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  • (2011) Low, Min Hui
    Biotic and abiotic surfaces submerged in aquatic systems are prone to rapid colonisation by marine organisms in a process called biofouling. Biofouling starts with the formation of an organic conditioning layer, which promotes adhesion of single celled microorganisms and the development of surface attached biofilm communities. Once established, biofilms provide a suitable environment for the settlement of macrofoulers, and this biofouling process results in major economic losses to various maritime industries. This study investigates the use of polydimethylsiloxane (PDMS) surfaces with specific micro-scaled surface topographies as a novel, nontoxic, alternative antifouling solution. The surfaces were placed in environmental chambers enclosed in 1.2 µm filters, and exposed to the marine environment. The effects of surface topographies on the architecture of natural established attached communities were assessed. Further, the impact of enhanced protozoan predation pressure by the addition of a heterotrophic flagellate, Rhynchomonas nasuta on biofilm architecture and composition was investigated. Results show that some micro-fabricated PDMS surfaces had microcolonies that grew along the textured grooves on the surface. Surprisingly, there was a high number of natural flagellates (2 - 5 µm) on the pre-established biofilms. Enhanced grazing by R. nasuta did not result in significant effects on biofilm biovolumes on micro-fabricated surfaces but the attached biovolumes were significantly affected by surface topographies. Four and 10 µm micro-scaled surfaces supported the lowest biovolumes compared to the flat PDMS control surfaces, indicating that these surfaces limited microbial attachment. The 10 µm surface also indicated that the enhanced grazing pressure reduced the attached community. Depending on seasonal variation, enhanced grazing pressure by R. nasuta induced shifts in microbial community composition. No correlation was observed between the micro-fabricated surfaces and community composition. This in situ study provides insights into the effects of PDMS micro-fabricated surfaces on attachment of microorganisms and the stability of the attached communities under grazing pressure. The 4 and 10 µm micro-fabricated surfaces may be promising nontoxic anti-microfouling surfaces for use in broad biomedical and industrial applications.