Assessment of marine litter in the Western Adriatic Sea and its impact on marine biota

Due to its environmental, safety, health and socio-economic impacts, marine litter has been recognized as a 21st century global challenge, so that it has been included in Descriptor 10 of the EU MSFD. For its morphological features and anthropogenic pressures, the Adriatic Sea is very sensitive to the accumulation of debris, but data are inconsistent and fragmented. This thesis, in the framework of DeFishGear project, intents to assess marine litter on beaches and on seafloor in the Western Adriatic sea, and test if debris ingestion by fish occurs. Three beaches were sampled during two surveys in 2015. Benthic litter monitoring was carried out in the FAO GSA17 during fall 2014, using a rapido trawl. Litter ingestion was investigated through gut contents analysis of 260 fish belonging to 8 commercial species collected in Western Gulf of Venice. Average litter density on beaches was 1.5 items/m2 during spring, and decreased to 0.8 items/m2 in summer. Litter composition was heterogeneous and varied among sites, even if no significant differences were found. Most of debris consisted of plastic sheets, fragments, polystyrene pieces, mussels nets and cottons bud sticks, showing that sources are many and include aquaculture, land-based activities and local users of beaches. Average density of benthic litter was 913 items/Km2 (82 Kg/Km2). Plastic dominated in terms of numbers and weight, and consisted mainly of bags, sheets and mussel nets. The highest density was found close to the coast, and sources driving the major differences in litter distribution were mussel farms and shipping lanes. Litter ingestion occurred in 47% of examined fish, mainly consisting of fibers. Among species, S. pilchardus swallowed almost all debris categories. Findinds may provide a baseline to set the necessary measures to manage and minimize marine litter in the Western Adriatic region and to protect aquatic life from plastic pollution, even accounting the possible implications on human health.

Characterization of microplastics ingested by marine benthos - a methodological and field-experimental study

Microplastics have become ubiquitous pollutants in the marine environment. Ingestion of microplastics by a wide range of marine organisms has been recorded both in laboratory and field studies. Despite growing concern for microplastics, few studies have evaluated their concentrations and distribution in wild populations. Further, there is a need to identify cost-effective standardized methodologies for microplastics extraction and analysis in organisms. In this thesis I present: (i) the results of a multi-scale field sampling to quantify and characterize microplastics occurrence and distribution in 4 benthic marine invertebrates from saltmarshes along the North Adriatic Italian coastal lagoons; (ii) a comparison of the effects and cost-effectiveness of two extraction protocols for microplastics isolation on microfibers and on wild collected organisms; (iii) the development of a novel field- based technique to quantify and characterize the microplastic uptake rates of wild and farmed populations of mussels (Mytilus galloprovincialis) through the analysis of their biodeposits. I found very low and patchy amounts of microplastics in the gastrointestinal tracts of sampled organisms. The omnivorous crab Carcinus aestuarii was the species with the highest amounts of microplastics, but there was a notable variation among individuals. There were no substantial differences between enzymatic and alkaline extraction methods. However, the alkaline extraction was quicker and cheaper. Biodeposit traps proved to be an effective method to estimate mussel ingestion rates. However their performance differed significantly among sites, suggesting that the method, as currently designed, is sensible to local environmental conditions. There were no differences in the ingestion rates of microplastics between farmed and wild mussels. The estimates of microplastic ingestion and the validated procedures for their extraction provide a strong basis for future work on microplastic pollution.

Monitoring of macro- and microlitter in the Venice lagoon and coastal area

Marine litter and plastics are a significant and growing marine contaminant that has become a global problem. Macrolitter is subject to fragmentation and degradation due to physical, chemical and biological processes, leading to the formation of micro-litter, the so-called microplastics. The purpose of this research is to assess marine litter pollution by using remote sensing tools to identify areas of macrolitter accumulation and to evaluate the concentrations of microplastics in different environmental matrices: water, sediment and biota (i.e. mussels and fish) and to contribute to the European project MAELSTROM (Smart technology for MArinE Litter SusTainable RemOval and Management). The aim is to monitor the presence of macro- and microlitter at two sites of the Venice coastal area: an abandoned mussel farm at sea and a lagoon site near the artificial Island of Sacca Fisola; The results showed that both study areas are characterised by high amounts of marine litter, but the type of observed litter is different. In fact, in the mussel farm area, most of the litter is linked to aquaculture activities (ropes, nets, mooring blocks and floating buoys). In the Venice lagoon site, the litter comes more from urban activities and from the city of Venice (car tyres, crates, wrecks, etc.). Microplastics is present in both sites and in all the analysed matrices. Generally, higher microplastics concentrations were found at Sacca Fisola (i.e., in surface waters, mussels and fish). Moreover, some differences were also observed in shapes and colours comparing the two sites. At Sacca Fisola, white irregular fragments predominate in water samples, blue filaments in sediment and mussels, and transparent irregular fragments in fish. At the Mussel Farm, blue filaments predominate in water, sediment and mussels, while flat black fragments predominate in fish. These differences are related to the different types of macrolitter that characterised the two areas.