Sub-samples (5 ml) were taken from each bag and filtered through 25 mm diameter (0.2 mm pore size: Millipore, UK)black polycarbonate filters (Millipore, UK). Cells were counted by epifluorescence microscopy in accordance with the method of Parkes and co-workers (1993) with the modification that 1X concentration of Sybr-Golds (Molecular Probes,USA) was used in place of Acridine orange. Fluorescing bacteria were observed using a Nikon Eclipse E600 microscope with a 100W mercury bulb, aB-2A excitation filter ,a 100_ planar objective lens and a 10_ eyepiece. Total prokaryotic abundance for each sample was determined by counting 30 random fields