Publications
A predominantly tropical influence on late Holocene hydroclimate variation in the hyperarid central Sahara
A new lake sediment record from Ounianga Serir oasis reveals that the central Sahara experienced hyperaridity more extreme than today around 4200 years ago. The hypersaline terminal lake, sustained by fossil groundwater inflow, remained stable throughout the late Holocene but exhibited sensitivity to local rainfall and evaporation variations. Geochemical proxies indicate that century-scale hydroclimate changes in this region were primarily driven by tropical West African monsoon intensity, with shorter-term fluctuations influenced by midlatitude Atlantic Ocean circulation shifts.
High prevalence of urinary schistosomiasis in a desert population: results from an exploratory study around the Ounianga lakes in Chad
A high prevalence of urinary schistosomiasis, reaching nearly 40%, was discovered among populations living around the UNESCO World Heritage Site Lakes of Ounianga in Chad. This finding challenges the assumption that such water-borne diseases are confined to tropical regions. The study, conducted in January 2019, employed a cross-sectional survey, focus group discussions, and malacological surveys to detect infections with Schistosoma haematobium and Schistosoma mansoni, as well as to identify intermediate host snails. Molecular genetic methods confirmed the presence of S. haematobium, with 51.5% of infected individuals suffering from heavy infections. The study also highlighted significant morbidity associated with urinary schistosomiasis and a critical lack of access to diagnostics and treatment in this desert population.
Staurophora ouniangaensis sp. nov. (Bacillariophyceae, Anomoeoneidaceae), a new diatom from the Ounianga Lakes in the Sahara, Chad
Researchers have identified and described a new species of diatom, Staurophora ouniangaensis, from the saline waters of the Ounianga Lakes in Chad's Sahara. This discovery, based on detailed microscopic observations, highlights the unique morphological traits of the species, including its valve outline and slightly twisted frustules. The study also distinguishes it from a similar species, Cymbella obtusa, by its finer stria density. Notably, Staurophora ouniangaensis supports the preference of this genus for inland saline environments, as it thrives in mesosaline to hypersaline waters within these lakes.
High Prevalence of Urinary Schistosomiasis in a Desert Population: Results from an Exploratory Study Around the Ounianga Lakes in Chad
A high prevalence of urinary schistosomiasis, reaching nearly 40%, was discovered among populations living around the UNESCO World Heritage Site of Ounianga Lakes in Chad. This finding challenges the assumption that such water-borne diseases are limited to tropical regions, highlighting significant public health risks even in desert environments. The study employed a cross-sectional survey, focus group discussions, and environmental sampling to detect Schistosoma haematobium and S. mansoni, confirming infections through molecular genetics and identifying intermediate host snails (Bulinus truncatus) that facilitate local transmission. While S. mansoni infections were detected, the absence of its intermediate hosts suggests limited relevance. Qualitative data underscored the morbidity burden of urinary schistosomiasis and the lack of access to diagnostics or treatment in this remote region, emphasizing the need for tailored interventions.
Contribution to knowledge of the Lakes of Ounianga by bathymetry and physicochemistry
A groundbreaking study of the Ounianga Lakes in Chad reveals significant variations in bathymetry and water physio-chemistry, contributing to our understanding of these unique ecosystems. The research found that Lake Yoan reaches depths of up to 27 meters, while Lake Teli is shallower with a maximum depth of 5.7 meters. Water temperatures in Teli Lake ranged from 20.8°C to 36°C, whereas Lake Yoan exhibited a broader range from 10.5°C to 32.9°C. Conductivity values also varied dramatically, with Teli Lake showing measurements between 69 and 111,700 μS/cm, and Lake Yoan ranging from 100 to 64,000 μS/cm. The study employed advanced bathymetric surveys and in situ physicochemical analyses, providing a comprehensive characterization of these lakes. This research not only advances our knowledge of continental hydrology but also highlights the ecological diversity within the Ounianga Lakes, which are part of the UNESCO World Heritage Site.
A new cichlid fish in the Sahara: The Ounianga Serir lakes (Chad), a biodiversity hotspot in the desert
A previously undescribed cichlid fish, Astatotilapia tchadensis, has been discovered in Lake Boukou, part of the Ounianga Serir lakes in Chad, a UNESCO-listed desert landscape. This new species, characterized by distinctive features such as black bars, orange spots on its anal fin, and unique pharyngeal dentition, highlights the remarkable biodiversity of these lakes, which are sustained by subsurface groundwater inflow. The discovery underscores the Ounianga Serir lakes as a critical hotspot for vertebrate diversity in one of the world's most arid regions, with at least six fish species belonging to three families thriving in this extreme environment.
Two new stygobiotic copepod species from the Tibesti area (Northern Chad) and a re-description of Pilocamptus schroederi (van Douwe, 1915)
A hydrobiological expedition to the Ounianga-Tibesti area of northern Chad uncovered two new stygobiotic copepod species, Haplocyclops henrii and Parastenocaris joi, alongside a re-description of Pilocamptus schroederi. These groundwater-dwelling crustaceans, previously unknown in this region, are part of a Tertiary-era fauna that once thrived across the Sahara. The discovery highlights the Tibesti area as a biodiversity hotspot and suggests these species may be relicts of Gondwanaland's ancient ecosystems. The study provides detailed morphological descriptions and ecological insights into these stygobiotic copepods, contributing to our understanding of subterranean life in desert environments.
Relict populations of Diaphanosoma (Cladocera: Ctenopoda) in the Chadian Sahara, with the description of a new species
Scientists have discovered two species of Diaphanosoma, the first ctenopods recorded in the Sahara desert. One species, D. excisum, found in a freshwater guelta on the Tibesti mountains, is tropical and considered a relict from Megachad times. The other, a newly described species (D. bopingi), inhabits a saline lake on the Ounianga plateau and is more salt-tolerant, suggesting it is a relict of cooler, more humid periods in the desert's history. This study highlights the unique biodiversity and evolutionary significance of these relict populations, providing insights into past environmental conditions in the Sahara.
A study of the relict fish fauna of northern Chad, with the first records of a polypterid and a poeciliid in the Sahara desert
A groundbreaking discovery reveals the presence of two previously unrecorded fish species in the Sahara Desert: Polypterus senegalus (Polypteridae) and Poropanchax normani (Poeciliidae). These relict populations, along with Tilapia zilli (Cichlidae), were found in Lake Boukou near Ounianga Serir, Chad, significantly expanding the known relict fish fauna of the region to six species. The study also clarified the specific status of Barbus macrops in Bachikere guelta within the Ennedi Mountains and documented the toad Amietophrynus regularis in Ounianga Kebir. This research sheds light on the unique biodiversity of Saharan water bodies, challenging assumptions about the distribution of aquatic species in extreme desert environments.
Varved sediments of Lake Yoa (Ounianga Kebir, Chad) reveal progressive drying of the Sahara during the last 6100 years
A 6100-year sediment record from Lake Yoa, part of the UNESCO World Heritage Site Lakes of Ounianga in Chad, reveals a progressive drying trend in the eastern Central Sahara. The study, utilizing high-resolution sedimentological and geochemical analyses, including X-ray fluorescence core scanning, demonstrates that decreasing monsoon rainfall combined with strong evaporation transformed the once hydrologically open and fresh lake into its current hypersaline state, which has persisted for about the last 1050 years. The data also indicate a gradual increase in aeolian input, supporting the notion of a progressive rather than abrupt transition from a humid to an arid Sahara during the Mid to Late Holocene.
Modern and early Holocene mollusc fauna of the Ounianga lakes (northern Chad): implications for the palaeohydrology of the central Sahara
A rich early Holocene mollusc fauna, including a new species (Gabbiella ouniangaensis), was discovered at the Ounianga lakes in northern Chad, suggesting these lakes were hydrologically isolated during that period. The modern mollusc community is impoverished and likely resulted from recent colonization events after the eradication of the early Holocene fauna due to high salinity or desiccation. The study analyzed fossil molluscs from diatomaceous limestone outcrops at Ounianga Serir, comparing them with other Saharan lake sites to infer past hydrological conditions in the central Sahara.
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