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The cytological characteristics of major green-tide-forming green algae Ulva prolifera collected from Yellow Sea were studied through cutting segments, long time low temperature or dark treatments. After being dried in the shade and preserved at -20°C for 30 days, the U. prolifera was cultured at 4°C in sterilized seawater under 40 μmol photons m-2·s-1 light intensity for 120 days, results indicated that the plastid of U. prolifera continuously shrank with the extension of treatment, and most cells turned white and died, only a small amount of cells still contained a few of visible inclusions at the 120d of treatment. Then those samples were transferred to 20°C and 40 μmol photons m-2·s-1 condition for recovery cultivation, after about 10 days, some recovery cells were observed in the thallus, and those cells developed to young thallus gradually and released germ cells almost in the same time. After about 60 days of recovery cultivation, the newly-grown green thallus broke through the original dead thallus, and the germ cells also grew to new individual thallus. Before dark treatment, the U. prolifera cells were filled with plastid, contained visible starch grain and discernible cell outlines, while after 120 days of dark treatment, the plastid shrank and degraded together with the disappearance of cell inclusions, and the cell outlines also blurred, then those samples were transferred to optimal culture conditions at 20°C in 40 μmol photons m-2·s-1 light intensity, and 15 days later, newly-grown cells appeared on the almost dead thallus, these cells divided continuously and grew to young thallus, and those newly-grown thallus also generated active germ cells, which developed to new thallus that cytologically identical to the original thallus. Observation of chopped tissue of U. prolifera cultivated at 20°C, 40 μmol m-2·s-1 showed that the morphological upper part cells turned to germ cells first, those germ cells including gametophyte and sporophyte, which released later and grew to new individual thallus. These findings provided cytological evidences for how U. prolifera live through stress conditions such as low temperature, darkness, and also useful for understanding the mechanism of the occurrence of green tide.

Conchocelis cultivation is a crucial step in the industrial growth of Pyropia (laver). However, our knowledge of the seawater microbiology community in Pyropia seedling pools is limited. This study investigated the temporal dynamics in seedling pool microbiota before and after outbreaks of yellow spot disease in Pyropia yezoensis conchocelis. A total of 18 water samples were collected to assess seedling pool health status, followed by the sequencing of microbiota 16S ribosomal RNA (rRNA). Analysis of 16,760,224 16S rRNA gene sequences indicated that the core microbe group comprised 207 genera. The microbial diversity of samples gradually increased from May to July. The bacterial diversity of seawater samples from diseased P. yezoensis seedling pools was significantly higher than samples from healthy seedling pools. It is noteworthy that each pool group had a distinctive microbial community composition. The relative abundance of two dominant bacteria genera, Sediminicola and Roseivirga, increased over time in healthy seedling pools, peaking in August, while Vibrio remained at constantly low levels. However, the abundance of Vibrio and Polaribacter increased sharply in diseased P. yezoensis seedling pools and decreased after fresh seawater exchange. This indicates that these bacteria are probably associated with the filament disease. Many disease-associated bacteria are negatively related to the HCO3 − concentration in seawater and positively related to pH. Changes in bacteria and environmental factors reflect the characteristics of microbial community succession in seedling pools and therefore have potential to be used as biomarkers and environmental signals for Pyropia disease monitoring.

Filamentous Bangia, which are distributed extensively throughout the world, have simple and similar morphological characteristics. Scientists can classify these organisms using molecular markers in combination with morphology. We successfully sequenced the complete nuclear ribosomal DNA, approximately 13 kb in length, from a marine Bangia population. We further analyzed the small subunit ribosomal DNA gene (nrSSU) and the internal transcribed spacer (ITS) sequence regions along with nine other marine, and two freshwater Bangia samples from China. Pairwise distances of the nrSSU and 5.8S ribosomal DNA gene sequences show the marine samples grouping together with low divergences (00.003; 0–0.006, respectively) from each other, but high divergences (0.123–0.126; 0.198, respectively) from freshwater samples. An exception is the marine sample collected from Weihai, which shows high divergence from both other marine samples (0.063–0.065; 0.129, respectively) and the freshwater samples (0.097; 0.120, respectively). A maximum likelihood phylogenetic tree based on a combined SSU-ITS dataset with maximum likelihood method shows the samples divided into three clades, with the two marine sample clades containing Bangia spp. from North America, Europe, Asia, and Australia; and one freshwater clade, containing Bangia atropurpurea from North America and China.

The photosynthetic characteristics of a Pyropia haitanensis red mutant mutated from a wild-type strain using chemical mutagens were studied. The aim was to compare the differences in photosynthetic characteristics between the red mutant and the wild type, and then to analyse the possibility of the red mutant as breeding material. The results indicated that the cytoplasm thickness of the red mutant and the wild type were similar, whereas the cell wall of the red mutant was significantly thinner than that of the wild type. Additionally, the chlorophyll a extract absorption spectra of both strains exhibited no obvious difference, whereas the absorption peaks at 498, 545, and 565 nm (which belong to phycoerythrin, PE) in the phycobiliprotein extract absorption spectra of the red mutant were clearly higher than those of the wild type. The PE content per area of the red mutant thallus was significantly higher than that of the wild type, and the ratios of PE to phycocyanin (PC) and PE to chlorophyll a were significantly higher in the red mutant than in the wild type. The net photosynthetic oxygen evolution rates of the red mutant and wild type cultured under different light intensities demonstrated that the oxygen evolution rates of all samples decreased with increasing light intensities, whereas the oxygen evolution rate of the red mutant was higher than that of the wild type under the same light intensities. The light response curves also indicated that the light-saturated photosynthetic rates (P max), light saturation points (LSPs), and light compensation points (LCPs) of both strains decreased to different degrees with increasing light intensities and that the P max and LSP values of the red mutant were significantly higher than those of the wild type under identical light intensities. In contrast, there were no obvious differences in the respiration rate (R d) and in the LCP. The F v/F m values of both strains were similar before light treatment, whereas the F v/F m of the red mutants after culture under different light intensities (120 and 200 μmol photons m−2 s−1) for 3 days were significantly higher than those values of the wild type. Moreover, ∆F/F m′ also exhibited a similar variation. Based on these results, the high content of PE in the P. haitanensis red mutant causes a steady red phenotype, and the increase in the PE concentration and the decrease in the thickness of the thallus may enhance its photosynthetic physiological activity. Thus, the red mutant of P. haitanensis may provide good material for Pyropia breeding.

A molecular taxonomic study was undertaken for the first time of the bladed Bangiales of the mainland coast of China (Northwest Pacific) based on sequence data of 201 plastid rbcL and 148 nuclear 18S sequences of historical and contemporary specimens. The results revealed that only one genus of bladed Bangiales, Pyropia, was present along Chinese coast. Species delimitation was determined using two empirical methods: the Automatic Barcode Gap Discovery (ABGD) and General Mixed Yule Coalescence (GMYC) coupled with detection of monophyly in tree reconstruction. At least fourteen species of Pyropia were recovered. Six species were confirmed that had been recorded previously based on morphology (Py. suborbiculata, Py. yezoensis, Py. haitanensis, Py. katadae, Py. tenera and Py. acanthophora), three species were recorded from China for the first time (Py. kinositae, Py. pseudolinearis and Py. tanegashimensis), and five cryptic species that did not match any molecular sequences were also discovered. The phylogeny of the concatenated rbcL and 18S dataset resolved three singletons and four clades. Each clades has a strong trend towards occupying a biogeographic region, but they are not confined to them. A transoceanic and antitropical pattern of distribution was found for Pyropia at both the subgeneric and species level. This together with high biodiversity (ca. 30% of all known Pyropia species) indicates that the Northwest Pacific might act as a centre of origin for modern distribution of Pyropia since the early Cenozoic.

The photosynthetic characteristics of thalli of cultured Pyropia yezoensis strains collected in January, February, and March in seaweed cultivation area of South China Yellow Sea were studied. Results showed that the maximum quantum efficiency (F v/F m) of all P. yezoensis thallus collected at different times was 0.65. The actual quantum efficiency (ΔF/F m′) of samples in January was the lowest of all samples, while the ΔF/F m′ of samples in March was significantly higher than those in January and February. The increase of temperature and photosynthetic pigments ratios of phycoerythrin and chlorophyll a (PE/Chla) and phycocyanin and chlorophyll a (PC/Chla) from January to March may be the important reasons for the increase in light use efficiency of thallus; although the thallus in March was significantly thicker than in January which may have reduced the light energy absorbed by photosynthetic pigments, the increase of relative high energy use efficiency also helped to maintain the photosynthetic oxygen evolution rate in March. The thicker thallus also reduced photodamage, and the thallus area was increased obviously in March, so the growth rate of thallus in March was over 35 % higher than that in February. Our research indicates that the photosynthetic characteristics of P. yezoensis strains thalli have a close relationship with their growth stage and environmental factors especially temperature, and those photosynthetic characteristics are also reflected in the growth rate of the thalli.

In this study, chlorophyll fluorescence parameters (∆F/F m′, F v/F m) and oxygen evolution of female vegetative tissues of Porphyra katadai var. hemiphylla in unisexual culture (FV) and in mixed culture with male vegetative tissues (FV-M) were followed at 5–20 °C, 10 and 80 μmol photons m−2 s−1. The formation of reproductive tissues was closely correlated with decreasing photosynthetic activities. At the same temperature the tissues cultured under 80 μmol photons m−2 s−1 showed a greater extent of maturation than those under 10 μmol photons m−2 s−1, and their decrease in photosynthesis was also larger. Under the same light intensity the extent of maturation increased with increasing temperature, and both cultures showed higher values of ∆F/F m′ and F v/F m at 10 and 15 °C, while their oxygen evolution became negative at 15–20 °C during the later period. Under the same culture condition the maturation of FV-M culture was relatively faster than that of FV culture, while their photosynthetic activity, especially ∆F/F m′, was lower.

Pyropia yezoensis (Ueda) M. S. Hwang et H. G. Choi (previously called Porphyra yezoensis) is an economically important alga. The blades generated from conchospores are genetic chimeras, which are not suitable for genetic similarity analysis. In this study, two types of blades from a single filament of P. yezoensis sporophyte filament were obtained. One type, ConB, consisted of 40 blades that had germinated from conchospores. The other type, ArcB, consisted of 88 blades that had germinated from archeospores released from ConB. Both of them were analyzed by amplified fragment length polymorphism. The low genetic similarity levels for both conchospore-germinated and archeospore-germinated blades demonstrated that the conchcelis we used was cross-fertilized. Furthermore, a higher polymorphic loci ratio (98.6%) was detected in ArcB than in ConB (80.7%), and the average genetic similarity of ArcB (average 0.61) was lower than that of ConB (average 0.71). These differences indicated that genetic analysis using ArcB gives more accurate results.

Photosystem II photochemistry and phycobiliprotein (PBP) genes of red algaeKappaphycus alvarezii, raw material ofκ-carrageenan used in food and pharmaceutical industries, were analyzed in this study. Minimum saturating irradiance (Ik) of this algal species was less than 115 μmol m−2 s−1. Its actual PSII efficiency (yield II) increased when light intensity enhanced and decreased when light intensity reached 200 μmol m−2 s−1. Under dim light, yield II declined at first and then increased on the fourth day. Under high light, yield II retained a stable value. These results indicate thatK. alvareziiis a low-light-adapted species but possesses regulative mechanisms in response to both excessive and deficient light. Based on the PBP gene sequences,K. alvarezii, together with other red algae, assembled faster and showed a closer relationship with LL-Prochlorococcuscompared to HL-Prochlorococcus. Many amino acid loci in PBP sequences ofK. alvareziiwere conserved with those of LL-Prochlorococcus. However, loci conserved with HL-Prochlorococcusbut divergent with LL-Prochlorococcuswere also found. The diversities of PE and PC are proposed to have played some roles during the algal evolution and divergence of light adaption.

Photosynthetic characteristics of four Porphyra yezoensis Ueda [a taxonomic synonym of Pyropia yezoensis (Ueda) M. S. Hwang et H. G. Choi] strains in conchocelis phase were investigated and compared with one wildtype of P. yezoensis and two strains of Porphyra haitanensis T. J. Chang et B. F. Zheng [a taxonomic synonym of Pyropia haitanensis (T. J. Chang et B. F. Zheng) N. Kikuchi et M. Miyata]. Results showed that experimental strains had higher contents of chl a and carotenoids, but a lower content of total phycobiliproteins than the wildtype. Meanwhile, photochemical efficiency of PSII was measured using pulse amplitude modulation (PAM) fluorometry technology. The value of PSII photosynthetic parameters of P. yezoensis strains were all higher than the wild strain, and the maximal quantum yields (Fv /Fm ), effective quantum yields Y(II), and relative photosynthetic electron transport rates (rETR) of P. haitanensis were higher than those of P. yezoensis. The present study verified the possibility of selective breeding of P. yezoensis using the filamentous sporophyte instead of the gametophytic thallus, the advantages being (i) nonrequirement of control of life cycle and (ii) direct and rapid cultivar improvement by artificial selection. We consider the method to be a promising technique for selective breeding of P. yezoensis cultivars.

The levels of photosynthetic pigments and chlorophyll fluorescence of Porphyra yezoensis strains selected from high-light environments were investigated. Sutong and Sulian strains originated from the same high-light environment but were selected from different sites on the Yellow Sea coast of Jiangsu Province, China. In January (a low temperature period), the Sulian strain and the WT (a widely cultivated strain) had higher levels of chlorophyll a, phycoerythrin, phycocyanin, and allophycocyanin, and higher actual photochemical efficiency of PSII (ΔF/F m′) than the Sutong strain. This indicated that Sulian and the WT may have better adaptation to low temperature. In March (an optimal temperature period), Sutong had higher levels of photosynthetic pigments and higher ΔF/F m′ than the WT and Sulian strains. This suggested that Sutong had higher light use efficiency at optimal temperatures and that most energy absorbed by PSII was used for photosynthetic electron transport. The differing areas of origin of these strains may have resulted in these differences in temperature adaptation.

The formation of archeospores is characteristic of Porphyra yezoensis Ueda and is important for Porphyra aquaculture. Recently, it has been regarded as a valuable seed source for propagation of thalli in mariculture. Cell wall composition changes are associated with archeospore formation in P. yezoensis. Here, we report changes of cell walls of P. yezoensis during archeospore formation. The surfaces of vegetative cells that were originally smooth became rougher and more protuberant as archeosporangia were formed. Ultimately, the cell walls of archeosporangia ruptured, and archeospores were released from the torn cell walls that were left at distal margins of thalli. With changes in cell walls, both effective quantum yield and maximal quantum yield of the same regions in thalli gradually increased during the transformation of vegetative cells to archeospores, suggesting that the photosynthetic properties of the same regions in thalli gradually increased. Meanwhile, photosynthetic parameters for different sectors of thalli were determined, which included the proximal vegetative cells, archeosporangia, and newly released archeospores. The changes in photosynthetic properties of different sectors of thalli were in accordance with that of the same regions in thalli at different stages. In addition, the photosynthetic responses of archeosporangia to light showed higher saturating irradiance levels than those of vegetative cells. All these results suggest that archeosporangial cell walls were not degraded prior to release but were ruptured via bulging of the archeospore within the sporangium, and ultimately, archeospores were discharged. The accumulation of carbohydrates during archeospore formation in P. yezoensis might be required for the release of archeospores.

In January and February 2010, heavy sea ice formed along the coast of the Bohai Sea and the northern Yellow Sea, China. Intertidal organisms were subjected to serious freezing stress. In this study, we investigated the freezing tolerance of the upper intertidal economic seaweed Porphyra yezoensis. The maximum photochemical efficiency of PS II (F v/F m) in undehydrated thalli remained high after 24 h at −2°C and that in dehydrated thalli decreased in a proportion to thallial water loss. F v/F m dropped sharply after 24 h at −20°C, regardless of absolute cellular water content (AWC). The F v/F m in frozen thalli recovered rapidly at 0–20°C. A wide range of water loss in the thalli enhanced their tolerance to freezing. F v/F m values in undehydrated thalli dropped sharply after 3 d at −2°C or 10 d at −20°C while those in dehydrated thalli (20–53% AWCs) remained at high levels after 9 d at −2°C or 30 d at −20°C. These results indicate that P. yezoensis has high freezing tolerance by means of dehydration during the ebb tide and rapid recovery of F v/F m from freezing. A strategy of P. yezoensis industry to avoid heavy loss during freezing season is discussed based on these findings.

Pigment mutants were used as genetic markers to study the early development and morphogenesis of blades in four species of Porphyra. In Porphyra haitanensis, P. yezoensis, and P. oligospermatangia, the first two divisions are transverse during conchospore germination, yielding four cells arranged in a line. These species are representative of linear development pattern in Porphyra. Resulting in blades with color sectors vertically arranged. In P. katadai var. hemiphylla, the first division is transverse and the upper cell divides vertically forming two side-by-side cells, and its blades are derived mostly from the upper cell showing a bilateral development pattern with two lateral parts of different colors. In this type of germination, most or the entire blade is derived from the upper cells. Some fronds of P. katadai var. hemiphylla developed in linear pattern. In addition, 9.3% of the conchospore germlings of linear development were produced at 10°C, 15.3% at 15°C, and 38.0% at 20°C for conchospore germlings of P. katadai var. hemiphylla. More linear development occurred at higher temperatures. The results revealed general trends of early developmental patterns and morphogenesis of blades within the genus of Porphyra. Developmental patterns and morphogenesis of blades are under the influence of temperatures.

Bangia fuscopurpurea (Rhodophyta) was cultivated in Putian (Fujian province, China). The characteristics of the life history concerned with cultivation were investigated and the cultivation procedure was presented. The gametophytic phase (thallus) and the sporophytic phase (conchocelis) occurred alternately in the life history of B. fuscopurpurea. Young thalli produced archeospores, and the number depended on the environmental factors. Temperature affected the number of archeospore release and percent of germination, and photo flux density (PFD) mainly affected the time of spore release and germination. Thalli matured from December to February and developed into the conchocelis phase through sexual reproduction. The conchocelis grown in shells had three developmental stages: vegetative conchocelis, conchosporangiall formation and conchospore formation. Pit-connections were present in the first 2 stages but absent after conchospore formation. Vegetative conchocelis and conchosporangial. branches can transform into each other. However, conchospores only developed into the gametophytic phase. Cultivation of B. fuscopurpurea was based on characterization of the life history, consisting of 3 steps: zygotospores collection, indoor cultivation of conchocelis and outdoor cultivation of thalli. Young thalli that developed from conchospores produced numerous archeospores before December. Over 90% of the crop was from the development of archeospores. The results indicated that conchosporelings were a good source of archeospores, and the development of the large quantity of archeospores acted as a more prevailing means to increase the population size. (C) 2008 Elsevier B.V. All rights reserved.

Nuclear divisions of carpospores, conchocelis and conchospores of Porphyra yezoensis, P. haitanensis, P. katadai var. hemiphylla and P. oligospermatangia from China were investigated. The observations showed diploid chromosome numbers of 2n = 6 for P. yezoensis and P. oligospermatangia, and 2n = 10 for P. haitanensis and P. katadai var. hemiphylla. For all four species, somatic pairing of chromosome sets was observed in late prophase. Sister chromosomes separated at anaphase as mitosis took place in carpospores, conchocelis filamentous cells, conchosporangial branch cells and sporangial cells (conchospore formation). Chromosome configurations of tetrad and ring-shaped in conchospore germination were observed, demonstrating the occurrence of meiosis. The characteristics of diploid nuclear division in 2n = 6 species are the same as those of 2n = 10 species. The influence of somatic pairing on nuclear division of diploid cells in Porphyra was discussed.

Background Red algae are primitive photosynthetic eukaryotes, whose spores are ideal subjects for studies of photosynthesis and development. Although the development of red alga spores has received considerable research attention, few studies have focused on the detailed morphological and photosynthetic changes that occur during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi) Papenfuss (Gracilariales, Rhodophyta). Herein, we documented these changes in this species of red algae. Results In the tetraspores, we observed two types of division, cruciate and zonate, and both could develop into multicellular bodies (disks). During the first 84 hours, tetraspores divided several times, but the diameter of the disks changed very little; thereafter, the diameter increased significantly. Scanning electron microscopy observations and analysis of histological sections revealed that the natural shape of the disk remains tapered over time, and the erect frond grows from the central protrusion of the disk. Cultivation of tissue from excised disks demonstrated that the central protrusion of the disk is essential for initiation of the erect frond. Photosynthetic (i.e., PSII) activities were measured using chlorophyll fluorescence analysis. The results indicated that freshly released tetraspores retained limited PSII photosynthetic capabilities; when the tetraspores attached to a substrate, those capabilities increased significantly. In the disk, the PSII activity of both marginal and central cells was similar, although some degree of morphological polarity was present; the PSII photosynthetic capabilities in young germling exhibited an apico-basal gradient. Conclusions Attachment of tetraspores to a substrate significantly enhanced their PSII photosynthetic capabilities, and triggered further development. The central protrusion of the disk is the growth point, may have transfer of nutritive material with the marginal cells. Within the young germling, the hetero-distribution of PSII photosynthetic capabilities might be due to the differences in cell functions.

Reproductive apparatus of Gracilaria/Gracilariopsis lemaneiformis collected from Qingdao city were studied with a light and a transmission electron microscope. The special superficial arrangement of spermatangium for this species was clearly observed, and the ultrastructure of spermatangial development revealed the similar cytodynamic pattern followed by all the Gracilariaceae members developed from spermatangial mother cells to spermatangium. The female reproductive apparatus before fertilization was also observed and trichogyne was found protruding above the cortex, contrary to the earlier reports. Tetrasporangium was formed by an outer cortical cell and the tetraspores became spherical and expended after being released.