Freshwater Microcosms-Based Assessment of Eco-toxicological Effects of a Chemical Effluent from the Pilcam Industry in Cameroon

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.

Acute toxicity of monocalm 400sl (<i>monocrotophos</i>) and profenalm 720ec (<i>profenofos</i>) on <i>Oreochromis niloticus</i> (Linnaeus, 1758)

“…It was found that the paralysis appeared after two to three weeks of exposure (Dinham, 1993). In agricultural areas, huge amounts of pesticides can be drained by storm water and discharged into nearby rivers plantations, jeopardizing, not only the survival of exposed organisms, but also the quality of these waters (Marchand, 1989;Monkiedje et al, 2004;Babut et al, 2006). Tests performed in laboratory microcosm, had previously shown different levels of tolerance of aquatic organisms to pesticides exposure (Monod, 2001).…”