1. Ostracods are important components of groundwater communities that are influenced by abiotic environmental conditions and biotic interactions. We aimed to identify the factors associated with ostracod assemblages inhabiting groundwaters accessed through dug wells in several regions of Benin in West Africa, exposed to chronic influences of anthropogenic disturbances such as nutrient enrichment from infiltration of sewage or fertilisers from the surface. 2. Ostracods were collected from 219 wells in seven catchment areas using two complementary methods: active sampling with a phreatobiological net and passive trapping with a baited trap. Associations with 31 statistical predictor variables (a range of abiotic descriptors of water, hydrology, protection, usage and the type of well) and ostracod occurrence was evaluated using distance-based linear models and redundancy analysis. 3. We identified 60 ostracod species representing two ecological groups: 36 species of stygobites of the family Candonidae, an endemic species flock of a vast evolutionary radiation, and 24 species of non-stygobites, mostly of the family Cyprididae. This is the first large groundwater ostracod species flock reported from the entire African continent. 4. A number of variables associated with the structure of ostracod assemblages were identified. Except for the descriptors of wells, these included well-known chemical and physical properties (electrical conductivity, pH, temperature or bicarbonate concentration), but also the concentration of NO2−. Although NO2− has not yet been demonstrated to be important for ostracod assemblages, stygobites occurred significantly less frequently in higher concentrations of NO2− than most non-stygobites. 5. We determined that stygobitic (candonid) ostracod species and genera may be a good potential environmental indicator of groundwater quality especially nitrite pollution of groundwater in tropical West Africa. 6. In tropical West Africa, many human populations rely on groundwater for domestic use and agricultural irrigation, while these aquatic resources are also often affected by anthropogenic disturbances. The use of stygobitic ostracods as potential indicators of groundwater quality offers a valuable tool for environmental monitoring and protection in tropical regions in West Africa, and may be also globally.
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RBINS Staff Publications 2025
The faunal remains are described from Nkile and Bolondo, two archaeological sites in the equatorial rainforest of the Democratic Republic of Congo. Both river-side settlements, located in the Ruki-Tshuapa basin and dating to between the 14th century to the second half of the 20th century, show a heavy reliance on aquatic food resources. The animal remains show that fishing was a major subsistence activity, whereas hunting, slaughtering of domestic stock and harvesting of molluscs were less frequent activities. The contribution to the diet of the different animal taxa suggested by the zooarchaeological data is in line with recently published stable isotope results obtained on humans and animals from Bolondo. The type of fish, and in particular their reconstructed sizes, show that the major exploited fishing grounds were shallow waters that became accessible during the low water seasons (nowadays July-August and a minor season in March at both sites). The proportions of the exploited fish taxa are comparable to those marketed nowadays in larger urban centres. Juvenile fish, and to some extent, small crocodiles, were heavily exploited but it is argued that at the time this was still a sustainable activity that did not deplete the fauna as much as today since human populations were smaller and the fishing gear less effective.
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RBINS Staff Publications 2022
