A new green-tide-forming alga, Ulva ohnoi Hiraoka et Shimada sp. nov. (Ulvales, Ulvophyceae) from Japan

Ulva ohnoi Hiraoka et Shimada sp. nov. (Ulvales, Ulvophyceae) is described from southern and western Japan and is characterized by the following combination of features: (i) the large, fragile, easily torn thalli, which are 30–55 μm thick in the upper and middle regions and often have microscopic marginal teeth; (ii) the production of zoids in the upper marginal region; (iii) a regular alternation of dioecious gametophytes and a sporophyte; (iv) the production of free‐floating thalli from torn‐off attached thalli, which reproduce vegetatively by fragmentation and form green tides in summer to autumn; (v) disorderly arranged cells that are polygonal or quadrangular in the upper and middle regions; and (vi) the chloroplast covering the outer face of cell, with 1–3 pyrenoids. Ulva ohnoi differs from U. armohcana Dion et al., U. fasciata Delile, U. reticulata Forsskal, U. scandinavica Eliding and U. spiulosaOkamura et Segawa, which all possess microscopic marginal serrations, in thallus shape, cell shape or life history pattern. It is also distinguished from morphologically similar species by sequences of the nuclear encoded internal transcribed spacers and the 5.8S ribosomal RNA gene and the plastid encoded large subunit of ribulose‐l,5‐bisphosphate carboxylase/oxgenase gene. Furthermore, crossing tests demonstrate that there is a reproductive boundary between U. ohnoi and the most closely related species, U. fasciata and U. reticulata.     

The effect of temperature and oxygen on the CO2 compensation point of the marine alga Ulva lactuca

Abstract The CO₂ compensation point of Ulva lactuca frond sections has been measured in artificial seawater using a sensitive gas-chromatographic method. Under nitrogen the compensation point remained relatively constant at 3–6 cm³ m⁻³ at temperatures from 10 to 30°C while in air-saturated medium (0.3 kg m⁻³ O₂) the compensation point rose from 5 cm³ m⁻³ at 10°C to 11 cm³ m⁻³ at 30°C. These responses of the compensation point to temperature and oxygen concentration indicate that there is little photorespiratory CO₂ loss in this marine macroalga, and the low values of these compensation points indicate that inorganic carbon is actively accumulated by the plant.     

Poly(dimethyl siloxane) (PDMS) network blends of amphiphilic acrylic copolymers with poly(ethylene glycol)-fluoroalkyl side chains for fouling-release coatings. II. Laboratory assays and field immersion trials

Amphiphilic copolymers containing different amounts of poly(ethylene glycol)-fluoroalkyl acrylate and polysiloxane methacrylate units were blended with a poly(dimethyl siloxane) (PDMS) matrix in different proportions to investigate the effect of both copolymer composition and loading on the biological performance of the coatings. Laboratory bioassays revealed optimal compositions for the release of sporelings of Ulva linza, and the settlement of cypris larvae of Balanus amphitrite. The best-performing coatings were subjected to field immersion tests. Experimental coatings containing copolymer showed significantly reduced levels of hard fouling compared to the control coatings (PDMS without copolymer), their performance being equivalent to a coating based on Intersleek 700?. XPS analysis showed that only small amounts of fluorine at the coating surface were sufficient for good antifouling/fouling-release properties. AFM analyses of coatings under immersion showed that the presence of a regular surface structure with nanosized domains correlated with biological performance.     

Spontaneous multiscale phase separation within fluorinated xerogel coatings for fouling-release surfaces

Four-component xerogel films consisting of 1 mole-% n-octadecyltrimethoxysilane (C18) and 50 mole-% tetraethoxysilane (TEOS) in combination with 1–24 mole-% tridecafluoro-1,1,2,2-tetrahydrooctyltriethoxysilane (TDF) and 25–48 mole-% n-octyltriethoxysilane (C8) and a 1:49:50 mole-% C18/TDF/TEOS were prepared. Settlement of barnacle cyprids and removal of juvenile barnacles, settlement of zoospores of the alga Ulva linza, and strength of attachment of 7-day sporelings (young plants) of Ulva were compared amongst the xerogel formulations. Several of the xerogel formulations were comparable to poly(dimethylsiloxane) elastomer with respect to removal of juvenile barnacles and removal of sporeling biomass. The 1:4:45:50 and 1:14:35:50 C18/TDF/C8/TEOS xerogels displayed some phase segregation by atomic force microscopy (AFM) pre- and post-immersion in water. Imaging reflectance infrared microscopy showed the formation of islands of alkane-rich and perfluoroalkane-rich regions in these same xerogels both pre- and post-immersion in water. Surface energies were unchanged upon immersion in water for 48 h amongst the TDF-containing xerogel coatings. AFM measurements demonstrated that surface roughness on the 1:4:45:50 and 1:14:35:50 C18/TDF/C8/TEOS xerogel coatings decreased upon immersion in water.     

The performance of aminoalkyl/fluorocarbon/hydrocarbon-modified xerogel coatings against the marine alga Ectocarpus crouaniorum: relative roles of surface energy and charge

The effect of a series of xerogel coatings modified with aminoalkyl/fluorocarbon/hydrocarbon groups on the adhesion of a new test species, the filamentous brown alga Ectocarpus crouaniorum, has been explored, and compared with the green alga Ulva linza. The results showed that E. crouaniorum adhered weakly to the less polar, low wettability coatings in the series, but stronger adhesion was shown on polar, higher surface energy coatings containing aminoalkyl groups. The results from a separate series of coatings tuned to have similar surface energies and polarities after immersion in artificial seawater (ASW), but widely different surface charges, demonstrated that surface charge was more important than surface energy and polarity in determining the adhesion strength of both E. crouaniorum and U. linza on xerogel coatings. No correlation was found between adhesion and contact angle hysteresis. X-ray photoelectron spectroscopy analysis of samples after immersion in ASW confirmed the presence of charged ammonium groups on the surface of the aminoalkylated coatings.     

江苏海域几种绿潮藻类rDNA ITS序列分析

于2009年5-7月定点采集了江苏海域绿潮藻类,测定、分析了这些藻类核糖体rDNA ITS序列,并进行分类鉴定。研究结果显示,ITS+5.8S序列片段长度为552-578 bp,其中ITS1序列部分长度为179-182 bp,5.8S序列全长为155-158 bp,ITS2序列全长为180-196 bp,序列的平均GC含量(contents)为61.6%-63.3%,不同ITS序列存在不同的插入/缺失位点。扩增得到27个序列中有7个不同序列,依据NCBI数据库相似性查找、系统进化关系及遗传距离等分析结果,确定有4个种类:浒苔(Ulva prolifeya),缘管浒苔(U.linza),石莼属(Ulva sp.)1种及盘苔属(Blidingia sp.)1种。分析表明,ITS序列可作为石莼科种类鉴定的标记。     

Growth and cell cycle of Ulva compressa (Ulvophyceae) under LED illumination

The cell‐cycle progression of Ulva compressa is diurnally gated at the G₁ phase in accordance with light–dark cycles. The present study was designed to examine the spectral sensitivity of the G₁ gating system. When blue, red, and green light‐emitting diodes (LEDs) were used for illumination either alone or in combination, the cells divided under all illumination conditions, suggesting that all colors of light were able to open the G₁ gate. Although blue light was most effective to open the G₁ gate, red light alone or green light alone was also able to open the G₁ gate even at irradiance levels lower than the light compensation point of each color. Occurrence of a period of no cell division in the course of a day suggested that the G₁ gating system normally functioned as under ordinary illumination by cool‐white fluorescent lamps. The rise of the proportion of blue light to green light resulted in increased growth rate. On the other hand, the growth rates did not vary regardless of the proportion of blue light to red light. These results indicate that the difference in growth rate due to light color resulted from the difference in photosynthetic efficiency of the colors of light. However, the growth rates significantly decreased under conditions without blue light. This result suggests that blue light mediates cell elongation and because the spectral sensitivity of the cell elongation regulating system was different from that of the G₁ gating system, distinct photoreceptors are likely to mediate the two systems.     

A COMPARISON OF PHOTOSYNTHETIC ELECTRON TRANSPORT RATES IN MACROALGAE MEASURED BY PULSE AMPLITUDE MODULATED CHLOROPHYLL FLUOROMETRY AND MASS SPECTROMETRY

The relationship between whole chain photosynthetic electron transport and PSII activity was investigated in Porphyra columbina (Montagne) (Rhodophyta), Ulva australis (Areschoug) (Chlorophyta), and Zonaria crenata ( J. Agardh) (Phaeophyta). Mass spectrometric measurements of gross O₂ evolution and gross O₂ uptake were combined with simultaneous measurement of pulse-modulated chl fluorescence under a range of irradiances and inorganic carbon (C_i) concentrations. At light-limiting irradiance, a good correlation between gross O₂ evolution and the electron transport rate (ETR) calculated from chl fluorescence ((F_m′− F_s)/F_m′) was found in the optically thin species (Ulva and Porphyra). The calculated ETR was equivalent to the theoretical electron requirement in these species but overestimated gross O₂ evolution in the thicker species Zonaria. In saturating light, especially when C_i availability was low, ETR overestimated gross O₂ evolution in all species. Excess electron flow could not be accounted for by an increase in gross O₂ uptake; thus neither Mehler-ascorbate-peroxidase reaction nor the photosynthetic carbon oxidation cycle were enhanced at high irradiance or low C _i. Alternative explanations for the loss of correlation include cyclic electron flow around PSII that may be engaged under these conditions or nonphotochemical energy quenching within PSII centers. The loss of correlation between ETR and linear photosynthetic electron flow as irradiance increased from limiting to saturating or at low C_i availability and in the case of optically thick thalli limits the application of this technique for measuring photosynthesis in macroalgae.     

Timing of disturbance,top‐down,and bottom‐up driving on early algal succession patterns in a tropical intertidal community

Herbivory and nutrient enrichment are major drivers of the dynamics of algal communities. However, their effects on algal abundance are under the influence of seasons. This study investigated the effects of herbivory and nutrient enrichment on early algal succession patterns using cages (uncaged and fully caged treatments) and two nutrient levels (ambient and enriched concentrations). To determine seasonal influences, experiment plots on dead coral patches were cleared during both dry and rainy season. Of the 17 algal species recruited in the experiment plots, three were dominant: Ulva paradoxa C. Agardh, Padina in the Vaughaniella stage, and Polysiphonia sphaerocarpa Børgesen. In this succession process, U. paradoxa was the earliest colonizer and occupied the cleared plots within the first month after clearing with the highest percentage of 83.33 ± 1.67% to 88.33 ± 9.28%. Then, it was replaced by the late successional algae, Padina in the Vaughaniella stage, and P. sphaerocarpa. The effects of herbivory and nutrient enrichment on algal abundance varied across algal functional groups and seasons. During the dry season, neither herbivory nor nutrient enrichment affected Ulva cover but during the rainy season, Ulva cover was influenced by nutrient enrichment. However, the abundance of algae in this early stage was not apparently affected by either herbivory or nutrient enrichment. Our results indicated that the timing of disturbance strongly influenced the algal abundance and successional patterns in this tropical intertidal community.