Biofilm structure and surrounding matrix – Aquatic
It is worth explaining the difference between mico fouling, such as that which occurs within the human body, and macro fouling, such as that which occurs on ships hulls after being submersed in seawater for an extended period of time.
When a surface is put underwater, in a matter of minutes or hours a conditioning film of 10-80 nm depth will develop. It is made up of microscopic polysaccharides, proteoglycans and glycoproteins which are found naturally in seawater.
A basic model of aquatic (marine or freshwater) biofouling normally includes:
A) Transport of dissolved organic molecules and bacteria towards a submerged surface
B) Deposition and adhesion of organic molecules onto the surface (conditioning film)
C) Attachment of microbes (bacteria and unicellular organisms) to the conditioned surface, forming a microbial film (biofilm). This creates a roughened surface, changes its colour, serves as food and changes the local water chemistry.
D) The roughness of the surface at this stage enables algal spores, marine fungi and protozoa to settle. This creates a complex community of grazers, multicellular organisms and decomposers.
E) The settlement and growth of calcareous fouling and algae.
Most microbes can attach to surfaces, but the rate of colonisation can vary considerably depending on surface characteristics, previous conditioning of it and water movement. The biofouling process at a macro scale is very dynamic and species composition varies depending on environmental conditions, such as salinity, nutrient availability, currents and temperature, but also biological factors such as competition and predation.
In reality, the basic model illustrated here, is often more dynamic in nature and macro fouling organisms frequently compete for settlement after the conditioning layer has formed.
An established aquatic biofilm is comprised of 79-95% water. It will also contain bacteria, aquatic fungi, phytoplankton (single celled plants), the polysaccharide substances that form the slimy, jelly like glue of the biofilm and inorganic matter such as trapped sediment.
As the fouling community develop, each group of organisms that settle provide the next group with a surface for attachment. This results in a fouling community consisting of many layers.
Algae attach to aquatic surfaces when in the spore phase of development.
Most marine invertebrate larvae have mobile life stages that search for a suitable home before they settle permanently.
Biofilms on a surface encourage settlement of polychaetes, sea urchins, barnacles, bryozoans and oysters.
This page is still under development. Can you help us complete it? Please contact us.