Impact of aquaculture on the physico-chemical quality and chlorophyll biomass of the waters of the Jacqueville aquaculture station (Ebrié Lagoon, Ivory Coast)

Résumé

Aquaculture in lagoon enclosures carried out at the Jacqueville aquaculture station is likely to harm the quality of lagoon waters and affect human and aquatic health. This study aims to evaluate the effects of aquaculture on the aquatic environment by studying the quality of the water of the Jacqueville station through physico-chemical parameters and the chlorophyll biomass. Six sampling stations were investigated monthly from January to December 2020. In-situ measurements were carried according to conventional methods. The chemical and biological characteristics were analysed respectively according to AFNOR 2005 standards and Lorenzen method. The organic pollution index (OPI), SEQ-water grid and trophic status were determined to assess the quality of the waters. The results show that dissolved oxygen, transparency and suspended matter fluctuate significantly from one station to another. Temperature, electrical conductivity, dissolved oxygen and salinity are significantly higher during the dry season. While, suspended matter, nitrogen concentration, phosphorus concentration, BOD₅ and COD are high in rainy season. The concentration of chlorophyll a is significantly higher during the main rainy season at all stations. The values of OPI indicates a moderate organic pollution (3.5). The results of trophic status showed that the waters of all stations are eutrophic. The results of this study indicate that aquaculture activity has had only an impact on the physico-chemical and biological quality of the lagoon waters. It is suggested that lagoon water monitoring systems be set up for early detection and timely management of potential negative impacts of human activities.

Keywords:  aquaculture, chlorophyll biomass, impact, Ebrie lagoon, physico-chemical