Ultraviolet radiation (UV-C): a potential tool for the control of biofouling on marine optical instruments

In an effort to develop a tool for controlling biofouling of marine optical instruments, the efficiency of ultraviolet radiation (UVR - 254 nm) in preventing biofouling was evaluated by conducting in situ experiments at different intensities (14.7, 9.6, 7.3 Wm(-2)) and exposure times (continuous, on for 30, 15, 5, 1 min h(-1)) using glass as test coupons. Although there was significant seasonal variation in environmental conditions and phytoplankton composition among each experiment, the amount of biofilm relative to the internal control demonstrated consistent trends. The efficiency of UVR in preventing biofouling increased significantly with increase in intensity and exposure time. UVR was effective even in reducing the population of microfoulers from already developed biofilms. UVR exposure for 30 min h(-1) at all intensities as well as for 5 and 15 min h(-1) at the highest intensity was found to be most effective. It was observed that UVR dose is not the sole determinant of UVR effectiveness. The reduction in transmission level of the UVR treated coupons was < 5% irrespective of exposure time except for 1 min h(-1). These results reveal that UV-C radiation can be used as a potential biofouling control tool for optical instruments.