Abstract

The aim of the study was to determine how mining operations affected the health of aquatic ecosystems. The investigation was carried out in the diamond, gold, and manganese mining areas of Tortiya, Hiré, and Lauzoua. Leaf litter bags were used to assess breakdown. To further identify macro-invertebrates in the laboratory, leaves from emerged large-mesh bags were preserved in 70% alcohol. The results showed that there was no statistically significant difference in lost masses between small mesh nets and large mesh nets for a foliar species at the same station. The breakdown rates of Alchornea cordifolia in large mesh nets at N'Teko station were significantly higher (p<0.05) than in small mesh nets (0.017 j-1). The majority of the macro-invertebrates found in leaf litter bag were insects and gastropods, with proportions exceeding 50%. Insects dominated the macroinvertebrate group involved in leaf litter decomposition in Lauzoua (91% of associated species) and Hiré (56.5%), whereas gastropods (Mesogastropoda and Basommatophora, 77% of related organisms) were most abundant in Tortiya. The functional feeding groups of macro-invertebrates involved in the breakdown of leaf litter were dominated by predators (46% of species) and scrapers grazers (27% of taxa). Shredders made up only 1% of the species associated with leaf litter. Macro-invertebrates’ contribution was significantly higher (Mann -Whitney test, p <0.05) at Bou 1 station. Insects and gastropods made up the majority of the macro-invertebrates involved in litter decomposition. Breakdown rates were relatively low at all stations.

Key words: Macro-invertebrates, contribution, breakdown rates, mining areas, streams.