Marine ecosystems are becoming increasingly vulnerable to cumulative anthropogenic effects and pressures. Therefore, various methodological approaches and tools have been designed to apply cumulative impact appraisal schemes and better assess the dynamics and interactions among pressures affecting marine ecosystems. This study aims to apply the Spatial Cumulative Assessment of Impact Risk for Management (SCAIRM) tool for the Black Sea coastal waters considering human activities, pressures, and effects on different ecosystem components coupled with one management scenario development for actual and new emerging sectors. According to the SCAIRM, the primary pressure on the marine ecosystem was identified as introducing or spreading non-indigenous species from shipping. Additionally, when considering cumulative impact, activities related to coastal defense and flood protection, particularly beach nourishment works, were found to have the highest impact. This is due to the cumulative scores associated with the physical loss from permanent alteration or removal of seabed substrates, and temporary or reversible physical disturbances to the seabed. The scenario development indicated that after shipping, oil and gas exploitation is anticipated to become the second-highest risk sector for additional impact in the Romanian Black Sea. Additionally, the increased military activities related to the war in Ukraine present escalating risks that must be considered in EBM strategies. The results assess the possible effects of human activities and the associated pressures to direct management toward achieving sustainability, biodiversity protection, and the marine ecosystem’s integrity.

Between 2013 and 2020, a total of 27 distinct zooplankton taxa, encompassing both holoplanktonic and meroplanktonic organisms spanning different classes and orders, were successfully identified along the Romanian Black Sea coastline. The seasonal dispersion patterns of these zooplankton taxa revealed a notable augmentation in species identification during the warmer periods, contrasting with reduced zooplankton diversity during the colder seasons. This phenomenon was underscored by the outcomes of SIMPER analysis, which highlighted that copepods, meroplankton, and cladocerans predominantly contributed to the community structure during warmer seasons. In contrast, during colder seasons, cladocerans were scarcely represented, and the density levels of copepods and meroplankton were diminished. From a quantitative perspective, the dinoflagellate Noctiluca scintillans, exhibited its highest density and biomass during the warm season, with a relatively lower representation during colder periods. The variation in the abundance of zooplankton was closely linked to changes in salinity and temperature, culminating in noticeable fluctuations, which were particularly evident during the cold season. During this period, the values of zooplankton abundance were notably lower compared to those observed in the warmer season. The comprehension of zooplankton dynamics stands as a critical facet for assessing biodiversity, monitoring ecosystem well-being, and guiding conservation endeavours.

In order to analyze how environmental factors affect planktonic organisms along the Romanian Black Sea coast, this study created semi-quantitative models of the causal relationships between phytoplankton, zooplankton, and physicochemical parameters by utilizing user-friendly modeling tools. Eleven years of time-series data (March–September 2008–2018) were used to investigate the relationships between phytoplankton, zooplankton, and environmental factors (such as temperature, salinity, and nutrients). Variables such as marine reporting units and phytoplankton species and classes were used to identify developmental patterns, utilizing the Mental Modeler platform to consider interactions between the physicochemical parameters and phytoplankton, phytoplankton and zooplankton, and zooplankton and physicochemical parameters. Although the increase in the overall number of elements and linkages was uncertain in waters with variable salinity compared to marine ones, the semi-quantitative models created for the three marine reporting units along the Romanian Black Sea coast were comparable in terms of complexity. Across the typical and examined types of phytoplankton proliferation (normal, abundant, and blooms), the number of components and connections in the case of phytoplankton blooms substantially decreased as species- and growth-promoting variables increased.

The paper contributes to the Sustainable Development Goals (SDGs) targeting Life Below Water by introducing user-friendly modeling approaches. It delves into the impact of abiotic factors on the first two trophic levels within the marine ecosystem, both naturally and due to human influence. Specifically, the study examines the connections between environmental parameters (e.g., temperature, salinity, nutrients) and plankton along the Romanian Black Sea coast during the warm season over a decade. The research develops models to forecast zooplankton proliferation using machine learning (ML) algorithms and gathered data. Water temperature significantly affects copepods and “other groups” of zooplankton densities during the warm season. Conversely, no discernible impact is observed on dinoflagellate Noctiluca scintillans blooms. Salinity fluctuations notably influence typical phytoplankton proliferation, with phosphate concentrations primarily driving widespread blooms. The study explores two scenarios for forecasting zooplankton growth: Business as Usual, predicting modest increases in temperature, salinity, and constant nutrient levels, and the Mild scenario, projecting substantial temperature and salinity increases alongside significant nutrient decrease by 2042. The findings underscore high densities of Noctiluca scintillans under both scenarios, particularly pronounced in the second scenario, surpassing the first by around 70%. These findings, indicative of a eutrophic ecosystem, underscore the potential implications of altered abiotic factors on ecosystem health, aligning with SDGs focused on Life Below Water.

Seagrass meadows, including those formed by Zostera noltei, play a crucial role in marine ecosystem health by providing habitat stability and coastal protection. In the Romanian Black Sea, Z. noltei meadows are critically endangered due to pressures from eutrophication, habitat loss, and climate change. This study presents a comprehensive baseline assessment of Z. noltei meadows near Mangalia, Romania, utilizing in situ field methods and UAV mapping conducted in the spring and summer of 2023. Seven meadow sites (Z1–Z7) were identified, with notable variability in density, shoot counts, and coverage across sites. Site Z1 exhibited the highest density (1223 shoots/m⁻²) and Z5 and Z7 the longest leaves (an average of 60 cm), reflecting possible environmental influences. Statistical analyses revealed significant inter-site differences in shoot density and leaf length, with density emerging as a primary differentiator. Ex situ analyses of epiphyte load indicated a median, balanced epiphyte load. This baseline dataset supported the selection of Z1 as a reference donor site for seagrass relocation activities along the Romanian coast in 2023. By providing critical insights into Z. noltei structure and health, this study supports future conservation efforts and evidence-based management of these vulnerable coastal habitats.

Gongolaria barbata has undergone a major decline along the Romanian Black Sea coast due to historical winter events of the 1970s and ongoing anthropogenic pressures and is currently listed as Critically Endangered in the Romanian List of Endangered Marine Species, highlighting the need for ex situ culture to support restoration and long-term preservation of this habitat-forming species. This study evaluates how different substrate types (travertine, shale and ceramic) influence early thallus development in G. barbata, and attachment and growth dynamics, and establishes an ex situ culture procedure tailored to Black Sea conditions. Germling-based culture was carried out under controlled conditions, with salinity maintained at 17.1 ± 0.5 PSU and seawater temperature at 19.0 ± 0.8 °C. After 216 days of ex situ culture, thalli reached comparable sizes across all substrates, with mean heights between 5 and 7 cm and maximum values ranging from 12 to over 20 cm. Thallus development progressed steadily across all substrates, each supporting comparable growth, a finding relevant for restoration, aquaculture, and large-scale cultivation. All tested hard substrates sustained early development, with travertine producing slightly more robust thalli and stronger holdfasts, highlighting its potential for future restoration initiatives along the Romanian Black Sea coast.