Activity 1
Lead: Nejib Kallel (Professor)
The Mediterranean region experienced several humid periods in the past, particularly during the Early and Middle Holocene. These phases are evidenced by a decrease in Mediterranean salinity and changes in vegetation observed across North Africa, the Middle East, and southern Europe.
During sapropel episodes, increased freshwater inputs promote water-column stratification and the accumulation of organic matter in the deep eastern Mediterranean. Its degradation leads to increased CO₂ concentrations, a decrease in pH, and acidification of deep waters, which reduces calcification in marine organisms such as foraminifera.
This research activity aims to investigate changes in the test mass of planktonic foraminifera over the last 20,000 years using sediment cores collected from the main Mediterranean basins. The objective is to determine whether the acidification observed during sapropel episodes was restricted to the eastern basin or affected the Mediterranean as a whole, while also investigating its relationship with the development of anoxic conditions in the deep marine environment.
Details of the research activity
Activity 2
Lead: Soumeya Bousetta (M.A)
Research has shown that Plio-Pleistocene calcretes (3.5 to 1 million years ago), which are widely distributed across North Africa and the Middle East, record climatic conditions that were considerably wetter than those of today. Their formation suggests a strongly seasonal climate, with wet winters favoring carbonate dissolution and long, dry summers promoting carbonate precipitation.
However, the origin of precipitation remains uncertain, whether Mediterranean or North Atlantic, as does the nature of the vegetation that prevailed at that time. To improve the reconstruction of these ancient environments, this research uses oxygen (δ¹⁸O) and carbon (δ¹³C) isotopes preserved in continental carbonates, including calcretes and speleothems.
The δ¹³C values provide information on climatic conditions and vegetation types, particularly C3 plants associated with temperate environments and C4 plants associated with more arid environments. The δ¹⁸O values help identify precipitation sources and the climatic factors influencing them, including evaporation source, latitude, altitude, continentality, and rainfall intensity.
Details of the research activity
Activity 3
Lead: Nejib Kallel (Professeur), Fekri Kamoun (Professeur)
In Tunisia, fluctuations in the water cycle over the last centuries, driven by climate variability and human activities, have been particularly pronounced in the arid regions of the south. The El Bibane and El Grine lagoons constitute natural archives that can be used to reconstruct extreme hydrological events through the sedimentary deposits they leave behind.
Previous studies have identified major floods during the last several millennia, which were responsible for the deposition of fine-grained continental sediments transported by ancient wadis. However, the impact of these events on benthic communities remains poorly understood.
This research activity aims to investigate the relationships between sediment inputs and the distribution of mollusks and benthic foraminifera in the El Bibane and El Grine lagoons. The working hypothesis is that fine sediments resulting from flood events favor tolerant lagoonal species, whereas periods of hydrological stability promote the development of more stable marine faunal communities.
The analysis of fauna along sediment cores will therefore provide insights into the evolution of the lagoonal ecosystem and its response to extreme hydrological events.
Details of the research activity
Activity 4
Lead: Chahira ZAIBI (M.A)
Major climatic fluctuations that affected Europe and the North Atlantic from the Medieval Climate Anomaly to the Little Ice Age (approximately 500–1850 AD) had significant effects on hydrological regimes in North Africa. In Tunisia, these variations in the water cycle resulted in substantial changes in precipitation, fluvial dynamics, and consequently sediment and nutrient inputs into coastal systems.
The Ghar El Melh lagoon, now isolated from the Gulf of Tunis, and the Khneiss lagoon provide valuable settings for investigating local responses to these hydroclimatic changes. Historically supplied with water and sediments from the Medjerda River, the Ghar El Melh lagoon, together with the Khneiss lagoon, has recorded the combined effects of climatic variability, deltaic transformation, and progressive anthropogenic influence in the region.
Initial results from our multidisciplinary research suggest that fluctuations in the hydrological cycle have strongly influenced sedimentation and the dynamics of benthic communities, particularly foraminifera, which are sensitive bioindicators of environmental stress.
As part of our research into past environmental dynamics, we have initiated a multidisciplinary study of the Ghar El Melh lagoon in northern Tunisia and the Khneiss lagoon. This project aims to reconstruct climatic and environmental changes that occurred over the last centuries, a particularly critical period for this sector of the Mediterranean coastline.
Preliminary results reveal significant changes in the composition of benthic foraminiferal assemblages, together with notable changes in sedimentary processes. These disturbances are closely associated with major transformations of the hydrosedimentary system of the Gulf of Tunis, particularly the infilling of the Utica Bay and the progressive isolation of the Ghar El Melh lagoon, as well as the recent anthropogenic transformation of the Khneiss lagoon.
The Medjerda River, the main river in northern Tunisia, has played a decisive role in this evolution through its substantial sediment inputs. These nutrient-rich sediments have contributed to changes in the trophic conditions of the lagoon and to the development of specific benthic assemblages, particularly among foraminifera.
Details of the research activity
Activity 5
Lead: Mohamed Kamoun (M.A)
The introduction of non-native benthic foraminifera represents a major ecological issue in coastal ecosystems subjected to anthropogenic pressures and climate change. Transported notably through ballast water or introduced through Lessepsian migration, tropical species such as Amphistegina lobifera, Pararotalia calcariformata, and Nonionella stella have progressively colonized the eastern Mediterranean, favored by increasing sea-surface temperatures.
These species exhibit substantial ecological plasticity and can tolerate stressful environmental conditions, including high temperatures, hypoxia, pollution, and turbidity, thereby facilitating their expansion into areas previously occupied by native species.
Their proliferation can alter the structure of benthic communities, biogeochemical processes such as bioturbation, carbonate production, and carbon sequestration, as well as sedimentary habitats, potentially affecting functional biodiversity.
Furthermore, the presence of non-native species, particularly Amphistegina lessoni and A. lobifera, in sedimentary archives provides a valuable bioindicator of episodes of sea-surface warming during the Quaternary.
Details of the research activity
