THE EARLY STAGES OF MARINE BIOFOULING AND ITS EFFECT ON 2 TYPES OF OPTICAL SENSORS

This paper records the results of an investigation into the effects of biofouling on optical marine sensors and the organisms responsible fo r the deterioration in sensor accuracy. Two kinds of commercial sub-su rface optical marine sensor, commonly used to measure water quality, w ere operated in a natural marine environment and allowed to foul while measurements of the actual conditions were made daily using clean ins truments. A number of glass and acrylic coupons were placed in the sam e environment and were removed at intervals throughout the trial. Thes e coupons were examined and the biological population quantified. Dete rioration in the optical properties of the coupons was measured using image analysis and UV-visible spectroscopy. The results from the coupo ns were compared with the results from the commercial instruments. It was observed that the major deterioration in instrumental accuracy occ urred when a bacterial population exceeding 10(5)/mm(2) was found on t he coupons. The algal population had little effect on the instruments over this time period. The acrylic coupons supported a lower fouling p opulation, apparently due to the increased solubility of acrylic in se awater. The two optical techniques returned similar patterns of result s for the surface area fouled, although the numerical values returned by each technique were different. Neither of these two techniques retu rned values directly comparable with the deterioration in accuracy of the commercial instruments. The trial took place on the Isle of Cumbra e in the Firth of Clyde on the west coast of Scotland, U.K. (C)1998 El sevier Science Ltd.