Coastal marine ecosystems undergo degradation resulting in biodiversity loss and shifts in benthic communities, therefore, assessing their Ecological Quality Status is a central objective. However, the lack of reliable pre-anthropogenic baseline conditions limits existing biotic indices and complicates evaluations of long-term ecosystem health.
The shallow continental shelf of the Eastern Mediterranean provides essential ecosystem services but is increasingly exposed to anthropogenic pressures. The Shafdan sewage outfall represented a primary source of chronic pollution between 1987 and 2017, enriching surrounding sediments with nutrients, organic matter, and heavy metals (HM). The subsequent reduction in sewage discharge permits investigation of benthic ecosystem responses to long-term disturbance and post-impact recovery.
Two gravity sediment cores (~0.8 m long) were collected at ~36 m water depth: one from a formerly polluted site proximal to the outfall and one from a distal reference site. Down-core grain-size distribution, total organic carbon, and HM concentrations were analyzed and integrated with benthic foraminiferal dead assemblages, complemented by living (Rose Bengal–stained) foraminifera from surface sediments. Ecological status was evaluated using Foram-AMBI, TSI-Med, and the diversity index Exp(H’bc), while HM accumulation was assessed on Ammonia beccarii shells.
Distinct assemblage shifts corresponding to pre-pollution, pollution, and post-pollution phases were identified at the impacted site. Pre-pollution sediments were dominated by sensitive taxa (Ammonia parkinsoniana, Adelosina spp.), whereas the polluted interval was characterized by a marked decline in sensitive species and dominance of opportunistic Ammonia tepida group taxa. Post-pollution sediments indicate partial recovery, with recolonization of sensitive taxa alongside persistent opportunistic species. Foram-AMBI effectively tracked pollution history, while TSI-Med was strongly influenced by sediment texture.
These results demonstrate the value of benthic foraminifera as microscopic witnesses of anthropogenic impact and recovery and will be interpreted in light of other major changes in the Eastern Mediterranean, such as Nile damming and the ongoing Lessepsian migration.