What structures does bio-fouling concern in the marine realm?
In the marine realm this includes such structures as: ships’ hulls, propellers, offshore platforms, buoys, power station cooling intakes, heat exchangers, fish farm netting, aquaculture cages, sensors etc.
What does not come under the biofouling bracket?
•Colonisation and growth of organisms on natural hard surfaces
•Colonisation and growth of organisms on living surfaces (epibiosis)
BUT many fouling species can and do colonise artificial and natural surfaces
What is a basibiont?
•“…the majority of ‘epibionts’ are not basibiont specific and generally occur on non-living substrata as well” Wahl & Mark (1999) MEPS 187 59-66
Crab under a barnacle.
Basibiont - It is the substrate organism, which is the host to epibiont.
What are organisms that settle on top of plants?
Spirorbis on Fucus
Fistulobalanus albicostatus on mangrove trunk
What is the organism growing on top of another organism.
Chelonibia testudinaria on turtle – ‘obligate commensal’
Balanus on crab – not specific
What are the consequences of biofouling on shipping?
– Increase in frictional drag leading to loss of speed > higher fuel consumption
– Translocation of potentially invasive species
What are the consequences of biofouling on aquaculture?
– Increased maintenance costs and production losses (oxygen depletion and poor water exchange leads to an increase in disease)
What are the consequences of biofouling on sensors?
– Biofouling affects data quality and increases cost of maintenance
What is the effect of biofouling on power industry?
• Power industry
– Fouling in intakes, heat exchanger tubes causes a decline in plant efficiency
What is the effect of biofouling on memebrane technology?
• Membrane technology
– Fouling on membranes leads to flux reduction, and increased energy and cleaning costs
What are the Drivers for research on biofouling and antifouling?
•Economic considerations (e.g. operational costs; cost of coatings)
•Improved performance (competitive edge/reputation)
•Regulatory challenges to biocide use
•Reduced emissions/translocation of invasive species
How diverse is biofouling?
•Biofilm + 8 eukaryotic phyla
•>4000 spp. described but does not take account of microbial diversity
How does biofouling begin?
•Adsorption of ‘conditioning layer’ within seconds of immersion
•Comprises dissolved organic material, mostly macromolecules – dynamic equilibrium reached in few hours
•Facilitates subsequent microfouling e.g. source of nutrients for bacteria; improved bacterial adhesion
Sucession hypothesis - not much in literature but the idea that two surfaces will become similar over time.
What is microbial fouling?
•Bacteria, unicellular algae, cyanobacteria (blue-green algae), protozoa and fungi
•Exopolymeric substance – ‘brown slime’
•Diatoms dominate microbial ‘slime’ layer
What are some characteristics of biofouling species?
Macrofouling organisms are typically pioneers
They grow to reproductive maturity rapidly (avoid being overgrown before they reproduce)
Have short generation times.
(Barnacle - whole process atkes about a month with 5 nauplei stages)
Give the generation time of an acorn barnacle.
Amphibalanus amphitrite is a species of acorn barnacle in the Balanidae family. Its common names include the striped barnacle, the purple acorn barnacle and Amphitrite's rock barnacle. It is found in warm and temperate waters worldwide.
Species : Balanus amphitrite
Reproduction : hermaphrodite
ca. 30 d
What is the pelagic benthic transition?
n keeping with benthic organisms, most macrofouling spp. have a dispersive phase which must return to the substratum to complete the life cycle
Point of attack in antifouling strategy - biocide which attacks this colonisation stage.
What contributes to the ability to foul species to colonise ships’ hulls?
- Natural adult populations of fouling spp. are abundant in places where ships frequent - harbours
- Potential colonisers (larvae and spores) generally not limiting factor
- Harbours generally lack predators of many of the adult stages of fouling organisms and ships’ hulls provide a refuge from predation. Nucella is uncommon on the ships hull.
- Hydrodynamic regimes in harbours and estuaries tend to retain the propagules of fouling spp. and larvae may have behavioural strategies for retention
- Food rarely limiting for adults and larvae
- Fouling spp. display many ways of ‘making a living’
- Local populations can rapidly utilise available space
What is the succession hypothesis that is being disproved by tony?
Succession hypothesis – a scheme developed by Wahl.
Says there is a sequence going from macromolecular - to bacteria to diatoms to larvae to spores. Increasing in size of organisms, with processes going from physical to biological. Barnacle adhesion is actually a physical process.
The idea that by stopping POM will stop a succession of colonisers - makes it an attractive scheme.
- Doesn’t always hold true
What does the term competence mean?
Competence – are they competent to settle
The larvae have the full senses and molecular machinery to detect surfaces and to transfer chemical-physical information to electrical signals in the brain to say – this is where we are going to settle.
Give a biofouling organism which develops into a competent stage quickly.
The Chaetopteridae is a family of marine filter-feeding polychaete worms.
Development to competent nectochaete stage typically takes only ~5d
Larvae may maintain competence for several weeks
Dramatic metamorphosis within minutes of exposure to mature biofilm
How do bacterial films affect Ulva spore settlement
This species is gregarious.
Ulva settling – a very dynamic process
Spored have the ability to choose and to reject surfaces – unlike diatoms which just sink with gravity.
Spores grow to sporelings and then adult plants with fronds.
What spores do not need a biofilm to settle, but the rate of settlement is stimulated by a mixed natural biofilm
Joint I et al . (2000) Biofouling
Number of attached zoospores
Ulva requires bacteria to grow normally but doesn't require bacteria to settle. Bacteria induce settlement above the control.
Do all bacteria stimulate Ulva development?
- 6 different strains of bacteria isolated from Ulva and rocks
- Identified by 16S rDNA
- Spore settlement assays on single-species biofilms of different age
- Some stimulate, some inhibit, most exert no effect on spore settlement
- Inhibition shown by several strains of Pseudoalteromonas, some cause spore lysis
Study opposing the idea that biofouling requires a biofilm.
B. amphitrite cyprids do not need a biofilm to settle, indeed settlement is inhibited by a natural biofilm.
A classic experiment was done with a wild biofilm – these were discs that were biofilmed in the field for different lengths of time. Put out in the field at a time when abundant Cyprus larvae were available. Can see clean surfaces attracted the most settlement – over time the more inhibitory it was – does not accord with the hypothesis.
B. amphitrite does not like biofilms but if you go to the lab you get a pretty confusing picture.
The contrasting result on settling barnacles - do care about the biofilm layer.
Result of the experiment from Hong Kong Lab
Looked at a choice of adding Cyprus larvae to Petri dishes and asked them to choose between biofilmed and unbiofilmed surfaces and did it for glass and plastic.
Found facilitation in this case by the older biofilm, contrary to the result for the field. The results were irrespective of cyprid age.
Little difference between glass and polystyrene – whereas in other studies there is a much greater difference.
Flow cell studies.
Zardus et al. (2008) Biol. Bull
Looked to see whether biofilm had an effect on adhesion of larvae of both barnacles and hydrozoans.
Found that for barnacles - for cyprids were more difficult to remove from surfaces when a biofilm was present.
This is complicated by the barnacles clearing areas of substrate using their thoracic appendages.
Settle gregariously in field
Induced to settle by biofilm and conspecifics
Desperate larva hypothesis predicts that as larvae age, more likely to respond to biofilm in the absence of conspecifics. Applies to lecithotrophic larvae - these are the ones you really need to target in terms of antifouling.
(limy tube worm)
Straight away after fertilisation equal settlement onto the biofilm and in relation to contraspecifics. Subsequently, after 1-week, settlement is in relation to the same species.
Opposite to the desperate larva hypothesis.
Some larvae may be designed to settle gregariously whilst some to settle on biofilm.
Bet hedging - will be able to settle on any surface.
The idea that is not so much the sequence of settlement, but instead a dynamic process. Doesn't have to be strict sequence of events described by succession hypothesis.
Study - hypoxia larvae
Hypoxia induces abnormal larval development and affects biofilm–larval interaction in the serpulid polychaete Hydroides elegans
Shin et al 2013
- Investigated how hypoxia affects development and settlement of H. elegans larvae.
- Recruitment rates of H. elegans are reduced when hypoxia levels increase.
- There was a higher proportion of deformed larvae when oxygen levels were at 1mg/l due to a reduction In clearance rate. Deformed larvae were characterized by a change in shape, unclear segmentation, or an enlarged hyposphere.
- Despite the type of biofilm (developed either under hypoxia or normoxia conditions) the larvae were given to settle on, the settlement rate was still reduced in hypoxic conditions. There was not one type of biofilm that enhanced settlement compared to another.
- Settlement rate was increased significantly after the resumption of DO (from 1mg/l to 6mg/l) after 24 hours. However, if the DO was kept at 1mg/l, the settlement rate was still incredibly low even after 48h.
- When the biofilm was developed under hypoxic conditions, only 5% of the larvae would settle on it.
- The effect that hypoxia has on the development of larvae, and how it affects the biofilm formation explains why recruitment of H. elegans declines in the summer.
- Under hypoxic conditions, larvae use their energy to escape hypoxic stress. The action of ciliary movement uses less energy than digestion, food assimilation and growth, so these processes are put on hold.
- When oxygen becomes more readily available, they resume growing and feeding.