Investigations of Diatom Community Structure on Modern Ship Hull Coatings

Biofilm formation is of particular concern to the shipping industry due to its persistence on today's ship hull coatings. The presence of biofilms causes increases in drag, fuel consumption, green house gas emissions and higher costs. In the marine environment, benthic diatoms comprise the majority of the biofilm and yet, little is known about their settlement on modern day ship hull coatings. This study investigated diatom community structure on ship hull coatings, the influence of hydrodynamics on diatom community structure and biofilm adhesion, the strength of diatom adhesion to fouling release coatings, and diatom community structure on in-service ship hulls. An experiment was also designed to investigate the attraction of the fouling diatom, Entomoneis, to copper based ship hull coatings.;Diatom community structure was found to be determined by antifouling coating type, geographical location, time, and hydrodynamic influence. The most common diatom genera found throughout the experiments were: Achnanthes, Amphora, Cocconeis, Entomoneis, Navicula, Nitzschia, Plagiotropis, and Synedra. Biofilm adhesion and diatom abundance were found to be greater on ship hull coatings exposed under dynamic conditions, compared to those subjected to static conditions. Conversely, statically treated ship hull coatings had higher diatom diversity than dynamic panels. Achnanthes, Amphora, Cocconeis, Navicula, and Synedra, had the highest adhesion to fouling release coatings, suggesting these species have the potential to contribute to biofilms remaining on ship hulls once a vessel is underway. Samples collected from in-service ship hulls showed the diatom community composition to vary with horizontal and vertical zonation, and within niche areas. The diatom, Entomoneis, was not found to be attracted to copper based antifouling coatings, suggesting there are more complex interactions occurring within the biofilm. Presented within this dissertation is one of the most extensive lists of diatom flora found on ship hull coatings. Several diatoms new to the biofouling literature are also reported, as they were found on a variety of ship hull coatings or on ship hulls: Cyclophora, Lampriscus, and Thalassiophysa. The results add to the knowledge of diatom settlement and adhesion to modern day ship hull coatings.