The Black Sea has had a turbulent 60 years, with increasing pressure from human activity and natural events including overfishing, pollution, coastal erosion, invasion of alien species and climate change. As a result of this significant and complex combination of stressors, its ecosystems have become less resilient, fish populations have plummeted, and the overall health of the waterbody has deteriorated since the 1960s, note researchers.
Despite being one of the most anthropogenically-disturbed marine ecosystems in the world, it is also one of the least assessed for its biodiversity. In addition, ecosystem-based management approaches in the sea have been limited to informing commercial fisheries policies. However, to protect the long-term health and resilience of the Black Sea ecosystem, wide-reaching policies and cooperation between all countries bordering the sea are needed – together with robust modelling to evaluate their efficacy. This is especially pressing given recent military activity in Ukraine, which is impacting coastal and marine ecosystems in the region via chemical and noise pollution, habitat damage and limitations on conservation activity.
This new research addresses this need for modelling, by presenting a spatial-temporal assessment of the Black Sea ecosystem since 1995, using the Blue2 modelling framework. This framework has beendeveloped by the European Commission and Joint Research Centre to support the implementation of policies such as the Marine Strategy Framework Directive, Water Framework Directive and Common Fisheries Policy. Blue2 is an advanced suite of tools to simulate marine ecosystems, accounting for various management and policy scenarios and encompassing environmental conditions, food web interactions, and anthropogenic stressors.
The model reveals the conditions of the Black Sea’s food web and fish stocks, considering all representative species and functional groups[1] in the ecosystem between 1995-2021. A wide range of ecosystem components across freshwater hydrology, marine oceanography, biochemistry, marine food webs and atmospheric forcing are taken into account.
Compared to previous modelling of the Black Sea, this study includes new functional groups: three dolphin species, three seabird groups, 24 fish groups, eight invertebrate groups, five planktonic groups, seagrass and seaweed, discards and detritus, and eight fishing fleet types. Input data were extracted, calculated, or inferred from literature, fish stock assessments, and the Blue2 model of the Mediterranean Sea. The researchers also used a mass balance model called Ecopath – which offers a snapshot of the ecosystem in time – and Ecosim – which simulates the dynamics of functional groups over space and time, considering hydrodynamics and biogeochemistry.
The study modelled the entire Black Sea, excluding the small, shallow Azov Sea, covering an area of roughly 423 000 square kilometres, to a maximum depth of 2,212 metres. Its simulation of the broad dynamics of the ecosystem showed that the total biomass of most functional groups decreased between 1995 and 2021. The model also identified that particular species – gulls, cormorants, sprat, horse mackerel and mullets – have a structuring, instrumental role in the food web. Meanwhile, fishing fleets had a notable indirect negative impact on not only commercially exploited species, but also other marine mammals.
Overall, the has model shown the degradation of the Black Sea ecosystem over time, and provides a valuable and much-needed reference baseline. It represents both historical and current states of the sea, spatially and temporally. This is important for future policymaking and management to mitigate environmental deterioration. As the model builds on an existing framework designed for EU-specific scenarios, it also enables comparison between the Black Sea and other regional water bodies such as the Mediterranean. Its outputs are highly relevant and suitable for use in assessing European policies and legislation.
Links:
The BLUE2 Project (European Commission): https://mcc.jrc.ec.europa.eu/main/dev.py?N=simple&O=455&titre_page=The%20BLUE2%20project
Reference:
Serpetti, N., Piroddi, C., Akoglu, E., Garcia-Gorriz, E., Miladinova, S. And Macias, D. (2025) State of the art modelling for the Black Sea ecosystem to support European policies. PLoS ONE 20(1): e0312170. https://doi.org/10.1371/journal.pone.0312170
[1] A species or group of species that share similar predator-prey interactions, biomass trends, ecosystem functioning, habitat preferences, and more, from primary producers to marine mammals and sea birds
