Chironomid bio-ecology in an anthropisized aquatic ecosystem in Yaounde (Cameroon):community diversity and relationship with the environmental variables of the water system

In this study, the Olezoa stream in Yaounde was assessed from November 2013 to May 2014 to identify the chironomid genera that are present in the water system, determine the physicochemical properties of the water, and describe the relationships between species composition of chironomid communities and environmental parameters. Samplings were carried out on monthly basis at three different stations of the hydrosystem.The results showed that, Olezoa stream is slightly acidic (6.8 ± 0.2 CU), moderately mineralized (312.8 ± 95.4 μS/cm), rich in organic matter and less oxygenized (1.8 ± 1.3 mg/L) and rich in suspended solids (247.4 ± 172.4mg/L). The low values obtained for most physicochemical quality of the aquatic ecosystem justifies the high biodiversity of the Chironomidaecommunity suggest their degree of tolerance and sensitivity to aquatic pollution. This is due to the fact that the chironomidae developmental stages exhibit a variety of adaptations in polluted areas which could be: morphological, physiological and behavioral, occurring simultaneously within each developmental form and the different genera. The relationship between the dynamics of the different genera and the physicochemical variable were confirmed by the Spearman correlation index. This indicated a positive correlation between the distribution of chironomid genera and some environmental variables such as Turbidity (r= -0.517 p<0.05), Suspended solids (r= 0.490, p<0.05) and Total Dissolved Solids (TDS) (r =-0.555, p=0.05) revealing their ecological impetus in the biological management of aquatic ecosystems.

Key words: Chironomid,Olezoa stream, pupalexuviae,Larva instars, aquatic pollution.

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