RESEARCH ARTICLES CURRENT SCIENCE, VOL. 96, NO. 2, 25 JANUARY 2009 238 *For correspondence. (e-mail: nbenson@covenantuniversity.com) Petroleum hydrocarbons contamination of sediments and accumulation in Tympanotonus fuscatus var. radula from the Qua Iboe Mangrove Ecosystem, Nigeria Nsikak U. Benson 1, * and Joseph P. Essien 2 1 Department of Chemistry, College of Science and Technology, Covenant University, P.M.B. 1023, Ota, Nigeria and Department of Atmospheric and Oceanic Sciences, McKinley Ocean Biogeochemistry Research Group, University of Wisconsin, Madison, WI 53706, USA 2 Department of Microbiology, Faculty of Science, University of Uyo, P.M.B. 1017, Uyo, Nigeria The pollution of coastal ecosystems as a result of petroleum-related activities is increasing, and the litera- ture on occurrence, levels and seasonal dynamics of petroleum hydrocarbons in sediments and biota from the impacted areas of the Niger Delta, Nigeria, is pra- ctically scanty. This study was set out to provide information on the status of contamination by petro- leum hydrocarbons in Tympanotonus fuscatus var. radula and sediments from Qua Iboe Estuary, Nigeria. Analyses for total petroleum hydrocarbons (TPHs) were performed on Tympanotonus fuscatus var. radula and sediment extracts using gas chromatograph with flame ionization detector (GC-FID). Seventy-two sam- ples each of mangrove epipellic (intertidal) and benthic (subtidal) sediments, and T. fuscatus var. radula were analysed monthly between June 2003 and February 2004, covering peak periods of the wet and dry sea- sons. Results revealed that the TPHs level in sedi- ments and T. fuscatus were highly variable. It ranged between 18.01 ± 0.04 and 210.23 ± 1.18 μg g –1 dry wt of epipellic sediment, 5.00 ± 0.82 and 232.00 ± 3.23 μg g –1 dry wt of benthic sediment and 9.40 ± 1.0 and 23.27 ± 1.0 μg g –1 dry wt of T. fuscatus. Summary continuous descriptives and correlation analyses re- vealed that TPH levels of the epipellic and benthic sediments showed a significant relation (r = 0.54, CI = 0.18–0.78), and correlated with levels in T. fuscatus. The overall levels of TPHs in the Qua Iboe Estuary when compared to similar ecosystems with substantial industrial and domestic coastal activities worldwide, revealed a moderate to high level of mineral hydro- carbon pollution. Keywords: Estuary, petroleum hydrocarbons, sediment, Tympanotonus fuscatus. IN recent times, contamination of the environment by petro- leum hydrocarbons is potentially widespread because modern society uses so many petroleum-based products (for example, gasoline, kerosene, fuel oil, mineral oil and asphalt). Hydrocarbons are quantitatively the most impor- tant constituents of petroleum, and arise from natural as well as anthropogenic sources 1,2 . Human-mediated sources of petroleum hydrocarbons include offshore oil production, marine transportation, atmospheric or aerial depositions from combustion of coal and gas flaring, direct ocean dumping, coastal, municipal and industrial wastes, and run- off 3 . However, among the anthropogenic sources, point discharges, contamination by urban run-offs, refineries and other coastal effluents are in aggregate substantial and are important in causing local, chronic pollution in the vicinity of estuaries, creeks, harbours and coastal settle- ments 4 . Studies of the accidental and intentional releases of petroleum-based products to the aquatic environment in- dicate that aquatic organisms are able to bioaccumulate some total petroleum hydrocarbon (TPH) fractions, parti- cularly polycyclic aromatic hydrocarbons 5,6 . Petroleum hydrocarbons are among the most common contaminants bound to estuarine sediments 2,6,7 . These substances, mostly of organic origin, may be deleterious to aquatic plants and animals. Where the spilled petroleum washes up onto beaches or shorelines, there may be short-term damage to fish and wildlife, as well as impacts to recreational use of shoreline or riparian areas for human swimming or fishing. Some heavier petroleum fractions are capable of accumu- lating in environmental substrates. This can lead to stress on bentho-pelagic organisms 8 . The effects of hydrocarbon- laden sediments on flatfish tissue and the fish itself, parti- cularly the juvenile stage have been reported by Moles and Norcoss 9 . Sediment contamination in estuaries needs to be pro- perly and fully assessed. Therefore, in assessing and moni- toring aquatic environments for hydrocarbons, it becomes necessary to adopt biological 10 and sediments assays 2,11 . Recent studies have revealed the use of biological indica- tors such as algae 12,13 , nearshore sediments, bivalves and fish 14–18 . Aquatic assessment using the shellfish Tympa- notonus fuscatus is rare, and considering its general con- sumption in the Niger Delta region, Nigeria, investigation