Deep-sea ecosystem collapse and recovery during stagnation phases in the Eastern Mediterranean Sea (DECODE)

• Applicants: Dr. Yvonne Milker; Professor Dr. Gerhard Schmiedl
• Subject Area: Palaeontology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 580438637

We propose to unravel the benthic foraminiferal record of deep-sea ecosystem collapse and recovery associated with stagnation phases in the Eastern Mediterranean Sea. The hypothesis to be tested is that the modern low-diverse ecosystems of the ultraoligotrophic deep basins of the Ionian and Levantine seas are characterized by recovery phases lasting several thousand years. Accordingly, modern ecosystems of these basins have probably not yet fully recovered from the last anoxic phase, which ended about 6,400 years ago. To test this hypothesis, we investigate the changes in diversity and species composition of benthic foraminifera in the size fractions 63-125 µm and >125 µm before, during and after the deposition of sapropel S1 from the early Holocene and sapropel S5 from the last interglacial period. To evaluate the recovery status after the S1, we refer to the recovery phase after the S5, which was followed by more than 15,000 years of normal sedimentation. The faunal analyses will be complemented by the quantification of test size distribution and pore density data of selected species to quantify changes in oxygen changes and to evaluate environmental impacts on test morphology. Specifically, we will address the following objectives: 1) Documentation of the temporal and spatial patterns of deep-sea benthic ecosystem collapse and recovery dynamics at centennial resolution across sapropels S1 and S5 in the deep Eastern Mediterranean basins. 2) Evaluation of the influence of changes in food fluxes and oxygen concentration on the collapse and recovery dynamics of the deep-sea benthic fauna. This aspect will be investigated by a comparative statistical analysis of the faunal records with existing environmental records from archives and model runs. 3) Assessing the recovery status of the deep-sea benthic ecosystems of today’s Eastern Mediterranean Sea. Our project contributes to understanding the temporal and spatial dynamics of deep-sea diversity and recolonization patterns of deep basins by benthic organisms in the context of strong and long-lasting disturbances. Our results will help to assess the overall vulnerability and recovery potential of oligotrophic deep-sea ecosystems in other oceans and how they may respond to large-scale natural and anthropogenic disturbances.

• DFG Programme: Research Grants