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Pierre Ngassam

  • Biodiversity Journal, 6 (1): 027-040

    Siméon Tchakonté, Gideon A. Ajeagah, Nectaire Lié Nyamsi Tchatcho, Adama Idrissa Camara, Dramane Diomandé & Pierre Ngassam
    Stream’s water quality and description of some aquatic species of Coleoptera and Hemiptera (Insecta) in Littoral Region of Cameroon

    ABSTRACT
    Aquatic insects are the dominant taxon group in most freshwater ecosystems and are particularly suitable for large scale and comparative studies of freshwater community responses to human-induced perturbations. Understanding these responses is crucial for establishing conservation goals. In this study, we used three families of aquatic insects (Coleoptera Gyrinidae, Hemiptera Gerridae and Veliidae) as surrogates to measure the aquatic health of urban streams in the city of Douala, and we described eight characteristic species. Aquatic insects were sampled monthly over a 13-month period in two forested sites and ten urbanized sites. Meanwhile, measurements of the environmental variables were taken. Overall, 20 species were identified; the family Gerridae was the most diversified with 11 species, followed by Veliidae (5 species), and Gyrinidae (4 species). All these species were present only at the two forested sites; no species was found in the urbanized area all over the study period. Morphological description of the eight best indicator species (Orectogyrus specularis Aubé, 1838, Orectogyrus sp.1, Orectogyrus sp. 2, Eurymetra manengolensis Hoberlandt, 1952, Eurymetra sp. 1, Eurymetra sp. 2, Rhagovelia reitteri Reuter, 1884 and Rhagovelia sp.) revealed not described characteristic features and potentially new species. This testified that in Cameroon, biodiversity of aquatic insects is yet entirely to be investigated, and that there is an urgent need in their taxonomic revision. Physicochemical analyses revealed the very poor health status of urban streams with highly polluted water, while suburban streams have unpolluted water. The results of redundancy analysis revealed that the presence of Gyrinidae, Gerridae and Veliidae species is undoubtedly favored by the high rate of dissolved oxygen, important canopy coverage and very low organic matter input. It is thus clear that polluted status of urban streams due to human activities is the primary cause of the extinction of aquatic insect species.