Ecotoxicological evaluation of surface waters in Northern Namibia.

Area of Science:

• Environmental Science
• Ecotoxicology
• Water Resource Management

Background:

• Central-northern Namibia's freshwater systems (Kunene River, Kavango River, Cuvelai-Etosha Basin) face significant anthropogenic pressure.
• Over 1 million people rely on these water resources, yet comprehensive ecological status and water quality data are lacking.
• Understanding ecosystem health and pollutant effects is vital for safe water resource management.

Purpose of the Study:

• To assess the ecological status and water quality of key Namibian freshwater systems.
• To evaluate the ecotoxicological effects of pollutants on different trophic levels.
• To identify specific risks, including mutagenicity, dioxin-like potential, and estrogenicity.

Main Methods:

• Surface water sampling across Kunene River, Kavango River, and Cuvelai-Etosha Basin.
• Application of three bioassays: algae growth inhibition, daphnia immobilization, and zebrafish embryo toxicity.
• In vitro assays for mutagenicity (Ames), dioxin-like activity (micro-EROD), and estrogenicity (YES).

Main Results:

• Acute toxicity to fish embryos and daphnia was prevalent across all sampled sites.
• The Iishana system within the Cuvelai-Etosha Basin exhibited the highest acute toxicity.
• Mutagenic and estrogenic effects were identified at three Iishana system sites; cellular effects were weak but higher in Iishana.

Conclusions:

• Namibian freshwater systems show significant ecotoxicological risks, particularly in the Iishana system.
• Anthropogenic pressures are leading to adverse effects on aquatic organisms and ecosystem health.
• Findings underscore the urgent need for robust water resource management strategies to mitigate pollution impacts.