Organic matter production and recycling in marine biofilm developing on common and new plastics.

To face the recent pandemic and comply with international legislation, new plastic objects (surgical masks, nitrile gloves, compostable plastics) have been produced, with a significant increase of their input into the marine environment, together with other common plastics. Given that floating plastic provides a suitable surface for settlement of micro-organism, biofilm accretion was studied in laboratory experiments. The characteristics of biofilm in terms of organic matter production and recycling were evaluated under natural and forced conditions, some of them resembling anthropogenic-affected states (eutrophication) and others environmental variability (darkness and oligotrophy). Under natural conditions, the different plastics, due to their structure and composition, hosted different biofilms. Thicker biofilm was observed on surgical mask and compostable plastic (organic carbon maxima of 35.0 ± 4.7 µg cm-2 and 4.3 ± 0.8 µg cm-2, respectively). Compostable plastic hosted a higher carbohydrate quantity than polyethylene terephthalate, polystyrene and nitrile (on average 8.0 ± 0.8 µg cm-2 vs 3.6 ± 1.6 µg cm-2 for the others). The multi-layer structure of masks and the composition of compostable plastic were the main factors responsible for these differences. Polystyrene and nitrile hosted a higher photoautotrophic biomass, with chlorophyll-a maxima higher than 50 µg cm-2 vs values lower than 10 µg cm-2 for compostable plastic. Inhibition of photosynthetic activity (darkness) allowed a greater biofilm mass, which in natural aphotic zone, may enhance the sinking of plastics. The large availability of carbon (eutrophication) allowed thicker biofilms, providing seawater of additional organic matter load. These biofilms could protect pathogenic organisms, especially on disposable protection equipment, allowing a larger spreading.

The allochthonous material input in the trophodynamic system of the shelf sediments of the Gulf of Tigullio (Ligurian Sea, NW Mediterranean).

The organic allochthonous material input in the benthic system of a NW Mediterranean shelf area was studied using a three-pronged approach, focusing firstly on the evaluation of the sedimentary stable isotope ratios and organic matter (OM) composition, then on the OM recycling processes performed by the microbial organisms, and finally on the potential trophic relationships between the macrobenthic organisms. The highest allochthonous signal, indicating continental input, was observed within the 50-m isobath, while at the 80-m isobath the marine signal was higher, pointing to a rather low continental influence approximately 5 km from the shore. Heavier rainfall, often generating abrupt allochthonous inputs by river outfalls, led to a wider spread of fine sediment particles. Carbohydrates were the compounds that best represented the continental input and these compounds were associated with potential recycling activities by microbiota, pointing to the entry of these C-containing allochthonous materials into the microbial food web. The macrofaunal deposit-feeders used sedimentary OM characterised by a continental signature as a food source, although the isotopic ratios of the organisms also pointed to selective feeding on materials that had a marine signature, especially at our offshore sampling stations. Predators fed on deposit- or suspension-feeders, with a potential selection of the latter during the highest inputs of continental materials occurring in winter.

Linking environmental forcing and trophic supply to benthic communities in the Vercelli Seamount area (Tyrrhenian Sea).

Seamounts and their influence on the surrounding environment are currently being extensively debated but, surprisingly, scant information is available for the Mediterranean area. Furthermore, although the deep Tyrrhenian Sea is characterised by a complex bottom morphology and peculiar hydrodynamic features, which would suggest a variable influence on the benthic domain, few studies have been carried out there, especially for soft-bottom macrofaunal assemblages. In order to fill this gap, the structure of the meio-and macrofaunal assemblages of the Vercelli Seamount and the surrounding deep area (northern Tyrrhenian Sea - western Mediterranean) were studied in relation to environmental features. Sediment was collected with a box-corer from the seamount summit and flanks and at two far-field sites in spring 2009, in order to analyse the metazoan communities, the sediment texture and the sedimentary organic matter. At the summit station, the heterogeneity of the habitat, the shallowness of the site and the higher trophic supply (water column phytopigments and macroalgal detritus, for instance) supported a very rich macrofaunal community, with high abundance, biomass and diversity. In fact, its trophic features resembled those observed in coastal environments next to seagrass meadows. At the flank and far-field stations, sediment heterogeneity and depth especially influenced the meiofaunal distribution. From a trophic point of view, the low content of the valuable sedimentary proteins that was found confirmed the general oligotrophy of the Tyrrhenian Sea, and exerted a limiting influence on the abundance and biomass of the assemblages. In this scenario, the rather refractory sedimentary carbohydrates became a food source for metazoans, which increased their abundance and biomass at the stations where the hydrolytic-enzyme-mediated turnover of carbohydrates was faster, highlighting high lability.

Urbanised beaches of the Ligurian coastal area (NW Mediterranean): a classification based on organic-matter characteristics and hydrolytic enzymatic activities.

The beaches of Liguria have been intensively affected by human activities for over a century, transforming nearly the entire coastline from natural to urbanised and significantly upsetting beach ecological properties. The present study aims to investigate 9 Ligurian beaches characterised by different degree of urbanisation, to test if and to what extent the organic-matter (OM) recycling processes can be linked to the human activity. Swash zone sediment, sampled during the spring-summer-autumn period, when the anthropogenic influence is at its maximum due to tourism, was analysed for OM features and recycling processes. Multivariate statistical analyses showed that huge amounts of detrital OM accumulated in the more urbanised sites, where the anthropogenic influence was at its peak, deriving from higher inhabitant number and density, from the presence of crowded roads very near to the swash zone and sewage treatment plants. The presence of torrent outlets on the beaches provided further OM accumulation. Lipids, carbohydrates and degraded autotrophic pigments were the OM fractions mainly responsible of the differentiation, and rather constant, high labile phosphorus contents were found in the more urbanised sites. The high activity values of the hydrolytic enzymes indicate the response of the microbial system to the OM accumulation in the urban sites. However, a decoupling of the trends of some enzymatic activities (namely glucosidase and lipase) and their target OM was observed in the highly urbanised conditions.

Organic matter features, degradation and remineralisation at two coastal sites in the Ligurian Sea (NW Mediterranean) differently influenced by anthropogenic forcing.

Organic matter (OM) features, degradation and remineralisation were studied in the seawater of a natural coastal site (Marine Protected Area of Portofino) and at an urbanised coastal site (Quarto, Genoa city) of the Ligurian Sea. The accumulation of low trophic value OM and the persistence of phytoplanktonic biomass throughout the year were observed only at the urbanised site. Efficient OM degradation and remineralisation via high-activity (two times higher than at the Portofino site) hydrolytic enzymatic activities (alkaline phosphatase and leucine aminopeptidase) were recorded. This active degradation indicated a generally good resistance of the Quarto system to environmental pressures (coastal inputs and anthropogenic influence). However, the high potential release of recycled inorganic nutrients and the favourable environmental conditions (i.e. higher seawater temperature at the Quarto site and allochthonous inputs), could encourage unpredictable development of the autotrophic fraction, including an already observed dystrophic blooming of toxic microalgae.

Organic matter recycling in a beach environment influenced by sunscreen products and increased inorganic nutrient supply (Sturla, Ligurian Sea, NW Mediterranean).

The beaches are sites where the human influence may be strong and the beach ecosystems have often shown a high sensibility to environmental alterations. These zones may be affected by a large series of anthropogenic-derived pressures, such as unbalanced inorganic nutrient input, that may cause anomalous development of primary production, altering the structure of the trophic webs. Furthermore, the utilisation of cosmetic sunscreen products is reaching unexpected levels, thus assuming a potentially important as well as unknown role in the contamination of marine environments. The present study was planned to test the response of the beach ecosystem to increases in inorganic nutrients (nitrate and phosphate) and to the input of a widely used cosmetic sunscreen product. A short-term laboratory experiment was carried out on microsystems consisting of sediments and seawater from the swash zone of a Ligurian city beach (Sturla). The processes related to organic matter (OM) recycling and some microbial food web components (bacteria and micro-autotrophic organisms) were analysed. The multivariate statistical analysis of the results showed that the increase in inorganic nutrients and sunscreen caused only a transient alteration in the OM recycling processes in the seawater. The sedimentary processes, instead, were different in the different systems, although starting from the same condition. In the sediment, surprisingly, an increase in inorganic nutrients did not lead to an increase in the primary biomass nor to significantly higher bacterial abundance, while the sunscreen caused increased OM recycling, especially devoted to protein and lipid mobilisation, supporting a growing bacterial and autotrophic community by reducing the bottom-up pressure. Additional toxicity tests performed on protozoa highlighted that, while the inorganic nutrients seemed to show no effects, sunscreen decreased the protozoan viability, thus likely favouring microautotrophic and bacterial increases by reducing the top-down pressure.

Characteristics of the mesophotic megabenthic assemblages of the vercelli seamount (north tyrrhenian sea).

The biodiversity of the megabenthic assemblages of the mesophotic zone of a Tyrrhenian seamount (Vercelli Seamount) is described using Remotely Operated Vehicle (ROV) video imaging from 100 m depth to the top of the mount around 61 m depth. This pinnacle hosts a rich coralligenous community characterized by three different assemblages: (i) the top shows a dense covering of the kelp Laminaria rodriguezii; (ii) the southern side biocoenosis is mainly dominated by the octocorals Paramuricea clavata and Eunicella cavolinii; while (iii) the northern side of the seamount assemblage is colonized by active filter-feeding organisms such as sponges (sometimes covering 100% of the surface) with numerous colonies of the ascidian Diazona violacea, and the polychaete Sabella pavonina. This study highlights, also for a Mediterranean seamount, the potential role of an isolated rocky peak penetrating the euphotic zone, to work as an aggregating structure, hosting abundant benthic communities dominated by suspension feeders, whose distribution may vary in accordance to the geomorphology of the area and the different local hydrodynamic conditions.

On the quantitative distribution and community structure of the meio and macrofaunal communities in the coastal area of the Central Adriatic Sea (Italy).

Many coastal areas have served as repositories of different anthropogenic and naturally induced organic material and nutrients. The major sources thereof are riverine inputs which strongly influence the spatial and temporal distribution of benthic communities. In this study, the benthic foraminiferal, meiofaunal, and macrofaunal colonies in front of three rivers in a poorly known, but environmentally valuable, area of the Central Adriatic Sea have been examined concurrently. The physico-chemical parameters of bottom water and sediment characteristics were determined in order to characterize both the sediment-water interface and the benthic environments. Although changes in the biota are neither univocal nor unidirectional, a moderate influence of riverine input on the different communities' components can be inferred. The most affected taxa are foraminifera and copepods and, to a lesser extent, meiofaunal polychaetes and platyhelminthes. These results are also tested by the ABC curves, which reveal that the macrofaunal communities closest to the river mouths are moderately disturbed. This integrated investigation documents, for the first time, how benthic communities can be used as an early warning indicator with which to monitor the health quality of a coastal ecosystem.

Organic matter characterisation and turnover in the sediment and seawater of a tourist harbour.

A survey of a Ligurian tourist harbour was carried out during winter 2006 and summer 2007 in order to study the organic matter (OM) turnover through extracellular enzymatic activity. Seawater and sediments were sampled at six stations, three inside the port boundaries, one outside the port and two in an area influenced by the outflow of a minor river (Boate). The seawater showed OM turnover times similar to other oligo-mesotrophic coastal areas, and low concentrations of chlorophyll-a and inorganic nutrients. The sediments, instead, revealed high OM loads and a predominance of proteolysis. A significant reduction of the OM loads was observed in the outside station, indicating that the OM accumulation was due to the structures and activities of the harbour and to the Boate influence. The OM biotic recycling via enzymatic activity was enhanced especially during summer. Although the carbohydrates were probably highly refractory, their turnover was notably faster, due to glycolytic enzymatic activity that was enhanced more than the proteolytic in both the sediment and in the seawater. This suggested that the removal and recycling of OM were potentially efficient, and prevented the shift to eutrophication of the Rapallo harbour area.