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Steam is a common medium in thermal engineering. When it flows through a throttling element, the aerodynamic noise may occur due to the disturbance. In this investigation, superheated steam flowing...

Biodegradable polymers are promising binders and carriers for natural antifoulants. In the present study, an antifouling (AF) coating was developed by adding a non-toxic AF compound (butenolide) to a bio-based and biodegradable poly(lactic acid)-based polyurethane. Mass loss measurement showed that the polymer degraded in seawater at a rate of 0.013

Running and running shoe biomechanics are usually measured in laboratory settings, capturing discontinuous running trials. Continuous running measured outdoors doesn’t allow comprehensive measureme...

Due to the merits of higher heat transfer efficiency, spirally corrugated tubes are widely used in a range of applications for heat transfer enhancement, especially in coaxial heat exchangers. This...

Fouling on heat exchanger surfaces can weaken the heat-transfer capability, increase the energy consumption, and even cause the failure of the whole system. In coaxial heat exchangers, spirally cor...

The episomal structures of all human bocavirus (HBoV) genotypes have been deciphered, including the circular genome of HBoV2 (HBoV2-C1). To discern the role of the circular HBoV2 genome, three distinct linearized HBoV2-C1 genomes were cloned into pBlueScript SKII(+) to obtain pBlueScript HBoV2 5043–5042 (retaining all secondary structures), pBlueScript-HBoV2 5075–5074 (retaining hairpin number 2 and the 5′ terminal structure), and pBlueScript-HBoV2 5220–5219 (retaining only the 5′ terminal structure at the 5′ -genome end). The recombinant plasmids were separately transfected HEK293 cells, revealing that more HBoV2 DNA had accumulated in the pBlueScript HBoV2 5043–5042-transfected HEK293 cells at 72 h post-transfection, as determined by real-time PCR. However, more mRNA was transcribed by pBlueScript-HBoV2 5075–5074 than by the other constructs, as determined by dot-blot hybridization and RNAscope. No significant differences in NS1-70 protein expression were observed among the three HBoV2 genomic clones. However, electron microscopy showed that HBoV2 virus particles were only present in the pBlueScript HBoV2 5043–5042-transfected HEK293 cells. By using three hetero-recombinant HBoV2 genomic clones in HEK293 transfected cells, only the genome with intact secondary structures produced virus particles, suggesting that retaining these structures in a circular genome is important for HBoV2 DNA replication and virus assembly.

Heat transfer enhancement is of great importance for energy efficiency improvement. The utilization of spirally corrugated tubes is one of the efficient ways to strengthen heat transfer. In this article, based on a validated numerical model, the effects of geometric parameters of a six-start spirally corrugated tube, including the pitch p and the corrugation depth e, on the shell side heat transfer and flow resistance performance are numerically investigated, in high Reynolds number conditions ranging from 10,000 to 60,000. The shell side secondary flow velocity distribution, longitudinal vortex distribution, and temperature distribution of a six-start spirally corrugated tube are presented, respectively. In addition, the heat transfer and flow resistance characteristics are evaluated by comparing the Nusselt number and the flow resistance coefficient with these of smooth tubes. Results show that the utilization of six-start spirally corrugated tubes can enhance the heat transfer performance at the expense of an increase of the flow resistance. However, with the same geometric parameters, the Nusselt number increases and the flow resistance coefficient decreases as Reynolds number increases. With the pitch increasing, the Nusselt number and the flow resistance coefficient decrease at a fixed Reynolds number. In contrast, as the corrugation depth increasing, the Nusselt number changes irregularly, and the flow resistance coefficient increases. Finally, correlations for the shell side Nusselt number and flow resistance coefficient of the six-start spirally corrugated tube are established. This work is of significance for engineers and scientists focusing on the heat transfer and the flow resistance characteristics of spirally corrugated tubes and their applications. (Less)

The Thorium-Based Molten Salt Reactor (TMSR) has been highlighted for its safety, economy, and nuclear nonproliferation. A program for developing the TMSR system has been launched in Shanghai Institute of Applied Physics, Chinese Academy of Sciences. In the TMSR system, mixtures of LiF and BeF2, termed FLiBe, are proposed and used as the primary coolant salt, in which tritium is produced mainly by the neutron reactions of lithium. In the TMSR system, at high temperatures, tritium can permeate through metal walls to the surroundings, leading to a potential radiological hazard. Thus, tritium control becomes a major problem hindering the development of the TMSR system. Evaluation of the tritium distribution is necessary for tritium control in the TMSR system. In this study, the Tritium Transport Analysis Code (TTAC) has been developed for simulating the tritium behaviors in the TMSR system (hence, the code TMSR-TTAC), such as tritium chemical forms in coolant salts, tritium transport behaviors, and t...

Butenolide is an environmentally friendly antifouling natural product, but its efficiency and mechanism in preventing biofilm formation have not been examined. Furthermore, controlling the release of butenolide from paints into seawater is technically challenging. A coating was developed by mixing butenolide with a biodegradable polymer, poly (ε-caprolactone)-based polyurethane, and a one-month in situ anti-biofilm test was conducted in a subtidal area. The constant release of butenolide from the surface suggested that its release was well controlled. Direct observation and confocal microscope investigation indicated that the coating was effective against both biofilm formation and attachment of large fouling organisms. Metatranscriptomic analysis of biofilm samples implied that the coating selectively inhibited the adhesion of microbes from a variety of phyla and targeted particular functional pathways including energy metabolism, drug transport and toxin release. These integrated analyses demonstrated the potential application of this butenolide/polymer coating as an anti-biofilm material.

An experiment was performed to evaluate the regulatory effects of varied amounts of sulfur (S) on selenium (Se) uptake and distribution within wheat (Triticum aestivum L.) in response to selenite (SeO32-). The results showed that an appropriate amount of SeO32- (≤5 mg kg−1) improved the agronomic traits of wheat, and the addition of S significantly alleviated wheat growth inhibition caused by excessive SeO32- (≥15 mg kg−1). The Se concentration of different fractions in wheat grain showed a tendency of alkali-soluble Se > alcohol-soluble Se > water-soluble Se > salt-soluble Se. The use of S significantly reduced Se accumulation in each wheat part when the addition of SeO32- was ≤15 mg kg−1, but the Se distribution ratio of various wheat parts was not influenced by S supply. Overall, the application of S fertilizer is an effective technical measure to promote wheat production safety in high-Se areas.

In this paper, we adopt the Bayesian approach to expectile regression employing a likelihood function that is based on an asymmetric normal distribution. We demonstrate that improper uniform priors for the unknown model parameters yield a proper joint posterior. Three simulated data sets were generated to evaluate the proposed method which show that Bayesian expectile regression performs well and has different characteristics comparing with Bayesian quantile regression. We also apply this approach into two real data analysis.

The deep-sea limpet Bathyacmaea nipponica is endemic to hydrothermal vents and hydrocarbon seeps in the Western Pacific. We report the complete mitochondrial genome of B. nipponica, which is 16,792...

Tritium was generated by the interaction of neutrons with the lithium and beryllium in the molten salt reactors (MSRs), which use Flibe as one of solvents of fluoride fuel. Tritium as by-product in the MSRs would be an important safety issue because it could easily diffuse through high temperature heat exchangers into environment. The experimental technique of gas driven permeation was used to investigate the transport parameter of hydrogen in Hastelloy C-276 which was considered as one of the candidate structure materials. The measurements were carried out at the temperature range of 400-800 degrees C with hydrogen loading pressures ranging from 5x10(3) to 4x10(4) Pa. The H diffusive transport parameters for Hastelloy C-276 followed an Arrhenius law in this temperature range and were decreased due to the existence of the alloying elements compared with Ni201.The possible reason may be the trapping effects, which were formed by the alloying elements of Mo and Cr in the matrix. At the same time, the thin oxidation layer formed by the high Cr content could lead to the slower dissociation process of H-2 at the surface.

This review covers 214 marine natural compounds and 23 of their synthetic analogs, which were discovered and/or synthesized from mid-2009 to August 2014. The antifouling (AF) compounds reported have medium to high bioactivity (with a threshold of EC50 < 15.0 mg ml−1). Among these compounds, 82 natural compounds were identified as new structures. All the compounds are marine-derived, demonstrating that marine organisms are prolific and promising sources of natural products that may be developed as environmentally friendly antifoulants. However, this mini-review excludes more than 200 compounds that were also reported as AF compounds but with rather weak bioactivity during the same period. Also excluded are terrestrial-derived AF compounds reported during the last five years. A brief discussion on current challenges in AF compound research is also provided to reflect the authors’ own views in terms of future research directions.

Copper matrix composites containing graphite and tungsten disulfide were prepared and tested under the loads of 1–5 N to investigate their friction and wear behaviors. The microstructure, worn surfaces, and cross section of worn subsurfaces were observed, and the lubricating films formed on the worn surfaces were analyzed. It is found that the Cu–24 vol% WS2 composite presents a higher mechanical performance and lower wear rate compared to the Cu–24 vol% graphite composite with same volume fraction of solid lubricant. This could be attributed to the high-strength chemical bonding of the interface between WS2 and the copper matrix. The high-strength interfacial bonding also helps prevent plastic deformation and the formation of cracks at the worn subsurfaces of the composites. The amount of lubricant on the outmost worn surfaces is significantly higher than that in the composite. The lubricating film of WS2 with relatively high thickness provides a low friction coefficient to the composites.

Paraescarpia echinospica is a conspicuous annelid living in the cold seeps and hydrothermal vents of the Western Pacific region and relying on their endosymbiont bacteria as a source of energy and ...

This is the first study applying Next-Generation Sequencing (NGS) technology to survey the kinds, expression location, and pattern of adhesion-related genes in a membranous-based barnacle. A total of 77,528,326 and 59,244,468 raw sequence reads of total RNA were generated from the prosoma and the basis of Tetraclita japonica formosana, respectively. In addition, 55,441 and 67,774 genes were further assembled and analyzed. The combined sequence data from both body parts generates a total of 79,833 genes of which 47.7% were shared. Homologues of barnacle cement proteins - CP-19K, -52K, and -100K - were found and all were dominantly expressed at the basis where the cement gland complex is located. This is the main area where transcripts of cement proteins and other potential adhesion-related genes were detected. The absence of another common barnacle cement protein, CP-20K, in the adult transcriptome suggested a possible life-stage restricted gene function and/or a different mechanism in adhesion between membranous-based and calcareous-based barnacles.

Various antifouling (AF) coatings have been developed to protect submerged surfaces by deterring the settlement of the colonizing stages of fouling organisms. A review of the literature shows that effective AF compounds with specific targets are ones often considered non-toxic. Such compounds act variously on ion channels, quorum sensing systems, neurotransmitters, production/release of adhesive, and specific enzymes that regulate energy production or primary metabolism. In contrast, AF compounds with general targets may or may not act through toxic mechanisms. These compounds affect a variety of biological activities including algal photosynthesis, energy production, stress responses, genotoxic damage, immunosuppressed protein expression, oxidation, neurotransmission, surface chemistry, the formation of biofilms, and adhesive production/release. Among all the targets, adhesive production/release is the most common, possibly due to a more extensive research effort in this area. Overall, the specific molecular targets and the molecular mechanisms of most AF compounds have not been identified. Thus, the information available is insufficient to draw firm conclusions about the types of molecular targets to be used as sensitive biomarkers for future design and screening of compounds with AF potential. In this review, the relevant advantages and disadvantages of the molecular tools available for studying the molecular targets of AF compounds are highlighted briefly and the molecular mechanisms of the AF compounds, which are largely a source of speculation in the literature, are discussed.

In this article, a new approach was established to estimate the fractional contributions of soil dust, biomass burning, biogenic emissions, coal burning, and vehicle exhaust to the carbonaceous particulate matter by carbon isotope and linear regression techniques of OC-K+ (organic carbon) and OC-EC (elemental carbon). Using the method described herein, the fractional distributions of these sources were quantitatively determined for the OC and semiquantitatively for the EC in the size-resolved particles (size ranges: 7.2 μm) collected in Jiading District, a suburb of Shanghai, China. Distinct size distribution of contributions of these sources to the OC and EC was observed. Generally, biomass burning contributed a large fraction to OC in the smaller particles and biogenic emissions shared a bigger fraction to OC in the larger particles. Soil dust made contributions solely to the OC, for no EC fraction was found in the soil dust. OC from coal burning concen...

Biofouling is ubiquitous in marine environments, and the barnacle Balanus amphitrite is one of the most recalcitrant and aggressive biofoulers in tropical waters. Several natural antifoulants that were claimed to be non-toxic have been isolated in recent years, although the mechanism by which they inhibit fouling is yet to be investigated. Poly-ether B has shown promise in the non-toxic inhibition of larval barnacle attachment. Hence, in this study, multiplex two-dimensional electrophoresis (2-DE) was applied in conjunction with mass spectrometry to investigate the effects of poly-ether B on barnacle larvae at the molecular level. The cyprid proteome response to poly-ether B treatment was analyzed at the total proteome and phosphoproteome levels, with 65 protein and 19 phosphoprotein spots found to be up- or down-regulated. The proteins were found to be related to energy-metabolism, oxidative stress, and molecular chaperones, thus indicating that poly-ether B may interfere with the redox-regulatory mechanisms governing the settlement of barnacle larvae. The results of this study demonstrate the usefulness of the proteomic technique in revealing the working mechanisms of antifouling compounds.

This paper shows that Bayesian estimation and comparison of multivariate generalized autoregressive conditional heteroscedasticity (MGARCH) and multivariate stochastic volatility (MSV) models with Markov Chain Monte Carlo methods could be straightforwardly and successfully conducted in WinBUGS package. And an algorithm based on the Cholesky decomposition is proposed to set as a prior for a correlation matrix. They are illustrated by applying three types of parsimonious MGARCH and MSV specifications nested in constant conditional correlations to weekly returns of five sector indexes of Shanghai Stock Exchange over the period of 28 June 2004 to 30 June 2008. Empirical results provide evidence for the superior performance of MSV models over MGARCH models and give support to the feasibility of the algorithm we presented. In addition, the estimation results also suggest the significant negative correlation between the persistency and the variability of volatilities in MSV models.

The red-pigmented marine bacterium Pseudoalteromonas sp. sf57 forms a biofilm that deters larval settlement of the tube-building polychaete Hydroides elegans. To investigate the correlation between pigmentation and larval settlement deterrence, mutants of sf57 with deficient or altered pigmentation were generated by transposon mutagenesis. Five groups of pigmented mutants were obtained, viz. white, yellow, pink, dark red, and white-to-red. The white mutant WM1, which exhibited a substantial increase in bacterial density in the biofilm, became inductive to larval settlement. The other mutants that showed a lesser increase in bacterial density in their biofilms either retained their deterrence or induced higher larval settlement rates, but did not become inductive strains. Analysis of the disrupted genes in these mutants suggests that the type II secretion pathway, the LysR transcriptional regulator, NAD(P)-binding proteins, exonuclease, pyruvate metabolism, flagella assembly, and cell membrane processes may play a role in the regulation of pigmentation in sf57.

Copper (Cu) contamination is a potential threat to the marine environment due to the use of Cu-based antifouling paints. Cu stress on larval settlement of the polychaete Hydroides elegans was investigated, and this was linked to Cu stress on biofilms and on the biofilm development process. The inductiveness of young biofilms was more easily altered by Cu stress than that of old biofilms, indicating the relative vulnerability of young biofilms. This might result from changes in bacterial survival, the bacterial community composition and the chemical profiles of young biofilms. Cu also affected biofilm development and the chemical high performance liquid chromatograph fingerprint profile. The results indicate that Cu affected larval settlement mainly through its effect on the process of biofilm development in the marine environment, and the chemical profile was crucial to biofilm inductiveness. It is strongly recommended that the effects of environmentally toxic substances on biofilms are evaluated in ecotoxicity bioassays using larval settlement of invertebrates as the end point.

Mizolastine, an antihistamine pharmaceutical, was found to significantly inhibit larval settlement of the barnacle Amphibalanus (=Balanus) amphitrite, the bryozoan Bugula neritina, and the polychaete Hydroides elegans with EC(50) values of 4.2, 11.2, and 4.1 microg ml(-1), respectively. No toxicity against the larvae of these three species was observed at the concentration range tested during incubations with mizolastine. To determine whether the anti-settlement activity of mizolastine is reversible, recovery bioassays using these three species were conducted. More than 70% of the larvae that had been exposed for 4 h to mizolastine at concentrations four-fold greater than their respective EC(50) values completed normal metamorphosis. The results of the recovery bioassay provide evidence that the anti-settlement effect of mizolastine is reversible in addition to being nontoxic. The anti-settlement activities of several intermediates of the synthesis process of mizolastine were also examined. One of the intermediates, 2-chloro-1-(4-fluorobenzyl)-1H-benzo[d]imidazole, inhibited larval settlement and metamorphosis with low toxicity. These results may improve the understanding of the key functional group responsible for the anti-settlement activity of mizolastine.

To determine whether they could serve as non-toxic or less damaging alternative antifouling (AF) agents, 17 flavone and isoflavone derivatives were isolated from terrestrial plant extracts, purified and examined for their ability to inhibit the settlement of barnacle (Balanus amphitrite) cyprids. In larval bioassays, eight compounds showed strong anti-larval settlement activities, with EC(50) values10 microg ml(-1). Through an analysis of the structure-activity relationship of these compounds, it was found that (1) the structural difference between flavones and isoflavones did not affect their AF activities; (2) the 5-hydroxyl group on the skeletons played a key role in AF activities; and (3) the presence of hydroxyl group or bulky group on C3 significantly reduced AF activities. A hydrolysis experiment using genistein, a typical active compound in this study, indicated that it was decomposed in the marine environment by hydrolysis reaction and that the degradation speed was significantly affected by pH. In a field AF test, genistein inhibited the attachment of B. amphitrite on panels coated with genistein-paint mixtures.

The Balanus amphitrite attachment inhibition assay, developed by Rittschof et al. (1992), has been widely used for screening antifouling compounds. One shortcoming of this assay, however, is the low (often40%) attachment rate of cyprids, including in the controls that contain seawater only. In this study, trapping of cyprids at the air-water interface was found to be a main contributor to the low attachment rate. Procedures to eliminate the air-water interface were thus introduced. With the improved bioassay, a much higher cyprid attachment rate (70%) was attained. To further illustrate the usefulness of the improved assay (ie eliminating the air-water interface), the effects of the length of cyprid storage and the effect of a reference biocide, tributyltin chloride, on the survival and attachment rate of the cyprids were examined. The length of cyprid storage was important, with newly molted cyprids, 3- to 9-day old cyprids and 12-day old cyprids having an attachment rate of 43%,75% and 36%, respectively. The low attachment rate in the newly molted cyprids was due to a high percentage of cyprids that still swam at the end of exposure period, whereas the low attachment rate in the 12-day old cyprids was due to a high mortality rate. The cyprids showed an EC50 of 22 microg l(-1) for attachment inhibition and LC50 of 25 microg l(-1) for mortality. It is concluded that the air-water interface has an important confounding effect on cyprid attachment rate in the conventional B. amphitrite attachment assay. By eliminating the air-water interface more robust quantitative assay results were obtained.

Modern antifouling coatings use heavy metals and toxic organic molecules to prevent biofouling, the undesirable growth of marine organisms on man-made substrata. In an ongoing survey of deep-sea microorganisms aimed at finding low toxic antifouling metabolites, an actinomycete bacterium was isolated from the Pacific sediment at the depth of about 5000 m. The bacterium was closely related to Streptomyces fungicidicus (99% similarity) according to 16S ribosomal RNA sequence information. The spent culture medium of this bacterium inhibited barnacle larval attachment. Bioassay-guided fractionation was employed to isolate antifouling compounds. The ethyl acetate extract was fractionated by using an open silica gel column. Active fractions were further purified on a HPLC C18 column. Five diketopiperazines, cyclo-(L-Leu-L-Pro), cyclo-(L-Phe-L-Pro), cyclo-(L-Val-L-Pro), cyclo-(L-Trp-L-Pro), and cyclo-(L-Leu-L-Val) were isolated for the first time from a deep sea bacterium, and the structures of the compounds were elucidated by nuclear magnetic resonance spectroscopy and mass spectrometry. The pure diketopiperazines were tested for antilarval activity using the barnacle Balanus amphitrite. Effective concentrations that inhibited 50% larval attachment (EC50) after 24 h ranged from 0.10- 0.27 mM. The data suggest that diketopiperazines and other compounds from deep-sea bacteria may be used as novel antifoulants.

Many soft-bodied sessile marine invertebrates such as sponges and soft corals defend themselves against fouling directly through the production of antifouling compounds, or indirectly through regulating the epibiotic microbes that affect larval settlement. In this study, 10beta-formamidokalihinol-A and kalihinol A were isolated and purified from the marine sponge Acanthella cavernosa (Dendy). The results indicated that both compounds inhibited the growth of bacteria isolated from the natural environment whereas kalihinol A suppressed larval settlement of a major fouling polychaete, Hydroides elegans with an EC50 of 0.5 microg ml(-1). Kalihinol A was incorporated in Phytagel that was exposed to the bacterial consortia in natural seawater for biofilm formation. Biofilms that developed on the Phytagel surfaces were analysed for bacterial abundance and bacterial species composition using a DNA fingerprinting technique, terminal restriction fragment length polymorphism (T-RFLP). The results showed that kalihinol A only slightly reduced bacterial abundance (t-test, p = 0.0497), but modified the bacterial species composition of the biofilms. Inhibition of H. elegans larval settlement was observed when biofilms developed under the influence of kalihinol A were exposed to larvae, suggesting that compounds like kalihinol A from the sponge A. cavernosa may change bacterial community composition on the sponge surface, which in turn, modulates larval settlement of fouling organisms.

The effects of the neurotransmitter blockers idazoxan and phentolamine on the larval settlement of three marine invertebrate species belonging to three different phyla were investigated by using in vitro concentration-response bioassays. Since neurotransmitters are known to influence metamorphic transitions in invertebrate larvae, neurotransmitter blockers were tested to evaluated their sublethal effects on larvae. The alpha-adrenergic antagonists idazoxan and phentolamine inhibited settlement of Balanus amphitrite (Cirripedia), Bugula neritina (Bryozoa) larvae, and larvae of the polychaete Hydroides elegans (Polychaeta) in a concentration-and taxon-dependent manner. At concentrations of 10(-3) M of both agents, larvae of all three species became immobile and subsequently died within 24 h. While cumulative settlement rates were observed after 48 h for B. amphitrite and H. elegans, and after 5 h for B. neritina,90% of the larvae that settled did so within 24 h for the first two species and within 1 h for B. neritina. The tendency of the hydrophobic idazoxan and phentolamine to accumulate at solid surfaces most probably contributes to their successful inhibition of larval settlement. This ability makes them particularly attractive as candidates for the development of slow-release carriers in antifouling paints.

The Harpacticoida reside in a wide range of habitats—from all marine situations to most freshwater habitats, and even moist terrestrial substrata like moss and litter. They exhibit free-living to parasitic life-styles and larval development with plankto- and lecithotrophy. Harpacticoid life cycles as a rule comprise six nauplius larvae and six copepodids, the sixth being the adult. Harpacticoid life history traits known from the field or from cohort analyses include differential fecundity, stage duration and survival, sex ratio, development and life span. Understanding life history traits, i.e. assessing the importance of various biotic and abiotic factors in regulating life cycle patterns, is essential for the interpretation of seasonal variations of population size. Evolutionary stable strategies (EES) of reproductive resource allocation and timing are determined by trade-offs between environmental conditions as well as by intrinsic factors. The latter are the genetic base, depending on the evolutionary...

A 2-year study was conducted in Hong Kong to examine the effects of substratum, season and length of submersion on the development of a subtidal epibiotic community using four types of settlement panels (concrete, steel, wood and tyre). The season and length of submersion had a strong influence on the total biomass and on community structure while the type of substratum had very little impact on the total biomass or the structure of the epibiotic community. The season of submersion determined the species composition of the newly submerged surfaces. In the spring and summer, tubeworms were the most abundant. In the autumn and winter, barnacles and tunicates dominated. Community succession was not obvious in the first year of submersion as it was intermingled with strong seasonal settlement, growth and death of barnacles and tunicates. In the second year of submersion, green mussels and tunicates settled and grew to occupy most of the panel surfaces, forming an assemblage that was characteristic of climax communities in the local subtidal waters. The results suggest that the type of construction material has limited impact on the development of epibiotic communities on artificial reefs deployed in Hong Kong; the season of submersion may affect community structure in the early successional stage, but not the characteristics of the climax communities. This study indicates that the type of substratum should not be of concern when deploying artificial reefs in the subtidal waters in this region. The design of artificial reefs should focus more on other physical and economical aspects such as durability, flow dynamics, stability, cost, and effects on the ambient environment.

The sponge, Mycale adherens, usually occurs within the fouling community of Hong Kong waters, yet its body surface is rarely fouled by other macro-organisms. In this study, sponge-associated bacteria were isolated using enrichment culture techniques and compared with indigenous bacterial isolates from an inanimate reference site in the close vicinity. Bacterial isolates were identified phylogenetically by 16S rRNA gene sequence analysis. The comparison between culturable bacterial communities from the sponge and indigenous benthic bacteria revealed differences both in the total number of isolates and their phylogenetic affiliation. Laboratory bioassays utilizing monospecies bacterial films revealed that a significant portion of sponge-associated bacteria had either an inhibitory or neutral effect on larval settlement of the fouling polychaete, Hydroides elegans. In contrast to natural biofilms, which harbor ca 65% of bacteria with at least some sort of inductive effect on H. elegans, statistical analysis showed that only 25% of sponge-associated bacteria were classified as "inductive" strains while the remaining 75% were classified as "non-inductive" strains. Waterborne metabolites of sponges affected the larvae of H. elegans in a concentration-dependent manner by either exerting a toxic or an anti-settlement effect. Organic solvent extracts of sponge tissue weakly inhibited growth of bacterial strains isolated from marine biofilms. A potential antifouling mechanism in the sponge M. adherens is discussed.

The green alga Ulva reticulata (Forsskal) is often free from biofouling in Hong Kong waters. An early study indicated that bioactive substances from this alga inhibit settlement of the polychaete Hydroides elegans (Haswell). It is also predicted that epibiotic bacteria protect this alga from micro- and macrofouling. In this study, bacterial strains from the surface of U. reticulata were isolated and their inhibitive activities on micro- and macrofouling assayed. The strains were identified by 16S rRNA analysis as belonging to the genera Alteromonas , Pseudoalteromonas and Vibrio . There was no significant effect of these strains or their extracts (aqueous and ethanol) on the growth of five Vibrio strains isolated from natural biofilm. Two bacterial strains ( Alteromonas sp. and Vibrio sp. 3) were non-toxic to the benthic diatom Nitzschia paleacea (Grunow) while the other five strains caused a low level of mortality. No one bacterial strain was toxic to the larvae of H. elegans . Aqueous extract of one of ...

Various algal diets of different lipid content and composition were used to rear batches of naupliar larvae of Balanus amphitrite. The cyprids in these larval batches differed in lipid content and were used to investigate the combined effect of cyprid lipid content and cyprid age on attachment and metamorphosis. For this purpose, cyprids were aged for 0,3 and 6 d at 8°C prior to utilization in laboratory attachment assays. The percentage attachment of cyprids with similar lipid content differed significantly among the three age categories. A strong and a weak positive relationship between cyprid lipid content and attachment were monitored in young and old cyprids, respectively. A significant interaction (two‐way ANOVA) between cyprid age and lipid content was observed, indicating that these factors jointly affect larval attachment and metamorphosis in B. amphitrite from the beginning of the cyprid stage.

Larval settlement of the barnacle Balanus amphitrite Darwin (Cirripedia, Balanidae) is influenced by natural biofilms. In previous work by others, discriminatory settlement of aged cyprids has been observed in response to biofilms of different age. This study extends prior work by considering the effect of the age of cyprids on the outcome of settlement assays. Settlement was investigated with 0‐day‐old (newly metamorphosed) and 5‐day‐old cyprids. Biofilms under investigation were developed in the field for periods of 5 d and 1 month, and were subsequently included in laboratory settlement assays with a choice between a filmed and an unfilmed substratum. The bioassay was modified from the conventional horizontal dish design in order to generate a low water surface‐to‐volume ratio, which served to suppress larval entrapment in an organic layer on the water surface. Irrespective of cyprid age, a clear discrimination between a filmed and an unfilmed substrata was observed, and the preference for filmed or un...

Field observations in Hong Kong waters have shown the marine macroalga Ulva reticulata Forsskal (Chlorophyta) to be free of fouling. In this study, the presumptive antifouling mechanism in this alga was investigated and attempts were made to distinguish between possible mechanisms. Waterborne algal compounds were analyzed in larval behavioral bioassays with the marine polychaete Hydroides elegans, a major fouling organism in tropical waters around the world. Larval attachment and metamorphosis in this sessile species is induced by specific bacterial strains in natural bio‐organic films. In bioassays with alga‐conditioned seawater, levels of larval metamorphosis were significantly reduced in comparison to controls. The results demonstrate that the inhibitive effect was caused by direct larval deterrence. Following a bio‐assay‐guided isolation procedure, an inhibitive fraction for larval metamorphosis was purified from U. reticulata‐conditioned seawater. Preliminary chemical analysis of the biologically act...

This study examined the inhibitory effect of 3 phenolic compounds and 12 strains of marine bacteria on the larval settlement of Balanus amphitrite amphitrite. The phenolic compounds used were phlorotannins, phloroglucinol and tannic acid. Phlorotannins are polymers of phloroglucinol (1,3,5‐trihydroxybenzene) known only from brown algae. Tannic acid, which exists in terrestrial plants, is composed of oligomers of phloroglucinol attached to a sugar molecule. The bacterial strains used were isolated from a natural biofilm. The following were investigated: 1) the toxicity of the phenolic compounds to B. a. amphirite in three different larval stages, viz. nauplius II, nauplius V and cyprid; 2) the potency of the compounds as inhibitors of larval settlement and the possible mechanism involved in settlement inhibition; and 3) the effects of the bacteria on larval settlement. The level of toxicity of the phenolic compounds varied widely for the larvae. Phlorotannins were most toxic, having LC50 values ranging fro...