Search

SUMMARY: "Monitoring Sites 1000" – Japan's long‐term monitoring survey was established in 2003, based on the Japanese Government policy for the conservation of biodiversity. Ecological surveys have been conducted on various types of ecosystems at approximately 1000 sites in Japan for 15 years now and are planned to be carried out for 100 years. Since 2008, seaweed communities had been monitored at six sites, featuring the kelp (e.g. Saccharina and Ecklonia; Laminariales) and Sargassum (Fucales) communities in the subarctic and temperate regions of Japan. Annual surveys were carried out during the season when these canopy‐forming seaweeds are most abundant. A non‐destructive quadrat sampling method, with permanent quadrats placed along transects perpendicular to the shoreline, was used to determine species composition, coverage, and vertical distribution of seaweeds at these sites; while destructive sampling was done every 5 years to determine biomass. The occurrence of canopy‐forming species Saccharina japonica (var. japonica) and Ecklonia cava have appeared to be stable at the Muroran (southwestern part of Hokkaido Island) and Shimoda (Pacific coast of middle Honshu Island) sites, respectively; whereas the coverage of Ecklonia radicosa (= Eckloniopsis radicosa) at the Satsuma‐Nagashima site in southern part of Kyushu Island was highly variable until its sudden disappearance from the habitat in 2016. Thalli of E. radicosa lost most of their blades through browsing by herbivorous fish, and thus, this may be one of the causes of the decline. A shift in the community structure related to environmental changes had also been observed at some other sites. Pre‐ and post‐disaster data revealed the impact of the 2011 earthquake and tsunami disasters, including a shift in the vertical distribution of Ecklonia bicyclis (= Eisenia bicyclis) to shallower depths at the Shizugawa site in the Pacific coast of northern Honshu Island, due to seafloor subsidence. [ABSTRACT FROM AUTHOR]

SUMMARY Trade‐offs are considered key to understanding mechanisms supporting the coexistence of multiple plant species. Thus, understanding the mechanisms underlying trade‐offs is expected to contribute to conservation and management of macroalgal beds composed of diverse macroalgae of rocky shore ecosystems. To test the occurrence of trade‐offs between productivity and thallus toughness as well as pair‐wise thallus trait relationships that are expected to indirectly relate to any trade‐offs, traits and relationships for 13 species of macroalgae from the central area along the Japan Sea coast of Honshu, Japan were examined. In each species we examined for photosynthetic capacity per unit biomass (as Amass) and nitrogen (i.e., photosynthetic nitrogen‐use efficiency, PNUE), nitrogen content (as Nmass), thallus mass per unit thallus area (as TMA) and force required to penetrate the thallus (as Fp, a common index of leaf toughness in land plants by punch test). A significant negative correlation indicating a trade‐off between productivity and thallus toughness was found between Amass or PNUE and Fp. Pair‐wise relationships that were expected to indirectly relate to the trade‐off were as follows. Amass was positively correlated with Nmass. Thalli with high Nmass extensively utilizing nitrogen in the photosynthetic parts, and consequently exhibiting elevated metabolic rates. Moreover, thalli with high Nmass tended to be associated with low TMA, and Nmass decreased with increasing TMA. A significant negative correlation was observed between TMA and Amass or PNUE because of the linkage of high Amass or PNUE with high Nmass and high Nmass associated with low TMA, while a significant positive correlation was observed between TMA and Fp. The two correlations indicate a physiological and structural trade‐off, which underlies the interdependency of thallus traits. Results of multivariate analyses also indicated that the thallus traits interdependently vary across a single axis based on the trade‐off. [ABSTRACT FROM AUTHOR]

Three new species of Fallacia, F. miyajimensis sp. nov., F. nodulifera sp. nov., and F. similigemmifera sp. nov. are described from intertidal sediments in Japan. Their morphologies are studied with light, scanning and transmission electron microscopy. Fallacia miyajimensis differs from congeners in the presence of an apical pore, a finely porous conopeum possessing finger-shaped extensions with uniseriate rows of pores and a thick layer adjacent to the raphe with isolated depressions with small pores inside. Fallacia nodulifera differs from congeners in the presence of a unique asymmetric internal central nodule. It can also be distinguished by the combination of stria density, conopeum with short extensions, and centrally convex lateral sterna. Fallacia similigemmifera differs from congeners by its lanceolate valve outline, more or less straight, distinct lateral areas and the presence of a rectelevatum on internal central nodule. We suggest that the structural combination of the structure of the conopeum and the lateral sterna is a stable feature in species discrimination and could be used to define species groups. The cingulum of F. similigemmifera comprises a wide open valvocopula and two linear bands with different ligulae. This type of cingulum structure is also present in F. tenera, F. hodgeana, and probably in F. litoricola and F. fracta as well, and likely occurs commonly in Fallacia. [ABSTRACT FROM AUTHOR]

SUMMARY We monitored an Eisenia bicyclis kelp bed during a survey of the rocky coast subtidal zone of Shizugawa Bay, the Sanriku Coast, northeastern Honshu, Japan, from 23 July 2008, to detail the biodiversity, which was subsequently directly impacted by the 2011 Great East Japan Earthquake (GEJE). To assess temporal changes in abundance of the dominant canopy forming kelp E. bicyclis and in the distribution patterns of macroalgae along a water depth gradient, percent coverage of macroalgae has been observed in permanent quadrats set near the lower limit of the Eisenia bed and in quadrats set along a water depth gradient. The GEJE, which induced huge tsunami waves and coseismic seafloor subsidence, occurred during the monitoring survey period and also affected the coastal communities in Shizugawa Bay. After the GEJE, the cover of E. bicyclis within the permanent quadrats near the lower limit of E. bicyclis gradually declined, and reached zero by July 2014. Also in the line transect survey, the offshore (deep) edge of the Eisenia bed showed a tendency to shift shoreward (upward) after the GEJE; the Eisenia bed near the pre‐earthquake offshore (deep) edge declined and finally disappeared after the GEJE. Combined with results of the permanent quadrat and line transect surveys, the post‐earthquake gradual decline and subsequent complete disappearance of the Eisenia bed within the permanent quadrats probably indicates an upward shift of the deep edge of the subsided kelp bed. Gradual change in the E. bicyclis bed over 2 years after the GEJE is a unique opportunity to document the response of a kelp bed to coseismic subsidence, demonstrating the slow and prolonged recovery process of E. bicyclis to subsidence caused by the mega‐earthquake to the pre‐earthquake depth zone. [ABSTRACT FROM AUTHOR]

The annual kelp Eckloniopsis radicosa is distributed along Japanese coasts and occurs within the area with a February isotherm ranging 15-18° C and August isotherm ranging 25-28° C. In this study, the effects of temperature on the gametophyte growth and maturation, and the young sporophyte growth of E. radicosa were examined and the results are discussed in relation to the distribution of other warm-adapted kelp species and the potential effects of climate change. The optimal temperature ranges for growth of male and female gametophytes were 23-27° C and 20-26° C, respectively. The upper survival temperature for gametophyte growth was 31° C for males and 30° C for females, respectively. The optimal temperature range for maturation of female gametophytes was ≤23° C. The optimal temperature range for growth of young sporophytes was 14-22° C. It was clarified that E. radicosa has the most warm-adapted characteristics for growth and maturation of gametophytes among members of the Laminariales studied so far. The natural seawater temperature ranges during the growth and maturation seasons for gametophytes of E. radicosa, as well as the growth season for young sporophytes near to the northern and southern distribution limits ( Izu- Oshima: 14.9-24.5° C, Ichiki-kushikino: 17.1-29.6° C), agreed with the experimentally determined temperature requirements. The warm-adapted gametophyte stage and annual lifecycle are major factors enabling survival of E. radicosa in warm waters near tropical regions along the Japanese coast. [ABSTRACT FROM AUTHOR]

Chara braunii is a charalean species that grows in a range of aquatic habitats from shallow water in paddy fields to the bottom of deep lakes. More than 30 infraspecific taxa have been proposed within this species because of its morphological variability. In order to reexamine the infraspecific taxa and habitat preference of C. braunii, we carried out molecular phylogenetic analyses and quantitative measurements of morphological characters used for infraspecific taxa, based on samples collected from various habitats and localities in Japan. Sequence data from the gene encoding the large subunit of Rubisco (rbcL) and the intergenic spacer regions between the beta subunit of the ATP synthase and rbcL genes demonstrated two robust clades (groups A and B). Samples of group A were collected mainly from shallow aquatic environments (< 15 cm in depth) such as paddy fields, while those of group B were mainly composed of samples found in deep aquatic environments (> 1 m in depth) such as lakes or ponds. Groups A and B therefore seem to represent closely related entities that have recently differentiated and might adapt to two different aquatic environments. However, the morphological measurements suggested these groups can be delineated by neither of the traditional diagnoses that were different between infraspecific taxa of Japanese plants of C. braunii. [ABSTRACT FROM AUTHOR]

Grazing effects of ayu, Plecoglossus altivelis Temminck et Schegel, on the benthic algal assemblages were investigated in the Chikuma River, Japan. Comparison of the algal composition on boulders with and without intensively grazed patches indicated that fish grazing decreased the abundance of diatoms and prostrate filamentous cyanobacteria and caused upright filamentous cyanobacteria to predominate. Differential consumption by ayu was estimated by comparing the relative abundance of algae in the stomach contents of ayu and that in the algal assemblages within the grazed patches. The results showed that ayu consumed the prostrate filamentous cyanobacteria proportionally to their abundance, whereas they ingested diatoms and the upright filamentous cyanobacteria in a larger and lower quantity, respectively, than that expected from their abundance. Differential consumption would involve the change in the algal composition toward the predominance of upright filamentous cyanobacteria under fish grazing conditions. [ABSTRACT FROM AUTHOR]

Taxonomic re-examination of Dictyopteris punctata Noda revealed vegetative and reproductive characters that were not described in the original description. The outer one-fifth to two-fifths of the blade margin was monostromatic. Reproductive organs of female and male gametophytes were observed for the first time. All reproductive organs (sporangia, oogonia, antheridia) were formed on middle to upper parts of thalli and between the midrib and distromatic area of the blades, and never produced on the monostromatic areas. Maturation starts earlier at the lower part. Sporangia were solitary and scattered. Oogonia were scattered singly or in small groups and more densely distributed than sporangia. Antheridial sori were scattered around a midrib, and raised above the wing surfaces. Antheridia were taller around the midrib than in the middle part of a wing. The monostromatic wings and lack of distinct oogonial sori are new taxonomic characters of Dictyopteris punctata and further define this species with scattered sporangia, the taxonomic character hitherto used. [ABSTRACT FROM AUTHOR]

The effects of salinity on growth, maturation and photosynthesis were examined in the filamentous algaRhizocloniumsp. (Cladophoraceae, Chlorophyta) growing in a brackish water habitat in a canal draining into Tokyo Bay, Japan. In this habitatRhizocloniumsp. was exposed to a wide salinity range, both daily, 5−23‰ during November 1996, and hourly, 6−24‰ during the spring tide day. From the results of culture experiments, growth and maturation ofRhizocloniumsp. occurred in the wide salinity range of 10−40‰ at 20 µmol photons m−2s−1 at 20°C, but did not occur at salinity of 0‰. Light saturation on the photosynthesis-irradiance curve at 20°C at 20‰ was reached at 100 µmol photons m−2s−1, which is characteristic for shade-adapted algae. On the photosynthesis-salinity curve at 20°C at saturated irradiance (160 µmol photons m−2s−1), the net photosynthetic rate increased with increasing salinity up to 30‰ but decreased at 40‰. On the photosynthesis-salinity curve at 20°C at 20 µmol photons m−2s−1 (at nearin situirradiance), the photosynthetic rates were almost the same in the salinity range from 0 to 40‰. Therefore, this species is able to grow, reproduce and photosynthesize with a relative efficiency in a wide salinity range, which shows that it is well adapted to a brackish water environment. [ABSTRACT FROM AUTHOR]

Physiological properties of the temperate hermatypic coral Acroporapruinosa Brook with symbiotic algae (zooxanthellae) on the southerncoast of the Izu Peninsula, Shizuoka Prefecture, central Japan,were compared between summer and winter. Photosynthesis and respirationrates of the coral with symbiotic zooxanthellae were measured insummer and winter under controlled temperatures and irradianceswith a differential gas-volumeter (Productmeter). Net photosyntheticrate under all irradiances was higher in winter than in summer at thelower range of temperature (12−20°C), while lower thanin summer at the higher range of temperature (20−30°C).The optimum temperature for net photosynthesis was apt to fall withthe decrease of irradiance both in summer and winter, whereas itwas higher in summer than in winter under each irradiance. At 25/50/100 µmolphotons m-2 s-1, it was nearly the sea­watertemperature in each season. Dark respiration rate was higher inwinter than in summer, especially in the range from 20−30°C.In both seasons the optimum temperature for gross photosynthesiswas 28°C under 400 µmol photons m-2 s-1 andlowered with decreasing irradiance up to 22°C under 25 µmolphotons m-2 s-1 in summer, while 20°Cunder the same irradiance in winter. The optimum temperature forproduction/respiration (P/R) ratio was higherin summer than in winter under each irradiance. Results indicatedthat metabolism of coral and zooxanthellae is adapted to ambienttemperature condition under nearly natural irradiance in each season. [ABSTRACT FROM AUTHOR]

Summary Transplanting experiments were carried out to determine whether the small type sporophytes with short stipe of Ecklonia cava Kjellman (Laminariales, Phaeophyta) growing in a locality with warm temperatures, change into larger type with a long stipe when transplanted to a locality with cooler temperatures. Juvenile E. cava sporophytes, having a stipe shorter than 5 cm long were collected from Tei in Tosa Bay (southern Japan) (seawater temperature 15-29°C) and transplanted to Nabeta Bay (central Japan) (seawater temperature 13-25°C), where larger type E. cava sporophytes characterized by long stipe (ca 1 m) grow. They were attached to artificial reefs at the sea bottom (9 m depth) in Nabeta Bay to monitor their growth. For comparison, juvenile E. cava sporophytes of almost similar size growing in Nabeta Bay were also transplanted in the same way to the same experimental site. Observations of growth of sporophytes from Tei and Nabeta were carried out monthly for 2 years from November 1995 to October 1997. The transplanted Tei and Nabeta sporophytes showed an increase in stipe length and diameter from winter to spring, whereas almost no increase was observed during summer and autumn. At the end of the study period, the stipe of Nabeta sporophytes reached 25.6 cm in length and 17.0 mm in diameter, whereas that of Tei sporophytes reached 11.1 cm in length and 11.2 mm in diameter. The primary blade length was 16.0 cm in Nabeta sporophytes, whereas it was 5.5 cm in Tei sporophytes. Thus, Tei sporophytes still remained smaller than Nabeta sporophytes even under the same environmental conditions. [ABSTRACT FROM AUTHOR]

Summary Sporophytes of Ecklonia cava Kjellman (Laminariales, Phaeophyta) were collected seasonally from within 3-4 replicate, 1-m2 quadrates, haphazardly placed in dense assemblages at 6-9 m depth in Tei, Tosa Bay (southern Japan; water temperature 15-29°C) from 1995 to 1996, and in Nabeta Bay, Shimoda (central Japan; water temperature 13-25°C) from 1996 to 1997. Growth rings were checked for all samples and mean values of each biometric parameter of sporophytes 1-year-old and over were compared. The plant length (stipe length + primary blade length) was always shorter in Tei sporophytes (24-52 cm) than Nabeta sporophytes (70-100 cm), the difference being mainly owing to the shorter stipe length in Tei sporophytes (7-14 cm) than in Nabeta sporophytes (54-83 cm). However, the primary blade length was sometimes longer in Tei sporophytes (12-38 cm) than in Nabeta sporophytes (14-21 cm). Stipe diameter, longest bladelet length and primary blade width were mostly less in Tei sporo­phytes (8.6-12.4 mm, 5.5-7.0 cm and 23.4-38.0 cm, respectively) than Nabeta sporophytes (16.4-20.2 mm, 9.2-12.0 cm and 43.0-52.6 cm, respectively). Nevertheless, the number of bladelets of sporophytes from Tei (15-28) and Nabeta (18-29) were within the same range. At Tei, 32-43% of the sporophytes had wrinkled blades in summer and autumn, whereas wrinkled primary blades or bladelets were not observed in Nabeta sporophytes throughout the experimental period. These morphometric differences of E. cava between the two localities are suggested to be dependent on environmental factors, especially seawater temperature. [ABSTRACT FROM AUTHOR]

SUMMARY Seasonal patterns of drifting seaweeds in the south-eastern coastal waters of Izu Peninsula of central Japan were examined by sampling 966 patches from spring to autumn 1991–1993. In total, 57 plant species appeared, including 10 epiphytic algal species. Monthly totals of the number of species, excluding epiphytic algae, were highest in May (33) and August (27), though 19–21 species of sargassaceous algae were found from May to August. The number of species, excluding epiphytic algae, in one patch of drifting seaweeds was 1 to 11 (x = 2.93 ± 2.06) with high richness in May a result of almost entirely sargassaceous species. The wet weight of each patch and maximum stipe length of plants varied from 5 to 6970 g and from 20 to 840 cm (x = 536.1 ± 782.3 g and 110.6 ± 76.8 cm), respectively, with highs in April and May. Out of 18 species common to all years, 10 species dominated the top or second rank in monthly pooled frequency of appearance. Seasonal changes of these 10 major species were examined. Sargassum horneri (Turner) C. Agardh and Hizikia fusiformis (Harvey) Okamura were abundant in April, but were replaced partly by Sargassum muticum (Yendo) Fensholt in May and largely by Sargassum yamamotoi Yoshida in June. In July, Sargassum nipponicum Yendo and Sargassum piluliferum (Turner) C. Agardh dominated. Subsequently, the major species shifted to Sargassum ringgoldianum Harvey and S . yamamotoi in August, Sargassum micracanthum (Kützing) Endlicher, Sargassum macrocarpum C. Agardh and Zostera marina Linnaeus in September, and S . ringgoldianum and S . micracanthum in October. However, the occurrence of S . yamamotoi , S . nipponicum and S . piluliferum in June or July were particularly heterogeneous compared with other areas of Japan. Dendrogram analysis was done based on frequency of appearance. Pooled monthly samples were divided into three groups characterized from the dominant species, degree of domination, weight,... [ABSTRACT FROM AUTHOR]

SUMMARYA new species of Cocconeis has been found growing on the green seaweed Caulerpa racemosa (Forsskål) J. Agardh var. laete-virens (Montagne) Weber van Bosse from Shikine Island in the Izu Islands on the Pacific coast of Japan; we propose the name Cocconeis shikinensis Hid. Suzuki and describe the species by light microscopy (LM) and electron microscopy (EM). This taxon was also collected from the plastic plates used for rearing in seed production systems of the abalone Nordotis discus hannai Ino and the horned turban Turbo cornutus Solander in the Toyama Prefectural Fisheries Research Institute facing the Sea of Japan. The main morphological features of C. shikinensis are as follows. The valves are elliptic. The valve face of the raphid valve (RV) is slightly concave and that of the araphid valve (AV) is complementary to the RV and convex. The single plastid is flat, C-shaped and elaborately lobed. The raphe on the RV is straight. The each terminal area expands to both sides along the valve margin, forming an arrowhead-shaped, thickened hyaline area. The striae consist of small, round areolae and are radiate and uniseriate. On the AV, the striae consist of several alveoli. Each alveolus opens internally by means of a circular foramen. The valvocopula of each valve is fimbriate and open. The cingulum attached to the AV consists of three girdle bands; a valvocopula and two bands (copula and pleura), which are open and have ligulae. The relationship between C. shikinensis and similar members of the genus Cocconeis is discussed. [ABSTRACT FROM AUTHOR]

Examines the reproductive structures of Dictyopteris undulata from Japan. Distinction of genus Dictyopteris from other genera of the Dictyotales; Analysis of the sporophytes of the male and female gametophytes; Development of tetrasporangia; Illustration of stalk cells from Dictyopteris species.

Morphological and hybridization experiments were performed on Caloglossa leprieurii (Montagne) J. Agardh collected from Japan, Singapore and Australia in order to evaluate taxonomic characters of this species. Within C. leprieurii at least four mating groups were recognized from the Indo-Pacific region. These mating groups could be characterized by the blade width at the internode and the cell-row numbers on the opposite side derived from the first axial cell at the main axis, though these properties showed a certain variability even in the same plant under both field and culture conditions. The phylogenetic relationship and geographic distribution of the four mating groups are discussed. [ABSTRACT FROM AUTHOR]

Systematic studies were undertaken on the Caloglossa continua (Okammura) King et Puttock complex from Japan, Singapore, and Austriala, based on morphology and reproductive compatibility. Specimens from Japan had two to six cell rows derived from a nodel axial cell, at the margin opposite the branch, whereas those from Austraila possessed only a single cell now. Specimens from Singapore formed one to four cell rows per nodal axial cell and always contained at least one single cell row on any one thallus. These differences were maintained in cultural materials over a range of temperagtures or salinities. Type material of C. continua had the same morphology as the Japanese specimens in this study. Carpospores discharged from the Japanese isolate germinated at 10°C, whereas those from Singapore and Australia died at this temperature. In hybridization experiments, the Japanese entity was completely nonfertile with both the Singaporean and Australian isolates. Many pseudocystocarps were produced in the crossing between the make from Australia and the female from Singapore, although the reciprocal combination did not produce any such structures. On the basis of the discontinuous morphology coupled with the complete reproducture isolation, the entiries from Singapore and Australia are described here as C. monosticha sp. nov. The entiries with multiple cell rows likely expanded their geographic range from tropical regions, where the majority of Caloglossa species are now distributed, to high-latitude regions, and such an expansion would be associated with acquining low-temperature tolerance. [ABSTRACT FROM AUTHOR]