Fig. 3. Dehydrogenase activity of microbial biomass in oil-spiked control and treated sediments. Mean and standard deviation of duplicates are shown. C, control; INTF, 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazoliumchloride (INT)-formazan; Ip, Inipol; Os, Osmocote; SN, soluble nutrients.