Abstract:

All over the world pharmaceuticals are widely used to treat human diseases and to maintain healthy life but the aquatic environment is awash with these drugs leading to environmental health concern. Pharmaceutical exposure leads to toxicity in many non-target organisms, such as freshwater shrimp, Gammarus pulex. In this study, the biological effects of diclofenac on growth, feeding and mortality of aquatic macro-invertebrate shrimp (Gammarus pulex) was investigated in a laboratory experiment. Test concentrations were selected to mimic environmental detection levels reported for UK rivers in the literature. Seventy-five (75) G. pulex assigned random among the five experimental groups. were exposed to environmentally relevant concentrations of diclofenac (202.2 ngL-1, 1596.45 ngL-1 and 2,990.7 ngL-1) for four (4) weeks. There was decrease in mass and the growth rate decreased (p<0.001) significantly compared to controls. Also, the feeding rates in the controls were higher hence, the amount of feed materials consumed were dose dependant and significantly influenced by diclofenac (p < 0.001).Mean mortality was more than 80 % in the high treatment in the 3rd week of the experiment and there were statistically significant differences between the treatments and controls ( p < 0.05). These results showed that exposure of G. pulex to environmentally relevant concentrations of diclofenac have significantly affected feeding activity, impacted growth and increased mortality, suggesting that prolonged exposure, use of sensitive points (behavioural signs) and use of susceptible test species (G. pulex) are more useful for assessing sublethal impacts of contaminants and are sensitive indicators of toxicity in benthic macroinvertebrates animals. Hence, these tools are useful in the aquatic environmental risk assessment of drugs. 

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