Critical Thinking

Augusta 2017). The importance of increase knowledges about

Augusta harbour, located in the MSFD sub-region Ionian
in Central Mediterranean Sea, represents a strategic site to improve starting
data for the Monitoring Plane related to the National Sub-programme Module 5T
and to provide data about other descriptor of MSFD as D1 (biodiversity), D2
(non-indigenous), D6 (sea floor integrity), D8(contaminants) and D10 (marine
litter).

Sediments grain size analysis, testified that the area
is mainly characterized by fine texture especially in the norther and southern
part, this may be due to its particular conformation close by artificial dams
that make the area scarcely affected by active currents (Romano
et al. 2013; Sprovieri et al. 2007). This particular hydrodinamism seems
also influenced the distribution of plastic litter, showing the
highest abundances in the most southern (Transect 1) and most northern
(Transect 4) areas. Indeed, as reported in several studies, the distribution of
plastic debris is closely linked with geomorpholical and hydrodynamic
characters of area, and, with the exception of some
accumulation zones in the open sea, is most abundant in shallow
waters or bay than continental shelf (Alomar
et al. 2006; Katsanevakis, 2008). Understanding the main causes,
the distribution and the sources of microplastic pollution, at different
spatial scales, is therefore essential to develop appropriate policies and lows,
in order to carry out a sustainable management of marine resources, especially
in coastal environments (Pasquini et al. 2016). At present, microplastics in
the marine environment represents one of emerging problems in the world. This
type of pollution, creating growing concerns among governments, scientists and
organizations all over the world; represents a major threat to environmental protection
and human security (Seltenrich 2017). The importance of increase knowledges about
to this current issue, was also highlighted by indicator 10.1.3 of MSFD, that
aims to find information on trends in the quantity, distribution and, if
possible, in the composition of microparticles, in particular microplastics
(Auta et al. 2017; Galgani et al. 2013, 2014). Microplastic abundance found in
this study area resulted lower than that recorded in other studies conducted in
shallow water as Aeolian archipelago where a maximum abundant of 1037 debris kg-1
dry sediment; was reported (Fastelli et al. 2016). Augusta plastics were also
lower than those reported in three ports of Balearic Islands as Andratx; Es Port
and Santa Maria, where a maximum abundance of 250; 160 and 100 debris kg-1
dry sediment was detected (Alomar et al. 2016). Also in Grand Harbour of La
Valletta the abundance of plastics found (59 debris kg-1 dry, 35 of
which belonging to microplastics) were higher than Augusta harbour (Romeo et
al. 2015). Nevertheless, microplastics found in Augusta was also higher than those
reported in other similar study conducted in the United Kingdom (Thompson et
al. 2009) and Singapore (Ng and Obbard 2006), where 3 and 8 plastic debris
fragments per kg of dried sediments were respectively recorded. The significant
negative correlations found in this study among plastic debris vs biodiversity and benthic indices
confirm as plastics in marine ecosystem represent a threat for biodiversity (Auta
et al. 2017). This may create
concern, indeed as reported in numerous studies, microplastic can be available
from a lot of invertebrate, causing both dead for suffocation of organism and
transport of contaminant along food chain (Avio et al. 2016; Green et al. 2016;
Van Cauwenberghe et al. 2015). Despite growing
international attention, the accumulation of these materials in the environment
continues to be high, both because of the increasing world production of
plastics and the continued improper disposal of plastic waste. In examined
sediments, all categories of plastics were found, among these, microplastic
resulted the most abundant. This could derive from both an indiscriminate
release in sea of any typology of plastic and from the lack of appropriate
national laws that limit its consumption and release (Browne
et al. 2011; Dubaish and Liebezeit 2013; Fendall and Sewell
2009; Thomson et al. 2004).

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Biotic indices are widely used in ecological studies
in order to understand the relationships between biodiversity and environmental
disturbance and to assess the environmental status of waters (van der Linden et
al. 2016). Their recognised importance is underlined, also, in MSFD, in which D6
is focused on the integrity of the seafloor and
safeguard 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 a
slight degree of environmental degradation. These findings agree with previous
studies, 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 of
stability of benthos community, also confirmed by values of biodiversity
indices that resulted high if confronted to other harbours of Mediterranean Sea
subject to similar anthropogenic pressure, as Malta (Romeo et al. 2015),
Trieste (Solis-Weiss et al. 2004) and Napoli (Bergamin et al. 2009). The
presence of six non-indigenous species, underlines the peculiar role of harbour
as 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-indigenous
species as marine traffic (either fouling or ballast water), mariculture and
interoceanic canals, species found in Augusta harbour are linked to shipping: B. bairdi, B. pharaonis, P. anomala
and K. dorsobranchialis (D’Alessandro
et al. 2015; Katsanevakis et al. 2012; ; Sarà et al., in press; Streftaris et
al. 2005) and to natural expansion from Canals: P. unibranchia and N.
aberans (Çinar et al. 2014). Among Polychaeta, three first records for
Ionian 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 be
related to the active marine traffic of the area, being one of most important
petrol-chemical pole of Ionian Sea. Our study testifies a correlation between
the structure of benthic community and the environmental status of the harbour
(Gray and Elliott 2009; Simboura et al. 2000;). Despite the high concentration
of human activities in the area, benthic indices calculated highlighted a
slightly disturbed classification. However, a general lesser stressed status
was recorded with the increasing of depth, as confirmed by statistical analysis
that ascribes the difference between depths to major abundance of opportunistic
species 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 are
the main source of organic and metallic pollutants (Cabrini et
al. 2017). The MSFD considers the concentration of contaminants in D8 and
imposes that their levels must not cause polluting effects. Abundance of heavy
metals in Augusta harbour seems to be related to human activities and to the presence
of rivers in this area, which receive industrial effluents, municipal
wastewater effluents and stack emissions from smelting operations and
fossil-fuel combustion (Nriagu 1980). Zn, Cr and Cu were trace elements that
showed the highest abundance in this study area. The main contributors to
worldwide 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 main
responsible of the recycling of metals, they constitute the main export route
of heavy metals and pollutants for terrestrial trophic webs causing human
health risks. (Fowler, 1982). Statistical analysis, also highlight as heavy
metal explicate their negative effects on biodiversity indices and macrobenthos
assemblage, facilitating this increase of opportunistic and
alien species (Gray and Delaney 2008; Qu et al. 2010;
Takarina at al., 2011).

As regard organic
pollutants, anthracene, benzo(b)fluoranthene and fluoranthene were the most
abundant PAHs. These hydrocarbons can become dangerous for human safety, especially
if they enter in food chain since some of PAHs and their metabolites can form
DNA adducts and thus induce mutations (Readman et al. 2002). However, PAH
compounds showed no worrying concentrations in the investigated area, even if
an increment of values was recorded in the southern part of the Rade. The
distribution of trace elements and contaminants within the study area, showing
highest abundance along Transect 1, testifies that their
main 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 in
Trieste (Solis-Weiss et al. 2004), Malta (Romeo
et 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 traffic
and the small neighbouring
rivers that enter in the Augusta Rade. Indeed, despite the restriction of TBT (Reg.
EC 782/2003) and the decrement of contamination level, the contaminated
sediments continue to act as source (Ritsema 1994; Stäb et al. 1995) and the
release of BTs still persists into terrestrial and aquatic environments at
levels considered chronically toxic for most organisms (Stäb et al. 1995). The
high concentrations of BT found in this study resulted similar to those
measured in sediments of heavily industrialized areas and harbours around the
world (Berto et al. 2007; Hoc 2003; Romeo et al. 2015). Moreover, considering
the EQS value reported by the European Directives (2000/60/EC, 2008/105/EC and
2013/39/EU) for the priority hazardous substance, TBT concentrations found in the
Augusta Rade sediments exceeds in the most of sampling sites. 

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