Distribution of Chironomidae (Diptera: Insecta): Bio-Indicators of Organic Pollution in the Bamenda River Basin, North West Region, Cameroon

Abstract

The influence of physical and chemical parameters on the abundance and diversity of chironomids has been studied in river mezam and its affluence which present a moderate to highly polluted water in Bamenda. Sampling was carried out on each of the rivers with its 13 sampling stations over a period of six months (January 2017– June 2017). Physico-chemically, we noted a relatively higher water temperature, low dissolved oxygen with a moderate organic pollutants concentration.

Eight chironomid genera were identified representing 18 species; Chironomus stigmaterus, Chironomus plumosus, Chironomus riparus, Chironomus staegeris, Chironomus crassicaudatus, Polypedilum illinoeuse, Polypedilum laetum, Polypedilum beckae, Polypedilum sp., Dicrotendipes neonodestus, Micropsectra sp., Radotanypus florens, Cantopelopia gesta, Brundiniella eumorpha, Procladius bellus, Tanypus sp. Zalutschia sp. and Eukiefferiella sp. were identified. Assessment of their relationships with several environmental variables was performed using multivariate analysis. Chironomus and Polypedilum which are generally considered resistant to organic pollution dominated in the dry season which is characterized by high accumulation of house hold waste in the rivers and other wastes from the various markets. Meanwhile, Zalutschia, Eukiefferiella, Radotanypus and Procladius which are less adopted to organic pollution dominated in the rainy season that is characterized by high water contain in dissolved oxygen compared to the dry season. Consequently, these aquatic communities were ecological disordered by organic pollution that caused a decreased in the different genus and loss of sensible species and the abundance of tolerant species. We found several significant correlations (p<0.05), but most of them were low (r<0.5). We can only highlight those that were higher (r>0.5). There were significant positive correlations between temperature and a number of chironomus species (r=0.270) and for the taxa we found a significant negative correlation between electrical conductivity, Total Dissolved Solids and Procladius bellus (r=-0.267), (r=-0.267) respectively and a significant positive correlation between nitrate concentration and Chironomus stigmaterus (r=0.230). The Shannon and weaver indice (2.75 bit/ind) and the Pelour (0.76) shows that all the sampling stations present a relatively high diversity.