Zone Of Japan Research Articles

Frontal Thrust Ramp‐Up and Slow Earthquakes Due To Underthrusting of Basement High in the Nankai Trough

AbstractRecently, integrated geophysical‐geological surveys in the Nankai subduction zone in Japan have revealed that slow earthquakes repeatedly occur beneath the outer wedge of the forearc. During December 2020 to February 2021, clustered slow earthquakes propagated around the frontal thrust of the accretionary wedge. The frontal thrust ramps up from the basal décollement and slips over trench‐filling sediment along the landward edge of the Nankai trough floor. Here, the Paleo‐Zenisu ridge has been subducted beneath the inner‐outer slope border. In addition, ocean floor topography and geologic structure revealed by seismic reflection surveys completed before 2022 document that the basement of the Philippine Sea Plate beneath the frontal thrust has a seamount and a horst‐like basement high. The northern edge of the basement high is located at the ramp‐up position of the frontal thrust. The 2020–2021 clustered slow earthquakes started at the Paleo‐Zenisu ridge and propagated to the topographic highs beneath the deformation front. Considering that the relative plate convergence between the upper Amurian Plate of the Nankai forearc and the subducting Philippine Sea Plate is ∼6.0 cm/year, the basement high at the deformation front has uplifted the frontal crest of the wedge at an average rate of 2.7–5.7 mm/year for several tens to hundred thousand years. These rates are among some of the highest rock uplift rates measured in the world. The slow earthquakes in the off‐Kumano Nankai Trough in 2020–2021 are a snapshot of a “living” Nankai frontal thrust during the megathrust interseismic period.

A Daytime Smoke Detection Method Based on Variances of Optical Flow and Characteristics of HSV Color on Footage from Outdoor Camera in Urban City

In order for detection of a fire in fields, it is effective to detect smoke since it often behaves as a precursor of the fire. One preferable way for early detection is to use visual information from outdoor cameras that widely monitor the filed. There have been many attempts to detect smokes via optical sensors on digital cameras using optical flow methods, but not fully successful from practical-use aspects. It is because the area of smokes occupying on the footage by outdoor cameras is not necessarily large enough. Moreover, in case of urban cities, discrimination of the smokes from other moving objects such as cars, trees and turbines is not easy. Herein we propose a novel method to detect daytime smokes based on variance of optical flow and characteristics of HSV (hue-saturation-value) color. We apply the method to a set of footage of three days obtained in an industrial zone in Japan. Successful results are obtained as over 90% of smokes are detected. Notable is that this method is independent of solar radiation conditions on sunny and cloudy days.

Fungi and bacteria in the rhizosphere of Cryptomeria japonica exhibited different community assembly patterns at regional scales in East Asia

Rhizosphere microbes are key components of soil biodiversity involved in forest ecosystem functions. However, the patterns of community structure and community assembly for different domains of microbes (i.e., fungi and bacteria) remains poorly understood at broad spatial scales. We examined community structure of rhizosphere fungi and bacteria in eight Cryptomeria japonica plantations distributed from cool temperate to subtropical zones in Japan and Taiwan. Beta diversity of fungal and bacterial communities significantly related to environmental (soil pH, C/N ratio or electrical conductivity) and spatial factors, but the fungal and bacterial communities were assembled by different ecological processes. Null model analysis showed that drift (34.4%) and dispersal limitation (48.9%) were the dominant drivers shaping fungal communities, and homogeneous selection (72.1%) were dominant in bacterial communities, indicating that stochasticity and determinism dominate community assembly of fungi and bacteria, respectively. Co-occurrence network analyses targeting frequently detected microbial taxa indicated that significant relationships were detected mostly between bacterial taxa (381/438) followed by between fungal and bacterial taxa (55/438). Putative biological interactions (40.2% and 75.0% between bacterial taxa and between fungal and bacterial taxa, respectively) and environmental filtering (33.6%–57.6%, 16.7%–20.9%) contributed highly to the co-present relationships of taxon pairs, and environmental filtering (55.3%–86.2%, 35.5%–71.0%) contributed highly to the mutually exclusive relationships of taxon pairs, indicating that not only environmental factors but also biotic interaction are important processes in aggregation among fungal and bacterial taxa. It was suggested that fungi are more influenced by stochastic processes than biotic and abiotic environmental filtering, whereas bacteria are more influenced by biotic interactions and abiotic factors such as soil properties and climate than stochastic processes at the regional scale. The results of this study provide a comprehensive view of microbial dynamics surrounding woody fine roots that can be useful for predicting the response of forest ecosystems to local and global environmental changes in East Asian cedar plantations.

Characteristics of beech mixed forest distributed at low elevations on Mt. Toishi, northern Kyushu, in the upper warm‐temperate zone of Japan

AbstractThe aim of this study was to clarify the structure and regeneration status of mixed beech (Fagus crenata) forest on Mt. Toishi in the Sangun mountain range in northern Kyushu, a relatively low‐latitude region in Japan, with emphasis on forests at lower elevations. We focused on a mixed beech forest at a low elevation of Mt. Toishi and compared the forest structure of the target stands, including tree species and size, with the forest structure near the peaks of Mt. Toishi and Mt. Sangun. Deciduous broad‐leaf trees were dominant near the peaks, while evergreen broad‐leaf trees dominated at lower elevations, whereas the relative dominance of beech trees was not significantly different. Near the peaks, the number of large‐diameter beech trees forming the canopy decreased, and small‐diameter trees were present. The proportion of small‐sized trees was lower in the low‐elevation forest area than in the forest area near the peak. Even at lower elevations, juvenile beech trees grew in limited areas on steep slopes along forest roads. These sites suggested that regeneration of beech populations is possible even at low elevation.

Seasonal variation in dietary patterns and trophic niche overlap among three sympatric medium-sized carnivores in a cool-temperate zone

To understand and sustain carnivore communities and ecosystems, it is important to determine the mechanisms of coexistence and potential competitive interactions among carnivores. This study examined how carnivores coexist and how climatic environmental shifts affect the potential competitive interactions among medium-sized carnivores. The seasonal trophic niche overlap of red foxes, Japanese martens, and raccoon dogs in the cool-temperate zone in Japan was evaluated, where there are distinct seasonal changes, especially from heavy snowfall. Faecal analysis of red foxes (n = 107), Japanese martens (n = 125), and raccoon dogs (n = 100) from 2019 to 2021 showed that carnivores share the main food items and their annual dietary overlap is relatively high despite the co-occurrence of carnivores. These results have indicated that the carnivores have potentially strong competitive interactions, and various competition avoidance mechanisms besides niche partitioning may facilitate the coexistence of carnivores in Japan. The study also found that the degree of trophic niche overlap varied by season, indicating that shifts in environmental conditions, particularly food abundance and snowfall, may affect potential competitive interactions among carnivore guilds.

Thai Boys Love drama fandom as a transnational and trans-subcultural contact zone in Japan

ABSTRACT Focusing on the online fandom of a Thai Boys Love (BL) drama in Japan, called tai-numa, this exploratory study examines its background, fan practices and experiences, and negotiations between fandoms and the mass media and within the fandom. Through interviews with 19 fans active in the fandom, which was shaped by external and internal factors, such as mediascape, characteristics of consuming BL, and the global pandemic, this research argues that the fandom is a transnational, transcultural, and trans-subcultural contact zone, enabling fans to create, learn, reflect, negotiate, and update each other’s values. Fandom activity was facilitated because it was equal and non-hierarchical, allowing for the engagement of a heterogeneous mix of fans from different subcultural backgrounds, and it offered a sense of simultaneity. Through fan voice and discussion, this paper suggests the potential impact of fandom activities on real life and what is needed for such fandoms to be established and sustained.

Effect of Major Diseases on Productivity of a Large Dairy Farm in a Temperate Zone in Japan

The objective of the present study was to investigate the associations between major diseases (clinical mastitis, peracute mastitis, metabolic disorders, peripartum disorders) and four parameters related to productivity (305-day milk yield, number of days open, culling rate, death rate) on a large dairy farm in a temperate zone with approximately 2500 Holstein cows. Data were collected from 2014 to 2018 and involved 9663 calving records for 4256 cows. We found negative effects of clinical mastitis, peracute mastitis, metabolic disorders, and peripartum disorders on the productivity of cows. Clinical-mastitis-suffered cows with multiple diseases had more days open compared with those with clinical mastitis alone and the healthy group, and they had a higher death rate than the healthy group, whereas there was no difference in death rate between the clinical mastitis only and healthy groups. Cows suffering from peracute mastitis, metabolic disorders, and peripartum disorders with either single or multiple diseases exhibited reduced productivity compared with the healthy group. Our findings clearly show that major diseases of cows in a temperate zone have severely negative effects on their productivity.

Past-Present-Future: Urban Spatial Succession and Transition of Rail Transit Station Zones in Japan.

In today’s environmentally conscious society, advocated by a global point of view, land and building use around rail transit stations have changed in the urbanization process. Promoting urban construction and development centered on rail transit stations not only meets the actual needs of urban sustainable development but is also an important means to guide the development of innovative cities. Therefore, it is meaningful to study the characteristics of urban spatial succession, development rules, and future trends based on this new perspective. We analyzed the relationship between rail transit networks and urban form in Japan using GIS by investigating changes in land and building use around rail transit stations over 30 years in the 1980s, 1990s and 2000s (from 1985–2010) using factor analysis and cluster analysis, and we discussed the impact of land consolidation planning and the setting and site selection of new stations based on urban development to understand the development trends inside and outside station zones and urban spatial succession. The results showed the following: (1) There are certain relationships between the development of urban form and traffic demand, and the rail transit network in Japan has the characteristics of high accessibility and aggregation of a small network; (2) Commercial development with a high plot ratio is dispersed and diverted by high-density rail transit stations in the commercial center of Japan; and (3) Commercial sub-centers form complexes by integrating multi-line transfers and form regional linkages through clustered commercial development. Regional business centers realize the agglomeration and radiation of functions through the compound development of station zones. This case study on rail transit zones and urban spatial succession in Japan has important enlightenment significance for urban construction toward optimizing the location and development of suburban rail transit lines, promoting the compact development of cities, exploring new ways to build more reasonable transport, planning city design and layout for rail transit station zones, and providing decision-making references for urban regeneration and sustainable development.

Regional Antimicrobial Stewardship Program in a Provincial Medical Zone in Japan: a Multifaceted Approach.

Antimicrobial resistance (AMR) is a threat to patient health. However, data to optimize antimicrobial use are limited. Furthermore, reducing antibiotic use raises concerns regarding patient safety. The effectiveness of antibiotics in reducing the prevalence of AMR is controversial. Researchers at the Japanese Red Cross Ishinomaki Hospital (JRCIH), the only tertiary care hospital in the medical zone, along with local medical and pharmacy associations and public health centers have been leading the AMR control program since 2018. The program involves lectures aimed at optimizing antimicrobial use, regular publication of surveillance data of drug-resistant strains at the JRCIH, and presentation of first-line treatments for community-acquired infections. The delivery of oral antimicrobial agents across the region in 2020 was 28.7% lower than that in 2013, with delivery of cephalosporins, quinolones, and macrolides decreasing by 34.8%, 46.8%, and 56.0%, respectively. Despite these reductions, there has been no associated increase in the number of patients with severe infectious diseases admitted to the JRCIH. The rates of representative drug-resistant bacterial strains, such as extended-spectrum beta-lactamase-producing Escherichia coli and methicillin-resistant Staphylococcus aureus, decreased by half. Herein, we demonstrated the potential of collaborative efforts to optimize antimicrobial agent use and reduce the AMR prevalence without compromising patient safety.

Diffusive methane burst during a blue tide, wind-driven event in a meromictic lake

Strong stratification has formed in Lake Abashiri, a typical meromictic lake in Hokkaido, in the subarctic zone in Japan. When the anoxic water of the lower layer is upwelled to the surface by a strong wind, fish and corbicula clams die due to a lack of dissolved oxygen. This event is called as blue tide. It was observed that the dissolved methane in the lake decreased more than 100 t after the blue tide which occurred in 2008. This is the discovery of the phenomenon that a large quantity of methane diffuses to the atmosphere caused by upwelling of anoxic water which contains dissolved methane. We named the event as “methane burst”. It is also the first report that the wind-driven upwelling is reproduced using a numerical analysis code and the methane burst is analyzed. During this blue tide, the methane flux was approximately 170 times greater than usual.

Consideration of Genetic Structure in the Ecologically or Biologically Significant Marine Areas Criteria: A Review of Convention on Biological Diversity Regional Workshops and A Case Study of Coral Reef Conservation Planning

In this study we reviewed the use of genetic information in the Ecologically or Biologically Significant Marine Areas (EBSA) of Convention on Biological Diversity (CBD). We also evaluated genetic indicators for each criterion of important marine areas. We proposed five genetic indices, mainly based on microsatellite analysis (e.g., private allele frequency and number of cryptic species), then selected EBSAs in tropical and temperate zones of Japan based on eight coral species as a case study. Finally, we compared the results with the findings from conventional species-based EBSAs. In the EBSAs genetic information was mainly used in the Northern Hemisphere, particularly in the Baltic Sea; it was rarely applied in the Southern Hemisphere and Asian regions. Although typically applied to large organisms, genetic information is used to various organisms, including benthic and bacterial communities. Genetic data are used as indicators of diversity and endemism. Genetic indices were available for all seven EBSA criteria, but only five indices of three criteria were used. Examination of important areas of corals in the temperate zone using these indices showed that the indices without genetic indicators extracted a large number of important areas in the tropics; however, the use of genetic indicators identified important locations, including in temperate zones. Comparison with conventional, mainly species-based non-genetic methods showed less than 50% agreement, although particularly important sites in marine protected areas were identified by both methods. While there is still more work to be done, such as consideration of the number of survey sites or target species, one reason is that species-based methods tend to evaluate tropical areas higher. Therefore, these genetic indices are useful for examining important regions, particularly in temperate zones; they revealed cryptic lineages, indicating that many unknown marine taxa should be considered in vulnerable marine areas. Some indicators could be extracted with additional effort, such as population size estimation, immigration, or the use of next-generation sequencing, thus guiding future studies. Because limited genetic information was available in the early stages of EBSA selection, there is a need for systematic surveys and evaluations, particularly in the Southern hemisphere, Asian region, and in small organisms.

Positive and negative effects of land abandonment on butterfly communities revealed by a hierarchical sampling design across climatic regions.

Land abandonment may decrease biodiversity but also provides an opportunity for rewilding. It is therefore necessary to identify areas that may benefit from traditional land management practices and those that may benefit from a lack of human intervention. In this study, we conducted comparative field surveys of butterfly occurrence in abandoned and inhabited settlements in 18 regions of diverse climatic zones in Japan to test the hypotheses that species-specific responses to land abandonment correlate with climatic niches and habitat preferences. Hierarchical models that unified species occurrence and habitat preferences revealed that negative responses to land abandonment were associated with species that have cold climatic niches and use open habitats, suggesting that species negatively impacted by land abandonment will decline more due to future climate warming. Maps representing species gains and losses due to land abandonment, which were created from the model estimates, showed similar geographical patterns, but some areas exhibited high species losses relative to gains. Our hierarchical modelling approach was useful for scaling up local-scale effects of land abandonment to a macro-scale assessment, which is crucial to developing spatial conservation strategies in the era of depopulation.

Competition and disturbance affect elevational distribution of two congeneric conifers.

Climatic change will affect elevational vegetation distribution because vegetation distribution is related to thermal conditions. However, how elevational species distributions are determined by biotic and abiotic factors is not clear. The long‐term plot census along an elevational gradient is indispensable to clarify mechanisms of elevational distribution of tree species. Two congeneric conifers, the less shade‐tolerant Abies veitchii and shade‐tolerant A. mariesii, dominate at low and high elevations, respectively, in the subalpine zone in Japan. This study investigated the population dynamics of the two species at three elevations (low, middle, high) for 13 years to examine why the two species dominated the different elevations from the viewpoints of competition and disturbance. This study showed that growth and survival rates were not highest at the most dominant elevations for each species. At the high elevation where A. mariesii dominated and small disturbances frequently occurred, the recruitment rate of A. mariesii was highest among the three elevations and that of A. veitchii was largely decreased by tree competition. However, A. veitchii was dominant earlier than A. mariesii at the low elevation after large disturbances by the high growth rate of individual trees. Therefore, A. mariesii was superior to A. veitchii at the high elevation because of its high recruitment rate and large reduction of recruitment of A. veitchii due to competition, while A. veitchii was superior to A. mariesii at the low elevation after large disturbances because of higher growth rate than A. mariesii. It is suggested that the elevational distributions of the two species were determined by elevational changes in population dynamics in relation to competition and disturbance. Long‐term observational studies of forest dynamics among various elevations are indispensable to predict the effects of climatic change on vegetation distribution.

Tricholoma alpinum, sp. nov., under five-needle pines in alpine and subalpine zones in Japan

ABSTRACT Alpine regions in Japan are characterized by the Siberian dwarf pine, Pinus pumila. Although these regions are conserved as national parks due to their unique biome, few reports of the fungal biota are available. We examined mushroom fungi under such vegetation and found a unique yellowish-capped Tricholoma species. Multilocus molecular phylogenetic analyses and morphological observation of specimens showed that the Tricholoma species is very similar to T. fumosoluteum known in North America. The Japanese yellowish-capped T. aff. fumosoluteum had larger basidiospores and basidia and shorter pileipellis hyphae compared with T. fumosoluteum. Therefore, we describe the Japanese entity as a new species, T. alpinum.

Comparison of seasonal changes in body weight of raccoon dogs between the warm and cool temperate zones in Japan

Comparison of seasonal changes in body weight of raccoon dogs between the warm and cool temperate zones in Japan

Preference Heterogeneity of Coastal Gray, Green, and Hybrid Infrastructure against Sea-Level Rise: A Choice Experiment Application in Japan

Coastal zones are bearing the brunt of an increase in the likelihood of extreme events, coupled with sea-level rise (SLR). Conventionally, gray infrastructures, such as seawalls, have been constructed to reduce risks in limited coastal zone spaces. Nature-based approaches, known as green infrastructure, have been used in coastal defense, and their ecosystem-based disaster risk reduction functions (Eco-DRR) have received growing attention. However, both gray and green infrastructure alone have limitations in responding to an ongoing increase in the intensity and frequency of natural hazards. To overcome these issues, hybrid infrastructure, which combine gray and green components, is needed, and they have been receiving growing attention. Meanwhile, a large-scale coastal development requires stakeholder agreement; thus, it is imperative to understand people’s demands and build a consensus between municipalities and coastal citizens in coastal development for long-term resilience. The author administered the online survey across Japan, applying it to the choice experiment, and obtained 840 valid responses. Therefore, this paper clarified the heterogeneities in coastal people’s preferences for coastal ecosystem services provided by gray, green, and hybrid structures in intertidal zones in Japan, recognizing seawalls as gray and coastal pine forests as green infrastructure. Consequently, while coastal citizens acknowledged gray’s coastal defense function, the diverse perceptions toward seawalls for SLR preparation were notable as its scenarios became severe. Another remarkable finding is that nearly 60% of respondents preferred Eco-DRR functions provided by coastal forests with JPY 695 in willingness-to-pay for expanding 100 m in width, even though there are uncertainties in their performances.

Dynamics of soil reinforcement by roots in a regenerating coppice stand of Quercus serrata and effects on slope stability

Regeneration by sprouting in secondary forests is a necessary technique not only for the utilization of forest resources, but also for maintaining forest health by regrowth and avoiding slope instability caused by over-sized aboveground biomass. The strength of soil reinforcement by roots generally decreases during the tree death process in deforestation, such as clear-cutting, whereas root system strength temporarily decreases in trees that regenerate sprouting after cutting. However, quantitative evaluation of decreasing soil reinforcement by roots and slope stability has not been conducted during regeneration. In this study, we evaluated changes in the number of roots and root distribution up to 3 years after cutting in the regeneration process of Quercus serrata, a major dominant species of secondary forests in warm and cool temperate zones in Japan. We also estimated soil reinforcement by roots: additional cohesion from roots using the root bundle model, and slope stability based on a factor of safety by dividing the effect of the tree root system into vertical and horizontal cohesion with soil physical properties. After cutting at the height of approximately 0.2 m, the aboveground sprouting branches immediately regenerated, whereas the belowground root system gradually decayed. The additional cohesion from roots in trees before cutting was calculated as 34.6 kPa, whereas it decreased significantly to 21.7 kPa in living stumps 3 years after cutting. The value for the factor of safety with a saturated soil thickness of 0.7 m was calculated as 1.20 in soil under trees before cutting, whereas it decreased significantly to 1.11 in soil under living stumps in the 3 years after cutting. The safety factor's value to 0.99 in soil under dead stumps, which did not regenerate sprouts within 3 years after cutting. We concluded that the probability of slope failure was significantly greater in the dead stumps than in the living stumps and could vary depending on the dynamics of above- and below-ground parts, including fine roots.

Paleocene–early Eocene post-subduction magmatism in Sikhote-Alin (Far East Russia): New constraints for the tectonic history of the Izanagi-Pacific ridge and the East Asian continental margin

New isotopic, geochemical and geochronological data justify the widespread occurrence of middle Paleocene to early Eocene (60–53 Ma) post-subduction felsic magmatism across the entire Sikhote-Alin territory (southeastern Russia), conform with previous observations in Northeast China, the southern Korean Peninsula, and the Inner Zone of Japan. This igneous activity in East Asia coincided with the reactivation (after tectonic quiescence between ~93–60 Ma) of left-lateral strike-slip displacements along the Tan-Lu and Central Sikhote-Alin faults and with the post-60 Ma cessation of subduction/accretion recorded in the Shimanto belt of SW Japan. The Sikhote-Alin post-subduction igneous A-type rocks present diverse mineralogical and geochemical features that suggest interactions of the subducting plate with anhydrous mantle upwelling through slab tears in the continental margin. The middle Paleocene–early Eocene magmatism is not related to subduction but is synchronous with strike-slip tectonics and the termination of accretionary prism development, suggesting a shift in tectonic regime from oceanic plate subduction at a convergent margin to parallel sliding and initiation of a transform continental margin. These new observations are inconsistent with the current tectonic model of 60–50 Ma Izanagi-Pacific ridge subduction beneath East Asian continental margin.

Demographic and clinical characteristics of foreign nationals accessing psychiatric services in Japan: a multicentre study in a metropolitan area

BackgroundInternational immigration to Japan, where homogeneous ethnicity is a population characteristic, has been growing. Although immigration is recognised as a risk factor for multiple mental-health related issues, there are few regional reports on foreign nationals accessing the psychiatric services in Japan. We aimed to reveal their current status and provide information to develop an optimal service system.MethodsA multicentre retrospective document review research was conducted. The subjects were foreign nationals who resided in Japan and presented at the psychiatry departments in three core regional hospitals in the Keihin region, which faces Tokyo Bay and is well known to include the largest traditional industrial zone in Japan, over a period of 3 years. We investigated the patients’ demographic and clinical information including country/region of origin, spoken language, use of a medical interpreter, pathway to hospitals and outcome.ResultsThe percentage of foreign patients among all patients (1.4%) was quite low. Their age distribution (45.8 years on average) was dissociated from the age distribution of foreign nationals who resided in Japan. Regarding the country/region of origin, China (35.1%) was the most common country, followed by the Philippines, Korea and Brazil. Several subjects (22.9%) could not speak Japanese; therefore, interpretation was required by family members/friends (17.1%) or a professional interpreter (5.4%). Neurotic and stress-related disorders were the most common diagnosis (24.4%). The proportion of psychoactive substance use was higher than that for Japanese national data as immigrants are known to be at risk for it.ConclusionsThe results suggest that foreign nationals who reside in Japan are less likely to contact appropriate services for mental illness, especially young people at relatively high risk of mental illness do not access services. Furthermore, lack of medical interpreters may impede the mental health conditions of foreign nationals. The development of a community-based integrated care system accessible to foreign nationals seems to be indispensable.

First report of Alexandrium (Dinophyceae) associated with marine macroalgae off Japan: Diversity, distribution, and toxicity

Macroalgal samples were collected from coastal waters in subboreal to subtropical zones in Japan (< 3–30 m depths) and 32 clonal strains of non-motile dinoflagellate-like protists were established. Molecular phylogenetic analyses of the LSU rDNA D1/D2, SSU rDNA, ITS region, and concatenated SSU rDNA + LSU rDNA D1/D2 sequences revealed that the strains nested within the genus Alexandrium. They were separated into three novel phylotypes: Alexandrium spp. type 1, type 2, and type 3. Analysis of the concatenated sequences revealed that the most closely related species for the three phylotypes was A. ostenfeldii. Most cells from strains of the three phylotypes were non-motile and hemispherical to spherical in shape. The average diameters of the non-motile cells were between 35 and 39 µm. Type 1 and type 2 were widely distributed in Japan from the temperate to subtropical zones, whereas type 3 was restricted to the temperate zone. Furthermore, type 2 was widespread from shallow to deep waters, whereas type 1 and type 3 were restricted to deep waters. Growth experiments in strains belonging to the three phylotypes revealed that the occurrence ratios of motile cells were very low (≤ 1.1% of the total cells). The production of paralytic shellfish poisoning toxins, tetrodotoxin, and cyclic imines was assessed in strains belonging to the three phylotypes by LC/MS/MS analysis. The strains did not produce any of the toxins tested. The strains of the three phylotypes showed lethal toxicity to mice by intraperitoneal administration. To the best of our knowledge, this is the first study to report the existence of Alexandrium associated with marine macroalgae from Japan.