Kelli Z. Hunsucker

Diatom community structure on in-service cruise ship hulls

Diatoms are an important component of marine biofilms found on ship hulls. However, there are only a few published studies that describe the presence and abundance of diatoms on ships, and none that relate to modern ship hull coatings. This study investigated the diatom community structure on two in-service cruise ships with the same cruise cycles, one coated with an antifouling (AF) system (copper self-polishing copolymer) and the other coated with a silicone fouling-release (FR) system. Biofilm samples were collected during dry docking from representative areas of the ship and these provided information on the horizontal and vertical zonation of the hull, and intact and damaged coating and niche areas. Diatoms from the genera Achnanthes, Amphora and Navicula were the most common, regardless of horizontal ship zonation and coating type. Other genera were abundant, but their presence was more dependent on the ship zonation and coating type. Samples collected from damaged areas of the hull coating had a similar community composition to undamaged areas, but with higher diatom abundance. Diatom fouling on the niche areas differed from that of the surrounding ship hull and paralleled previous studies that investigated differences in diatom community structure on static and dynamically exposed coatings; niche areas were similar to static immersion and the hull to dynamic immersion. Additionally, diatom richness was greater on the ship with the FR coating, including the identification of several new genera to the biofouling literature, viz. Lampriscus and Thalassiophysa. These results are the first to describe diatom community composition on in-service ship hulls coated with a FR system. This class of coatings appears to have a larger diatom community compared to copper-based AF systems, with new diatom genera that have the ability to stick to ship hulls and withstand hydrodynamic forces, thus creating the potential for new problematic species in the biofilm.

Analysis of long-term mechanical grooming on large-scale test panels coated with an antifouling and a fouling-release coating

Long-term grooming tests were conducted on two large-scale test panels, one coated with a fluorosilicone fouling-release (FR) coating, and one coated with a copper based ablative antifouling (AF) coating. Mechanical grooming was performed weekly or bi-weekly using a hand operated, electrically powered, rotating brush tool. The results indicate that weekly grooming was effective at removing loose or heavy biofilm settlement from both coatings, but could not prevent the permanent establishment of low-profile tenacious biofilms. Weekly grooming was very effective at preventing macrofouling establishment on the AF coating. The effectiveness of weekly grooming at preventing macrofouling establishment on the FR coating varied seasonally. The results suggest that frequent mechanical grooming is a viable method to reduce the fouling rating of ships’ hulls with minimal impact to the coating. Frequent grooming could offer significant fuel savings while reducing hull cleaning frequencies and dry dock maintenance requirements.

Analysis of mechanical grooming at various frequencies on a large scale test panel coated with a fouling-release coating.

Abstract A mechanical grooming test was performed on large scale steel test panels coated with a fouling-release (FR) coating (International Intersleek 900), at four different frequencies, during the high fouling season in Port Canaveral, Florida. Grooming at frequencies of three or two times per week was effective at removing heavy biofilm growth and significantly reduced macrofouling settlement. Mechanical grooming at lower frequencies of weekly or bi-weekly removed heavy biofilm growth but was much less effective at reducing macrofouling settlement. The results indicated that frequent mechanical grooming could reduce the fouling rating of ships coated with FR coatings. The reduction in the fouling rating of ships’ hulls by frequent grooming could offer significant reductions in drag, fuel consumption, and the emission of exhaust gases. Frequent grooming could also eliminate the need for hull cleaning and increase the time between dry docking which would reduce the operational costs for many vessel operators.

Transported biofilms and their influence on subsequent macrofouling colonization

Abstract Biofilm organisms such as diatoms are potential regulators of global macrofouling dispersal because they ubiquitously colonize submerged surfaces, resist antifouling efforts and frequently alter larval recruitment. Although ships continually deliver biofilms to foreign ports, it is unclear how transport shapes biofilm microbial structure and subsequent macrofouling colonization. This study demonstrates that different ship hull coatings and transport methods change diatom assemblage composition in transported coastal marine biofilms. Assemblages carried on the hull experienced significant cell losses and changes in composition through hydrodynamic stress, whereas those that underwent sheltered transport, even through freshwater, were largely unaltered. Coatings and their associated biofilms shaped distinct macrofouling communities and affected recruitment for one third of all species, while biofilms from different transport treatments had little effect on macrofouling colonization. These results demonstrate that transport conditions can shape diatom assemblages in biofilms carried by ships, but the properties of the underlying coatings are mainly responsible for subsequent macrofouling. The methods by which organisms colonize and are transferred by ships have implications for their distribution, establishment and invasion success.

Influence of hydrodynamic stress on the frictional drag of biofouling communities

Abstract The role of hydrodynamic wall shear stresses on the development of the fouling community structure and resulting frictional drag were examined using a commercially available fouling release coating. Immersed test panels were exposed to three different hydrodynamic treatments, one static and two dynamic (corresponding to an estimated wall shear stress of 7.0 and 25.5 Pa). The drag of the panels was measured in a hydrodynamic test chamber at discrete time intervals over 35 days. The fouling community composition on the static panels was significantly different from the organisms observed on the dynamic panels. Despite different fouling community composition, the drag forces measured on the panels were very similar. This suggests that the frictional drag of low form and soft fouling communities are similar and that there may be a stepwise increase in frictional drag associated with the presence of mature calcareous organisms.

Specialized Grooming as a Mechanical Method to Prevent Marine Invasive Species Recruitment and Transport on Ship Hulls

Biofouling on ship hulls is one of the primary vectors of non-indigenous species transport. The most common method to prevent biofouling settlement is through the application of ship hull coatings. However, there is no perfect coating and the ship hull will eventually become colonized by biofouling. Hull husbandry techniques are often employed to remove the biofouling from the ship hull, which adds in restoring the ships functional abilities and prevents the transport of biofouling organism as invasive species. Two such techniques are in-water cleaning and grooming. The cleaning of a ship hull may damage hull coatings, release both biocides and fouling organisms into the local environment, and is regulated or banned in many ports around the world. A more recent mechanical approach to biofouling, is grooming, a frequent and gentle wiping of the hull, which works in synergy with ship hull coatings to prevent the growth of biofouling organisms. By incorporating grooming into the ship maintenance, invasive species recruitment and transport is prevented.

Dynamic field testing of coating chemistry candidates by a rotating disk system

Abstract Quick and reliable testing is crucial for the development of new fouling release (FR) coatings. Exposure of these coatings to natural multispecies communities is essential in evaluating their efficacy. To this end, we present a rotating disk setup for dynamic field exposure. To achieve a well-defined flow on the surface of the disk, an easy to use sample mounting system was developed that provides a smooth and even surface. We related the angular velocity of the disk to the wall shear stress on the surface with a hydrodynamic model. The wall shear stress was adjusted to values previously found to be suitable to discriminate dynamic diatom attachment on different coating chemistries in the lab. The effect of the dynamic conditions was shown by comparing polystyrene slides under static and dynamic exposure. Using a set of self-assembled monolayers, the discrimination potential of the assay in a multispecies environment was demonstrated.

Biofilm community structure and the associated drag penalties of a groomed fouling release ship hull coating

Abstract Grooming is a proactive method to keep a ship’s hull free of fouling. This approach uses a frequent and gentle wiping of the hull surface to prevent the recruitment of fouling organisms. A study was designed to compare the community composition and the drag associated with biofilms formed on a groomed and ungroomed fouling release coating. The groomed biofilms were dominated by members of the Gammaproteobacteria and Alphaproteobacteria as well the diatoms Navicula, Gomphonemopsis, Cocconeis, and Amphora. Ungroomed biofilms were characterized by Phyllobacteriaceae, Xenococcaceae, Rhodobacteraceae, and the pennate diatoms Cyclophora, Cocconeis, and Amphora. The drag forces associated with a groomed biofilm (0.75 ± 0.09 N) were significantly less than the ungroomed biofilm (1.09 ± 0.06 N). Knowledge gained from this study has helped the design of additional testing which will improve grooming tool design, minimizing the growth of biofilms and thus lowering the frictional drag forces associated with groomed surfaces.

Fouling-Release Properties of Dendritic Polyglycerols against Marine Diatoms

Dendritic polyglycerols (PGs) were grafted onto surfaces using a ring-opening polymerization reaction, and the fouling-release properties against marine organisms were determined. The coatings were characterized by spectroscopic ellipsometry, contact angle goniometry, ATR-FTIR, and stability tests in different aqueous media. A high resistance toward the attachment of different proteins was found. The PG coatings with three different thicknesses were tested in a laboratory assay against the diatom Navicula incerta and in a field assay using a rotating disk. Under static conditions, the PG coatings did not inhibit the initial attachment of diatoms, but up to 94% of attached diatoms could be removed from the coatings after exposure to a shear stress of 19 Pa. Fouling release was found to be enhanced if the coatings were sufficiently thick. The excellent fouling-release properties were supported in dynamic field-immersion experiments in which the samples were continually exposed to a shear stress of 0.18 Pa.

Iodine-infused aeration for hull fouling prevention: a vessel-scale study

Abstract Biofouling is a significant economic and ecological problem, causing reduced vessel performance and increases in fuel consumption and emissions. Previous research has shown iodine vapor (I2)-infused aeration to be an environmentally friendly method for deterring the settlement of fouling organisms. An aeration system was deployed on a vessel with hull sections coated with two types of antifoulant coatings, Intersleek® 1100 (fouling-release) and Interspeed® BRA-640 (ablative copper biocide), as well as an inert epoxy barrier coating, to assess the effectiveness of aeration in conjunction with common marine coatings. I2-infused aeration resulted in consistent reductions of 80–90% in hard fouling across all three coatings. Additionally, aeration reduced the soft fouling rate by 45–70% when used in conjunction with both Intersleek® and Interspeed® BRA versus those coatings alone. The results of this study highlight the contribution of I2-infused aeration as a standalone mechanism for fouling prevention or as a complement to traditional antifouling coatings.