in the establishment of a faunal community that differs from the assemblage present before the dredging (Desprez, 2000; Boyd et al., 2002, 2005; Barrio Froján et al., 2011). Recognising the potential for such changes, Govern- ment policy (ODPM, 2002) requires developers to leave the seabed in a similar physical condition to that present before dredging. This measure is designed to enhance the possibility of, and rate at which, the seabed recovers physically and biologically to its pre- dredged condition. Whilst this policy has a clear scientific justifica- tion and is consistent with the principle of sustainable develop- ment, two important questions arise. Firstly, how can we decide what does, and does not, constitute an acceptable ‘similar’ physical condition? Secondly, how important is the preservation of sedi- ment granulometry for faunal recovery in different localities? This question arises given the results from Kenny et al. (1991) and Rees et al. (1999), working at dredge sites off the east coast of the UK. They identified a combination of tidally induced sediment mobility and the abrasive effects of sand in suspension as important factors influencing benthic communities, and not simply sediment granul- ometry. The importance of sediment stability in controlling com- munity structure is also highlighted in Newell et al. (1998). In addition, Seiderer and Newell (1999), Newell et al. (2001) and Coo- per et al. (2007) all reported the a lack of a close correspondence between the distribution of different sediment types and benthic communities observed in the vicinity of marine aggregate dredging sites in areas of high natural disturbance. For this reason, Seiderer and Newell (1999) suggest that a return of sediment composition may not always be a pre-requisite for faunal recovery. Improving our understanding of the relationship between sedi- ment granulometry and the structure and function of macrofaunal communities is important for the management of marine 0025-326X/$ - see front matter Crown Copyright Ó 2011 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2011.07.021 ⇑ Corresponding author. E-mail address: keith.cooper@cefas.co.uk (K.M. Cooper). Marine Pollution Bulletin 62 (2011) 2087–2094 Contents lists available at SciVerse ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul