Abstract
Marine nematodes from Bizerte lagoon sediments (Tunisia, Northern Mediterranean) were treated with the penicillin G in microcosm experiment for 30 days. Sediment was treated with five concentrations of this antibiotic (D1: 3 mg.L-1, D2: 30 mg.L-1, D3: 300 mg.L-1, D4: 600 mg.L-1, D5: 700 mg.L-1). Differences in univariate indices for trophic structure of nematode assemblages occurred between control and treatments. Results from multivariate analyses of trophic group abundance demonstrated that the responses of nematode were dependent on the concentrations used for the sediment treatment. Microvores (M), Deposit feeders (DF) and Ciliate consumers (CF), most abundant in control microcosm, were very much affected and their abundance decreased significantly in response to antibiotic contamination. Suckers of epistrates (EF) seems unaffected by the treatment but abundance of optional Predators (FP) and exclusive Predators (Pr) showed significant increase in dominance compared to the control.