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SUMMARY: The subtidal brown algal species Sporochnus dotyi Brostoff (Sporochnales, Phaeophyceae), which has been regarded as a Hawaiian endemic, is reported from Kushimoto, Kii Peninsula, Pacific coast of central Honshu, Japan, for the first time outside Hawai'i. The species grew on subtidal rocks ca. 5–20 m deep attached by a small conical holdfast. The erect thalli were 5–30 cm high, terete, robust and alternately branched in 1–2 orders. When mature, pedicellate receptacles developed on the branches, and formed elliptical sori 1 mm long with a pedicel 3–5 mm long. The apical parts of the thalli and the receptacles were terminated with a tuft of simple assimilatory filaments of up to 4 mm long and showed prominent green to yellow underwater iridescence. Reproductive filaments (paraphyses) were densely packed, simple, up to 200 μm long and bore 4–6 mostly unilateral unilocular zoidangia 20–22 μm long and 5–6 m in diameter. In the genetic analyses, the Sporochnus alga from Kushimoto had partial rbcL sequence identical to S. dotyi from Hawai'i. The cox3 phylogeny revealed that this alga formed a fully supported clade with S. dotyi. Therefore, we identified the alga from Kushimoto as S. dotyi. This finding of S. dotyi from Japan, together with the recent reports of the mesophotic macroalgae Ryuguphycus kuaweuweu (=Umbraulva kuaweuweu), Ulva iliohaha and Newhousia imbricata from various localities in the Pacific Ocean including Japan, suggest closer biogeographical connections of subtidal/mesophotic macroalgae in the Pacific than previously recognized. [ABSTRACT FROM AUTHOR]

To elucidate the effect of macroalgae blooms on dissimilatory nitrate reduction pathways (denitrification, anammox, and DNRA) in sediments of the hypereutrophic Yatsu tidal flat, eastern Japan, sediment denitrification, anammox, and DNRA rates were measured using a 15N tracer technique at two sites affected and unaffected by macroalgae (Ulva) blooms and in incubation experiments with and without Ulva. Anammox was insignificant at both sites and in both experiments. The denitrification rate was consistently higher than the DNRA rate, and its contributions to the total dissimilatory nitrate reduction were 82% and 85% at sites affected and unaffected by Ulva, respectively. In a sediment incubation experiment with Ulva, the contribution of DNRA had increased to approximately 30% on day 7, which is when the sulfide concentration was the highest. Sulfide produced by sulfate reduction during macroalgae blooms inhibited denitrification and did not change the DNRA, and consequently increased the DNRA contribution. On day 21, after reaching the peak sulfide concentration during the late macroalgae collapse, the DNRA contribution decreased to 15%. These results indicated that the DNRA contribution was greater during the macroalgae blooms than at the collapse, although denitrification dominated DNRA regardless of the macroalgal status. Therefore, vigorous macroalgae cover and sulfide production under the macroalgae cover had an important impact on the nitrogen dynamics. [ABSTRACT FROM AUTHOR]

SUMMARY: Genetic analysis of type material of various Ulva species has shown that many names have been misapplied. DNA sequences of two of the specimens on the lectotype sheet of U. australis from South Australia showed that U. australis is conspecific with specimens called U. pertusa from Japan. However, type material of U. pertusa has not been sequenced, nor have other type specimens with type localities in Japan and Australia, including U. conglobata f. conglobata and U. conglobata f. densa from the former, and U. laetevirens and U. spathulata from the latter. To determine if these names have been correctly applied, targeted DNA sequencing of the rbcL gene was performed on (i) the lectotype specimen of U. laetevirens, (ii) the lectotype and two syntype specimens of U. pertusa, (iii) the lectotype and two syntype specimens of U. congoblata f. conglobata and (iv) two specimens on the holotype sheet of U. conglobata f. densa. In addition, high‐throughput sequencing (HTS) analysis was carried out on an isotype specimen of U. spathulata. Phylogenetic analysis of the resulting rbcL gene sequences supports the taxonomic conclusions that U. laetevirens, U. pertusa and U. spathulata are synonyms of U. australis, and U. conglobata f. conglobata and U. conglobata f. densa represent a single separate and distinct species, U. conglobata. These genetic data contribute to the taxonomy of Ulva and further demonstrate that analyzing DNA from type material is the only currently known reliable method to correctly apply names in this genus. [ABSTRACT FROM AUTHOR]

Green tides caused by Ulvales group macroalgae have been reported from many eutrophic waters around the world. The asari clam Ruditapes philippinarum is an important fisheries resource in Japan and co-exists in coastal waters with Ulvales macroalgae. This study examined a possible impact of fresh Ulva fronds on the growth of juvenile, adult, and spat asari clams by conducting rearing experiments. Significant inhibition of juvenile and spat growth, but not adult growth, was observed when fresh Ulva fronds were floated on rearing water at 42.7 g/l (or 0.68 g/cm2), a density per area corresponding to the vegetation at Ajina flat on June 2006. This growth inhibition was experimentally observed at a level of 1.8 mg C/l (or a 0.47 mg C/l increase against blank rearing water) of dissolved organic matter (DOM) released from Ulva fronds. On the other hand, coastal waters with Ulva blooms contained higher levels of DOM (mean ± SD) at 2.3 ± 0.8 mg C/l (or 1.6 mg C/l higher than neighboring waters with sparse Ulva vegetation), suggesting that similar inhibition of asari clam growth may be occurring in the natural water environment with prevalent Ulva blooms. [ABSTRACT FROM AUTHOR]

SUMMARY: The macroalga Ulva ohnoi constitutes a considerable fraction of green tides in coastal areas of Japan, but little is known about the physiological characteristics of this species. To investigate the environmental factors that promote the formation of green tides, we tested the responses of U. ohnoi and another common Japanese species, Ulva pertusa, to various levels of irradiance at different water temperatures. Because the two species are morphologically similar, we identified them using the PCR‐restriction fragment length polymorphism method. Under laboratory conditions, we evaluated the photosynthetic, dark respiration, and relative growth rate at a range of water temperatures (5 to 35°C) and photosynthetically active radiation (0 to 1000 μmol photons m−2 s−1). The maximum gross photosynthetic rate of U. ohnoi was larger than that of U. pertusa. The dark respiration rates revealed no significant differences among the species and temperature conditions. At 500 μmol photons m−2 s−1, the relative growth rate of U. ohnoi was larger than that of U. pertusa in higher temperature and the difference was the largest at 20°C. The estimated compensation irradiance and estimated saturation irradiance of U. ohnoi and U. pertusa ranged from 0.709 to 5.510 and 40.530 to 58.674 μmol photons m−2 s−1, which were lower than those in other intertidal green macroalgae, from 6 to 11 and 50 to 82 μmol photons m−2 s−1, respectively. Thus, U. ohnoi which exists as free‐floating near the water surface and accumulating inside the green tide can survive extensively in the water column of the intertidal zone, furthermore, the species can maintain rapid growth in this situation. Therefore, as a result of this study, it is suggested that the ecological success of U. ohnoi in shallow waters such as the tidal flats, estuarine, and coasts of the inner bay in comparison with U. pertusa. [ABSTRACT FROM AUTHOR]

Ulva meridionalis is one of the causal green macroalgae for green tides in Japan and exists in coastal areas of China. In the present study, complete chloroplast (cp) genome sequence of Ulva meridionalis was reported, and the total length of this species was 88,653 bp (GenBank accession number MN889540). The overall base composition of cp genome was A (37.1%), T (39.0%), C (11.4%) and G (12.5%), similar to other Ulva macroalgae within cp genome, and the percentage of A + T (76.1%) was higher than C + G (23.9%). U. meridionalis cp genome encoded 113 genes, including 80 protein-coding genes, 27 transfer RNAs genes and 6 ribosomal RNAs genes. The maximum likelihood phylogenetic analysis shows that Ulva linza is the closest sister species of U. meridionalis. [ABSTRACT FROM AUTHOR]

The identification of imported green algal products represents a critical challenge to the Japanese Customs Service in terms of ensuring effective control of imported quota items (species of genera Monostroma and Enteromorpha and their products). To assist officials in this difficult task, we tested the applicability of phylogenetic analyses using the nuclear-encoded ribosomal DNA internal transcribed spacer 2 (nrITS2) and 5S ribosomal DNA (rDNA) spacer regions to identify green algal products at the species level. Our nrITS2-based phylogenetic analysis was able to roughly separate the Ulva-related samples into three clades: the Ulva linza- procera- prolifera (LPP) complex and two other clades, and identified the Monostroma-related samples as M. nitidum. Subsequent detailed analysis within the LPP complex using the 5S rDNA spacer region divided the samples into two groupings (the U. linza clade and U. prolifera clade), while it detected possible hybrid samples of U. linza and U. prolifera from a number of commercial green algal products. [ABSTRACT FROM AUTHOR]

Abstract: Field surveys and laboratory experiments were conducted to examine the effect of desiccation and salinity on the outbreak of a green tide of Ulva pertusa at Osaka Nanko bird sanctuary. Reduction of biomass of Ulva spp. was observed at stations where the exposure rate to air was from 30 to 40%. In addition, the exposure rate of 30–40% to air showed no negative impacts on the biomass of benthic microalgae, infauna and non-motile epibenthos. Laboratory experiments revealed that photosynthetic activity of U. pertusa decreased when exposed to air for 4–7 h at 25–35 °C. Salinity decreases from 30 to 25 or 20 accompanied with exposure to air drastically reduced the rate of photosynthesis of this species. These results suggest the possibility of controlling a green tide of U. pertusa without serious physico-ecological damage to benthic microalgae, infauna and non-motile epibenthos by a combination of exposure to air with low salinity. [Copyright &y& Elsevier]

Abstract  Green tides at Yatsu tidal flat, Tokyo Bay, Japan, were first reported in 1995 and formed by a bloom only of free-floating Ulva species. On the tidal flat, the bloom area in well-developed periods increased after 1995 and covered 27.1 ha in May 2002. Based on vertical aerial photographs, green tide remaining in winter during 1996–2007 covered 4.7 ha when first observed in 1999 and increased to 17.5 ha in January 2002 thereafter. We found that the expansion of green tide was related to such factors as an increase in Kira’s Warmth Index, a decrease in annual cumulative hourly air temperatures below 7°C in December, an increase in salinity, and unintentional introduction of Ulva ohnoi. We also found that green tide at Yatsu tidal flat occurred in the course of the improvement of water quality. [ABSTRACT FROM AUTHOR]

Ulva limnetica Ichihara et Shimada, sp. nov. (Ulvales, Ulvophyceae) is described from the Ryukyu Islands, Japan, and is characterized by thalli that are: (i) branched, tubular, fragile and wrinkled; (ii) up to 80 cm in height and up to 2 cm in diameter; (iii) light to yellowish green in color; and (iv) having an asexual reproduction by means of quadriflagellate swarmers. Rhizoidal cells bear tubular extensions on the outside of the cell layer in the stipe. Ulva limnetica is distinguished from species with similar thalli by chloroplast disposition, branching pattern, number of pyrenoids per cell and gross morphology. It is also distinguished by sequences of the nuclear-encoded 18S ribosomal RNA gene, internal transcribed spacer 2 region and the plastid-encoded large subunit of ribulose-1,5-bisphosphate carboxylase/oxgenase gene ( rbcL). Ulva limnetica was clustered with other Ulva species in an early diverging lineage within the genus. [ABSTRACT FROM AUTHOR]

Abstract  A new “germling cluster” method is proposed for tank cultivation of seaweed in a free-floating form. This method was applied to the tank cultivation of Ulva prolifera using deep seawater (DSW) pumped up from over 300 m depth off the cape of Muroto in southwest Japan. Numerous zoids of U. prolifera were induced by cutting thalli into 1–2 mm long pieces. Three days after fragment production, the zoids were released. The zoid suspension was concentrated to a density of more than 104 zoids per mL medium, and placed in a Petri dish for culture. The dense, germinating zoids began to adhere to each other and form aggregations. The germling aggregations were then removed from the bottom of the dish and torn into a large number of small “germling clusters” using an electric mixer. Each cluster contained 10–100 germlings. Once the germling clusters had attained more than 5 mm diameter in culture, they were transplanted as free-floating forms to a 500 L outdoor tank with continuous aeration, to which DSW was supplied at an exchange rate of 3 volumes per day. As a result, the average daily growth rate (DGR) in the tank throughout the year was 37%, though the DGR fluctuated with seasonal temperature changes. [ABSTRACT FROM AUTHOR]

The objective of this study is to clarify the effect of ulvoid (Ulva spp.) accumulation on the structure and function of an eelgrass bed by the coast of Iwakuni, Seto Inland Sea, Japan. We monitored eelgrass shoot density and volume of ulvoid accumulation in the study site and evaluated effects of the accumulated ulvoid canopy on the percent survival, seedling density, growth rates, photosynthetic photon flux density (PPFD) and carbon contents of eelgrass. Eelgrass shoot density decreased by the accumulation of ulvoid. Also, seedling density decreased by the increase in the ulvoid volumes. Shoot density, seedling density and leaf elongation were negatively correlated with ulvoid volume. Carbon contents in eelgrass decreased by the accumulation of ulvoid (canopy height: 25cm). These results suggest that accumulation of ulvoid bloom has significant negative impacts on the structure and function of eelgrass bed, i.e. decreases in vegetative shoot density, seedling density, shoot height and growth rate. [Copyright &y& Elsevier]

Ulva meridionalis, a green macroalgae, is one of the causal species for green tides in Japan and spread into the coast of China. During this research, we sequenced the complete mitochondrial genome of U. meridionalis. The mitogenome is 62,887 bp in length, including 28 encoding genes and 29 tRNA genes. Compared with the Ulva species from mitogenome, the gene order and organization of this mitogenome are similar to most of other determined Ulva mitogenomes, with the nucleotide base composition of A 33.6%, T 32.2%, C 16.2%, and G 18.0%. Phylogenetic analysis shows U. meridionalis is closely related to Ulva flexuosa. [ABSTRACT FROM AUTHOR]

The article discusses the result of the study regarding the isolation and structure determination of algicidal compounds from Ulva fasciata, in Japan. Among the seaweeds tested, the green alga Ulva fasciata showed the strongest algicidal activity. The isolation of algicidal compounds was due to the bioassay-guided fractionation of the methanol extract of U. fasciata. The structures of these compounds were determined and showed potent algicidal activity against the red-tide phytoplankton Heterosigma akashiwo.

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. armoricana Dion et al., U. fasciata Delile, U. reticulata Forsskål, U. scandinavica Bliding and U. spinulosa Okamura 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-1,5-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. [ABSTRACT FROM AUTHOR]

Crossing tests were made to determine the relationship between the identified Ulva pertusa, which commonly grows in Japan as an attached form on exposed rocks, and the floating Ulva forming "green tide" inside calm bays. The floating Ulva thalli were collected from five major green tide sites in Japan (Yokohama, Mikawa, Miyajima, Kochi and Hakata). Reproductive maturation was induced in U. pertusa and the floating thalli from each site. Mating between induced gametes was observed. It is therefore believed that the floating thalli from Yokohama, Mikawa and Miyajima were mainly U. pertusa, while those from Kochi and Hakata were of a different species (Ulva sp.1). Furthermore, the Ulva species found in Mikawa is also a species (Ulva sp.2) different from both U. pertusa and Ulva sp.1. [ABSTRACT FROM AUTHOR]

The green macroalga Ulva prolifera has a number of variants, some of which are asexual (independent from sexual variants). Although it has been harvested for food, the yield is decreasing. To meet market demand, developing elite cultivars is required. The present study investigated the genetic stability of asexual variants, genotype (hsp90 gene sequences) and phenotype variations across a temperature gradient (10–30 °C) in an apomictic population. Asexual variants were collected from six localities in Japan and were isolated as an unialgal strain. The hsp90 gene sequences of six strains were different and each strain included multiple distinct alleles, suggesting that the strains were diploid and heterozygous. The responses of growth and sporulation versus temperature differed among strains. Differences in thermosensitivity among strains could be interpreted as the result of evolution and processes of adaptation to site-specific environmental conditions. Although carbon content did not differ among strains and cultivation temperatures, nitrogen content tended to increase at higher temperatures and there were differences among strains. A wide variety of asexual variants stably reproducing clonally would be advantageous in selecting elite cultivars for long-term cultivation. Using asexual variants as available resources for elite cultivars provides potential support for increasing the productivity of U. prolifera. [ABSTRACT FROM AUTHOR]

Cites a study on the life history of Ulva fasciata collected from Nomozaki in western Kyushu, Japan. Formation and description of the gametes and zoospores; Germination and development of the zygotes into lanceolate thalli; Dimension of dentate cells formed along the marginal parts after thalli.

The green invasive macroalgae Ulva ohnoi and U. pertusa are known for their capacity to form green tides across many geographic regions. Given their global ecological and economic impact, photosynthetic responses of both Ulva spp. were tested in laboratory experiments using short-term (3 h, and 5 h) exposure to different temperatures (27–36 °C) and light regimes, simulating light deprivation during ballast water transport conditions. Heat treatment of ship's ballast water has been widely advocated as a possible treatment to prevent biological contamination. In addition, the physiological performance of U. ohnoi was assessed in long-term experiments (14 days). We examined several photosynthetic parameters and physiological variables such as growth and pigment content as a measure of physiological fitness. Both species maintained stable values of Fv/Fm over several hours across temperatures, although Ulva ohnoi presented higher values of Fv/Fm, photosynthetic efficiency and NPQmax than U. pertusa, and activated dissipative protective mechanisms earlier. In the long-term experiment, U. ohnoi died by the 4th day at 36 °C. In surviving samples, Fv/Fm increased by day 7, regardless of temperature and decreased by day 14; lower values pertained to 34 °C. Photosynthetic efficiency of U. ohnoi decreased after 1 week at 27 and 29 °C, but at 31 and 34 °C, an increase was recorded after 7 days. The highest rETRmax was recorded at 29 °C, while growth optimum occurred at 27–31℃. We postulate that short-term thermal stress affects dispersal risk, which may also explain the seasonal replacement of the two Ulva spp. in Japan; and that U. ohnoi has a higher thermal tolerance that allows its settlement in new areas, resulting in a wide distributional range. Its physiological performance under the temperatures tested suggests that U. ohnoi may pose a greater risk of dispersal and settlement than U. pertusa. [ABSTRACT FROM AUTHOR]