biofouling Flashcards
what is biofouling
The growth of living material on man-made structures e.g. biofilm layer, hard foulers, sort foulers
- Also issue in medicine e.g. bacteria growing on catheters or implants etc
what does the succession of biofouling look like
- Adhesion of organic molecules (within minutes)
- Bacterial adhesion (within 24 hours) - form biofilm
- Spores of macroalgae (7d)
- Macrofoulers (2-3 wks)
3 main Consequences of marine biofouling
aquaculture, shipping + Heavy industry, power plants, renewable energy
how does biofouling affect shipping
- Fouled hulls reduce efficiency of transport - increasing power requirements (up to 86%)
- Increased fuel consumption means more carbon footprint, air pollution and cost
- Cause people to dry dock their boat – costly, loss of earnings, releases toxic chemicals
how does biofouling affect aquaculture
- assortment of submerged components (cages, floats, nets, ropes)
- Finfish: fouling of infrastructure restricts water exchange, increases disease risk and causes deformation of cages and structures – decreases O2 availability within the nets etc
- Shellfish: direct fouling of animals causes physical damage, mechanical interference (e.g. ability to filter feed), biological competition and environmental modification
- Direct costs: 5–10% of production costs (equivalent to US$ 1.5 to 3 billion yr−1)
- Indirect costs = animals have to be cleaned by hand of any fouling to be sold
what are the common fouling organisms
- Barnacles (dominant hard foulers worldwide)
- Bivalves - Zebra mussels (Dreissena polymorpha) - block pipelines
- Bryozoans
- Tubeworms (polychaetes)
- Ascidians
- Hydroids
- Sponges
- Algae
what is the most successful system to control biofouling
Tributytlin (TBT) self-polishing co-polymer paints (toxic)
- estimated to save over 7 million tonnes of fuel ( = ca. 20 million tonnes of greenhouse gases) and over $3 billion a year
- lipid soluble – can get into cells
what are the effects of TBT on non-target organisms
- Imposition of “imposex”: induction of male characteristics in females
- Started seeing female dog whelks with penises
- Little as < 1 ng L-1 causes imposex in gastropods
what happened in the Bay of Arcachon
- 1975-1982 oyster production severely affected: stunted growth problems, complete lack of reproduction, misformed shells - Lost millions of revenue
- Absence of spatfall shown to be caused by TBT concentrations in the bay waters
what happened to TBT legislation
-France was the first country to ban TBT-containing paints + Many countries instigated their own ban on TBT-based paints for pleasure craft
- The International Maritime Organisation announced a ban on TBT-based paints on all vessels in 2003 but some areas are not policed very well e.g. carribean
what are the New antifoulants
Paints containing copper
Novel biocides (toxic chemicals) - highly regulated
Silicone-based fouling release coatings
what is Silicone-based fouling
- Minimises the adhesion strength of attached organisms
- Movement of vessel then removes foulers (or mechanical cleaning)
- Expensive and prone to damage
- Successful for high speed/high activity vessels
- Less successful for low/moderate speed vessels or those that spend a lot of time at anchor, such as navy fleets
what is copper paints
- Paints containing copper have now largely replaced TBT-based coatings and present a much reduced risk
- Concern over observations of higher copper concentrations in water sediments and biological tissues close to marinas and harbours, however
3 Salmon farm antifouling techniques (aquaculture)
- Copper-based coatings on nets combined with washing of nets in situ or in specialised onshore facilities
- Copper-based coatings on nets combined with drying of nets on site
- Uncoated nets combined with frequent cleaning of nets (safest but most expensive)
what is recommended for antifouling methods
- biocide-free
- should not release any toxic ingredients into the environment
- its effectiveness should be based on the physical properties of the coating
