Assessment of microalgae diversity in relation to hydrocarbon pollutants in port sediments: Case study of Sfax port-Tunisia

Abstract

The present research has been particularly oriented to characterize the organic pollutants as phthalates, hydrocarbons and in Sfax port sediments. As the microalgae performed good results in their bioaccumulation and biodegradation, the microalgae species in both port sediments and column waters were counted and identified. Di-n-butyl phthalate, Di-2-ethylhexyl phthalate as well as aliphatic and polycyclic aromatic hydrocarbons were identified through GC-MS chromatograms released on sediment extracts of three samples taken from the Sfax port basins located on the eastern Tunisian coast. Microalgae identification and cell counts of sediment samples as well as water columns were performed applying the sedimentation method of Utermöhl. The chromatograms revealed developed peaks of phthalates compared to those of aliphatic hydrocarbons with successive humps corresponding to an unresolved complex mixture, corroborating an advanced degree of biodegradation. The n-alkanes distribution and the development of the bb-epimers of C_{27 − 29} steranes proved the petrogenic hydrocarbons origin. This result was equally confirmed by the ratio of fluoranthene and pyrene PAHs concentrations. The hydrocarbons degradation was assigned to the relative abundance of certain microalgae species, already recognized to degrade hydrocarbons pollutants such as diatoms Skeletonema costatum and Nitzschia sp.. The proliferation of toxic dinoflagellates as Karenia selliformis enhanced the high pollution degree of port sediments. Whereas other microalgae species displaying high abundance in port sediments, revealed their capacities to degrade organic matter and PAHs. The microalgae-cyanobacteria consortium as Pinnularia sp.- Merismopedia sp. seemed to display a powerful tolerance to both trace metals and organic pollutants.