Investigations into the Effect of Grooming and Cleaning on the Settlement and Recruitment of Fouling Communities.

摘要

Biofouling control is important for the efficient operation of ships (IMO 2011). Shipping, which accounts for 90% of the transport of world trade goods, requires smooth fouling free hulls for efficient operation (Dafforn et al 2011, IMO 2011). Additionally, ships, particularly those that are fouled, transport invasive species (Dafforn et al 2008, Fernandez 2008, Piola & Johnston 2008a, Hopkins & Forrest 2010, IMO 2011). Modern ship hull coatings are unable to prevent fouling completely and in water maintenance is required. Traditionally, hull cleaning has been performed on ships that become fouled between dry dockings. Hull grooming is a new method that has been proposed as a way to prevent hulls from becoming fouled (Tribou & Swain 2010). The purpose of this dissertation was to examine the effect of different methods of hull husbandry on settlement, recruitment and fouling community structure using silicone fouling release coatings. The general hypotheses tested were: 1) cleaning and grooming will lower fouling cover and diversity compared to freely fouling panels; 2) cleaning will remove more fouling than grooming; 3) groomed surfaces are less attractive to settling larvae than ungroomed surfaces; 4) fouling communities that develop on transplanted panels will more closely resemble the community at the original site; and 5) fouling community structure after transplant will be altered by prior husbandry. The first experiment (Ch. 2) examined the effect of frequent cleaning and grooming on recruitment and fouling community structure and examined the efficacy of the different hull husbandry methods. Surfaces that were frequently cleaned or groomed were found to have low macrofouling cover and low taxonomic richness. The results from this experiment led to two parallel lines of investigation: 1) Is the pattern of low macrofouling cover on groomed surfaces due to settlement preference? 2) Are community structure and recolonization of specific organisms altered by prior fouling or hull husbandry after silicone panels are transplanted? The first question was addressed by investigating settlement behavior of barnacle cyprids in the laboratory and natural larvae in the field using a novel settlement flume (Ch. 3). The second question was addressed during two transplant experiments, the first looking at the effect of prior location (Ch. 4) and the second looking at both prior location and husbandry (Ch. 5) at sites along the east coast of Florida.;Grooming and cleaning were found to alter settlement, recruitment and fouling community structure. Panels that were frequently cleaned or groomed had low macrofouling cover and taxonomic richness. Evenness, however, was high on frequently cleaned and groomed panels. Unlike frequently cleaned panels, panels that were cleaned bimonthly had similar macrofouling cover and fouling community structure to uncleaned freely fouling panels. Hydroids were the only organism that frequently had high cover on groomed and cleaned surfaces and were the exception to the general pattern. Cleaning removed all visible fouling from panel surfaces, whereas grooming was most effective at removing biofilms. When macrofouling was present, grooming was not always successful at complete removal. Groomed surfaces were less attractive to settling larvae. Cyprids moved more quickly across groomed surfaces in laboratory experiments and there was a general nonsignificant trend of cyprids having shorter tracks and spending less time on groomed surfaces. Natural larvae also seemed to have a nonsignificant pattern of shorter tracks, faster speed and shorter time on groomed surfaces. Prior location and husbandry were found to condition surfaces and affect the recolonization of silicone coatings. Original location was found to affect the recruitment of specific organisms after panels were transplanted. Three major patterns were seen: 1) higher cover of organisms in a new location that had been a dominant component of the fouling community in their original location; 2) higher cover of local dominants on untransplanted panels; 3) organisms that had variable patterns of preferential recruitment after transplant. Grooming and cleaning also continued to affect recruitment, even after treatment was stopped, with preferences found for surfaces that had been ungroomed, cleaned and groomed.