Hydrocarbon accumulation by picocyanobacteria from the Arabian Gulf R.H. Al-Hasan, M. Khanafer, M. Eliyas and S.S. Radwan Department of Biological Sciences, Faculty of Science, Kuwait University, Kuwait 756/01/01: received 31 January 2001, revised 2 April 2001 and accepted 12 April 2001 R.H. AL-HASAN, M. KHANAFER, M. ELIYAS AND S.S. RADWAN. 2001. Aims: The objective of this work was to study picocyanobacteria in the Arabian Gulf water in relation to oil pollution. Methods and Results: Epi¯uorescent microscopic counting showed that offshore water samples along the Kuwaiti coast of the Arabian Gulf were rich in picocyanobacteria which ranged in numbers between about 1 ´ 10 5 and 6 ´ 10 5 ml )1 . Most dominant was the genus Synechococcus; less dominant genera were Synechocystis, Pleurocapsa and Dermocarpella. All isolates grew well in an inorganic medium containing up to 0á1% crude oil (w/v) and could survive in the presence of up to 1% crude oil. Hydrocarbon analysis by gas liquid chromatography (GLC) showed that representative strains of the four genera had the potential for the accumulation of hydrocarbons (the aliphatic n-hexadecane, aromatic phenanthrene and crude oil hydrocarbons) from aqueous media. Electron microscopy showed that the cells of these strains appeared to store hydrocarbons in their inter thylakoid spaces. Analysis by GLC of constituent fatty acids of total lipids and individual lipid classes from representative picoplankton strains grown in the absence and presence of hydrocarbons showed, however, that the fatty acid patterns were not markedly affected by the hydrocabon substrates, meaning that the test strains could not oxidize the accumulated hydrocarbons. Conclusions: The Arabian Gulf is among the water bodies of the world richest in picocyanobacteria. These micro-organisms accumulate hydrocarbons from the water body, but do not biodegrade these compounds. It is assumed that hydrocarbon-utilizing bacteria that were always found associated with all picocyanobacteria in nature may carry out the biodegradation of these compounds. Signi®cance and Importance of the Study: The results shed light on the potential role of picocyanobacteria in controlling marine oil pollution. INTRODUCTION Legal activities (e.g. production and transport of crude oil) as well as illegal actions (e.g. disposal of oily wastes) charge the marine environment worldwide with huge amounts of petroleum hydrocarbons. It was estimated a couple of decades ago that 6±10 million tons of petroleum pollute the marine ecosystem yearly (Blumer et al. 1971; National Academy of Science 1975). Since then, this has probably grown steadily, given the increasing oil production and transport activities. The problem of oil pollution is especi- ally acute in an oil-producing area such as the Arabian Gulf, where about 60% of the marine-transported oil in the world is produced (British Petroleum Co. 1980) and transported through this rather shallow and enclosed sea (Hunter 1982). It has been estimated that the Arabian Gulf has, in the past, had petroleum hydrocarbon concentrations of 1á2±546 lg ml )1 compared with 0á4±66á8 lg ml )1 in the Gulf of Mexico (Sen Gupta and Kureishy 1981; Marchand et al. 1982; El Samra et al. 1986). The situation for this environment became even worse during the occupation of Kuwait (2 August 1990±26 February 1991) after the Iraqi forces released about 500 000 tons of crude oil into the Gulf from the Mina Al-Ahmadi terminal. Correspondence to: S.S. Radwan, Department of Biological Sciences, Faculty of Science, Kuwait University, PO Box 5969, Safat, 13060, Kuwait. ã 2001 The Society for Applied Microbiology Journal of Applied Microbiology 2001, 91, 533±540