INVENTORY OF AQUATIC MOLLUSCS IN THE SOUBRE RIVER-LAKE DAM AREA TO ASSESS THE BIOLOGICAL STATUS OF THIS AQUATIC ECOSYSTEM (SASSANDRA RIVER, COTE DIVOIRE, WEST AFRICA)

Abstract

The aim was to study the population dynamics of aquatic molluscs in relation to abiotic variables in the fluvio-lacustrine zone of the Soubre hydroelectric dam, in order to determine its bioecological status. The Mollusc class and physico-chemical parameters were sampled monthly in two periods, the first from July 2019 to February 2020 and the second from March 2021 to June 2021 at six (06) sampling stations. The total abundance was 16,885 individuals divided into 16 taxa belonging to two (02) classes, five (05) orders and ten (10) families were identified. The stations located in the lake recorded the highest number of individuals, while the TIE station (Tieme, 13 taxa) located in the fluvial environment was the most diverse of all the sampling sites. Taxa such as Melanoïdes tuberculata, Indoplanorbis exustus and Viviparus sp. appeared frequently in all the sampling stations. Focused Principal Correspondence Analysis (FPCA) revealed that turbidity, TDS and dissolved oxygen had a strong influence on the abundance of molluscs at the sites studied. Several species studied in our environment are important intermediate hosts of parasites, in particular Planorbidae (Indoplanorbis exustus), which represents a potential risk to public health. However, three invasive taxa, Aplexa marmorata, Indoplanorbis exustus and Melanoïdes tuberculatawere collected. The biological condition of the sampling sites was generally good. Assuming that the ecological state of the sediments in the lake environment is not yet damaged.