Southern Hokkaido Research Articles

Seasonal changes in the protist communities of Hakodate Bay, southern Hokkaido, from 2020 to 2022

Hakodate Bay at the southern end of Hokkaido experiences physical and chemical environmental changes in the adjacent Tsugaru Strait. Harmful algal blooms have occurred since 2015. However, information on the response of protist community composition, photosynthetic activity to environmental variables or the mechanisms causing harmful blooms in the Hakodate Bay is lacking. We investigated the seasonal changes in the protist community using weekly sampling to reveal the relationship between the protist community and environmental variables in the Hakodate Bay. Based on cluster analysis, six groups were identified: Winter, Spring, Late Spring, Summer, Benthic, and Karenia. High Fv/Fm was seen in the Summer, Benthic and Spring groups supported by high nutrients, warm temperature and sufficient irradiance. From the Winter to Spring group, a species transition from low-temperature-adapting Thalassiosira spp. to Chaetoceros spp. was found. The Summer group comprised high salinity-tolerant species (the diatom Leptocylindrus danicus and dinoflagellate Prorocentrum spp.) because of high fluctuations in salinity due to precipitation. The other groups (Late Spring, Benthic, and Karenia) randomly filled the spaces between the three groups. The dinoflagellate Scrippsiella spp. was dominant in the Late Spring group because of accumulation by wind-driven currents. Because a strong relationship between benthic species and wind speed was exhibited, the Benthic group comprised benthic diatoms released into the water by mixing. The Karenia group was observed only from late August 2021 to early January 2022, when higher ammonium and lower light conditions (i.e., cloudy conditions) were detected. Owing to environmental conditions, diatom growth was restricted by low light intensity, whereas that of Karenia mikimotoi increased by taking advantage of the abundant nutrients. Seasonal changes in the protist community of the Hakodate Bay can generally be explained by temperature; however, in the short term (1–2 weeks), changes were also influenced by meteorological conditions (solar radiation, wind, and precipitation).

Phylogenetic, population structure, and population demographic analyses reveal that Vicia sepium in Japan is native and not introduced

Vicia sepium (bush vetch) is a perennial legume widely distributed throughout the Eurasian continent. However, its distribution in Japan is limited to Mt. Ibuki and small parts of central and southern Hokkaido. Therefore, each Japanese V. sepium lineage has been considered to have been introduced separately from Europe. Here, we examined whether the species was introduced or not on the basis of cpDNA sequences and genome-wide SNPs from Japanese and overseas samples. Both the cpDNA haplotype network and the nuclear DNA phylogenetic tree showed that Japanese V. sepium is monophyletic. Furthermore, although the nuclear DNA phylogenetic tree also showed that each lineage is clearly monophyletic, genetic admixture of the genetic cluster dominated in the Hokkaido lineage was also detected in the Mt. Ibuki lineage. Population divergence analysis showed that the two lineages diverged during the last glacial period. The Mt. Ibuki lineage showed a sudden population decline 300–400 years ago, indicating that some anthropogenic activity might be involved, while the Hokkaido lineage showed a gradual population decline from 5000 years ago. Consequently, these two lineages show low current genetic diversity compared with overseas lineages. These results show that the Japanese V. sepium is not introduced but is native.

Gender identification of the horsehair crab, Erimacrus isenbeckii (Brandt, 1848), by image recognition with a deep neural network

Appearance-based gender identification of the horsehair crab [Erimacrus isenbeckii (Brandt, 1848)] is important for preventing indiscriminate fishing of female crabs. Although their gender is easily identified by visual observation of their abdomen because of a difference in the forms of their sex organs, most of the crabs settle with their shell side upward when placed on a floor, making visual gender identification difficult. Our objective is to use deep learning to identify the gender of the horsehair crab on the basis of images of their shell and abdomen sides. Deep learning was applied to a photograph of 60 males and 60 females captured in Funka Bay, Southern Hokkaido, Japan. The deep learning algorithms used the AlexNet, VGG-16, and ResNet-50 convolutional neural networks. The VGG-16 network achieved high accuracy. Heatmaps were enhanced near the forms of the sex organs in the abdomen side (F-1 measure: 98%). The bottom of the shell was enhanced in the heatmap of a male; by contrast, the upper part of the shell was enhanced in the heatmap of a female (F-1 measure: 95%). The image recognition of the shell side based on a deep learning algorithm enabled more precise gender identification than could be achieved by human-eye inspection.

Four-year field survey on francisellosis in Yesso scallops Mizuhopecten yessoensis cultured in southern Hokkaido, Japan

Lethal impact of the bacterium Francisella halioticida on Yesso scallops Mizuhopecten yessoensis has been experimentally demonstrated, but epidemiological information for this bacterium infection in scallop farms has been limited. Thus, the present study conducted a monthly epidemiological survey for 4 years on adult scallops ear-hung from 2017 to 2020 on a scallop farm in northern Japan. As a result, the prevalence of F. halioticida in low temperature period increased for all year groups, but any association with scallop mortality was recognized. On the other hand, in the 2017–2019 year groups, increase of the prevalence and rapid declines of scallop survival were recognized in high-temperature periods. Additionally, overall survival in these year groups were apparently lower than the 2020 year group without increase of the prevalence in high-temperature period, suggesting that infection of F. halioticida in high-temperature periods may be associated with mortality of scallops. Abscess lesions in the adductor muscle were found to be associated with F. halioticida infection, but not always formed in infected scallops. Thus, presence of abscess lesions may serve as an indicator for francisellosis, but not necessarily a definitive symptom for this disease.

Intraguild scavenging on carnivore carcasses is delayed enough to allow successful dispersal of maggots for pupation

AbstractVertebrate carcasses are a valuable resource for a wide range of organisms, although their consumption rates can vary greatly by the type of carcasses. Studies have indicated that mammalian carnivores rarely consume carnivore carcasses, particularly in the early stages of decay, and thus these carcasses may potentially serve as a reproductive resource for necrophagous arthropods such as blowflies. However, it is unknown whether delays in consumption by carnivores are sufficient for necrophagous arthropods to complete their life cycle in the carcasses. This study addressed this question by monitoring 69 raccoon carcasses using camera traps in Yakumo, southern Hokkaido, Japan, during the summer seasons of 2016–2019. The decay stages of the carcasses were categorized by carefully observing the videos captured by the camera traps, and the timing of maggot dispersion was estimated. The first visitation and first consumption of vertebrate scavengers were also modelled, and the proportion of carcasses visited or consumed by vertebrate scavengers prior to maggot dispersion was determined each year. The proportion of carcasses visited by vertebrate scavengers before maggot dispersal ranged between c. 50% in 2017 and c. 30% in other years. However, only c. 20% of carcasses in each year were consumed before maggot dispersal, and consumption was only partial. The first species to scavenge at carcasses were red foxes and raccoon dogs, with the exception of two carcasses that were first scavenged by large‐billed crows. These results suggest that while delayed visitation of carcasses may partly explain delayed consumption, active avoidance of phylogenetically related species may increase the chances of successful maggot dispersal. Our approach of using careful video observations and statistical modelling may apply to a wide range of habitats and could improve our understanding of the ecological consequences of the taboo against cannibalism.

Eruption dynamics and plumbing system of Shikabe Geyser in southern Hokkaido, Japan, revealed by field observation inside and outside the conduit

The development of observation and data analysis techniques has advanced the understanding of the plumbing systems that contribute to the eruption dynamics of geysers. However, the interrelations between the plumbing system, dynamic and thermal processes inside the conduit, and surface phenomena remain unclear. We recorded video images, pressure, and temperature inside and outside the conduit of the Shikabe Geyser, a geysering well in southern Hokkaido, Japan. Video observations revealed that numerous bubbles are generated in the deep part of the conduit immediately after the eruption begins. However, the water temperature at depth is lower than the boiling point throughout the eruption cycle. The directly measured volume of discharged water indicate that the water supply rate during the eruption phase is significantly higher than that during the recharge phase. At the Shikabe Geyser, there may be void spaces composed of cracks and porous media around the deep part of the conduit, and high-temperature water containing dissolved CO2 gas is likely supplied from the reservoir. Dissolved CO2 plays a critical role in decreasing the boiling point of water. When an eruption occurs, steam with CO2 gas nucleation and expansion owing to decompression drives the vigorous discharge of water at the vent. Simultaneously, bubbles are generated inside the cracks in the aquifer owing to decompression, which may contribute to oversupply during the eruption.

Development and characterization of EST-SSR markers from Thujopsis dolabrata var. hondae RNA-sequencing data

ABSTRACT Thujopsis dolabrata Siebold et Zucc. var. hondae Makino (hiba), an endemic conifer of Japan, is naturally distributed in northern Honshu and southern Hokkaido. The species is one of the important woody materials for buildings, such as cultural assets, temples, and shrines, because of its long-term durability and has been planted since ancient times in Aomori, Niigata, and Ishikawa Prefectures. A linkage map is an important basis for marker-assisted selection and map-based cloning of desirable genes. In this study, to increase the number of available markers for linkage mapping, we used RNA-sequencing data for two parent individuals of the mapping family in T. dolabrata var. hondae to develop expressed sequenced tag simple sequence repeat (EST-SSR) microsatellite markers. Among 126 designed primer pairs, 62 showed amplifications. Sixteen of the 62 showed clear and stable allele peaks in 32 plus-trees and were used to assess the degree of polymorphism. The number of alleles per locus varied from 2 to 16, and the observed and expected heterozygosity values varied from 0.219 to 0.906 and from 0.242 to 0.897, respectively. All 16 markers developed in this study can be used in future linkage analysis. These EST-SSR markers will be useful for population genetic studies as well as linkage analysis in T. dolabrata var. hondae.

<i>Francisella halioticida</i> Infection of Intermediately Cultured Juvenile Scallops <i>Mizuhopecten yessoensis</i> in Southern Hokkaido

Field surveys of the bacterium Francisella halioticida infection among intermediate-cultured juvenile scallops Mizuhopecten yessoensis in southern Hokkaido revealed that the mortality of juvenile scallops was positively associated with the prevalence of F. halioticida, and that both mortality and prevalence increased in September and January. ​In the intermediate culture experiments, juvenile scallops reared under high density during September and October resulted in high prevalence of F. halioticida and scallop mortality after October, while rearing density from October to March was not associated with infection and mortality, indicating that the high rearing density between September and October determined the infection of F. halioticida and scallop mortality in the following period. ​Furthermore, shell deformity rates, as a proposed index for poor physiological condition of juvenile scallops, were high in the experimental groups with higher density from September to October. ​The high rearing density in this term may have caused a decline in physiological status and, reduced resistance to francisellosis in juvenile scallops, although there is still a possibility that shell deformity was caused by francisellosis.

Low‐elevation warm‐edge Fagus crenata populations in the core of the species range are glacial relicts with high conservation value

AbstractWarm‐edge populations, that is, those usually small and isolated populations at the boundary of species maximum temperature range limit, are of particular scientific and conservation interest. This is especially the case for those that have long been geographically isolated, possibly through multiple glaciations, as they can contribute significantly to species' overall genetic diversity. However, distinguishing between glacial relict and more recently established warm‐edge populations is difficult especially in the absence of a continuous fossil record. In this study, we investigate the origin of anomalously low‐elevation warm‐edge populations of the dominant cool temperate Japanese tree Fagus crenata in the northeast Kanto (NEK) region. We sought to determine whether these populations are glacial relicts or, rather, were established via dispersal in the Holocene using chloroplast and nuclear genetic data, species distribution modeling and comparison with populations in a well‐established glacial refugia (south‐central Kyushu [SCK]) and of mid‐late Holocene age (southern Hokkaido [SH]). Whole chloroplast genome “mining” revealed a similar amount of haplotype diversity in NEK and SCK while there was no chloroplast variation in SH. Populations in NEK, particularly the lowest elevation sites, harbored unique haplotypes providing evidence for their persistence since the Last Glacial Maximum as supported by species distribution models under two of three general circulation models. NEK populations also lacked the genetic signatures of recent expansion that characterize the most northern‐edge populations in SH. We conclude that warm‐edge populations in NEK are most likely relicts of glacial refugia and should be given high priority for conservation.

Seasonal home range and habitat selection patterns of sika deer Cervus nippon in southern Hokkaido, Japan

In 1980 and 1981, eight and nine individual sika deer Cervus nippon were reintroduced in southern Hokkaido, Japan, respectively, to address population declines in this species during 1900s. As recent population growth has led to human–wildlife conflicts, this study investigated the responses of sika deer to resource availability and geomorphic factors during the summer and winter seasons in southern Hokkaido. Global positioning system‐collared data collected from 2016 to 2018 were used to assess the home range patterns and habitat selection of 14 female sika deer located in Mount Esan and Shiriuchi. The core home range size was defined using a 50% kernel density estimation that indicated a larger home range in winter than summer for all deer. Habitat selection was assessed using generalized linear mixed models. The results showed variation in habitat selection between resident deer of Mount Esan and Shiriuchi, as well as migratory deer in Shiriuchi during summer. Resident deer in Mount Esan and Shriuchi preferred areas closer to crops during summer. Interaction effects revealed that migratory deer utilized natural grassland close to forest edge habitat in Shiriuchi. By contrast, resident deer in Shiriuchi selected forest edge habitat and natural grasslands close to crops. In winter, low elevation was the most important habitat factor for all deer across the study area. Thus, sika deer habitat selection depends on resource availability in summer and topographic factors in the winter.

A comprehensive overview of studies related to the ecology and genetics of Fagus crenata Blume (Siebold's beech, Japanese beech) at the species' northernmost range limit

AbstractTemperate forest species, including Fagus crenata Blume, have been experiencing distributional shifts during the climate oscillation throughout the Holocene epoch. This review describes the distinctive context of F. crenata populations at the northern range from the perspective of past distribution shifts, future expansion predictions, biotic and abiotic interactions in population establishment, forest vegetation characteristics, and genetic diversity during the expansion process. The current northern distribution limit of F. crenata is in southern Hokkaido and Okushiri Islands. Since 1900, a dozen of northern limit hypotheses has advocated the presence of restriction factors; however, the species shows signs of expanding its habitat northward at present. The current northern limit is not determined by physiological limitations because of the fact that artificial plantations of F. crenata grow well beyond its range. Several studies regarding climate scenarios have predicted species persistence in the future. Sociological studies revealed that a decline in vegetation units is observed from the southern to the northern populations on the Oshima Peninsula, Hokkaido. Also, vegetation on Okushiri Island includes remnants of warm temperate flora indicating a physiographic constraint of the F. crenata forest on the island, reflecting a past distributional shift. Most of the current northern marginal populations were revealed to be established at the time of large forest disturbance. The genetic diversity of local populations has been lost during the northward distribution shift due to the founder effect in the colonizing process. Then, the gene flow from rearward populations has dwindled by the completion of the population establishment.

Modeling Tree Recovery in Wind-Disturbed Forests with Dense Understory Species under Climate Change

Future climate conditions will alter the frequency and intensity of typhoons. Thus, post-windthrow management, which can enhance tree recovery in wind-disturbed forests with dense understory species, is essential for sustainable forest management to adapt to climate change. This study explores management options that can recover the above-ground biomass (AGB) and tree species composition after windthrow damage even under climate change. A case study area was established in the Oshima–Hiyama National Forest in southern Hokkaido, northern Japan, which were damaged by typhoons in late August 2016. We incorporated the understory species Sasa kurilensis as understory vegetation into the LANDIS-II Net Ecosystem Carbon and Nitrogen Succession extension v6.3 model to simulate the outcome of tree establishment under climate change. AGB recovery up to the year 2100 at 1,753 damaged grid cells was simulated for the Intergovernmental Panel on Climate Change representative concentration pathway (RCP) 2.6 and 8.5 scenarios. Different post-windthrow management cases were designed by varying the treatment of fallen trees and the types of trees planted. The results demonstrated that salvage logging and planting successfully recovered the AGB by 2050 at the landscape scale regardless of the climate change scenario, whereas leaving fallen trees in the damaged site or salvage logging only did not facilitate the recovery of AGB. Leaving fallen trees in damaged grid cells as ecological legacies recovered the AGB only in damaged grid cells with a sufficient number of advanced seedlings of adequate types of species irrespective of the climate change scenario. The decreasing water equivalent of snowpack in the RCP scenarios caused Sasa kurilensis mortality and promoted the recovery of AGB of trees. The dominant species recovered in natural forests, which experienced either salvage logging or leaving trees in the damaged site, varied among climate change scenarios. The warmer climate condition facilitated the recovery of Fagus crenata by 2100. These results can help designing a robust forest recovery even in uncertain future climate.

Processing it all: Starch residues on Jomon Period ground stone from southern Hokkaido, Japan

For the Jomon Period, ground stone technology related to processing activities, such as handstones and querns, are commonly associated with plant foods. In many cases, these tools are considered to be an indicator for the consumption of tree nuts. In this study, ground stone artifacts from 15 sites across southern Hokkaido were analyzed for starchy residues to examine the relationship between grinding tools and economic plant taxa in Jomon daily practices. Overall, 24 of the 76 artifacts examined here had observable starch grains, meaning a large percentage of tools did not appear to have been in contact with starchy plants. The starch types commonly found in underground storage organs (USOs) were the most prominent component of the observed grains, indicating the use of yams, lilies, and other roots or tubers. The evidence for Poaceae grasses, legumes, and nuts is less clear, but present alongside the USO starch granules. These results suggest that grinding implements were not limited to processing plant foods, and would not have been restricted to specific resources, such as nuts.

Rheological properties of halloysite soil slurry: a case study of weathered tephra involved in a shallow landslide triggered by the 2018 Eastern Iburi earthquake in Hokkaido, Japan

The 6.7 Mw Eastern Iburi earthquake of 6 September 2018 triggered destructive landslides in southern Hokkaido, Japan, many of which were characterized by the flow-like downslope movement of volcanic soils formed from weathered tephra containing halloysite. This study aims to elucidate the mechanism of landslide generation through rheological characterization of halloysite soil slurries. The examined slurries were prepared from either oven-dried or moist soil. Both slurries showed a power-law correlation between measured yield stress and moisture content. However, at a given water content, slurry made from dried soil showed stresses that are one-to-two orders of magnitude lower than those of slurry made from moist soil. Compared with the measurements for the slurry of dried soil, those for the slurry of moist soil are closer to prior numerical modeling of a specific landslide, indicating that the soils involved were moist. The yield stress also varied with slurry pH, generally increasing with decreasing pH, which is in part explained by the DLVO force model based on the electrical double layer and van der Waals forces between the colloidal particles. The pH dependence is more prominent in the slurry of moist soil, and thus the mechanical state of the slope appears to vary significantly with rainfall-induced changes in subsurface chemistry. Dynamic viscoelasticity measurement indicated that both initially solid-like slurries can become fluid under an applied oscillatory strain of 0.5 to 10 Hz: the susceptibility to fluidization depends greatly on water content and frequency. The ground motion during the earthquake easily fluidized the slurry, indicating this was a factor contributing to the observed flow-like landslides.Graphical

6. Recent studies on kelp cultivation in southern Hokkaido

6. Recent studies on kelp cultivation in southern Hokkaido

Late Holocene centennial to millennial-scale variability in lower trophic level productivity off southern Hokkaido, Japan, and its response to dissolved iron-replete Coastal Oyashio dynamics

AbstractLittle is known about the dynamics of marine food chains spanning primary to higher trophic levels on centennial and longer timescales, especially where the supply of dissolved iron limits primary productivity. To elucidate the long-term dynamics of biological productivity in the Coastal Oyashio (CO), which is a major pathway for transporting dissolved iron into the western North Pacific from winter to spring, we reconstructed the lower trophic level productivity over the last 3000 years in the CO. Our results demonstrate that the concentrations and mass accumulation rates of both Chl-a (chlorophyll a and its derivatives) and biogenic opal used as proxies of primary productivity, and steryl chlorin esters (SCEs) used as that of zooplankton productivity, show a millennial-scale increasing trend and centennial-scale variability beginning ca. AD 400. SCEs were positively correlated with Chl-a, indicating that changes in zooplankton productivity were induced by bottom-up control of primary productivity. The Chl-a and SCEs showed synchronous centennial-scale patterns with a relative abundance of sea-ice-associated diatom species transported by CO, and with a ventilation index in the Okhotsk Sea Intermediate Water. This synchronous pattern indicates that lower trophic-level productivity during the spring bloom responded to the intensity of iron-replete CO.

Plan of hydrogen supply chain in Hakodate using offshore wind power in southern Hokkaido

Plan of hydrogen supply chain in Hakodate using offshore wind power in southern Hokkaido

Issues and Status of Biologics Indicated for Psoriasis in Southern Hokkaido

Issues and Status of Biologics Indicated for Psoriasis in Southern Hokkaido

Damage Transition and Timing of Insecticide Application for Resseliella soya in Soybean in Southern Hokkaido

Damage Transition and Timing of Insecticide Application for <i>Resseliella soya</i> in Soybean in Southern Hokkaido

TECTONIC STRESS FIELD AT INTERMEDIATE DEPTHS OF THE SOUTHERN FLANK OF THE KURIL-KAMCHATKA SEISMIC ZONE

The study has been done on the orientation of the principal axes of tectonic stress field at intermediate depths of earthquakes of the southern flank of the Kuril-Kamchatka subduction system separately for the upper and lower double seismic focal zones. Use has been made of the NIED and GlobalCMT catalogue data. The computation-based results are presented on schemes of the stressed state of the investigated areas and in tables. In the context of the southern Kuril Islands, evidence has been provided for predominance of the maximum compressive stresses along the slab plane in the upper layer and minimal compressive stresses (deviation extension) in the lower layer. However, the principal axes of maximum and minimum compression are displaced in direction relative to the slab dip: by 30–40° counterclockwise for the compression axis in the upper layer, which coincides with the direction of plate movement, and clockwise for the extension axis in the lower layer. This might be caused by the right-lateral strike-slip component of the Pacific Plate subduction. Unlike the general trend, the orientation of the principal axes of the stress field beneath the central Hokkaido-related segments in the upper layer is almost identical to that in the lower layer. There have also been found the segments exposed to shear stress, with the most extensive located opposite the northern Kunashir Island and beneath the southern Hokkaido Island. The results obtained for major large groups of clusters show good accordance with those published by other authors. The discrepancies relate primarily to small groups of isolated clusters showing local stress field heterogeneities.