P3: Discerning Dose Response for Antifouling Treatments in Marine Capillary Flow Cells

Prevention of biological fouling is critical to maintenance of optimal function and extended life for equipment and materials deployed in aquatic and marine settings.  Efficacy of copper plus a proprietary antifouling treatment was established in a previous study using epifluorescent microscopy to visualize biofilm formation in situ in capillary flow cells exposed to filtered ambient seawater over a two-month period.  In this study, capillary flow cells were exposed to filtered seawater at a rate of approximately 1 mL per minute with a constant influx of copper.  Replicate capillary flow cells were then exposed to three dose levels (33%, 66%, or 100%) of an external proprietary treatment, with replicates undergoing copper treatment alone serving as the baseline control.  Flow was maintained for 36 days, and then all capillaries were removed from the system and maintained at 4°C until analysis.  Single-photon confocal microscopy was performed to assess the extent of biofouling in each capillary; biofilms were stained with Cyto-9 and propidium iodide and images captured on an Olympus FV 1000 Multiphoton microscope in single-photon mode.  Additional control flow cells were included with each analysis set:  a negative control prepared with water, a positive control colonized for 24 days with Halomonas pacifica and Skeletonema costatum, and a background control consisting of an untreated capillary cell.  The results showed that the proprietary external treatment was highly effective at preventing biofilm formation in capillary flow cells, even at a dose of 33%.  Copper treatment alone was not sufficient to prevent biofilm formation.