Author's personal copy High bacterial biodiversity increases degradation performance of hydrocarbons during bioremediation of contaminated harbor marine sediments Antonio Dell’Anno a, * , Francesca Beolchini a , Laura Rocchetti a , Gian Marco Luna b , Roberto Danovaro a a Department of Life and Environmental Sciences, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy b Institute of Marine Sciences e National Research Council (CNR), Castello 9 1364/a, 30122 Venezia, Italy article info Article history: Received 12 December 2011 Received in revised form 22 March 2012 Accepted 23 March 2012 Keywords: Marine sediments Bioremediation Facilitative interactions Hydrocarbons abstract We investigated changes of bacterial abundance and biodiversity during bioremediation experiments carried out on oxic and anoxic marine harbor sediments contaminated with hydrocarbons. Oxic sedi- ments, supplied with inorganic nutrients, were incubated in aerobic conditions at 20  C and 35  C for 30 days, whereas anoxic sediments, amended with organic substrates, were incubated in anaerobic conditions at the same temperatures for 60 days. Results reported here indicate that temperature exerted the main effect on bacterial abundance, diversity and assemblage composition. At higher temperature bacterial diversity and evenness increased significantly in aerobic conditions, whilst decreased in anaerobic conditions. In both aerobic and anaerobic conditions, biodegradation efficiencies of hydro- carbons were significantly and positively related with bacterial richness and evenness. Overall results presented here suggest that bioremediation strategies, which can sustain high levels of bacterial diversity rather than the selection of specific taxa, may significantly increase the efficiency of hydrocarbon degradation in contaminated marine sediments. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Hydrocarbon contamination is a widespread environmental problem, especially in coastal areas subjected to high anthropo- genic inputs (Clark, 2001). Among these, harbors are systems chronically contaminated with hydrocarbons deriving from a wide variety of anthropogenic sources such as oil spills, urban runoff, shipping and industrial activities (Beolchini et al., 2009). The high hydrocarbon concentrations accumulated in surface and subsurface sediments pose serious concerns for the environmental and human health, especially when sediments undergo natural re-suspension or dredging is carried out for maintaining the navigable depths of ports, which can cause the formation of contaminated plumes spreading in adjacent areas. At the same time, due to the high contamination levels, the dredged sediments cannot be re-used (e.g. for building industries or for beaches nourishment; Ahlf and Forstner, 2001; USEPA, 2005). Therefore, there is an urgent need to reduce contaminant concentrations to allow the re-use of dredged sediments (Beolchini et al., 2009; Dell’Anno et al., 2009). Bioremediation is an environmental-friendly strategy gaining increasing prominence for its potential to clean up oil- contaminated marine sediments (Prince, 1993; Swannell et al., 1996; Head and Swannell, 1999; Head et al., 2006; Beolchini et al., 2010). Several field and laboratory experiments demon- strated that biodegradation processes of organic contaminants in the sediments can be speeded up through the addition of different electron acceptors and/or donors able to stimulate the autochtho- nous microbial assemblages (Atlas, 1995; Coates et al., 1996, 1997; Head and Swannell, 1999; Kasai et al., 2002a; Röling et al., 2002, 2004; Head et al., 2006; Miralles et al., 2007; Atlas and Bragg, 2009). For instance, it is well known that biodegradation rates of hydrocarbons are mainly limited by oxygen as well as by N and P bioavailability (Atlas, 1981; Swannell et al., 1996; Head and Swannell, 1999; Head et al., 2006). Nevertheless, recent findings provided evidence that biodegradation processes of hydrocarbons can occur to a large extent also under reducing conditions (Heider et al., 1999; Rothermich et al., 2002; Meckenstock et al., 2004; Miralles et al., 2007; Dell’Anno et al., 2009; Gieg et al., 2009). Such findings suggest that biostimulation strategy potentially applicable for sediment decontamination should be selected not only on the basis of the technical feasibility associated with the release of the suitable compounds (Coates et al., 1996, 1997), but also on the basis of the actual metabolic requirements of the microbial assemblages (Lovley, 2003; Head et al., 2006; Dell’Anno et al., 2009). Different studies demonstrated that the addition of inorganic compounds to sediments artificially contaminated with petroleum stimulated the * Corresponding author. E-mail address: a.dellanno@univpm.it (A. Dell’Anno). Contents lists available at SciVerse ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol 0269-7491/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2012.03.043 Environmental Pollution 167 (2012) 85e92