Eutrophication, driven by excessive nutrient enrichment from sources like agricultural runoff, industrial discharge, and urbanisation, has severely impacted the Black Sea since the 1980s. This study aimed to assess eutrophication dynamics in the Romanian Exclusive Economic Zone from 2020 to 2022 using the Black Sea Eutrophication Assessment Tool (BEAST), an integrated approach to the causes and effects of eutrophication. Data were collected from 68 stations during five oceanographic expeditions, analysing 617 water samples for nutrients, chlorophyll a, zooplankton species Noctiluca scintillans, and dissolved oxygen. Additionally, 179 zoobenthic and 251 phytobenthic community samples were collected. The results indicate that coastal waters exhibit higher nutrient levels and algal blooms compared to offshore waters, necessitating significant reductions in nutrient concentrations to achieve good environmental status. In transitional waters, within the Danube Delta Biosphere Reserve, a 55% reduction in inorganic phosphorus and a 43% reduction in inorganic nitrogen concentrations are required, while coastal waters need reductions of 38% and 37%, respectively. The study highlights the need for improved wastewater treatment, stricter agricultural runoff controls, and continuous monitoring. Effective ecosystem-based management strategies, integrated coastal zone management, and international cooperation are essential to mitigate eutrophication and promote the long-term health of the Black Sea ecosystem.

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.

This study investigates how environmental gradients shape the structure and interactions of coastal biotic assemblages in the Romanian Black Sea. A multi-trophic analysis was conducted across a network of stations in June 2023, integrating phytoplankton, microzooplankton, mesozooplankton, macrozooplankton, ichthyoplankton, and macrozoobenthos with key physico-chemical parameters. Principal component analysis revealed strong north–south contrasts: the northern sector was characterized by nutrient enrichment (nitrate, ammonium, and silicate) supporting phytoplankton blooms and microzooplankton peaks, while the southern sector showed more saline conditions and extended trophic coupling from phytoplankton through mesozooplankton to ichthyoplankton. The central sector appeared transitional, with community structure more closely related to oxygen and phosphate levels. In the north and south, plankton dynamics were strongly linked to nutrient availability, while macrozooplankton consistently aligned with salinity and silicate, reflecting their preference for more marine waters and partial decoupling from nutrient-driven pathways. Fuzzy Cognitive Map analysis indicated combined bottom-up and top-down control, with phytoplankton supporting mesozooplankton and macrozooplankton exerting strong negative pressure. Phytoplankton functioned as the main network driver, with mesozooplankton as the central mediator, and the persistent negative macrozooplankton effect suggests direct biological regulation beyond salinity influence. These findings highlight the dual structuring of Black Sea food webs and provide an integrative, multi-trophic baseline for ecosystem-based management and Marine Strategy Framework Directive Descriptor 4 (Food webs) implementation.

The number of alien species recorded in the Black Sea has increased over recent decades, raising concerns regarding their long-term ecological consequences. Among the taxa currently extending their distribution within the basin are the Pacific oyster, Magallana gigas, and the Chesapeake blue crab, Callinectes sapidus. This study presents new records of both species from the Romanian Black Sea coast obtained through citizen-reported observations. Five specimens of M. gigas collected from Constanța and Mangalia harbours were examined, together with one ovigerous female specimen of C. sapidus collected from Vadu Beach. In addition, two male C. sapidus records from Sinoe Lake were documented and validated based on photographic evidence. The finding of M. gigas in Mangalia Harbour extends the known distribution of the species along the Romanian coastline and suggests that the species is more widespread than previously documented. The occurrence of an ovigerous C. sapidus female confirms that reproduction is taking place in Romanian Black Sea waters. Morphometric measurements and reproductive traits were within the ranges reported from other Black Sea and Mediterranean populations. While none of these species can currently be regarded as invasive in Romanian coastal waters due to the absence of documented ecological impacts, the increasing frequency of records suggests that both warrant continued monitoring. The results further indicate that citizen-reported observations, when validated by specialists, can complement conventional surveys and provide valuable information on the occurrence and spread of conspicuous alien marine species, thereby supporting sustainable marine biodiversity monitoring and informed ecosystem management.