Marine biofouling results in substantial environmental and economic consequences. Whether the surface is a ship hull or an aquaculture net, microbes are available and capable of rapid community development on those surfaces.
What should be done to prevent biological fouling on those surfaces?
In order to answer this question we first need to understand the mechanism of biofouling and biofilm. We will discuss marine antifouling techniques right after.
What is biofouling in the marine environment?
Biofouling definition: Biofouling, or biological fouling is understood as the unwanted accumulation of biological matter such as microorganisms, plants, algae, or small animals on surfaces submerged in water.
Ship hulls, pier pylons, submarine hulls, grates, underwater pipework, water inlets and aquaculture equipment may suffer mechanical dysfunction, structural or other deficiencies if no antifouling measures are in place.
According to Science direct, more than 4000 marine species have been identified as fouling organisms, all of which are sessile forms.
Biofouling effects on aquaculture equipment & ships
Biofouling increases ship hull decline, corrosion, fuel consumption, and engine stress. Moreover it adds considerable weight to aquaculture equipment increasing the costs related to buoyancy and anchoring systems. If fouling occurs, the functional capacity of the surface is no longer the same as before. Therefore systems protecting underwater equipment are required.
What causes biofouling?
Even though biofouling occurs in many different situations, it has a common main cause, which is biofilm creation. All five causes in detail are the following:
- Biofilm formation: Development of the microorganism community.
- Flocculant overuse: Overuse of organic polymers such as flocculant for water purification.
- Corrosion inhibitor usage: The use of biodegradable corrosion prevention substances increases biofouling.
- Water contamination: Water bodies get contaminated by fertilizers leading to microbial metabolites causing fouling.
- Invasive species: Some invasive species brought by operating ships can also cause fouling because they disrupt native underwater ecosystem balance.
Where does biofilm form?
As mentioned by the Montana State University, biofilms are responsible for billions of dollars in lost industrial productivity, as well as product and capital equipment damage each year.
Biofilms can grow in almost any moist environment where there are nutrients and a surface. These bio-structures have been found at the bottom of the ocean growing on surfaces of objects natural or manmade. Bacteria attach to the surfaces with which they come into contact, but this causes many problems for a wide range of industries.
Biofilms are known for causing pipe plugging, corrosion and water contamination.
Scientists have documented the colonization of surfaces in ocean waters by a series of organisms. Everything begins with microbial biofilms. Later on higher organisms are taunted to colonize the surface and fouling starts to form.
How to detect biofouling?
Research has shown that a sustainable antifouling strategy includes:
- Fouling situation analysis
- Suitable antifouling processes
- Monitoring of biofilm development
How can biofouling be prevented?
Early biofouling detection research using fluorescence-based extracellular enzyme activity gave promising results as to how we can identify biofouling at an early stage. A fluorescence-based sensor for early fouling formation detection measured extracellular enzyme activity in a biological fouling model monitoring bacterial accumulation.
Source: Science Direct – Early biofouling detection using fluorescence-based extracellular enzyme activity
Currently biofouling resistance involves techniques using:
- Highly specialized coatings for hull protection (releasing active compounds in a controlled manner)
- Copper-based antifouling paints applied to the nets combined with frequent washing to prevent biomass accumulation
Other antifouling solutions may combine:
- High UV radiation protection
- Enhanced material purity for longer service life
- In-situ cleaning of aquaculture nets
These tactics can prevent colonization by the biofouling organisms.
What is a biofouling management plan?
The biofouling management plan should be specially designed for every vessel and it’s usually included in the ship’s operational documentation. Such a plan should address the following issues:
- Relevant parts of IMO guidelines for minimizing the transfer of invasive aquatic species
- Details of the antifouling systems and operational practices or treatments used
- Hull parts susceptible to fouling
- Schedule of planned inspections, repairs and maintenance of anti-fouling systems
- Details of the recommended operating conditions regarding the antifouling systems
- An up-to-date antifouling treatment record
The management plan should be updated as necessary so that it covers all issues related to fouling prevention and equipment restoration.
Why control over biofouling is required in aquaculture?
Fouling organisms settle onto infrastructure such as ropes or other floating or submerged equipment causing breakages and costly repairs. In aquaculture though, fouling to the surfaces of cultured commodities can prove to be more problematic. Maintaining clean shells for example is a priority to preserve the appearance and marketability of shellfish.
How much should you invest in biofouling prevention?