Effet du Benzo (a) pyrene sur la communaute phytoplanctonique du canal et de la lagune de Bizerte (Tunisie)

Abstract

The Bizerte lagoon is becoming a key receptor for several micro-pollutants, which are sometimes toxic and may pose a threat to the ecosystem. Among these pollutants, polycyclic aromatic hydrocarbons (PAH) were selected as priority pollutants. The present study investigated for the first time the effect of Benzo(a)pyrene [B(a)py] on phytoplankton community in a lagoonal station (station moderately polluted by the B(a)py) and a station at the channel (station highly polluted by B(a)py) of Bizerte in summer (July) and autumn (November) 2009. For this, phytoplankton communities collected from these stations were maintained in culture for 6 days under three different treatments: a control (uncontaminated) and two contaminations with 0.5 mg l super(-1) (treatment B1) and 1 mg super(-1) (treatment B2) of B(a)py. During the incubations, chlorophyll a (Chl a), the growth rate of phytoplankton were measured for the three treatments. The results showed that at the channel, both contaminations with B(a)py did not induce any effect neither on Chl a nor on microalgal growth in November. High B(a)py contamination was even followed by a stimulation of phytoplankton growth in July. This suggests that the phytoplankton originated from the channel was more resistant to high concentrations of B(a)py, because this area, located approximately of ciment industry is among the most polluted areas by B(a)py. However, at the lagoonal station, the growth rates of phytoplankton declined after both PAH contaminations. This indicates that the microalgae present in this station, environment less polluted than the channel, were sensitive to B(a)py.