Comparative microplastic load in two decapod crustaceans Palinurus elephas (Fabricius, 1787) and Nephrops norvegicus (Linnaeus, 1758).

The present work compares microplastics (MPs) contamination in two charismatic crustaceans: European spiny lobster Palinurus elephas and langoustine Nephrops norvegicus. Samples (P. elephas n = 14; N. norvegicus n = 15) were collected between 76 and 592 m depth, from four sites in west Sardinia, Italy. An extraction protocol was applied on stomachs and intestines, separately, and over 500 particles were further characterized through µFT-IR. We document 100 % occurrence in specimens from both species, with P. elephas being significantly more contaminated (9.1 ± 1.75 vs. 3.2 ± 0.45 MPs individual-1), ingesting larger MPs with different polymeric composition. The scavenging-based feeding strategy of both species could explain such exposure to MPs, mostly derived by single-use plastic. The overall results highlight that both species are clearly affected by plastic pollution, being valuable bioindicators and charismatic species that could thus represent excellent flagship species for raising awareness toward the global issue of plastic in the marine environment.

Effects of Field Simulated Marine Heatwaves on Sedimentary Organic Matter Quantity, Biochemical Composition, and Degradation Rates.

Since rising temperature (T) will enhance biochemical reactions and coastal marine sediments are hotspots of carbon cycling, marine heatwaves' (MHWs') intensification caused by climate change will affect coastal biogeochemistry. We investigated the effects of MHWs on sediment organic matter (OM) in a nearshore locality (NW Sardinia, Mediterranean Sea) receiving an artificial warm water plume generating T anomalies of 1.5-5.0 °C. Sediments were collected before and after 3 and 11 weeks from the initial plume release. Both MHWs influenced sedimentary OM quantity, composition, and degradation rates, with major effects associated with the highest T anomaly after 3 weeks. Both MHWs enhanced sedimentary OM contents, with larger effects associated with the highest T anomaly. Phytopigment contents increased in the short term but dropped to initial levels after 11 weeks, suggesting the occurrence of thermal adaptation or stress of microphytobenthos. In the longer term we observed a decrease in the nutritional quality of OM and a slowdown of its turnover mediated by extracellular enzymes, suggestive of a decreased ecosystem functioning. We anticipate that intensification of MHWs will affect benthic communities not only through direct effects on species tolerance but also by altering benthic biogeochemistry and the efficiency of energy transfer towards higher trophic levels.

Environmental Status and Geomorphological Characterisation of Seven Black Coral Forests on the Sardinian Continental Shelf (NW Mediterranean Sea).

Marine animal forests are key mesophotic ecosystems that are under threat from increasing natural and human pressures. Despite the fact that various international agreements strive to preserve these fragile ecosystems, the environmental status of the majority of these animal-structured environments is unknown. Assessing their environmental status is the first step needed to monitor these essential habitats' health over time and include them within conservation and protection frameworks, such as the Marine Strategy Framework Directive. Based on Multibeam data and ROV footage, we characterized the geomorphological setting and evaluated the environmental status of seven black coral forests in the centre of the Western Mediterranean Sea, using the Mesophotic Assemblages Conservation Status (MACS) Index. The presence of two antipatharians, Antipathella subpinnata and Leiopathes glaberrima, characterized the seven investigated sites, dwelling on rocky substrate characterized by different environmental drivers (i.e., depth, slope of the substrate, terrain ruggedness, topographic positioning index, and aspect). From the combined evaluation of the associated benthic community status and the anthropogenic impacts affecting it, a "high" and "good" environmental status was assessed for five out of the seven studied black forests, with only two forests classified as having a "moderate" and "poor" status, respectively. Overall, our study showed a site-specific variability of mesophotic black coral forest status, explained by different biological community structures and environmental conditions mainly associated with morphological and anthropogenic factors.

Deep-Dwelling Populations of Mediterranean Corallium rubrum and Eunicella cavolini: Distribution, Demography, and Co-Occurrence.

Corallium rubrum and Eunicella cavolini are two octocorals, reported as co-occurring species in the deep rocky habitats of the Mediterranean Sea with a high hydrodynamic and moderate eutrophication. Their spatial distribution and demography in the deep sea are mainly affected by temperature and direct and indirect anthropogenic activities; however, knowledge of the factors that potentially influence their co-existence is scarce. This paper provides novel data on the distribution and demography of these two species, at depths between 50 and 290 m in the Western Mediterranean Sea, providing insights on their co-occurrence. Both species exhibited the highest population density at deeper sites (>150 m), showing an inverse size-density relation. Density values ranged from 0.03 colonies m-2 to 32 and 80 col. m-2 for yellow gorgonian and red coral, respectively. The two species co-occurred in 13% of the total frames examined, mostly dwelling between 120 and 160 m depth. Distance-based linear modeling (DistLM) emphasized that when co-occurring the variability of the two species' densities were significantly driven by the density-rather than the morphology (i.e., height)-of the other species. We stress the need for further studies to elucidate the possible mutual effects of suspension feeders and to test the role of different environmental factors potentially influencing inter-specific relationships.

Scattered accumulation hotspots of macro-litter on the seafloor: Insights for mitigation actions.

Marine litter is an ever-increasing problem that demands immediate reduction plans and mitigation actions that should act synergically to efficiently meet ambitious goals. Since the seafloor has been recognized as the major sink for marine debris, the study of litter accumulation dynamics represent a fundamental tool to evaluate possible removal actions. We analysed a 7 years (2013-2019) standardized data series collected along Sardinian fishing grounds through MEDiterranean International Trawl Survey, for which estimates of density and weight of seafloor macro-litter were calculated for over 707 hauls. Results show the absence of any temporal trend in seafloor macro-litter density and weight, but rather indicate a spatial and bathymetric segregation of different litter categories. Our data showed how different sources and physical features of macro-litter items (i.e., plastic and fishing gear, rubber, glass, metals, and cloth) led to spatially segregated accumulation hotspots. We also point out here how the identification of seafloor macro-litter hotspots using aggregated data that include plastic items could obscure the identification of other segregated but yet relevant hotspots of other macro-litter categories accumulated in the marine environment. These hotspots often occurred at shallower depths and closer to coastlines, thus representing potential spots where eventual future litter removal action could be prioritized.

Scattered accumulation hotspots of macro-litter on the seafloor: Insights for mitigation actions.

Marine litter is an ever-increasing problem that demands immediate reduction plans and mitigation actions that should act synergically to efficiently meet ambitious goals. Since the seafloor has been recognized as the major sink for marine debris, the study of litter accumulation dynamics represents a fundamental tool to evaluate future removal actions. We analysed a 7 years (2013-2019) standardized data series collected along Sardinian fishing grounds through MEDiterranean International Trawl Survey, for which estimates of density and weight of seafloor macro-litter were calculated over 707 hauls. Results show the absence of any temporal trend in seafloor macro-litter density and weight, but rather indicate a spatial and bathymetric segregation of different litter categories. Our data showed how different sources and physical features of macro-litter items (i.e., plastic and fishing gears, rubber, glass, metal and textile) led to spatially segregated accumulation hotspots. These hotspots often occurred at shallower depths and closer to coastlines, representing spots where future litter removal action could be prioritized. We also point out here how the identification of seafloor macro-litter hotspots using aggregated data that include plastic items could indeed hide the identification of hotspots of other less abundant but yet detrimental macro-litter categories accumulated in the marine environment.

Foraging of the sea urchin Paracentrotus lividus (Lamarck, 1816) on invasive allochthonous and autochthonous algae.

Attempts to control marine invasive alien species (IAS) with native predators gained contrasting results, so far. To explore the feasibility of this approach to control the invasive marine alga Caulerpa cylindracea, we investigated the foraging behaviour of the sea urchin Paracentrotus lividus on three native macroalgae (Ulva sp., Penicillus capitatus and Cystoseira compressa) and on C. cylindracea. The consumption rate of C. cylindracea fresh biomass resulted larger than that of the other algae, when offered separately or in combination. C. cylindracea, however, was not the most attractive food item. The larger consumption rates of C. cylindracea can be explained by its specific caloric content (as assessed by its biochemical composition) that is lower than that of the other algae. Our results confirm that P. lividus can feed on C. cylindracea, but do not fully support its use to control C. cylindracea, unless in conditions where this alga is largely dominant because of other factors.

Benthic Crustacean Digestion Can Modulate the Environmental Fate of Microplastics in the Deep Sea.

Microplastics (MPs) are ubiquitous contaminants of the marine environment, and the deep seafloor is their ultimate sink compartment. Manipulative and field experiments provided evidence of the ingestion of MPs by deep-sea fauna, but knowledge of MPs' fate once ingested still remains scant. We provide evidence of MP partial retention and fragmentation mediated by digestion activity of a Norwegian langoustine, a good bioindicator for MP contamination of the deep sea. We report here that MPs in the intestines were more abundant and significantly smaller (up to 1 order of magnitude in surface) than those in the stomachs. Our results show that the stomach can act as a size-bottleneck for ingested MPs, enhancing the retention of larger particles within the stomach and promoting fragmentation into smaller plastic debris, which is then released in the intestine. Our results provide evidence that the langoustine is responsible for the fragmentation of MPs already accumulated in sediments through its scavenging activity and digestion. These findings highlight the existence of a new peculiar kind of "secondary" MPs, introduced in the environment by biological activities, which could represent a significant pathway of plastic degradation in a secluded and stable environment such as the deep sea.

Microplastics in the crustaceans Nephrops norvegicus and Aristeus antennatus: Flagship species for deep-sea environments?

Ingestion of microplastics (MPs) has been documented in several marine organisms, but their occurrence in deep-sea species remains almost unknown. In this study, MPs were investigated in two economically and ecologically key crustaceans of the Mediterranean Sea, the Norwegian lobster Nephrops norvegicus and the shrimp Aristeus antennatus. Both the species were collected from 14 sites around Sardinia Island, at depths comprised between 270 and 660 m. A total of 89 and 63 stomachs were analysed for N. norvegicus and A. antennatus respectively, and more than 2000 MPs-like particles were extracted and sorted for identification and characterization by µFT-IR. In N. norvegicus, 83% of the specimens contained MPs, with an average abundance of 5.5 ±â€¯0.8 MPs individual-1, while A. antennatus showed a lower frequency of ingestion (67%) and a lower mean number of MPs (1.66 ±â€¯0.1 MPs individual-1). Composition and size of particles differed significantly between the two species. The non-selective feeding strategy of N. norvegicus could explain the 3-5 folds higher numbers of MPs in its stomach, which were mostly composed of films and fragments derived by polyethylene and polypropylene single-use plastic items. Contrarily, most MPs in the stomachs of A. antennatus were polyester filaments. The MPs abundance observed in N. norvegicus is among the highest detected in Mediterranean species considering both fish and invertebrates species, and provides novel insights on MPs bioavailability in deep-sea habitats. The overall results suggest that both N. norvegicus and A. antennatus, easily available in common fishery markets, could be valuable bioindicators and flagship species for plastic contamination in the deep-sea.

European spiny lobster recovery from overfishing enhanced through active restocking in Fully Protected Areas.

Fully protected areas (FPAs) help preserving biodiversity and reversing the global decline of fishery resources. Stocks of the European spiny lobster Palinurus elephas (Fabr. 1787), among the most precious gourmet seafood worldwide, are currently facing a dramatic decline. Previous attempts of recovery based on fishery restrictions or active post-larval restocking in marine reserves provided unsuccessful outcomes. Here we present results of a 5-year restocking program carried through a Collaborative Fishery Research (CFR) project, in three ad-hoc established FPAs replenished using below-legal size wild juveniles. Results showed that Catch per Unit Effort (CPUE) in terms of both density and biomass burst (by ca. 300-700%) just 2 years since FPAs establishment, regardless of location. We also report tangible spillover effects (ca. 30-50% increase in density and biomass CPUE outside the FPAs) by the end of the program. Data from a 15-years lasting monitoring of a pilot FPA established in 1998, where the restocking protocol was conducted and protection kept in force once restocking ceased, demonstrated the persistence in time of restocking' benefits. We foster that creation of FPAs assisted with local restocking under oriented CFR programs can represent an option for the recovery of European spiny lobster stocks from overfishing.

Shelf-life and labels: A cheap dating tool for seafloor macro litter? Insights from MEDITS surveys in Sardinian sea.

The global plastic economy demands to reduce the flow of plastic into oceans and promote remedial actions for already accumulated seafloor litter. In this perspective, baseline levels of contamination and tools for dating litter items in order to assess the efficacy of those actions, are thus needed. In this note we discuss the utility of introducing the acquisition of shelf-life and labels features from litter items into already established standardized protocols such as the one proposed by MEDiterranean International Trawl Survey (MEDITS). Our investigation was conducted on 612 high resolution images of litter items collected in each haul, which was retrieved during 6 years of surveys (2013-2018) around Sardinian sea (central western Mediterranean). While for the majority of items (89%) expiration date or labels were not present or legible, over 50% of dated items were likely dumped at sea from a period <5 years. In this perspective, this sort of data could represent a useful tool for monitoring the effectiveness of input reduction actions that implicitly rely on the gradual reduction of recently dumped items.

Dumping to the abyss: single-use marine litter invading bathyal plains of the Sardinian margin (Tyrrhenian Sea).

This study reports data on benthic litter abundance, composition and distribution obtained during deep-sea trawl surveys conducted along the Sardinian continental margin down to the bathyal plain, at depths comprised from 740 to 1740 m. None of the investigated sites was litter free. Density ranged from a minimum of 4 to a maximum of >1300 litter items per km2, with a mean value of 258 ±â€¯59 items. Plastic accounted for 56% of the total collected items, followed by glass (24%), metal (10%). Most items, irrespectively of the category, were single-use items. Fish abundance in all of the investigated catches was significantly higher than the number of litter items, the weight of which was similar to the reared fish biomass. Our results confirm that anthropogenic waste has reached the deep Mediterranean Sea, and that the most recent EU legislation banning single-use plastic tools represents a timely and necessary measure.

Amount and distribution of benthic marine litter along Sardinian fishing grounds (CW Mediterranean Sea).

Reports of marine litter pollution first appeared in scientific literature of the early 1970s; yet, more than 40 years later, no rigorous estimates exist of the amount of litter existing in the marine environment. To cope with this global urgency, this study reports the status of marine litter abundance along fishing grounds surrounding the island of Sardinia (CW Mediterranean Sea; FAO Geographical Sub-Area 11) through three years of trawl surveys. A total of 302 hauls, covering a total of 18.4 km2 of trawled surface were carried out in the framework of the MEDITS campaign, at depths comprised between 0 and 800 m. A total of 918 items were collected and sorted, with the highest concentration observed above 200 m depth. Overall, plastic was the dominant component of litter, followed by glass and metal. Comparing our results with other areas from the Mediterranean basin, Sardinian waters showed a lower impact, possibly as a consequence of multiple factors such as the lower human population density and the low flow of the main rivers, among others. In addition, fishermen behaviour with respect to marine litter was investigated by mean of anonymous questionnaires, emphasizing the necessity to further develop management policies and infrastructures supporting litter disposal.

Submarine canyons along the upper Sardinian slope (Central Western Mediterranean) as repositories for derelict fishing gears.

By means of ROV surveys, we assessed the quantity, composition and bathymetric distribution of marine litter in 17 sites along the Sardinian continental margin (Central Western Mediterranean) at depths ranging from 100 to 480m. None of the investigated sites was litter free, but the mean density of litter (0.0175±0.0022itemsm-2) was lower than that reported from other Tyrrhenian regions. The difference in the total litter density among sites was negligible, but the density of derelict fishing gear (DFG) items (most of which ascribable to small scale fishery) in submarine canyons was higher in submarine canyons than in other habitats. Our result suggest that submarine canyons (known to be highly vulnerable ecosystems) act as major repositories of DFGs, and, therefore, we anticipate the need of specific measures aimed at minimizing the loss and abandonment of DFGs in submarine canyons.