Biofouling is the undesirable accumulation of microorganisms, plants, algae, or small animals on submerged surfaces. This widespread natural process affects objects in aquatic environments.
The Initial Adhesion and Biofilm Formation
Biofouling begins with the rapid formation of a “conditioning film” on a submerged surface. This film consists of organic molecules, such as proteins and polysaccharides. The properties of this conditioning layer influence subsequent microbial attachment.
Following the conditioning film, microscopic organisms like bacteria and diatoms attach to the surface, initiating a “biofilm.” A biofilm is a complex, slimy layer of microorganisms embedded within a self-produced matrix of extracellular polymeric substances (EPS). This EPS matrix provides secure attachment and protection to the microbial community.
The Growth of Complex Communities
The initial microbial biofilm acts as a foundation, attracting larger aquatic organisms. The microbial layer provides chemical cues and a suitable physical surface for attachment. Algae and invertebrate larvae then colonize the established biofilm.
Protozoa and larger algae attach to the biofilm, followed by invertebrate larvae like barnacles, mussels, tubeworms, and bryozoans. As these organisms grow, they form complex, multi-layered communities. This progression significantly increases biomass and structural complexity on the submerged surface.
Common Environments for Biofouling
Biofouling is a pervasive issue in numerous aquatic environments and applications. In marine settings, it commonly affects ship hulls, offshore oil and gas platforms, aquaculture nets, and port infrastructure.
Freshwater systems are similarly impacted. Biofouling occurs in industrial cooling towers, pipelines, water treatment plants, and on hydroelectric dam structures. The biological composition of fouling communities differs between marine and freshwater ecosystems.
Specialized applications are also susceptible. Medical devices like catheters and implants can experience “biocontamination” from microbial biofilms. Heat exchangers in industrial settings are also prone to biofouling, impairing their efficiency.
Why Biofouling Matters
Biofouling has considerable economic, environmental, and operational consequences. Economically, it increases hydrodynamic drag on ship hulls by up to 60%, requiring up to a 40% increase in fuel consumption. This translates to higher operational costs for the shipping industry.
Biofouling reduces efficiency in power generation and industrial processes, such as in heat exchangers and water intake systems. It also escalates maintenance costs for infrastructure like pipelines and offshore platforms. Aquaculture operations face significant production losses due to biofouling on nets and cages.
Environmentally, biofouling is a primary vector for transferring invasive aquatic species (IAS). Organisms on ship hulls can be transported, establishing reproductive populations in non-native environments. These invasive species out-compete native species, disrupt food webs, and cause widespread ecological damage, threatening biodiversity.
Operationally, biofouling can clog pipes and filters, impeding fluid flow in industrial and water treatment facilities. It also causes underwater sensor malfunction. Biofouling can contribute to the structural degradation of marine assets through microbially influenced corrosion and make vessels harder to steer.