Abstract

We studied the acute toxicity of a raw effluent from a battery manufacturing plant (Pilcam) in Douala, Cameroon, to a freshwater fish (Oreochromis niloticus), and subsequently evaluated its sub-acute effects on water quality and the biota in freshwater microscosms. The acute toxicity test was based on 96 hrs static renewal bioassays that resulted in 96-h LC50 and LC90 values of 16 and 20.7% (v/v), respectively. The sub-acute experiments were conducted by exposing several species of aquatic organisms (plankton, macroinvertebrates and mollusks) to lower effluent concentrations [1.6%, 8.0%, 16% (v/v)] for six weeks, and monitoring their survival rates, as well as the physical and chemical characteristics of water. These concentrations were based on 10%, 50%, and 100% of the 96 h - median lethal concentrations (LC50) of the effluent to the freshwater fish, Oreochromis niloticus. Significant effects on functional parameters, such as, chlorophyll-a and total protein could not be demonstrated. However, the activity of alkaline phosphatase was significantly inhibited at all concentrations tested. Phytoplankton, zooplankton, macro-invertebrate communities and snails were negatively affected by the effluent application at concentrations ? 8% (v/v), with chlorophyta, ciliates, ostracoda, annelida, planaria and snails being the most sensitive groups. The snails were eliminated after 24 h exposure from microcosms treated with effluent at concentration ? 8% (v/v). Effluent exposure also caused significant effects on water quality parameters (DO, pH, hardness, conductivity, color, turbidity, ammonia) in general at concentrations ? 8% (v/v). Temperature and alkalinity were not significantly affected. Overall, data from this research indicate that a dilution of the Pilcam effluent down to 1.6% does not provide protection against chronic toxicity to aquatic organisms. Further studies are needed to determine the no observable adverse effect level (NOAEL), as well as a chronic reference concentration for this effluent.

Highlights

  • Cameroon is located along the end of the West side of West African Coast of the Gulf of Guinea in the Atlantic Ocean

  • The country's coastline is 402 km long and extends from the Rio del Rey Estuary at the boundary with the Federal Republic of Nigeria, and to the Kribi coast along the boundaries with Equatorial Guinea and Gabon. It is the major sink for discharge of pesticides and persistent organic pollutants (POPs) by inland rivers that drain into the Atlantic Ocean

  • About 39% of the population in this zone has an annual average consumption of 7.02 kg of fish harvested from the Atlantic Ocean

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Summary

Introduction

The country's coastline is 402 km long and extends from the Rio del Rey Estuary at the boundary with the Federal Republic of Nigeria, and to the Kribi coast along the boundaries with Equatorial Guinea and Gabon. It is the major sink for discharge of pesticides and persistent organic pollutants (POPs) by inland rivers that drain into the Atlantic Ocean. About 39% of the population in this zone has an annual average consumption of 7.02 kg of fish harvested from the Atlantic Ocean

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