Free-living nematodes, bio-indicators of the evolution of hydrocarbon concentrations in the bay of Bizerta (Tunisia).

Free-living nematodes, bio-indicators of the evolution of hydrocarbon conce ntrations in the bay of Bizerta (Tunisia). A first monitoring in the bay of Bizerta during July 1992, based upon seven sampling stations, indicated a refinery and tankers, berthing at proximity, to be the cause of high amount s of hydrocarbon noted in the region. The nematodes, omnipresent, show a st atistically significant decrease in densities, biomasses and specific diver sity, in relation to concentrations of hydrocarbon deposited in sediments. After an apparent improvement of the qualify of waste waters discharged by the refinery, a similar study was repeated in July 1996. The results indica te an increasing amount of hydrocarbons in the sediments in 1996 to which t he nematodes have responded by a quantitative and qualitative impoverishmen t of their community.