Programma della conferenza

The Marine Strategy Framework Directive aims to protect EU marine waters by achieving good environmental status. Descriptor 6 focuses on seafloor integrity, threatened by activities like bottom trawling. Bottom trawling disturbs the seafloor, alters marine diversity, and impacts habitat functions. This study assesses the impact of trawling on the benthic community of the Sicilian continental shelf, examining its longevity composition while considering the spatial scale, historical pattern, and intensity of trawling. Impact was assessed using three indicators, providing a continuous pressure-response curve at a 1 km² resolution: L1 - proportion of the community with life spans exceeding trawling intervals;, L2, median longevity decrease; and population dynamics PD - relative biomass decrease to carrying capacity. Fishing intensity data were used with varying temporal and spatial resolutions to identify optimal modelling conditions for accuracy. Median longevity, influenced by depth and fishing intensity, remains 8-9 years across models. Selected models suggest that in middle-outer shelf areas, increased fishing intensity shifts the community towards species with shorter lifespans, while in shallower areas, the opposite occurs. The L1 approach shows low spatial variation due to high SAR values and high median longevity but still indicates notable impact. The L2 approach reveals a 20% decrease in median longevity on the eastern Adventure Bank and south of Capo Passero, critical trawling areas. The PD approach is the clearest, detecting impact hotspots corresponding to trawling intensity peaks. In these critical areas, the PD method indicates that the benthic community is diminished by nearly 100% of its relative carrying capacity, highlighting significant impact. The findings of this study provide a method to map these impacts and assist policymakers in identifying sensitive areas and managing spatial planning effectively. The significant negative impacts near the eastern Adventure Bank and northwestern Malta Bank, crucial nursery grounds for commercial species, are particularly emphasized.

Marine soft sediments contribute to the edification of continental margins, which represent one of the largest ecosystems on Earth and a hot spot of ecosystem services. Their integrity, however, is increasingly put at risk by anthropogenic disturbance, most notably by demersal fisheries. The need for global action to minimize the impacts of destructive fishing techniques on marine soft sediments is an urgent need. The assessment of the consequences of such impacts, however, has been limited, as global predictions are challenging, and because poor validations and oversimplified assumptions have led to large uncertainties. By exploring the scientific literature dealing with trawling impacts on marine sediments, we mapped out where, what and when such a disturbance has been studied and measured so far. We built up an open-access data repository about sedimentary and biogeochemical properties of trawled sediments. Then, using such a repository, we carried out a global meta-analysis to quantify the effects of demersal fishing on specific properties.

Studies examining the direct (control vs. impact) effects of bottom fishing revealed significant reductions in chlorophyll-a (-17%), phaeopigments (-24%) and proteins (-32%), with the largest impact detected on the top surficial sediment, where reductions in total organic carbon (-12%) were also detected. Conversely, fishing intensity gradient studies showed an increase in TOC in chronically fished areas. Recovery once fishing ceased was observed for the most labile organic matter components (e.g., phytopigments, total nitrogen, and proteins). We noticed also that natural factors such as bottom current velocity and surface primary productivity can influence both the direction and magnitude of the fishing effects.

We highlight knowledge gaps that might create bias in regional and global models that require empirical data for validation, emphasizing the implications of methodological biases as a result of inappropriate sampling in trawling impact studies and the importance of context-dependent effect size.

Coastal wetlands are socio-ecological systems of immense value, supporting high biodiversity and a wide range of human activities, including aquaculture, agriculture, fisheries, and tourism. Despite their importance, coastal wetlands face various anthropogenic pressures. Among these, invasive species pose a leading threat to biodiversity in these environments, representing a significant portion of their biota in many areas. Additionally, plastic contamination has emerged as a pervasive problem in these systems in recent years, further altering their biota and ecosystem functioning.

The red swamp crayfish (Procambarus clarkii) and the eastern mosquitofish (Gambusia holbrooki), originally from North America, are now distributed in temperate aquatic environment worldwide. Both species are generalist feeders and often coexist, utilizing different habitats—benthic for crayfish and pelagic for mosquitofish. Several studies have shown microplastic (MP) uptake in these species. Since Procambarus and Gambusia are significant prey for terrestrial and aquatic organisms, they can serve as potential vectors for transporting contaminants between land and water environments.

Stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N) have been widely used to assess trophic relationships, determining long-term assimilation of food by consumers, and identifying nutritional deficiencies in predators. They have proven effective in detecting biomagnification processes, and recently, these isotopes have also been applied in MP studies.

In this study, we utilized stable isotope analysis alongside microplastic (MP) examination to assess MP contamination levels and estimate the trophic position of two co-invading invasive species, Procambarus clarkii and Gambusia holbrooki, across different zones within the Torre Flavia wetland in the Lazio region. Additionally, we investigated variations in carbon (C) and nitrogen (N) in relation to MP accumulation and explored potential biomagnification processes.

Invasive alien plant species (IAPS) provide ecological threats due to their adverse effects on native biodiversity and ecosystem functioning. However, recent observations suggest that some IAPS may provide an unexpected ecosystem service by trapping riverine macrolitter, particularly macroplastics. This study aimed to quantify the role and capacity of aquatic and riparian IAPS to trap riverine macrolitter in central Italy rivers. To assess the impact of alien species that occurred in some rivers, we calculated an alloctony degree in a plot as the number of alien species on the total species. We investigated how vegetation structure (i.e., roots, branches, leaves) and community/diversity structure (i.e., number of species, type of vegetation) play a key role in plastic entrapment. Our results indicate that most of the alien riparian species occurred in the Tiber River’s middle and lower courses, while alien aquatic species in smaller watercourses or lower courses. Among all the species occurring in the plots, although few were alien species, they entrapped a part of total macrolitter. Among the riparian species, Amorpha fruticosa and Acer negundo mainly blocked plastic packaging and plastic pieces, while Vitis riparia blocked most hygienic/sanitary towels and pieces, Ficus carica mainly bandages, and Datura stramonium entrapped clothes, aluminium cane, and plastic cups. Regarding aquatic species, Eichhornia crassipes and Arundo donax trap mostly packaging and plastic bottles. The plastic entrapment has been compared among the native and alien species. Among the species, we found that the higher the community structure and alloctony degree in a plot (number of alien species on the total species), the higher the plastic entrapment by vegetation. Here, we introduced the concept of “plastics vs alien plants”, highlighting this new ecosystem service carried by vegetation. Given that IAPS significantly contribute to trapping macrolitter, these alien plants may potentially mitigate plastic pollution in aquatic systems.

Microplastics represent a significant and pervasive threat to aquatic organisms. Due to the various ways microplastics can enter aquatic ecosystems, researchers focused on studying their ingestion and impact on aquatic organisms. However, there is a significant lack of research into how microplastics influence ecological responses across various levels of the ecological hierarchy, accompanied by considerable fragmentation of data in the existing literature. Functional traits, having indirect effects on individual fitness represent the main door through which anthropogenic disturbance can impact community structure, composition and ultimately aquatic ecosystems. This meta-analysis synthesizes data from 82 scientific papers encompassing studies on both benthic organisms and fish. The findings reveal that microplastics significantly impair functional traits across different habitats, life stages and trophic levels. Specifically, microplastics affect metabolism, growth and reproduction in benthic organisms, while significantly altering behavior in fish. These disruptions in functional traits may have cascading effects on energy transfer and trophic interactions within ecosystems. The study also highlights the critical role of experimental design (e.g. microplastic size, shape, type) in influencing observed outcomes. Integrating trait-based indicators with standardized protocols for analysing the impact of microplastics on aquatic organisms and ecosystems could represent a crucial step. This integration could provide guidelines for policymakers to develop adequate management and mitigation plans aimed at safeguarding ecosystems and the valuable goods and services they provide.

Freshwater biodiversity is declining worldwide. Understanding fish behaviour is essential for mitigating this decline and ensuring the survival of fish populations. The increased occurrence and intensity of extreme hydrological events, closely linked to climate change, represents a potential threat to freshwater ecosystems. The Mediterranean ecoregion, in particular, is expected to face more frequent drought and flood events. Despite its ecological and management importance, comprehensive knowledge about the effects of such events on fish movement patterns remains largely unexplored, particularly for small, endemic species. Our research investigates the movement behaviour of the endemic Italian riffle dace, Telestes muticellus, within a small unregulated stream in the northern Apennines. We used PIT (passive integrated transponder) telemetry to track individual fish movements over droughts that caused intermittent flows and flood events. We compared the movement patterns during extreme events with those observed during periods without such flow disturbances. During drying and flood events, the fish expanded their linear ranges, showing the capability to adjust. High-flow conditions notably facilitated both downstream and upstream dispersal of T. muticellus. Under intermittent flow conditions occurring during drought events, the fish directed their movements towards aquatic refuges, demonstrating their resilience to drying riverbeds. These findings are particularly noteworthy given the strong site fidelity and confined home ranges observed during normal conditions throughout the study. The fish movement responses were possible due to the absence of anthropogenic barriers, underscoring the importance of preserving longitudinal river connectivity for mitigating the detrimental effects of increasingly frequent extreme flow conditions.