RAPID DETECTION OF SEWAGE CONTAMINATION IN MARINE WATERS USING A FLUOROMETRIC ASSAY OF BETA-D-GALACTOSIDASE ACTIVITY

A simple, rapid method for the detection of faecal coliform bacteria i n marine waters is described. The method involves the detection of bet a-D-galactosidase, an enzyme marker of coliform bacteria. A fluorogeni c substrate (methylumbelliferyl-beta-D-galactoside) is added to a buff ered seawater sample and incubated at 44.5-degrees-C for 60 min. The a mount of fluorescent label liberated by enzymatic hydrolysis is then d etermined by instrumental fluorescence spectrometry. Initial field tri als show that enzyme activity levels correlate well with faecal colifo rms concentrations measured by conventional membrane filtration method s. The enzyme activity level corresponding to the European Community g uideline limit for bathing waters of 100 faecal coliforms/100 ml was e asily detectable. The method is intended for use as an 'early warning' indicator of sewage contamination events in coastal waters.