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Benthic biodiversity is of global significance for the provision of ecosystem services and the mediation of global biogeochemical cycles. The lack of detailed spatial distributions of the functions and vulnerabilities of the benthos critically prevents us from protecting benthic biodiversity and its functioning in the context of increasing human perturbations and climate change. Here, we propose a multidisciplinary approach to bridging in situ benthic data to the maps of macrobenthic functions and vulnerabilities at the scale of the northwestern shelf of the Black Sea. Our findings show that oxygen availability is a key driver of the functional trait composition of macrozoobenthic communities. Shallower well-oxygenated areas support high biomixing and bioirrigation on muddier-sandier substrata and high biodeposition on coarser substrata associated with mussel reef communities. In contrast, at depleted oxygen areas at the edge of the shelf, macrobenthic communities are functionally impoverished with only a combination of a few typical opportunistic traits, and those communities have a negligible impact on ecosystem functions. Mapping of vulnerabilities and functions of benthic communities can support marine management strategies aligned with the United Nations Sustainable Development Goal 14: Life Below Water.

The Mangalia–Limanu coastal lake system, located in southeastern Romania along the Black Sea, represents a transitional aquatic environment shaped by the interplay between freshwater and marine influences. This study provides an integrated assessment of its physicochemical water parameters, sedimentological and geochemical properties, and benthic macroinvertebrate communities, aiming to evaluate its current ecological status and environmental dynamics. Field measurements using a multiparameter sonde revealed a predominantly freshwater to oligohaline system with moderate spatial heterogeneity. DO levels frequently reached supersaturation (>180%), coupled with high pH (~9.1), indicating intense daytime photosynthetic activity. Conductivity, TDS, and salinity increased longitudinally toward the port water area, while nitrate concentrations showed stronger signals upstream. Sediments were dominated by organic matter (18–88%), with lower carbonate (3–53%) and siliciclastic (8–49%) contents. Organic-rich deposits prevailed in the western-central sector, where reduced hydrodynamics and submerged vegetation favor autochthonous organic accumulation, whereas the eastern sector, exposed to marine action, showed more siliciclastic-rich substrates. Geochemical analyses revealed localized exceedances of Cr, Ni, Cu, Zn, and Pb regulatory thresholds (Order 161/2006), suggesting potential contamination hotspots. Benthic communities included 26 taxa, dominated by polychaetas, gammarids, and gastropods, with moderate diversity (H′ < 2). The results highlight a system under moderate anthropogenic pressure but retaining transitional lagoon characteristics, emphasizing the need for continued ecological monitoring and integrated management measures.

Bacteria colonizing bivalves play a critical role in host health by supporting digestion, nutrient cycling, and immune defense. While the microbiomes of marine bivalves have been studied globally, their diversity and functional roles across specific organs remain underexplored. This study investigates the structural and predicted functional diversity of bacterial communities associated with different organs (siphon, gills, and stomach) of the marine bivalve Mya arenaria Linnaeus, 1758, along with the surrounding sediments from the Romanian Black Sea coast, using 16S rRNA gene sequencing with Illumina technology. Bacterial communities within the bivalve differed markedly from those in the sediments and varied across organs. Sediment samples exhibited greater taxonomic diversity (19 phyla) than bivalve organs (14–15 phyla). Verrucomicrobiota dominated the siphon and gills, Spirochaetota were most abundant in the stomach, and Desulfobacterota predominated in sediments. Nitrate-reducing bacteria, particularly those from the genus Persicirhabdus , were prevalent in all organs and may contribute to host resilience under hypoxic conditions. The presence of Sulfurimonas in the stomach suggests a possible nutritional association, while halotolerant Woeseia species identified in sediments likely play a role in environmental nutrient cycling. Predictive functional profiling indicated potential bacterial involvement in various metabolic processes, including carbohydrate, amino acid, and energy metabolism. Additionally, pathways related to xenobiotic degradation and antibiotic biosynthesis were inferred across all sample types, indicating a potential capacity for broader ecological and possibly biotechnological roles. However, these functions were inferred from 16S rRNA data and require further validation through metagenomic or transcriptomic approaches. To our knowledge, this is the first detailed analysis of microbiome variability across different organs of M. arenaria , offering new insights into host–microbe interactions in this species.

Benthic ecological data are crucial to study and manage ecosystems. On the one hand, abiotic and species data provide complementary information to identify habitats. On the other hand, trait data, describing taxon characteristics, are required to predict anthropogenic impacts on marine ecosystems. Indeed, species traits are now widely used to understand natural selection in communities or to highlight ecosystem functions. While trait data are in growing demand, compiling them is challenging, time-consuming and there are no properly established procedures for major marine ecosystems. Here, we share a data set comprising macrozoobenthic occurrences for 215 taxa over the Black Sea northwestern shelf, between 1995 and 2017, and 27 traits documented for 127 taxa that related to life cycle and ecosystem function. In addition, we provide an abiotic data set of physical and chemical variables generated by a model or compiled from in-situ data. This data set aims to fill the functional knowledge gap in the Black Sea and offers research opportunities to future studies covering ecosystem functions, biodiversity conservation, and management.

The North-Western Black Sea shelf is extremely vulnerable to disturbances of its habitats and ecosystems. In the past 10 years, this area has become targeted by beam trawl fisheries for the invasive gastropod Rapana venosa (Valenciennes, 1846), with a potentially destructive impact on the area’s soft bottoms. Not many studies have been performed in the region, and most investigations have focused on gear selectivity and by-catch rates. In this context, our novel research aimed, on the one hand, to assess and quantify the actual impact of beam trawling and, on the other hand, to propose effective spatial/temporal management measures for a sustainable zonation of the North-Western Black Sea shelf (marine zone of the Danube Delta Biosphere Reserve). The methodology used integrated beam trawl catch dynamics information, VMS data, geophysical investigations, and macrozoobenthos sampling. Our findings show that beam trawling activities can cause changes in the benthic habitat structure (lower number of taxa, lower values of ecological indicators, and an overall non-GES status). Further in-depth investigations are needed to underpin the ecosystem-based management of this marine protected area (MPA), aiming to allow the recovery of the affected benthic habitats, by alternating defined areas undergoing fishing with biological recovery polygons.

Bacteria associated with marine invertebrate play a fundamental role in the biology, ecology, development and evolution of their hosts. Although many studies have been focused on the microbial populations of benthic and pelagic habitats, little is known about bacteria colonizing tube-dwelling polychaete. In this context, the current study provided the first characterization of the Melinna palmata Grube, 1870 microbiome based on Illumina sequencing of 16S rRNA gene of the polychaete tissue and proximate sediments collected from the Black Sea, Romania, along a 24.2 m – 45.4 m depth-gradient. The diversity, taxonomic composition and deduced functional profile of the tissue and sediments associated bacterial communities were compared and analyzed in relation with the environmental parameters. This polychaete harbored a distinct bacterial assemblage as compared to their sediments and independent on the depth of their habitat, including 8 phyla in tissues dominated by Proteobacteria, and 12 phyla in sediments majorly represented by Actinobacteriota, respectively. At order level, Synechococcales, Rhodobacterales and Actinomarinales were highly represented in the M. palmata microbiome, while Microtrichales, Anaerolineales and Caldilineales were mostly found in sediments. A significant correlation was observed between Cyanobacteria taxa and the dissolved oxygen concentrations in shallow waters impacted by the Danube inputs. Meanwhile, this phylum showed a positive correlation with Planctomycetota colonizing the invertebrate tissues, and a negative one with Actinobacteriota and Chloroflexi found in sediments. The deduced functional profile of these bacterial assemblages suggested the prevalence of the amino acid and carbohydrate metabolism for both analyzed matrices. This pioneering report on the M. palmata microbiome highlighted the environment contribution to bacterial species enrichment of the polychaete, and provided a glimpse on the putative role of microbial communities associated with this marine organism.

This survey reports the spatial distribution of gastropods belonging to Caenogastropoda, Architaenioglossa, Littorinimorpha, Cycloneritida and Hygrophila orders, and malacostracans from Amphipoda and Mysida orders in the lower sector of the Danube River, Romania, using DNA barcoding based on the cytochrome C oxidase I (COI) gene sequence. Sampling was performed for eight locations of Danube Delta branches and Bechet area during three consecutive years (2019–2021). Molecular identification of sixteen gastropods and twelve crustacean individuals was confirmed to the species level, providing the first molecular identification of gastropods from the Lower Danube sector. Phylogenetic analysis showed that species of gastropods and crustaceans clustered in monophyletic groups. Among gastropods, Microcolpia daudebartii acicularis, Viviparus viviparus, Bithynia tentaculata, Physa fontinalis, Ampullaceana lagotis and Planorbarius corneus were identified in Chilia and Sulina branches; and the Bechet area was populated by Holandriana holandrii, Theodoxus transversalis and Gyraulus parvus. The amphipods and mysids were present along the three main Danube branches. The calculated density of these species revealed an abundant community of crustacean Chelicorophium robustum on Sulina branch, and Dikerogammarus haemobaphes and D. villosus in extended areas of the Danube Delta. The presence of these invertebrates along Danube River was reported in relation to the sediment type and water depth.

Fisheries Restricted Areas (FRAs), as area-based fisheries management tools, can be effective in providing protection for fisheries and biodiversity, in addition to traditional Marine Protected Areas (MPAs), and are already in effect in waters above 1,000 m of the Mediterranean and the Black Seas. Whereas in the North-Western part of the Black Sea all fishing activities are concentrated in the shallow area (at depths of maximum 90 m), where species and habitats of conservation interest are present, this restriction is completely irrelevant. In this context, given that a FRA can also be established nationally (nFRA), the main objective of this research was pre-identifying suitable area(s) at the Romanian coast and providing the scientific substantiation for such an endeavor. In addition to being a traditional fishing ground for small-scale local fishermen, the study perimeter, which includes the Northern Romanian coast (part of the Marine Zone of the Danube Delta Biosphere Reserve), was chosen for various reasons. First, because of the uniqueness of the habitats found here, it serves as a vital forage area for fish species that are valuable both from a conservation and economic standpoint. Additionally, during the past ten years, beam trawl fishing for the gastropod Rapana venosa (Valenciennes, 1846) has affected the area, potentially causing harm to benthic habitats. A variety of data sources were integrated as part of the research strategy, including the composition and spatial distribution of macrozoobenthos, an inventory of the local fish fauna conducted through scientific fishing (both for commercial fish and species of conservation interest), fish stomach content analysis (by dissection or gastric lavage), and records of fishing effort and catch. The identified Sf. Gheorghe - Sahalin nFRA, covering 272.76 km 2 between the 40 m and 50 isobaths, proved to be appropriate according to both ecological and fisheries criteria, and, after public consultation, was established by law, thus becoming the first national Fisheries Restricted Area in the Black Sea, to the benefit of both nature conservation, by spillover effects to adjacent areas, and the livelihood of local coastal communities.

The Northwestern Black Sea shelf, strongly influenced by Danube discharge and coastal activities, provides an effective setting for separating lithogenic controls from localized anthropogenic inputs. We applied a multi-proxy geochemical–radiometric approach to Romanian shelf waters and surface sediments. A CTD–Rosette was used to quantify nutrients, chlorophyll-a, TOC, and TN. Dissolved metals and PAHs were measured in seawater, while surface sediments were analyzed for CaCO3, TOC, trace metals, and γ-emitting radionuclides. Multivariate statistics (PCA/FA) were used to resolve the dominant environmental controls. Summer stratification was characterized by the bottom-layer maxima of PO43−, SiO44−, and NH4+ and a pronounced subsurface chlorophyll-a maximum at 12–16 m. Surface-water Σ16PAH ranged from 134 to 347 ng L−1 and was dominated by low-molecular-weight compounds, with episodic nearshore enrichment in high-molecular-weight species. In sediments, CaCO3 ranged from 7.6 to 29.9% and TOC from 0.11 to 0.96%. Trace metals were generally low. Pb and Hg peaked at nearshore station S23, whereas mean Ni (38.88 ppm) slightly exceeded the 35 ppm guideline, consistent with natural Fe/Mn-oxide association. PCA/FA identified a terrigenous axis (Fe-Al-Ti-V-Ni-Cr), a carbonate axis (CaCO3; Sr where available), and an anthropogenic factor (Pb, Hg, HMW-PAHs). γ-spectrometry provided a compatible radiometric baseline that supports the multi-proxy interpretation.

Mangalia area harbors in the western Black Sea a distinctive marine environment thriving under specific hydrochemical conditions, largely influenced by a significant number of sulphurous springs occurring in shallow marine waters. These springs led to the designation of the area as part of the Natura 2000 Marine Protected Area (MPA) network at European level (Underwater Sulphurous Springs from Mangalia - ROSAC0094), as unique hydro-geomorphological features in the region. In 2021 and 2023, two research cruises led by GeoEcoMar investigated underwater sulphurous springs primarily located offshore of Mangalia (Constanţa County, Romania). The study area, located between 17-29 meters water depth and 1.8-3 km offshore, encompasses two marine protected areas: the Underwater Sulphurous Springs from Mangalia (ROSAC0094) and Cape Aurora (ROSCI0281). The research combined geophysical and geochemical techniques and sediment sampling. Considering the susceptibility of these natural systems to human activities such as fishing and dredging, as well as the impact of ecological and climate changes, this paper offers significant insights contributing to the development of effective conservation and management strategies for these environments. The surveys were conducted for benthic habitats mapping, with the objective of improving our understanding of these ecosystems’ distribution, composition and dynamics. As these sulphurous waters are rich in methane, a powerful greenhouse gas, our results also contribute to the inventory of greenhouse gas sources. The results presented in this paper provide valuable new insights into this specific environment, contributing to the understanding of its complex functioning and evolution.