Biofilms and Biofouling
In general, four types of fouling can be considered: biological, corrosion, particulate, and precipitation fouling. Biological and corrosion types of fouling are mediated by microorganisms adhered to metal surfaces or embedded in a gelatinous organic matrix called biofilm. Biofilms behave as structured assemblages of microorganisms embedded in exopolymers. They are also complex communities consisting of colonies, consortia, newly arrived cells, dying cells, extracellular products, polymers, and trapped inorganic material. Immediately after its immersion in seawater, a metal surface undergoes a sequence of biological and chemical changes that lead to biofouling formation and may lead to metal protection. In the presence of a biofilm, the biologically and electrochemically conditioned interface is the result of interactions between corrosion product layers and the various components of microbial films. Abiotic corrosion processes probably influence the rate, extent, and distribution of colonizing microbial species, as well as the chemical composition and physical properties of the resulting biofilm.