Foraminiferal Records of Pollution and Environmental Resilience in the Eastern Mediterranean Sea

The shallow marine environment of the Eastern Mediterranean Sea is an ultra-oligotrophic system that provides essential ecosystem services, yet it is increasingly exposed to anthropogenic pressures, including fish farming, desalination activities, and municipal and industrial pollution. Understanding ecosystem responses to disturbance and subsequent recovery is therefore critical for sustainable marine management.

For three decades (1987-2017), the primary source of anthropogenic pollution along the Israeli coast was the Shafdan sewage outfall, which enriched the surrounding environment with nutrients, organic matter, and heavy metals. This long-term pollution history, followed by recent recovery, offers a unique natural laboratory to investigate benthic foraminiferal responses to sustained anthropogenic stress and post-impact recovery.

Two sediment gravity cores were collected at ~36 m water depth near the Shafdan outfall: one from a formerly polluted site (PL3; 0.2 km north of the outfall) and one from a more distal reference site (PL29; 5.5 km north). Sedimentological and geochemical analyses included total organic carbon, grain-size distribution, and mineral and elemental composition. Micropaleontological analyses focused on down-core dead benthic foraminiferal assemblages, complemented by living (Rose-Bengal stained) foraminifera from surface sediments. We assessed changes in species composition, community structure, dominant taxa, and diversity patterns. Ecological status was evaluated using three biotic indices (Foram-AMBI, TSI-Med, FSI) and two diversity indices (ES100 and Exp(H’bc)).

Distinct assemblage shifts corresponding to pre-pollution, pollution, and post-pollution phases were identified at the Shafdan site. Pre-pollution sediments (20-6 cm in core-depth) were characterized by predominance of sensitive taxa such as Ammonia parkinsoniana and Adelosina species whereas the polluted interval (6-2 cm) was characterized by a marked decline in sensitive species and dominance of opportunistic taxa as foraminifera from Ammonia tepida group. During the post-pollution phase (2-0 cm), sensitive taxa recolonized the sediments; however, opportunistic species remain abundant, indicating that recovery is ongoing and not yet complete. Foram-AMBI values clearly increased during the pollution interval, while TSI-Med fluctuations were strongly influenced by grain-size variability. In contrast, FSI and diversity indices showed limited down-core variation.

These results highlight the value of benthic foraminifera as sensitive tracers of both anthropogenic impact and recovery, and demonstrate the robustness of Foram-AMBI for reconstructing historical environmental conditions. Incorporating down-core foraminiferal records into monitoring frameworks can substantially improve long-term assessments of ecological status and inform marine conservation and management strategies in ultra-oligotrophic systems.

This research was conducted as part of the project no. 0005817 «REFORM – REFerence conditions based on historical FORaminiferal Monitoring» funded by the Israeli Ministry of Science and Technology (2024–2026) and the University of Haifa Institutional Postdoctoral Scholarship funded by Graduate Studies Authority – Bloom Graduate School (2024–2025).