Topographic cues guide the attachment of diatom cells and algal zoospores

Surface topography plays a key role in the colonization of substrata by the colonizing stages of marine fouling organisms. For the innovation of marine antifouling coatings, it is essential to understand how topographic cues affect the settlement of these organisms. In this study, tapered, spiked microstructures and discrete honeycombs of varying feature dimensions were designed and fabricated in order to examine the influence of topography on the attachment of zoospores of the green macroalga Ulva linza and cells of the diatom (microalga) Navicula incerta. Contrasting results were obtained with these two species of algae. Indeed, the preferred location of cells of N. incerta was dominated by attachment point theory, which suggested a positive correlation between the density of cells adhering and the amount of available attachment points, while the settlement of spores of U. linza was mainly regulated by both Wenzel roughness and local binding geometry.     

Algal antifouling and fouling-release properties of metal surfaces coated with a polymer inspired by marine mussels

The marine antifouling and fouling-release performance of titanium surfaces coated with a bio-inspired polymer was investigated. The polymer consisted of methoxy-terminated poly(ethylene glycol) (mPEG) conjugated to the adhesive amino acid l-3,4-dihydroxyphenylalanine (DOPA) and was chosen based on its successful resistance to protein and mammalian cell fouling. Biofouling assays for the settlement and release of the diatom Navicula perminuta and settlement, growth and release of zoospores and sporelings (young plants) of the green alga Ulva linza were carried out. Results were compared to glass, a poly(dimethylsiloxane) elastomer (Silastic T2) and uncoated Ti. The mPEG-DOPA3 modified Ti surfaces exhibited a substantial decrease in attachment of both cells of N. perminuta and zoospores of U. linza as well as the highest detachment of attached cells under flow compared to control surfaces. The superior performance of this polymer over a standard silicone fouling-release coating in diatom assays and approximately equivalent performance in zoospore assays suggests that this bio-inspired polymer may be effective in marine antifouling and fouling-release applications.     

Fluorine-free mixed amphiphilic polymers based on PDMS and PEG side chains for fouling release applications

Fluorine-free mixed amphiphilic block copolymers with mixtures of short side groups of polydimethyl siloxane (PDMS) and polyethylene glycol (PEG) were synthesized and studied for their ability to influence the surface properties and control the adhesion of marine organisms to coated surfaces. The settlement (attachment) and strength of adhesion of two different marine algae, the green seaweed Ulva and the diatom Navicula, were evaluated against the surfaces. It is known that hydrophobic coatings based on polydimethyl siloxane elastomers (PDMSe) are prone to protein adsorption and accumulation of strongly adherent diatom slimes, in contrast to PEG-based hydrophilic surfaces that inhibit protein adsorption and moderate only weak adhesion of diatoms. By incorporating both PDMS and PEG side chains into the polymers, the effect of incorporating both polar and non-polar groups on fouling-release could be studied. The dry surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). The ability of these mixed amphiphilic polymers to reconstruct in water was examined using underwater bubble contact angle and dynamic water contact angle experiments. To understand more about surface reconstruction behavior, protein adsorption experiments were carried out with fluorescein isothiocyanate-labeled bovine serum albumin (BSA-FITC) on both dry and pre-soaked surfaces.     

Effect of bacterial biofilms formed on fouling-release coatings from natural seawater and Cobetia marina,on the adhesion of two marine algae

Previous studies have shown that bacterial biofilms formed from natural seawater (NSW) enhance the settlement of spores of the green alga Ulva linza, while single-species biofilms may enhance or reduce settlement, or have no effect at all. However, the effect of biofilms on the adhesion strength of algae, and how that may be influenced by coating/surface properties, is not known. In this study, the effect of biofilms formed from natural seawater and the marine bacterium Cobetia marina, on the settlement and the adhesion strength of spores and sporelings of the macroalga U. linza and the diatom Navicula incerta, was evaluated on Intersleek® 700, Intersleek® 900, poly(dimethylsiloxane) and glass. The settlement and adhesion strength of these algae were strongly influenced by biofilms and their nature. Biofilms formed from NSW enhanced the settlement (attachment) of both algae on all the surfaces while the effect of biofilms formed from C. marina varied with the coating type. The adhesion strength of spores and sporelings of U. linza and diatoms was reduced on all the surfaces biofilmed with C. marina, while adhesion strength on biofilms formed from NSW was dependent on the alga (and on its stage of development in the case of U. linza), and coating type. The results illustrate the complexity of the relationships between fouling algae and bacterial biofilms and suggest the need for caution to avoid over-generalisation.     

Larval behavioral,morphological changes,and nematocyte dynamics during settlement of actinulae of Tubularia mesembryanthemum,Allman 1871 (Hydrozoa: Tubulariidae)

The marine colonial hydroid Tubularia mesembryanthemum produces a morphologically unique dispersive stage, the actinula larva. Detailed observations were made on the behaviors and nematocyte dynamics of actinula larvae during attachment and morphogenesis by employing microscopic and time lapse video techniques. These observations produced four primary results. (1) Actinula larvae demonstrated two forms of attachment: temporary attachment by atrichous isorhiza (AI)-nematocysts discharged from the aboral tentacle (AT) tips-and permanent settlement by cement secretion from the columnar gland cells of the basal protrusion. (2) During larval settlement, numerous AIs were discharged from the AT tips with sinuous movement and rubbing of the tentacles onto the substrata, leading to "nematocyte-printing" around the settlement site. (3) Simultaneous with the discharge of the AIs, migration of stenoteles, desmonemes, and microbasic mastigophores occurred, resulting in a dramatic change of nematocyte composition in the ATs after larval settlement. This was in parallel with changes in larval behavior and the tentacle function. (4) Nematocyte-printing behavior during settlement could be recognized as metamorphic behavior responsible for irreversible changes in AT function, from attachment to feeding and defense.     

Antifouling properties of zinc oxide nanorod coatings

In laboratory experiments, the antifouling (AF) properties of zinc oxide (ZnO) nanorod coatings were investigated using the marine bacterium Acinetobacter sp. AZ4C, larvae of the bryozoan Bugula neritina and the microalga Tetraselmis sp. ZnO nanorod coatings were fabricated on microscope glass substrata by a simple hydrothermal technique using two different molar concentrations (5 and 10?mM) of zinc precursors. These coatings were tested for 5?h under artificial sunlight (1060?W?m^?2 or 530?W?m^?2) and in the dark (no irradiation). In the presence of light, both the ZnO nanorod coatings significantly reduced the density of Acinetobacter sp. AZ4C and Tetraselmis sp. in comparison to the control (microscope glass substratum without a ZnO coating). High mortality and low settlement of B. neritina larvae was observed on ZnO nanorod coatings subjected to light irradiation. In darkness, neither mortality nor enhanced settlement of larvae was observed. Larvae of B. neritina were not affected by Zn²⁺ ions. The AF effect of the ZnO nanorod coatings was thus attributed to the reactive oxygen species (ROS) produced by photocatalysis. It was concluded that ZnO nanorod coatings effectively prevented marine micro and macrofouling in static conditions.     

LIGHT BOUNDARIES AND THE COUPLED EFFECTS OF SURFACE HYDROPHOBICITY AND LIGHT ON SPORE SETTLEMENT IN THE BROWN ALGA HINCKSIA IRREGULARIS (PHAEOPHYCEAE) 1

We examined the effects of light and surface hydrophobicity individually and in tandem on Hincksia irregularis (Kützing) Amsler spore settlement. Hincksia irregularis spores were determined to be negatively phototactic by the use of computer‐assisted motion analysis. Spore settlement was significantly influenced by surface hydrophobicity and by light, individually and in tandem. Experiments conducted using culture plates modified to reduce well edge artifacts revealed significantly higher settlement on hydrophobic surfaces and in dark environments when compared with negatively charged surfaces and lighted environments. Experimental light/dark boundaries elicited distinct spore settlement responses, with spores displaying dissimilar settlement patterns on plates with different surface hydrophobicities. The results of this study indicate H. irregularis spores possess the capacity for complex responses to their environment. These complex responses may influence dispersal and aid spores in the detection of suitable settlement locations in marine microenvironments.     

Effects of adsorbed organic and primary fouling films on bryozoan settlement

Marine primary fouling films, which consist of molecular organic and microbial components, have been reported to facilitate colonization of immersed surfaces by marine fouling organisms. Larvae of the cosmopolitan fouling bryozoan Bugula neritina (Linnaeus) were offered various substrata for attachment and metamorphosis. The materials were offered (a) after detergent washing, (b) after sorption of dissolved organic molecular films, and (c) after formation of primary films consisting of both microbial and adsorbed organic material. Wettability of the substrata by sea water was determined by contact angle measurements for each substratum. On washed substrata, attachment was favored with contact angles greater than ≈45° (cos contact angle <0.7). Adsorbed surface films had no effect on the low settlement of larvae on glass and high settlement on plastics. Microbial primary films, however, made glass attractive and plastics unattractive. These settlement preference changes did not correlate with the changes in wettability observed on these substrata. Dispersion of larvae over the settlement surface was random except on wettable surfaces coated with bacterial films, where settlement was strongly clustered (contagious).     

Modulation of barnacle (Balanus amphitrite Darwin) cyprid settlement behavior by sulfobetaine and carboxybetaine methacrylate polymer coatings

Zwitterionic polymers such as poly(sulfobetaine methacrylate) (polySBMA) and poly(carboxybetaine methacrylate) (polyCBMA) have demonstrated impressive fouling-resistance against proteins and mammalian cells. In this paper, the effects of these surface chemistries on the settlement and behavior of an ubiquitous fouling organism, the cypris larva of the barnacle Balanus amphitrite (=Amphibalanus amphitrite), were studied in the laboratory. Conventional settlement assays and behavioral analysis of cyprids using Noldus Ethovision 3.1 demonstrated significant differences in settlement and behavior on different surfaces. Cyprids did not settle on the polySBMA or polyCBMA surfaces over the course of the assay, whereas settlement on glass occurred within expected limits. Individual components of cyprid behavior were shown to differ significantly between glass, polySBMA and polyCBMA. Cyprids also responded differently to the two zwitterionic surfaces. On polySBMA, cyprids were unwilling or unable to settle, whereas on polyCBMA cyprids did not attempt exploration and left the surface quickly. In neither case was toxicity observed. It is concluded that a zwitterionic approach to fouling-resistant surface development has considerable potential in marine applications.     

First report of the potentially toxic marine diatom Pseudo‐nitzschia simulans (Bacillariophyceae) from the East Australian Current

Certain species of the marine diatom genus Pseudo‐nitzschia are responsible for the production of the domoic acid (DA), a neurotoxin that can bioaccumulate in the food chain and cause amnesic shellfish poisoning (ASP) in animals and humans. This study extends our knowledge by reporting on the first observation of the potentially toxic species Pseudo‐nitzschia simulans from this region. One clonal strain of P. simulans was isolated from the East Australian Current and characterized using light and transmission electron microscopy, and phylogenetic analyses based on regions of the internal transcribed spacer (ITS) and the D1–D3 region of the large subunit (LSU) of the nuclear‐encoded ribosomal deoxyribonucleic acid (rDNA), as well as examined for DA production as measured by liquid chromatography–mass spectrometry. Although this strain was non‐toxic under the defined growth conditions, the results unambiguously confirmed that this isolate is the potentially toxic species P. simulans – the first report of this species from the Southern Hemisphere.     

Fluorine-free mixed amphiphilic polymers based on PDMS and PEG side chains for fouling release applications

Fluorine-free mixed amphiphilic block copolymers with mixtures of short side groups of polydimethyl siloxane (PDMS) and polyethylene glycol (PEG) were synthesized and studied for their ability to influence the surface properties and control the adhesion of marine organisms to coated surfaces. The settlement (attachment) and strength of adhesion of two different marine algae, the green seaweed Ulva and the diatom Navicula, were evaluated against the surfaces. It is known that hydrophobic coatings based on polydimethyl siloxane elastomers (PDMSe) are prone to protein adsorption and accumulation of strongly adherent diatom slimes, in contrast to PEG-based hydrophilic surfaces that inhibit protein adsorption and moderate only weak adhesion of diatoms. By incorporating both PDMS and PEG side chains into the polymers, the effect of incorporating both polar and non-polar groups on fouling-release could be studied. The dry surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). The ability of these mixed amphiphilic polymers to reconstruct in water was examined using underwater bubble contact angle and dynamic water contact angle experiments. To understand more about surface reconstruction behavior, protein adsorption experiments were carried out with fluorescein isothiocyanate-labeled bovine serum albumin (BSA-FITC) on both dry and pre-soaked surfaces.     

INFLUENCE OF LOW LIGHT AND A LIGHT: DARK CYCLE ON NO3– UPTAKE,INTRACELLULAR NO3–, AND NITROGEN ISOTOPE FRACTIONATION BY MARINE PHYTOPLANKTON1

The nitrogen isotope enrichment factor (ɛ) of four species of marine phytoplankton grown in batch cultures was determined during growth in continuous saturating light, continuous low light, and a 12:12‐h light:dark cycle, with nitrate as a nitrogen source. The low growth rate that resulted from low irradiance caused an increased accumulation of the intracellular nitrate pool and/or a reduction in cell volume and was correlated to a species‐specific increase in the measured ɛ value, compared with the saturating light conditions. The largest response was in the diatom Thalassiosira weissflogii (Grun.) Fryxell et Hasle, which showed a nearly 3‐fold increase between high and low light conditions (6.2–15.2‰). The smallest response was in T. pseudonana (Hustedt) Hasle et Heimdal, which showed no change in the ɛ value of approximately 5‰ in both high and low light conditions. There was significant but smaller increases in the ɛ value for the diatom T. rotula Meunier (2.7–5.6‰) and the prymnesiophyte Emiliania huxleyi (Lohm.) Hay et Mohler (4.5–9.4‰) between high and low light levels. In the light:dark experiments, all three diatoms but not the prymnesiophyte exhibited an increase in ɛ. This increase was linked to the ability of diatoms to assimilate nitrate at night. The results of the these experiments suggest that the light regime influences the relative uptake, assimilation, and efflux rates of nitrate and results in differences in the expression of the isotope effect by the enzyme nitrate reductase. Therefore, variations in nitrate isotope fractionation in nature can be more accurately interpreted when the light regime and species composition are taken into consideration.     

Microfluidic accumulation assay probes attachment of biofilm forming diatom cells

Testing of fouling release (FR) technologies is of great relevance for discovery of the next generation of protective marine coatings. In this paper, an accumulation assay to test diatom interaction under laminar flow with the model organism Navicula perminuta is introduced. Using time lapse microscopy with large area sampling allows determination of the accumulation kinetics of the diatom on three model surfaces with different surface properties at different wall shear stresses. The hydrodynamic conditions within the flow cell are described and a suitable shear stress range to perform accumulation experiments is identified at which statistically significant discrimination of surfaces is possible. The observed trends compare well to published adhesion preferences of N. perminuta. Also, previously determined trends of critical wall shear stresses required for cell removal from the same set of functionalized interfaces shows consistent trends. Initial attachment mediated by extracellular polymeric substances (EPS) present outside the diatoms leads to the conclusion that the FR potential of the tested coating candidates can be deducted from dynamic accumulation experiments under well-defined hydrodynamic conditions. As well as testing new coating candidates for their FR properties, monitoring of the adhesion process under flow provides additional information on the mechanism and geometry of attachment and the population kinetics.     

UV‐EXCITED BLUE AUTOFLUORESCENCE OF PSEUDO‐NITZSCHIA MULTISERIES (BACILLARIOPHYCEAE)1

A flow cytometer coupled to a scanning monochromator and a fluorescence microscope were used to characterize the fluorescence spectrum of Pseudo‐nitzschia multiseries (Hasle) Hasle, a pennate diatom that produces the neurotoxin domoic acid, a lethal amnesic. In this research, we characterize the fluorescence spectrum of P. multiseries in vivo over the wavelength range of 360 to 850 nm and show that this diatom autofluoresces blue when excited with UV light (350–365 nm). The autofluorescence characterization of Pseudo‐nitzschia may provide new methods for rapid in situ monitoring of diatom populations and reiterates the usefulness of flow cytometry in the analysis and study of marine phytoplankton.     

Temperature- and Light-Dependent Performance of the Cyanobacterium <Emphasis Type="Italic">Leptolyngbya Foveolarum</Emphasis> and the Diatom <Emphasis Type="Italic">Nitzschia Perminuta</Emphasis> in Mixed Biofilms

This paper investigates the role of species interactions as a mechanism determining the changing seasonal abundance of microphytobenthic species. Different kinds of interactions can occur between microphytobenthic species, e.g., interference competition (a species directly hindering the growth of another) or resource competition. If such interactions are strong, the capacity of species to exploit parts of the seasonal spectrum of temperature and light conditions could be greatly affected. A model system of two freshwater benthic phototrophs, the cyanobacterium Leptolyngbya foveolarum (Rabenhorst ex Gomont) Anagnostidis et Komárek and the diatom Nitzschia perminuta (Grunow) M. Pergallo, was used to study the capacity of each species to grow in ranges of temperature (7, 15 and 25 °C) and light (5, 40 and 200 μmol m⁻² s⁻¹) conditions in single-species and two-species cultures. Growth was followed for 14–17 days by measuring chlorophyll a and maximum photosynthetic capacity using spectrophotometry and pulse amplitude modulated (PAM) fluorimetry. A PHYTO-PAM fluorimeter facilitated simultaneous observations in mixed cultures on the two species. In mixed cultures, the diatom appeared to be a ‘cool season species’ (low temperature and low light intensity) and the cyanobacterium a ‘summer or autumn species’ (higher temperature and light intensities). This is different than predicted by monoculture experiments, where a wide range of optimal growth conditions was found. Two-species biofilm tests indicated inhibitory effects of the cyanobacterium on the diatom species, especially under conditions favorable to the cyanobacterium. High or low light intensities, increase of local pH caused by depletion of inorganic carbon, and limitation of other inorganic nutrients (resource competition) were examined as factors contributing to diatom inhibition, but none provided an acceptable explanation for observed growth patterns. Our results pointed towards interference competition.     

Effect of cytoplasmic streaming on photosynthetic activity of chloroplasts in internodes of <Emphasis Type="Italic">Chara corallina</Emphasis>

Cytoplasmic streaming plays an important role in cell processes since it promotes solute exchange between the cytoplasm and organelles and enables lateral transport for extensive distances. The role of cyclosis in chloroplast functioning should be most conspicuous under conditions mimicking natural mosaic illumination and consequent alternation of cell regions with dominant dark and photosynthetic metabolism. Based on this assumption, we examined the light response curves and the induction kinetics of fluorescence-based parameters of chloroplast photosynthetic activity on small regions (d ∼ 100 μm) of Chara corallina Klein ex Willd. internodal cells exposed to local and overall illumination under conditions of normal cytoplasmic streaming and after suppression of cyclosis by cytochalasin B, an inhibitor of actin microfilaments. Under control conditions, the whole cell illumination caused non-photochemical quenching (NPQ) of chlorophyll fluorescence, which approached the saturation at a photon flux density of about 40 μmol/(m² s). By contrast, illumination of a small (2 mm wide) cell part did not cause significant NPQ at light intensities up to 100 μmol/(m² s), indicating that the chloroplast photosynthetic activity was substantially higher under conditions of localized illumination. After the inhibition of cyclosis by cytochalasin B, the light response curves were represented by nearly identical sigmoid curves, irrespective of the illumination pattern. When the cyclosis was restored in the cells washed from the inhibitor, the light response curves measured under overall and localized illumination returned to their original divergent shapes. These and other data indicate that different photosynthetic activities of chloroplasts in cells exposed to entire and partial illumination are directly related to the flow of compositionally nonuniform cytoplasm between the cell parts with prevalent photosynthetic and respiratory metabolism.     

Settlement, early growth and survival of Haliotis rubra in response to different algal species

Five diatom species were isolated from settlementplates at Southern Ocean Mariculture, Victoria,Australia (Navicula sp., Naviculajeffreyi, Cylindrotheca closterium, Cocconeis sp., Amphora sp.) and tested insettlement experiments with Haliotis rubralarvae. Settlement was very low on single speciesdiatom films and varied between 1%–6%. Depending onthe species combination larvae preferred to settle onfilms with mixed diatom species than single speciesfilms. The highest settlement was achieved with amixed film of Navicula sp. and Amphora sp.Five and ten-day-old germlings of Sporolithondurum induced settlement of the abalone Haliotisrubra. However, the settlement rate was significantlylower on germlings than on the whole thallus of thealga. Germlings inoculated with the diatom Navicula sp. induced higher settlement than films ofthe diatom species alone. High settlement of up to52% was also achieved with germlings of the greenalga Ulvella lens. Settlement was reduced onU. lens squares inoculated with the diatom Navicula sp. but higher than on films of the diatomalone. The settlement rate was higher if plates withU. lens were previously grazed by juvenileabalone.Post-larval growth rates were higher on monospecificdiatom films than on U. lens or on S.durum. The best growth rate was obtained with Navicula sp. U. lens and S. durum areboth good settlement inducers, but are notsufficient to support rapid growth of young H.rubra post-larvae. Survival was low on U. lensand on the diatom C. closterium. We suggest thatcommercial nursery plates seeded with U. lenswill result in high and consistent settlement, whilean inoculum with Navicula sp. will ensuresufficient food for rapid growth of the post-larvae.     

CELL DIVISION PERIODICITY IN 13 SPECIES OF MARINE PHYTOPLANKTON ON A LIGHT: DARK CYCLE1

The division rates of 26 clonal cultures representing 13 species of planktonic marine algae (6 diatoms, 2 flagellated chrysophytes, 2 coccolithophores, 1 cryptomonad flagellate, I dinoflagellate, 1 green alga) were determined every 2 h for 48 h during exponential growth on a 14:10 LD cycle in nutrient-replete batch culture. Cyclic oscillations in the division rate were detectable in 22 of these clones. Of 14 diatom clones examined, four displayed nearly constant division rates throughout the LD cycle and ten showed strong periodicity favoring division during the light periods. In contrast, all other algae (12 clones) exhibited division rate maxima during periods of darkness, and clearly detectable decreases in cell number for time intervals of 4–8 h during periods of illumination. Intraspecific differences in division periodicity were found among eight clones of the diatom Thalassiosira pseudonana (Hustedt) Hasle & Heimdal and six clones of the coccolithophore Emiliania huxleyi (Lohm.) Hay & Mohler.     

The effect of bacterial and diatom biofilms on the settlement of the bryozoan Bugula neritina

Biofilms of marine bacteria and diatoms and their combinations were examined in laboratory choice assays to determine their effects on the attachment and successful metamorphosis of the larvae of the bryozoan Bugula neritina (Linnéus). The larval settlement in response to unfilmed surfaces, a natural biofilm (NBF) and adsorbed cells of three strains of bacteria, five strains of pennate diatoms and combinations of the two at different densities. Bacterial and diatom strains showed different effects on the larval settlement of B. neritina. Bacterial monospecific strains of an unidentified α-Proteobacterium and Vibrio sp. mediated the same percentage of settlement as a filtered seawater control. Biofilms of Pseudoalteromonas sp. caused significantly lower larval settlement. Larval settlement of B. neritina was negatively correlated with increasing densities of Pseudoalteromonas sp. The highest percentages of settlement were mediated by the biofilms of the diatom species Achnanthes sp., Amphora cofeaeformis, Amphora tenerrima, Nitzschia constricta and a 5-day-old natural biofilm, while the lowest settlement was found on a N. frustulum film. A three-way analysis of variance demonstrated that the density of bacteria and the presence of particular species of diatoms and bacteria in combined biofilms, significantly affected the settlement of B. neritina larvae. High settlement of larvae (50-90%) at all treatments indicated that B. neritina larvae are much more indiscriminate settlers than previously expected. Hence, using this species as a monitoring organism to trace ecologically relevant subtle changes of settlement cues in the natural environment should be carefully re-examined.     

Barnacle settlement and the adhesion of protein and diatom microfouling to xerogel films with varying surface energy and water wettability

Previous work has shown that organosilica-based xerogels have the potential to control biofouling. In this study, modifications of chemistry were investigated with respect to their resistance to marine slimes and to settlement of barnacle cyprids. Adhesion force measurements of bovine serum albumin (BSA)-coated atomic force microscopy (AFM) tips to xerogel surfaces prepared from aminopropylsilyl-, fluorocarbonsilyl-, and hydrocarbonsilyl-containing precursors, indicated that adhesion was significantly less on the xerogel surfaces in comparison to a poly(dimethylsiloxane) elastomer (PDMSE) standard. The strength of adhesion of BSA on the xerogels was highest on surfaces with the highest and the lowest critical surface tensions, γ_C and surface energies, γ_S, and duplicated the ‘Baier curve’. The attachment to and removal of cells of the diatom Navicula perminuta from a similar series of xerogel surfaces were examined. Initial attachment of cells was comparable on all of the xerogel surfaces, but the percentage removal of attached cells by hydrodynamic shear stress increased with γ_C and increased wettability as measured by the static water contact angle, θ_Ws, of the xerogel surfaces. The percentage removal of cells of Navicula was linearly correlated with both properties (R ² = 0.74 for percentage removal as a function of θ_Ws and R ² = 0.69 for percentage removal as a function of γ_C). Several of the aminopropylsilyl-containing xerogels showed significantly greater removal of Navicula compared to a PDMSE standard. Cypris larvae of the barnacle B. amphitrite showed preferred settlement on hydrophilic/higher energy surfaces. Settlement was linearly correlated with θ_Ws (R ² = 0.84) and γ_C (R ² = 0.84). Hydrophilic xerogels should prove useful as coatings for boats in regions where fouling is dominated by microfouling (protein and diatom slimes).