Foliar cuticular waxes of cultivated species and varieties of Coffea

The cuticular waxes of leaves of Coffea arabica cv. ‘Catuaí Vermelho’, C. arabica cv. ‘Obatã’, Coffea canephora cv. ‘Apoatã’, Coffea racemosa and two hybrids between C. arabica and C. racemosa were extracted by rapid washing of the surface with chloroform. The waxes were fractionated by thin layer chromatography over silicagel. The fractions of the constituent classes were characterized by infrared spectroscopy and the distribution of the homologs of the n-alkanes and n-primary alcohols was determined by GC/MS and GC/FID. Among the samples analyzed, leaves of C. racemosa have the highest content of foliar wax (22.9 μg cm⁻²). Most samples contain either n-alkanes (C. canephora and C. racemosa) or n-primary alcohols (C. arabica) as predominant wax constituents. The distribution of n-alkanes allowed the distinction of C. racemosa from the other samples; the distribution of alcohols allowed the distinction of the three species. The two hybrids have waxes similar to the wax of C. arabica.     

Composition of epicuticular wax layer of two species of Mandevilla (Apocynoideae,Apocynaceae) from Rio de Janeiro,Brazil

The chemical composition of epicuticular waxes of Mandevilla guanabarica and Mandevilla moricandiana was comparatively analyzed by extraction in n-hexane and chloroform. The mean wax content per unit of leaf area in the n-hexane extract was about 13–30 μg cm⁻² for M. guanabarica, containing 20–28% n-alkanes and 55–63% triterpenes; for M. mori-candiana, the mean content was 19 μg cm⁻², containing 73% n-alkanes and 14% triterpenes. In the chloroform extract, the wax yield was 40–80 μg cm⁻² for M. guanabarica, with about 9–11% n-alkanes and 75–82% triterpenes; while for M. moricandiana, the wax yield was 110 μg cm⁻², with 52% n-alkanes and 14% triterpenes. The major compounds identified were lupeol, pentacyclic triterpenes of the α- and β-amyrin class, and n-alkanes such as nonacosane, hentriacontane and tritriacontane. These results indicate that the quantitative chemical profiles of epicuticular waxes of M. guanabarica and M. moricandiana are distinct and could be used as an additional feature in taxonomic identification.     

Chemotaxonomic significance of n-alkane distributions from leaf wax in genus of Sinojackia species (Styracaceae)

Sinojackia is a Chinese endemic genus of Styracaceae, containing eight species. The taxonomy of one species, Sinojackia dolichocarpa (≡Changiostyrax dolichocarpa), is controversial. Here we investigate the distribution of leaf wax n-alkanes to clarify the chemotaxonomic position of S. dolichocarpa. Leaf samples of six Sinojackia species from Wuhan Botanical Garden in central China were collected during April, July, and December in 2010 to capture different developmental stages of the epicuticular waxes. Our results show that the waxes of S. dolichocarpa differ from the other five species by having a lower abundance of nC₃₁ but a higher abundance of nC₃₃. Although developmental variations of n-alkane distributions were observed during the sampling periods, cluster analysis based on the percentages of n-alkanes from C₂₇ to C₃₃ separates S. dolichocarpa from the other Sinojackia species. Based on these finding, we suggest S. dolichocarpa is a species independent of the Sinojackia genus.     

Purification and characterization of four key enzymes from a feather-degrading Bacillus subtilis from the gut of tarantula Chilobrachys guangxiensis

A feather-degrading bacterium was isolated from the gut of the tarantula Chilobrachys guangxiensis, and was classified as Bacillus subtilis (named Bacillus subtilis CH-1) according to both the phenotypic characteristics and 16S rRNA profile. The improved culture conditions for feather-degrading were 10.0 g l⁻¹ mannitol, 10.0 g l⁻¹ tryptone, 0.1 g l⁻¹ MgCl₂, 0.4 g l⁻¹ KH₂PO₄, 0.3 g l⁻¹ K₂HPO₄, 0.5 g l⁻¹ NaCl, and 2.0 g l⁻¹ intact feather, with pH 8.5 and 37 °C. In the optimized medium, the intact black feather was completely degraded by Bacillus subtilis CH-1 in 24 h. Furthermore, four kinds of enzymes which include extracellular protease Vpr, peptidase T, γ-glutamyl transpeptidase and glyoxalmethylglyoxal reductase were identified as having principal roles. Simultaneously, the relationship between the disulfide bond reducing activity (DRT) and the keratinase activity (KT) in B. subtilis CH-1 fermentation system was discussed. This is the first report for a feather-degrading enteric bacterium from tarantula. The identification of the enzymes shines a light on further understanding the molecular mechanism of feather-degrading by microbes.     

Seasonal variations in photosynthetic irradiance response curves of macrophytes from a Mediterranean coastal lagoon

The main photosynthesis and respiration parameters (dark respiration rate, light saturated production rate, saturation irradiance, photosynthetic efficiency) were measured on a total of 23 macrophytes of the Thau lagoon (2 Phanerogams, 5 Chlorophyceae, 10 Rhodophyceae and 6 Phaeophyceae). Those measurements were performed in vitro under controlled conditions, close to the natural ones, and at several seasons. Concomitantly, measurements of pigment concentrations, carbon, phosphorous and nitrogen contents in tissues were performed. Seasonal intra-specific variability of photosynthetic parameters was found very high, enlightening an important acclimatation capacity. The highest photosynthetic capacities were found for Chlorophyceae (e.g. Monostroma obscurum thalli at 17 °C, 982 μmol O₂ g⁻¹ dw h⁻¹ and 9.1 μmol O₂ g⁻¹ dw h⁻¹/μmol photons m⁻² s⁻¹, respectively for light saturated net production rate and photosynthetic efficiency) and Phanerogams (e.g. Nanozostera noltii leaves at 25 °C, 583 μmol O₂ g⁻¹ dw h⁻¹ and 2.6 μmol O₂ g⁻¹ dw h⁻¹/μmol photons m⁻² s⁻¹ respectively for light saturated net production rate and photosynthetic efficiency). As expected, species with a high surface/volume ratio were found to be more productive than coarsely branched thalli and thick blades shaped species. Contrary to R_d (ranging 6.7–794 μmol O₂ g⁻¹ dw h⁻¹, respectively for Rytiphlaea tinctoria at 7 °C and for Dasya sessilis at 25 °C) for which a positive relationship with water temperature was found whatever the species studied, the evolution of P/I curves with temperature exhibited different responses amongst the species. The results allowed to show summer nitrogen limitation for some species (Gracilaria bursa-pastoris and Ulva spp.) and to propose temperature preferences based on the photosynthetic parameters for some others (N. noltii, Zostera marina, Chaetomorpha linum).     

Changes in leaf epicuticular wax,gas exchange and biochemistry metabolism between <Emphasis Type="Italic">Jatropha mollissima</Emphasis> and <Emphasis Type="Italic">Jatropha curcas</Emphasis> under semi-arid conditions

Jatropha curcas and Jatropha mollissima plants were evaluated under conditions of high (HSM) and low (LSM) soil moisture in a semi-arid environment, as changes in the content and concentration of epicuticular wax and the leaf metabolism which could have a relationship with drought tolerance. Besides epicuticular wax, gas exchange, antioxidant system and biochemical parameters of the photosynthetic metabolism were measured. The epicuticular wax content increased only in J. mollissima leaves 95 % under LSM, when compared with HSM conditions. Therefore, J. curcas invested less in the production of long-chain n-alkanes than did J. mollissima under LSM conditions. J. mollissima plants showed the highest CO₂ assimilation rate during the HSM period compared to J. curcas. Both species showed high stability in some leaf biochemistry products, highlighting the highest sugar content, free amino acids, total soluble protein, and photosynthetic pigments in the leaves of J. mollissima plants under both of the soil moisture conditions. Moreover, the stability and performance of the different parameters, such as morphologic variables, seem to allow J. mollissima plants to tolerate semi-arid conditions.     

Production of ethanol and xylanolytic enzymes by yeasts inhabiting rotting wood isolated in sugarcane bagasse hydrolysate

Yeasts associated with rotting wood from four Atlantic Rain forest sites in Brazil were investigated using a culture medium based on sugarcane bagasse hydrolysate. A total of 330 yeast strains were isolated. Pichia manshurica, Candida pseudolambica, and Wickerhamomyces sp. 3 were the most frequently isolated species. Fourteen novel species were obtained in this study. All isolates were tested for their ability to ferment d-xylose and to produce xylanases. In the fermentation assays using d-xylose (30 g L⁻¹), the main ethanol producers were Scheffersomyces stipitis (14.08 g L⁻¹), Scheffersomyces sp. (7.94 g L⁻¹) and Spathaspora boniae (7.16 g L⁻¹). Sc. stipitis showed the highest ethanol yield (0.42 g g⁻¹) and the highest productivity (0.39 g L⁻¹h⁻¹). The fermentation results using hemicellulosic hydrolysate showed that Sc. stipitis was the best ethanol producer, achieving a yield of 0.32 g g⁻¹, while Sp. boniae and Scheffersomyces sp. were excellent xylitol producers. The best xylanase-producing yeasts at 50 °C belonged to the species Su. xylanicola (0.487 U mg⁻¹) and Saitozyma podzolica (0.384 U mg⁻¹). The results showed that rotting wood collected from the Atlantic Rainforest is a valuable source of yeasts able to grow in sugarcane bagasse hydrolysate, including species with promising biotechnological properties.     

Microbial degradation kinetics of solid alkane dissolved in nondegradable oil phase

An Acinetobacter species was isolated and found to be able to grow on crude oil n-alkanes and solid alkanes at room temperature as the sole carbon source. The growth of the isolate on n-heneicosane dissolved in non-biodegradable pristane has been studied. A kinetic model of the growth of microorganism on the hydrophobic substrate dissolved in non-biodegradable oil droplet assuming direct contact of cell with oil droplet was developed and validated with a model system of crude oil biodegradation. The model was focused on the substrate transport to the cell being contact with the surface of droplet. The high value of saturation constant of n-heneicosane, K_s = 0.086 kg m⁻³, and the maximum specific growth rate, μ_m = 0.60 h⁻¹, were obtained. The transport limitation was considered and estimated. The high value of attached cell fraction was reasonable to explain the observed growth rate by the direct contact model and varied with time till it reached a plateau at the stationary growth phase. By considering the direct contact of the cells with the surface of pristane and the transport of n-heneicosane to the cell, the degradation of hydrophobic substrate in the oil phase could be elucidated.     

Smoke-saturated Water and Karrikinolide Modulate Germination,Growth, Photosynthesis and Nutritional Values of Carrot (Daucus carota L.)

Plant-derived smoke is a positive regulator of seed germination and growth with regard to many plant species. Of the several compounds present in plant-derived smoke, karrikinolide or KAR₁ (3-methyl-2H-furo[2,3-c]pyran-2-one) is considered to be the major active growth-promoting compound. To test the efficacy of smoke-saturated water (SSW) and KAR₁ on carrot (Daucus carota L.), two separate pot experiments were simultaneously conducted in the same environmental conditions. SSW and KAR₁ treatments were applied to the plants in the form of aqueous solutions of variable concentrations. Prior to sowing, seeds were soaked in the solutions of SSW (25.8 µg L⁻¹_, 51.6 µg L⁻¹,103.2 µg L⁻¹ and 258.0 µg L⁻¹) and KAR₁ (0.015 µg L⁻¹, 0.150 µg L⁻¹, 1.501 µg L⁻¹ and 15.013 µg L⁻¹). Percent seed germination, vegetative growth, photosynthesis and nutritional values were the major parameters through which the plant response to the applied treatments was investigated. The results obtained indicated a significant improvement in all the plant attributes studied. In general, SSW (51.6 µg L⁻¹) and KAR₁ (1.501 µg L⁻¹) proved optimum treatments for most the parameters. As compared to the control, 51.6 µg L⁻¹ of SSW and 1.501 µg L⁻¹ of KAR₁ increased the percent seed germination by 58.0% and 54.4%, respectively. Over the control, the values of plant height and net photosynthetic rate were enhanced by 33.9% and 40.9%, respectively, due to 51.6 µg L⁻¹ of SSW, while the values of these parameters were increased by 25.2% and 34.0%, respectively, due to 1.501 µg L⁻¹ of KAR₁. In comparison with the control, treatment 51.6 µg L⁻¹ of SSW increased the contents of β-carotene and ascorbic acid by 32.7% and 37.9%, respectively, while the treatment 1.501 µg L⁻¹ M of KAR₁ enhanced these contents by 42.0% and 48.4%, respectively. This study provides an insight into an affordable and feasible method of crop improvement.

     

In vitro assays on the susceptibility of four species of nematophagous fungi to anthelmintics and chemical fungicides/antifungal drug

Using nematophagous fungi for the biological control of animal parasitic nematodes will become one of the most promising strategies in the search for alternative chemical drugs. The purpose of this study was to check the in vitro activity of four anthelmintics, four chemical fungicides and two antifungal drugs on the spore germination of nematophagous fungi: Duddingtonia flagrans (SF170), Arthrobotrys oligospora (447), Arthrobotrys superba (435) and Arthrobotrys sp. (PS011). A modified 24-well cell culture plate assay was conducted to evaluate the susceptibility of nematophagous fungi against drugs tested by calculating the effective middle concentrations (EC₅₀) of each tested drug to inhibit the germination of fungal spores. EC₅₀ ranged between 0·7 and 47·2 μg ml⁻¹ for fenbendazole, thiabendazole and ivermectin, except levamisole (546·5–4057·8 μg ml⁻¹). EC₅₀ of tested fungicides was 0·6–2·3 μg ml⁻¹ for carbendazim, 55·9–247·4 μg ml⁻¹ for metalaxyl, 24·4–45·2 μg ml⁻¹ for difenoconazole, and 555·9–1438·3 μg ml⁻¹ for pentachloronitrobenzene (PCNB). EC₅₀ of two antifungal drugs was 0·03–3·4 μg ml⁻¹ for amphotericin B and 0·3–10·9 μg ml⁻¹ for ketoconazole. The results showed that 10 tested drugs, except for levamisole and PCNB, had in vitro inhibitory effects on nematophagous fungi. The chlamydospores of D. flagrans had the highest sensitivity to nine tested drugs, except for ketoconazole.     

Bioproduction of phenylethanoid glycosides by plant cell culture of Scrophularia striata Boiss.: from shake-flasks to bioreactor

Phenylethanoid glycosides (PeG) are a class of polyphenols found in some plants that have pharmaceutical effects as anti-inflammatories and anti-oxidants. The presence of PeG (acteoside) in the aerial parts of Scrophularia striata Boiss. has been demonstrated. Considerable progress has been made using plant cell cultures to stimulate formation and accumulation of secondary metabolites. The present study optimized phenylethanoid production from shake flasks to bioreactor using a cell culture of S. striata. The optimal conditions for production of cell biomass by scale-up to a bioreactor were determined to be a pH of 4.8, air flow rate of 0.5–1.5 l min⁻¹, and mixing speed of 110–170 rpm at 25 ± 1 °C in darkness. Growth parameters and PeG production were measured and compared with the results from the shake flasks. The results showed that cell biomass was high in the bioreactor (15.64 g l⁻¹ DW) and in the shake flasks (14.16 g l⁻¹ DW). The acteoside content in the bioreactor was 1404.20 μg g⁻¹ DW, which is threefold higher than in the shake flasks (459.71 μg g⁻¹ DW). The echinacoside concentration in the bioreactor was 1449.39 μg g⁻¹, 1.36-fold lower than in the shake flasks (1973.03 μg g⁻¹ DW). This study established an efficient way for production of acteoside, the major PeG, in a bioreactor.

     

Complex biopolymeric systems at stalk/epicuticular wax plant interfaces: A near infrared spectroscopy study of the sugarcane example

Naturally occurring macromolecules present at the epicuticular wax/stalk tissue interface of sugarcane were investigated using near infrared spectroscopy (NIRS). Investigations of water, cellulose, and wax‐cellulose interrelationships were possible using NIRS methods, where in the past many different techniques have been required. The sugarcane complex interface was used as an example of typical phenomena found at plant leaf/stalk interfaces. This detailed study showed that sugarcane cultivars exhibit spectral differences in the CH_n, water OH, and cellulose OH regions, reflecting the presence of epicuticular wax, epidermis, and ground tissue. Spectrally complex water bands (5276 cm^?1 and 7500–6000 cm^?1) were investigated via freeze‐drying experiments which revealed sequentially a complex band substructure (7500–6000 cm^?1), a developing weak H‐bonding system (～7301 cm^?1), and strong H‐bonding (～7062 cm^?1) assigned to water—cellulose interactions. Principal component analysis techniques clarified complex band trends that developed during the desorption experiment. Bands from wax‐free stalk were minimized in the 4327–4080 cm^?1 region (C? H_n vibrational modes associated with long chain fatty compounds), while bands from the stalk tissue (particularly lignin and moisture) became more pronounced. This work is a comprehensive guide to similar studies by scientists involved in a variety of plant and fiber research fields. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 642–651, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Effects of flooding on photosynthesis and root respiration in saltcedar (Tamarix ramosissima), an invasive riparian shrub

The introduced shrub Tamarix ramosissima invades riparian zones, but loses competitiveness under flooding. Metabolic effects of flooding could be important for T. ramosissima, but have not been previously investigated. Photosynthesis rates, stomatal conductance, internal (intercellular) CO₂, transpiration, and root alcohol dehydrogenase (ADH) activity were compared in T. ramosissima across soil types and under drained and flooded conditions in a greenhouse. Photosynthesis at 1500 μmol quanta m⁻² s⁻¹ (A₁₅₀₀) in flooded plants ranged from 2.3 to 6.2 μmol CO₂ m⁻² s⁻¹ during the first week, but A₁₅₀₀ increased to 6.4–12.7 μmol CO₂ m⁻² s⁻¹ by the third week of flooding. Stomatal conductance (g_s) at 1500 μmol quanta m⁻² s⁻¹ also decreased initially during flooding, where g_s was 0.018 to 0.099 mol H₂O m⁻² s⁻¹ during the first week, but g_s increased to 0.113–0.248 mol H₂O m⁻² s⁻¹ by the third week of flooding. However, photosynthesis in flooded plants was reduced by non-stomatal limitations, and subsequent increases indicate metabolic acclimation to flooding. Root ADH activities were higher in flooded plants compared to drained plants, indicating oxygen stress. Lower photosynthesis and greater oxygen stress could account for the susceptibility of T. ramosissima at the onset of flooding. Soil type had no effect on photosynthesis or on root ADH activity. In the field, stomatal conductance, leaf water potential, transpiration, and leaf δ¹³C were compared between T. ramosissima and other flooded species. T. ramosissima had lower stomatal conductance and water potential compared to Populus deltoides and Phragmites australis. Differences in physiological responses for T. ramosissima could become important for ecological concerns.     

Leaf wax <Emphasis Type="Italic">n</Emphasis>-alkane chemotaxonomy of bamboo from a tropical rain forest in Southwest China

The leaf waxes of 23 woody bamboo species of three subgenera, Dendrocalamus, Bambusa and Dendrocalamopsis, from the Xishuangbanna tropical rain forest in Southwest China were analyzed by gas chromatography and coupled gas chromatography–mass spectrometry. The waxes of the Dendrocalamus species are dominated by C₂₇ and C₂₉ n-alkanes and their average chain length (ACL) has an average of 28.3. In marked contrast to the Dendrocalamus species, the wax composition of the Bambusa species is characterized by a broad distribution of major n-alkanes from C₂₇ to C₃₅, greater ACL values (>29) and an enhanced relative abundance (>30%) of n-alkanes with a carbon number greater than 30. Unlike the Dendrocalamus species and the Bambusa species, the Dendrocalamopsis species do not have a distinct n-alkane distribution; in some species the n-alkane distribution is comparable to that in the Bambusa species and in others to that in the Dendrocalamus species. The lipid data suggest that it might be reasonable to classify the controversial Dendrocalamopsis group as an independent genus separate from the Bambusa genus. On the basis of their smaller diversity of the dominant n-alkanes and their lower ACL values, the Dendrocalamus species might be more evolutionarily advanced than the Bambusa species, with the Dendrocalamopsis species being at an intermediate stage. The evolution and classification of the woody bamboos inferred from leaf wax n-alkanes are consistent with morphological investigations reported previously.     

Taxonomic significance of the distribution of constituents of leaf cuticular waxes of Croton species (Euphorbiaceae)

Foliar epicuticular waxes of specimens of 13 Croton species native in Brazil were extracted. The fractions containing alkanes and primary alcohols were isolated by preparative thin layer chromatography. Derivatized n-primary alcohols were identified by gas chromatography (GC) coupled with mass spectrometry and n-alkanes by GC and comparison with known standards. Relative abundances were estimated by GC coupled with flame ionization detector. The distribution of constituents of both classes was analyzed by cluster analysis, using the UPGMA method and Euclidean distances. The chemical affinities among species were compared with published data of molecular phylogenetic relationships. The distribution of n-alkanes and primary alcohols were shown to be useful markers of Croton species. Primary alcohols were more consistent than n-alkanes for species fingerprinting.     

Study of genotypic variation of cultivars of winged bean [Psophocarpus tetragonolobus (Stickm.) DC.] with the help of n-alkane profile

The leaf cuticle is covered by epicuticular wax consisting mainly of straight-chain aliphatic hydrocarbons with a variety of substituted groups. Studies have been concentrated on n-alkanes in epicuticular wax of Winged bean [Psophocarpus tetragonolobus (Stickm.) DC.]. Hydrocarbon constituents especially n-alkane analyses of seven cultivars of Winged bean [Psophocarpus tetragonolobus (Stickm.) DC.] have been undertaken. All the n-alkanes in between C₁₄–C₁₈ and C₂₀–C₃₈ are present in each of the species. Among the species, amount of n-alkanes is maximum in IC112417 and relatively low in EC38825. Scanning electron microscopic views were also taken for epicuticular layers and their hydrocarbons of the leaves of all the genotype species of the plant. Qualitative and quantitative characterization of n-alkanes present in the epicuticular wax extracted from the mature leaves can be used as an effective tool in chemo taxonomical work and also for the study of genotypic variation of the different cultivars.     

Ochrosin,a new biosurfactant produced by halophilic Ochrobactrum sp. strain BS-206 (MTCC 5720): Purification,characterization and its biological evaluation

A new bioactive molecule characterized as 4-dimethylaminobenzaldehyde (designated as Ochrosin) was isolated from a halophilic Ochrobactrum sp. strain BS-206 (MTCC 5720). Ochrosin exhibited good antimicrobial activity against both Gram-positive and Gram-negative bacteria and different Candida strains with minimum inhibitory concentration (MIC) values ranging from 4.68 to 150 μg mL⁻¹. It also exhibited anti-adhesive activity against various bacterial pathogens. Ochrosin caused an increase in the reactive oxygen species (ROS) levels to 32.4% and 28% and increased the NAD⁺/NADH ratio by 2.61 and 2.26 in S. aureus and E. coli, respectively. Ochrosin appears to interfere with ergosterol biosynthetic pathway in different Candida strains as it reduced the ergosterol content. Ochrosin showed insecticidal activity against three major stored-product grain pests like Tribolium castaneum, Callosobruchus chinensis and Sitophilus oryzae with LC₅₀ values of 7.3, 8.9 and 7.6 μg cc⁻¹, respectively. The anti-feedant index (ED₅₀) values observed were 1.07 and 1.35 μg cm⁻² of leaf area against Achaea janata and Spodoptera litura, respectively. This is the first report on Ochrosin, a multifunctional biosurfactant, produced by Ochrobactrum sp. BS-206 exhibiting promising antimicrobial, anti-adhesive, anti-feedant and insecticidal activities.     

Estimating the role of three mesopredatory fishes in coral reef food webs at Ningaloo Reef,Western Australia

Within the complex food webs that occur on coral reefs, mesopredatory fish consume small-bodied prey and transfer accumulated biomass to other trophic levels. We estimated biomass, growth and mortality rates of three common mesopredators from Ningaloo Reef in Western Australia to calculate their annual turnover rates and potential contribution to local trophic dynamics. Biomass estimates of the serranid Epinephelus rivulatus (4.46 ± 0.76 g m⁻²) were an order of magnitude greater than two smaller-bodied mesopredatory fishes, Pseudochromis fuscus (0.10 ± 0.03 g m⁻²) and Parapercis clathrata (0.23 ± 0.31 g m⁻²). Growth parameters generated from a von Bertalanffy growth function fitted to size-at-age data, however, indicated that mortality rates for the three mesopredators were similar and that 32–55 % of fish survived each year. Consequently, interspecific differences in annual turnover rates among E. rivulatus (1.9 g m⁻² yr⁻¹), Pa. clathrata (0.10 g m⁻² yr⁻¹) and Ps. fuscus (0.07 g m⁻² yr⁻¹) were an artefact of differences in local biomass estimates. The rapid turnover estimates for E. rivulatus suggest this species is an important conduit of energy within the isolated patch reef habitat where it is typically found, while Ps. fuscus and Pa. clathrata channel smaller amounts of energy from specific habitats in the Ningaloo lagoon. Apparent differences in habitat, diet and turnover rates of the three species examined provide an insight into the different roles these species play in coral reef food webs and suggest that life-history traits allow for variability in the local and spatial contribution of these species at Ningaloo Reef. Moreover, calculating turnover rates of a broader suite of fish species from a range of trophic groups will help better define the role of fishes in coral reef trophic dynamics.

     

The effects of light intensity on the growth of Japanese Gambierdiscus spp. (Dinophyceae)

Marine toxic dinoflagellates of the genus Gambierdiscus are the causative agents of ciguatera fish poisoning (CFP), a form of seafood poisoning that is widespread in tropical, subtropical and temperate regions worldwide. The distributions of Gambierdiscus australes, Gambierdiscus scabrosus and two phylotypes of Gambierdiscus spp. type 2 and type 3 have been reported for the waters surrounding the main island of Japan. To explore the bloom dynamics and the vertical distribution of these Japanese species and phylotypes of Gambierdiscus, the effects of light intensity on their growth were tested, using a photoirradiation-culture system. The relationship between the observed growth rates and light intensity conditions for the four species/phylotypes were formulated at R > 0.92 (p < 0.01) using regression analysis and photosynthesis-light intensity (P-L) model. Based on this equation, the optimum light intensity (L_max) and the semi-optimum light intensity range (L_s-opt) that resulted in the maximum growth rate (μ_max) and ≥80% μ _max values of the four species/phylotypes, respectively, were as follows: (1) the L_max and L_s-opt of G. australes were 208 μmol photons m⁻² s⁻¹ and 91–422 μmol photons m⁻² s⁻¹, respectively; (2) those of G. scabrosus were 252 and 120–421 μmol photons m⁻² s⁻¹, respectively; (3) those of Gambierdiscus sp. type 2 were 192 and 75–430 μmol photons m⁻² s⁻¹, respectively; and (4) those of Gambierdiscus sp. type 3 were ≥427 and 73–427 μmol photons m⁻² s⁻¹, respectively. All four Gambierdiscus species/phylotypes required approximately 10 μmol photons m⁻² s⁻¹ to maintain growth. The light intensities in coastal waters at a site in Tosa Bay were measured vertically at 1 m intervals once per season. The relationships between the observed light intensity and depth were formulated using Beer’s Law. Based on these equations, the range of the attenuation coefficients at Tosa Bay site was determined to be 0.058–0.119 m⁻¹. The values 1700 μmol photons m⁻² s⁻¹, 500 μmol photons m⁻² s⁻¹, and 200 μmol photons m⁻² s⁻¹ were substituted into the equations to estimate the vertical profiles of light intensity at sunny midday, cloudy midday and rainy midday, respectively. Based on the regression equations coupled with the empirically determined attenuation coefficients for each of the four seasons, the ranges of the projected depths of L_max and L_s-opt for the four Gambierdiscus species/phylotypes under sunny midday conditions, cloudy midday conditions, and rainy midday conditions were 12–38 m and 12–54 m, 1–16 m and 1–33 m, and 0 m and 0–16 m, respectively. These results suggest that light intensity plays an important role in the bloom dynamics and vertical distribution of Gambierdiscus species/phylotypes in Japanese coastal waters.     

The effect of salinity on the survival,growth, sporulation and infection of Phytophthora ramorum

Phytophthora ramorum has been found in waterways outside infested nurseries, but little is known about its behavior in water. This study examined the effect of salinity on survival, growth, sporulation, and infection. P. ramorum survival and growth was negatively correlated with salt concentration (range of 0–45 g l⁻¹), but showed a level of tolerance even at 45 g l⁻¹. No sporangia were observed in cultures with higher than 20 g l⁻¹ of salt and zoospores were not released from sporangia above 14 g l⁻¹. Water sources with different salinity were used to understand the environment where P. ramorum can survive and infect host material. Water from natural bodies and water amended with different salt concentrations were added to P. ramorum-infested sand and baited with rhododendron leaf disks. Infection decreased with increasing salt concentration and increased with higher initial concentration of P. ramorum. This research helps to better understand the effects of water quality on survival and infectivity of P. ramorum, expanding the potential survey range.