Characterization and comparison of microbial communities from different tourist ports in Mediterranean Sea and evaluation of applicability of bioremediation treatments

Marine ecosystems represent the greatest volume of the biosphere and the largest surface of the planet. They are home to an enormous diversity of animals, plants and microbes and are crucially important resource for fishing, transport, mining and recreation. Humans have been dependant on the seas and oceans for many millennia and have used the coastal waters as a prehistoric resource for food and expansion around the planet (Moore et al., 2013). Coastal region are frequently areas of great natural beauty and are used extensively for recreation and tourism as reflected in the mass migration of people to the coasts in the holiday seasons (Golyshin et al., 2003). The Mediterranean has become one of the most demanded destinations for organized touristic routes (increasing cruising market) and "self-made" ones (boating and chartering). Despite the strict link between tourism development in coastal areas and port facilities, the sector growth has not been sustained neither by an adequate expansion nor by an adaptation of the ports. Ports have a decisive role in the development of coastal areas and the risk of impact of infrastructures construction and maritime traffic on the coastal zone is high. Ports are part of the logistics chain and the transport networks with a decisive role in the development of coastal areas. However, the risk of impact of infrastructures construction and maritime traffic on the coastal zone is high. The problem with any port expansion is the balance between environmental and social-economic issues (sustainable development). In fact, if on one hand the development of infrastructures has to take into account environmental impact and restoration to ecological standards, on the other hand, denial of port expansion for environmental reasons may favour other competing ports. Due to their strategic location between sea and land, ports are particularly critical environments as they can receive pollution coming from land, ships and from the port facilities themselves. Furthermore, ports are not closed systems and their pollution may impact large parts of the adjacent coastal areas. Specifically, pollution by petroleum hydrocarbons is one of the major environmental problems in ports and it is mainly associated with the heavy ship/boat traffic and the related facilities located in these areas. The ship transport in ports is powered by diesel. The present study was carried out in the framework of the MAPMED project (Management of Port areas in the Mediterranean Sea Basin). The general objective of the project was to improve the environmental sustainability of tourist coastal areas in the Countries of the Mediterranean Sea Basin through the promotion of a long term cooperation between Institutional Authorities and the scientific community and, at a more specific level, to optimize, validate and transfer tools to guide Institutional Authorities in the sustainable management of tourist ports/harbours with regard to monitoring and reduction of hydrocarbon pollution. Strategies for cleaning up hydrocarbon pollution are greatly affected by a variety of factors, such as type of oil, characteristics of the spill site, and occasionally political considerations. A number of approaches and technologies have been developed for controlling oil pollution in marine environments. Bioremediation has emerged as one of the most promising treatment options for oil removal since its successful application after the 1989 Exxon Valdez spill. The general objective of this work was to evaluate and compare the applicability of different bioremediation approaches of seawaters and sediments in Mediterranean tourist ports. Particularly, it was directed to contribute to the answer to two following main questions: -Do different tourist ports share the same bacterial communities? -Do bioremediation strategies have similar applicability in different tourist port areas? The specific aims of the present study were: 1. Definition and comparison of the pollution status of seawater. 2. Comparison of the bacterial communities in seawater. 3. Characterization of the dominant cultivable hydrocarbon-degrading bacteria from seawater and sediments. 4. Comparison of the effects of biostimulation treatment on bacterial communities in seawater at laboratory scale. 5. Comparison of the effect of bioaugmentation treatments on PAH degradation in sediments at laboratory scale. Three tourist ports located across the Mediterranean Sea were selected as case study sites representative tourist harbours in the Basin: Cagliari (Sardinia, Italy) in the western part, El Kantaoui (Tunisia) in the central part, and Heraklion (Crete, Greece) in the eastern part. Beside their geographic position, port selection was also based on other different elements, such as categories of maritime traffic, port dimension and existing information on pollution. The maritime traffic inside the three tourist ports is represented by recreational boats, passenger ships and fishing vessels. In addition to the marine traffic, the major pollution sources related to the three port areas are wastewater discharges into the sea, river mouth, fuelling stations, and fishing activities. Data demonstrated that Cagliari port was characterized by a high level of eutrophication. Coherently with the high nutrient load, the viable title of heterotrophs was one-log higher in the seawater of Cagliari port when compared with values found in the other ports. The structure of the microbial communities in seawater from Cagliari and El Kantaoui were more similar to one another than the others while Heraklion presented different community structures. During the biostimulation treatment in seawater microcosms, comparable degradation kinetics were found for Cagliari and Heraklion sites. Furthermore, nutrient amendments in El Kantaoui microcosms resulted in a two-fold increase in the degradation rates as compared to the other two port areas. The structures of the bacterial communities of El Kantaoui were more homogenous than those from Cagliari, while Heraklion presented a moderate change in community structures during bioremediation treatment. Moreover, different community structures were found for the three sites at the end of the treatment. The community of cultivable degraders from seawater of the Cagliari port was dominated by copiotrophic bacteria belonging to the genus Pseudomonas whereas the majority of the isolates from Port El Kantaoui were Alcanivorax. Both OHCBs and non-professional hydrocarbonoclastic bacteria were equally represented in the community from Heraklion port. The autochthonous population from the sediments of El Kantaoui does not possess the metabolic routes necessary to metabolize BaP being the addition of an allochthonous strain a successful strategy for promoting BaP degradation. Thus, a selectivity of the bioaugmentation treatments was demonstrated both in terms of typology of PAHs and sediments.