Microbial ecology of hydrocarbon-polluted coastal sediments

Coastal shorelines suffer a variety of pollution injuries from both sides, from the sea, predominantly by crude oil from shipping and offshore mining, and from the land, principally through agricultural practices, urban wastewaters, and industrial activities. As a result, multi-pollution hot spots are found along shorelines, especially in estuaries and harbors. Microbial communities have evolved to adapt their metabolism to the presence of multi-contaminants (Duran et al. 2008; Gillan et al. 2005; Iannelli et al. 2012; Kaci et al. 2014; SabadiniSantos et al. 2014; Wang and Tam 2012). However, hydrocarbon compounds and crude oil-derived products are the most abundant pollutants, the more spectacular source being oil spill as illustrated by the recent catastrophe of Deepwater Horizon in 2010, the largest oil spill so far observed (Atlas and Hazen 2011). Although they are frequently found at unacceptably high concentrations, hydrocarbons are natural compounds, and thus, most of them can be biodegraded by the collective catabolic diversity of microorganisms (Duran and Goni Urriza 2010; Head et al. 2006; Leahy and Colwell 1990; Miralles et al. 2007; Paisse et al. 2011; Paisse et al. 2010), particularly demonstrated in coastal marine ecosystems such as salt marshes with microbial mat structures (Bordenave et al. 2004a; Bordenave et al. 2008; Bordenave et al. 2007; Bordenave et al. 2004b), mangroves (Brito et al. 2009; Brito et al. 2006) and estuaries (Chronopoulou et al. 2013; Coulon et al. 2012). However, coastal marine sediments constitute particular ecosystems submitted to fluctuating oxygenation and redox conditions from the tidal cycles and burrowing activities of the macrofauna that in turn drive microbial degradation processes (Cravo-Laureau and Duran 2014). The biodegradation of hydrocarbon compounds in such oxic/anoxic oscillating environments still remains poorly understood (Cravo-Laureau et al. 2011; Cuny et al. 2011; Vitte et al. 2013; Vitte et al. 2011). The understanding of the particular microbes involved, their ecology, their genetic and enzymatic capacities, their interactions, as well as their functioning in the changing redox conditions, is crucial for the implementation of efficient bioremediation strategies (Goni-Urriza et al. 2013; McGenity 2014). The DECAPAGE project (ANR CESA-2011-006 01; http://ipremeem.univ-pau.fr/live/DECAPAGE), funded by the French National Agency for Research (ANR), was precisely devoted to understand the adaptation mechanisms driving the reorganization of bacterial communities in response to petroleum in coastal sediments. In this special issue, the scientists involved in the DECAPAGE project present their contribution for understanding the microbial ecology in hydrocarbon-polluted mudflat sediments. The special issue also includes articles from scientists involved in other projects and programs in order to enlarge the topic to diverse ecosystems, to different biological organization levels from microbial and macrobenthic communities to bacterial populations, and addressing remediation strategies as well. Thus, the 15 articles compiled in this special issue explore diverse facets of the microbial ecology of hydrocarbon-polluted coastal sediments. The article of Acosta-Gonzalez et al. (2015) reviews the impact of the Prestige oil spill, an accident that occurred in 2002 at the Responsible editor: Philippe Garrigues