Marine Biofouling and Antofouling Flashcards

Question

Study opposing the idea that biofouling requires a biofilm.

Answer 1

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.

Answer 2

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.

Answer 3

**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.

Answer 4

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.

Answer 5

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.

Answer 6

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.