Augusta harbour, located in the MSFD sub-region Ionianin Central Mediterranean Sea, represents a strategic site to improve startingdata for the Monitoring Plane related to the National Sub-programme Module 5Tand to provide data about other descriptor of MSFD as D1 (biodiversity), D2(non-indigenous), D6 (sea floor integrity), D8(contaminants) and D10 (marinelitter).Sediments grain size analysis, testified that the areais mainly characterized by fine texture especially in the norther and southernpart, this may be due to its particular conformation close by artificial damsthat make the area scarcely affected by active currents (Romanoet al. 2013; Sprovieri et al.
2007). This particular hydrodinamism seemsalso influenced the distribution of plastic litter, showing thehighest abundances in the most southern (Transect 1) and most northern(Transect 4) areas. Indeed, as reported in several studies, the distribution ofplastic debris is closely linked with geomorpholical and hydrodynamiccharacters of area, and, with the exception of someaccumulation zones in the open sea, is most abundant in shallowwaters or bay than continental shelf (Alomaret al. 2006; Katsanevakis, 2008). Understanding the main causes,the distribution and the sources of microplastic pollution, at differentspatial scales, is therefore essential to develop appropriate policies and lows,in order to carry out a sustainable management of marine resources, especiallyin coastal environments (Pasquini et al. 2016).
At present, microplastics inthe marine environment represents one of emerging problems in the world. Thistype of pollution, creating growing concerns among governments, scientists andorganizations all over the world; represents a major threat to environmental protectionand human security (Seltenrich 2017). The importance of increase knowledges aboutto this current issue, was also highlighted by indicator 10.1.3 of MSFD, thataims to find information on trends in the quantity, distribution and, ifpossible, in the composition of microparticles, in particular microplastics(Auta et al. 2017; Galgani et al.
2013, 2014). Microplastic abundance found inthis study area resulted lower than that recorded in other studies conducted inshallow water as Aeolian archipelago where a maximum abundant of 1037 debris kg-1dry sediment; was reported (Fastelli et al. 2016). Augusta plastics were alsolower than those reported in three ports of Balearic Islands as Andratx; Es Portand Santa Maria, where a maximum abundance of 250; 160 and 100 debris kg-1dry sediment was detected (Alomar et al. 2016). Also in Grand Harbour of LaValletta the abundance of plastics found (59 debris kg-1 dry, 35 ofwhich belonging to microplastics) were higher than Augusta harbour (Romeo etal. 2015).
Nevertheless, microplastics found in Augusta was also higher than thosereported in other similar study conducted in the United Kingdom (Thompson etal. 2009) and Singapore (Ng and Obbard 2006), where 3 and 8 plastic debrisfragments per kg of dried sediments were respectively recorded. The significantnegative correlations found in this study among plastic debris vs biodiversity and benthic indicesconfirm as plastics in marine ecosystem represent a threat for biodiversity (Autaet al. 2017). This may createconcern, indeed as reported in numerous studies, microplastic can be availablefrom a lot of invertebrate, causing both dead for suffocation of organism andtransport of contaminant along food chain (Avio et al. 2016; Green et al. 2016;Van Cauwenberghe et al.
2015). Despite growinginternational attention, the accumulation of these materials in the environmentcontinues to be high, both because of the increasing world production ofplastics and the continued improper disposal of plastic waste. In examinedsediments, all categories of plastics were found, among these, microplasticresulted the most abundant. This could derive from both an indiscriminaterelease in sea of any typology of plastic and from the lack of appropriatenational laws that limit its consumption and release (Browneet al. 2011; Dubaish and Liebezeit 2013; Fendall and Sewell2009; Thomson et al. 2004). Biotic indices are widely used in ecological studiesin order to understand the relationships between biodiversity and environmentaldisturbance and to assess the environmental status of waters (van der Linden etal.
2016). Their recognised importance is underlined, also, in MSFD, in which D6is focused on the integrity of the seafloor andsafeguard of benthic ecosystems. The dominance in the harbour of opportunistic(e.g.: C.
gibba, P. fauveli and N. aberans)and tolerant (e.g.
: A. pseudoarticolata) species suggests aslight degree of environmental degradation. These findings agree with previousstudies, that reported similar communities, and which could be ascribable to”heterogeneous communities” described by Peres and Picard 1989 ( Crocetta 2009;Romano et al.
2013). However, our study testifies a general situation ofstability of benthos community, also confirmed by values of biodiversityindices that resulted high if confronted to other harbours of Mediterranean Seasubject to similar anthropogenic pressure, as Malta (Romeo et al. 2015),Trieste (Solis-Weiss et al. 2004) and Napoli (Bergamin et al. 2009). Thepresence of six non-indigenous species, underlines the peculiar role of harbouras hot-point alien species (D’Alessandro et al. 2015; Occhipinti et al. 2011).
Even though there are main vectors for the introduction of the non-indigenousspecies as marine traffic (either fouling or ballast water), mariculture andinteroceanic canals, species found in Augusta harbour are linked to shipping: B. bairdi, B. pharaonis, P. anomalaand K. dorsobranchialis (D’Alessandroet al. 2015; Katsanevakis et al.
2012; ; Sarà et al., in press; Streftaris etal. 2005) and to natural expansion from Canals: P.
unibranchia and N.aberans (Çinar et al. 2014). Among Polychaeta, three first records forIonian Sea, L. geldiaij(Carrera-Parra, Çinar and Dagli, 2010), A.bidentata (D’Alessandro et al. 2014) and P.
anomala (Gravier 1900) were also recorded. These data could berelated to the active marine traffic of the area, being one of most importantpetrol-chemical pole of Ionian Sea. Our study testifies a correlation betweenthe structure of benthic community and the environmental status of the harbour(Gray and Elliott 2009; Simboura et al. 2000;). Despite the high concentrationof human activities in the area, benthic indices calculated highlighted aslightly disturbed classification. However, a general lesser stressed statuswas recorded with the increasing of depth, as confirmed by statistical analysisthat ascribes the difference between depths to major abundance of opportunisticspecies at lower depth (C.
gibba and P. fauveli) and of sensible species (A. pseudoarticolata) in deeper stations.
In general, benthic community seems to have adapted to environmental stress,showing a well-structured assemblage (Romano et al. 2013).Marine sediments arethe main source of organic and metallic pollutants (Cabrini etal. 2017). The MSFD considers the concentration of contaminants in D8 andimposes that their levels must not cause polluting effects.
Abundance of heavymetals in Augusta harbour seems to be related to human activities and to the presenceof rivers in this area, which receive industrial effluents, municipalwastewater effluents and stack emissions from smelting operations andfossil-fuel combustion (Nriagu 1980). Zn, Cr and Cu were trace elements thatshowed the highest abundance in this study area. The main contributors toworldwide anthropogenic emissions of these metal are the fossil fuel combustion,production of commercial metal, urban drainage and wastes (Cabrini et al.
2017;Christensen et al. 1979). Benthic invertebrates do to their poor locomotion,are strongly subject to heavy metals present in the sediments (Qu et al. 2017). Moreover, being among the mainresponsible of the recycling of metals, they constitute the main export routeof heavy metals and pollutants for terrestrial trophic webs causing humanhealth risks. (Fowler, 1982). Statistical analysis, also highlight as heavymetal explicate their negative effects on biodiversity indices and macrobenthosassemblage, facilitating this increase of opportunistic andalien species (Gray and Delaney 2008; Qu et al.
2010;Takarina at al., 2011).As regard organicpollutants, anthracene, benzo(b)fluoranthene and fluoranthene were the mostabundant PAHs. These hydrocarbons can become dangerous for human safety, especiallyif they enter in food chain since some of PAHs and their metabolites can formDNA adducts and thus induce mutations (Readman et al. 2002). However, PAHcompounds showed no worrying concentrations in the investigated area, even ifan increment of values was recorded in the southern part of the Rade. Thedistribution of trace elements and contaminants within the study area, showinghighest abundance along Transect 1, testifies that theirmain input is attributable to industrial pole located in the southern sector.
Another distinct point of source is located in the northern part of the Rade,while the central part is the less influenced by contamination. In general,trace elements and PAHs values resulted lower compared to that observed inTrieste (Solis-Weiss et al. 2004), Malta (Romeoet al. 2015) and Napoli (Bergamin et al. 2009) harbours.Different results were recorded for the organotin contaminants (TBT, MBT, DBT),which showed the highest abundances in the central area of the Augusta harbour.
This peculiar situation may be due to the presence of a high maritime trafficand the small neighbouringrivers that enter in the Augusta Rade. Indeed, despite the restriction of TBT (Reg.EC 782/2003) and the decrement of contamination level, the contaminatedsediments continue to act as source (Ritsema 1994; Stäb et al. 1995) and therelease of BTs still persists into terrestrial and aquatic environments atlevels considered chronically toxic for most organisms (Stäb et al. 1995). Thehigh concentrations of BT found in this study resulted similar to thosemeasured in sediments of heavily industrialized areas and harbours around theworld (Berto et al.
2007; Hoc 2003; Romeo et al. 2015). Moreover, consideringthe EQS value reported by the European Directives (2000/60/EC, 2008/105/EC and2013/39/EU) for the priority hazardous substance, TBT concentrations found in theAugusta Rade sediments exceeds in the most of sampling sites.