Multivariate analysis of attachment of biofouling organisms in response to material surface characteristics.

Multivariate analyses were used to investigate the influence of selected surface properties (Owens-Wendt surface energy and its dispersive and polar components, static water contact angle, conceptual sign of the surface charge, zeta potentials) on the attachment patterns of five biofouling organisms (Amphibalanus amphitrite, Amphibalanus improvisus, Bugula neritina, Ulva linza, and Navicula incerta) to better understand what surface properties drive attachment across multiple fouling organisms. A library of ten xerogel coatings and a glass standard provided a range of values for the selected surface properties to compare to biofouling attachment patterns. Results from the surface characterization and biological assays were analyzed separately and in combination using multivariate statistical methods.

Barnacles and biofouling.

Biofouling, the attachment and growth of organisms on submerged, man-made surfaces, has plagued ship operators for at least 2500 years. Accumulation of biofouling, including barnacles and other sessile marine invertebrates, increases the frictional resistance of ships' hulls, resulting in an increase in power and in fuel consumption required to make speed. Scientists and engineers recognized over 100 years ago that in order to solve the biofouling problem, a deeper understanding of the biology of the organisms involved, particularly with regard to larval settlement and metamorphosis and adhesives and adhesion, would be required.

Variation in toxicity of copper pyrithione among populations and families of the barnacle, Balanus amphitrite.

Inter- and intra-population variation in the toxicity of the antifouling biocide copper pyrithione (CuPT) was examined for nauplius larvae of the barnacle Balanus amphitrite. Nauplii were collected from brooding adults from four sites within the Newport River estuary (NC), chosen based on an initial estimation of recent and historical human activities that affect local contamination levels. Each site was characterized for the presence of polycyclic aromatic hydrocarbons and for the frequency of gastropod imposex, an indicator of contamination by organotins.

Sonication of bacteria, phytoplankton and zooplankton: Application to treatment of ballast water.

We investigated the effect of high power ultrasound, at a frequency of 19 kHz, on the survival of bacteria, phytoplankton and zooplankton, in order to obtain estimates of effective exposure times and energy densities that could be applied to design of ultrasonic treatment systems for ballast water. Efficacy of ultrasonic treatment varied with the size of the test organism. Zooplankton required only 3-9s of exposure time and 6-19 J/mL of ultrasonic energy to realize a 90% reduction in survival.

Interspecific variation in patterns of adhesion of marine fouling to silicone surfaces.

The adhesion of six fouling organisms: the barnacle Balanus eburneus, the gastropod mollusc Crepidulafornicata, the bivalve molluscs Crassostrea virginica and Ostrea/Dendrostrea spp., and the serpulid tubeworms Hydroides dianthus and H. elegans, to 12 silicone fouling-release surfaces was examined.

The effect of solid surface tension and exposure to elevated hydrodynamic shear on Pseudomonas fluorescens biofilms grown on modified titanium surfaces.

The solid surface tension of titanium was varied by using organosilane monolayers of various terminations, minimising differences in other material properties. Both the quantity of Pseudomonas fluorescens biofilms grown on the modified surfaces, and the percentage of biofilm remaining after exposure to hydrodynamic shear stress, varied significantly as a function of solid surface tension. The quantity of biofilm was less on chloropropyl-terminated surfaces than on an alkyl-terminated surfaces.

Variation among families for characteristics of the adhesive plaque in the barnacle Balanus amphitrite.

A quantitative genetics approach was used to examine variation in the characteristics of the adhesive plaque of the barnacle Balanus amphitrite Darwin attached to two silicone substrata. Barnacles settled on silicone polymer films occasionally form thick, soft adhesive plaques, in contrast to the thin, hard plaques characteristic of attachment to other surfaces. The proportion of barnacles producing a thick adhesive plaque was 0.

Evaluation of hydrodynamic drag on experimental fouling-release surfaces, using rotating disks.

Fouling by biofilms significantly increases frictional drag on ships' hulls. A device, the friction disk machine, designed to measure torque on rotating disks, was used to examine differences among experimental fouling-release coatings in the drag penalty due to accumulated biofilms. Penalties were measured as the percentage change in the frictional resistance coefficient Cf.

Evaluation of brushes for removal of fouling from fouling-release surfaces, using a hydraulic cleaning device.

A portable hydraulic device has been developed for use in optimizing the design of brushes and cleaning units that may be employed to maintain fouling-release coatings. Laboratory tests showed that characteristics of experimental cleaning brushes, including bristle stiffness, density, and angle, significantly affected the shear and normal forces imparted to the surface and thus, to any encrusting organisms. The standoff distance between the cleaning unit and the surface also influenced the forces generated.