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An explosive volcanic eruption occurred in the Ogasawara Islands on 13–15 August 2021, bringing unprecedented amounts of floating pumice to the coast of Okinawa Island in the Ryukyu Archipelago, 1300 km west of the volcano, approximately 2 months later. The coast of Okinawa Island, especially along the northern part, is home to many typical subtropical seascapes, including coral reefs and mangrove forests, so the possible impact of the large amount of pumice is attracting attention. Here, we report early evidence of ecosystem changes as a result of large-scale pumice stranding on coastal beaches, in estuaries and mangrove forests and passage across fringing coral reefs. Massive pumice drifts are major obstacles to fishing activities and ship traffic, but short and long-term changes in coastal ecosystems can also occur. The phenomena observed on Okinawa Island can be a preview of coastal impacts for the Kyushu, Shikoku, Honshu Islands, where pumice has subsequently washed ashore.

Effective conservation of patchy marine habitats, such as those around islands, requires an understanding of ecological networks maintained through larval dispersal. In the Nansei Islands of Japan, previous studies suggested that the genetic connectivity of reef-building corals was independent of geographic distance along this near-linear island chain, likely due to the Kuroshio Current. However, this has not yet been confirmed using an integrated approach combining population genetics and physical oceanography. Here, we conducted biophysical modelling of larval dispersal and population genomic analysis across the Nansei Islands for a major reef-building coral, Acropora digitifera . Modelled larval dispersal networks showed that dispersal from the southern to northern ends of the archipelago occurred more than six times as frequently as dispersal to the central islands. Genetic differentiation between sites showed a stronger association with modelled dispersal ( R  = -0.44) than with geographic distance ( R  = 0.26). Kume Island served as a key stepping stone in the larval dispersal network, despite being outside the area’s national parks. This study provides fundamental insights into the dispersal pathway connecting distant locations along the Kuroshio Current—which we refer to as the ‘Kuroshio Corridor’—a concept that is crucial for connectivity-based conservation.

Environmental conservation becomes more effective when ecological connectivity between patchy habitats is maintained. The coral reef ecosystems of the Yaeyama and Miyako Islands (YAE) in Japan are highly biodiverse and culturally significant but have deteriorated over recent decades. Although coral larvae are expected to be supplied to YAE via the Kuroshio Current from regions outside Japan, previous population genetic and biophysical studies have focused exclusively on connectivity among Japanese coral populations. In this study, we conducted biophysical modelling of 30 years of larval dispersal across the Northwest Pacific using Lagrangian particle tracking, aiming to identify major sources of coral larvae to YAE. The model showed that 86% of virtual larvae reaching YAE represented self‐recruitment. Of the externally sourced virtual larvae, ~70% came from the Philippines, ~20% from Taiwan and only a few percent from Japan. The Kuroshio Current acted as a corridor facilitating dispersal from the northeast Philippines and eastern Taiwan, while simultaneously serving as a barrier to retrograde or transverse dispersal from northern Taiwan and Japan. These findings suggest that most externally supplied larvae to YAE originate from regions outside Japan, upstream of the Kuroshio Current. This study highlights that transboundary collaboration is crucial to understanding and maintaining connectivity between coral reef ecosystems along ocean currents. We conducted biophysical modelling of 30 years of larval dispersal across the Northwest Pacific to identify major sources of coral larvae to the Yaeyama and Miyako Islands (YAE) in Japan. Of the externally sourced larvae reaching YAE, approximately 70% came from the Philippines, around 20% from Taiwan and only a few percent from Japan. Our findings highlight that transboundary collaboration is crucial to understanding and maintaining connectivity between coral reef ecosystems along the Kuroshio Current.

We examined the potential of environmental DNA (eDNA) for identifying tsunami deposits in the geological record using lake-bottom sediments in the Tohoku region, Japan. The presence of eDNA from marine organisms in a lacustrine event deposit provides very strong evidence that the deposit was formed by an influx of water from the ocean. The diverse DNA assemblage in the deposit formed by the 2011 Tohoku-oki tsunami included DNA of marine origin indicating that eDNA has potential as an identifying proxy for tsunami deposits. Subsequently, we examined the applicability of eDNA for recognizing paleo-tsunami events using the deposits formed by the 869 CE Jogan tsunami and a prehistoric event (2400–2900 cal year BP). The taxa detected in the tsunami deposits were markedly different from those of the background sediments. Many taxa that were represented in the Jogan tsunami deposit were also detected in the layer immediately above the tsunami deposit. This layer was indistinguishable from the overlying peat by visual observation, but the eDNA results suggest that it is likely to be a muddy tsunami deposit. The results of this study indicate that eDNA has the potential to elucidate the origin of event deposits that have been difficult to identify.

Birgus latro (coconut crab) is an edible crustacean that has experienced serious overharvesting throughout its whole habitat range; however, the negative effects of overharvesting on the genetic diversity within B. latro populations have not been elucidated. Here, we report sex ratio, body size, and genetic diversity in populations of B. latro in the Ryukyu Islands where large-male–biased overharvesting of B. latro has continued. In 2 of the study populations, the sex ratio was significantly skewed toward females, and in all of the study populations large males were rare, which we attributed to sex- and size-biased overharvesting. We found no differences in genetic diversity between small and large individuals, suggesting that genetic diversity, even among the large (i.e., old) individuals, may have had already been negatively affected by overharvesting. Continued monitoring of sex ratio, body size and genetic diversity are needed for effective management of the study populations.

Pacific crown-of-thorns starfish (Acanthaster cf. solaris) are known to be widely distributed, and previous studies (showing limited genetic structure) suggest that there are high levels of connectivity at regional scales. It is possible, however, that methods used in previous studies (e.g., microsatellites) did not effectively resolve genetic differentiation and structure for crown-of-thorns starfish. This study examined patterns of genetic structure for populations of the A. cf. solaris in the Ryukyu Archipelago and at Miyazaki, Japan, using restriction-site-associated DNA sequencing (RADseq) analysis, to identify genome-wide single nucleotide polymorphism (SNP) loci to examine genetic diversity and gene flow of CoTS populations. We obtained 186 biallelic SNPs completely shared among 33 individuals by utilizing the published genome sequence of CoTS. Population genomic analysis with biallelic SNPs confirmed that there is limited genetic differentiation and seemingly strong connectivity and gene flow among CoTS populations in the Ryukyu Archipelago and at Miyazaki, Japan. Our findings likely reflect the rapid range expansion of CoTS through southern Japan or panmixia facilitated by the northward flowing Kuroshio Current.

In 2016, global temperatures were the highest on record, and mass coral bleaching occurred world-wide. However, around Sesoko Island, Okinawa, southwestern Japan, the heat stress assessed by degree heating week (DHW) based on local temperature measurements was moderate in 2016; in 1998, DHW was three times higher than in 2016 (10.6 vs. 3.3 in September in respective years). On a reef flat of Sesoko Island where the effect of severe coral bleaching on coral assemblage was monitored in 1998, significant coral bleaching occurred in 2016. Bleaching of the heat stress sensitive Acropora corals began in July 2016 on the reef flat as seawater temperature rose. We observed the bleaching and post-bleaching mortality status of individual colonies of Acropora spp. in 2016 in fixed plots on the reef flat. In total, 123 Acropora colonies were followed for six months after seawater temperature became normal by multiple surveys. At the beginning of September 2016, 99.2% of colonies, were either completely (92.7%) or partially (6.5%) bleached. Of those, the dominant species or species groups were A. gemmifera ( Ag ), A. digitifera ( Ad ), and tabular Acropora (t A ). For all Acropora colonies, the overall whole and partial mortality was 41.5% and 11.4%, respectively. Whole mortality rate differed significantly among species; 72.5%, 17.9%, and 27.8% in Ag , Ad , and t A , respectively. Mortality rates at the end of the surveys were similar in smaller (≤10 cm in diameter) and larger Ag , but the former suffered mortality earlier than the latter. Higher survival of smaller colonies was observed only in t A (100%), which may be associated with large morphological differences between smaller and larger colonies. Some of the dominant Acropora colonies had survived without partial mortality including 15.0% survival of the most vulnerable Ag at the end of the surveys. These results suggest that moderate heat stress may have a potential for selecting heat-tolerant genotypes. A longer period of mortality lasting for six months, was observed in Ag in addition to immediate whole mortality after bleaching, due to the continuous loss of living tissue by partial mortality. This highlights the need for multiple surveys at least during several months to accurately assess the impact of thermal stress event to corals. In contrast to DHW based on local measurements, DHW obtained from satellite data were similar between 1998 and 2016. Although satellite-based measurement of sea surface temperature is very useful to reveal variations in heat stress at a large spatial scale, temperature should be measured on site when variations at smaller spatial scales are of interest.

BackgroundIn patients with chronic kidney disease (CKD), dysbiosis in the gastrointestinal microbiome is thought to be associated with increased production of uremic toxins, such as indoxyl sulfate (IS) and p-cresyl sulfate (PCS). Sucroferric oxyhydroxide (SFO), an iron-based phosphate binder, may affect the gastrointestinal microbiome and the production of uremic toxins. We aimed to examine whether SFO administration affected distribution of gastrointestinal microbiome and serum uremic toxin levels in CKD patients undergoing hemodialysis.MethodsIn this single-center, open-label, interventional study, 18 maintenance hemodialysis patients with hyperphosphatemia were prescribed with SFO. We collected serum samples before and after 3 months of administration, and serum levels of IS and PCS were measured. A control group of 20 hemodialysis patients without SFO was evaluated. We evaluated gastrointestinal microbiome of patients pre- and post-SFO administration by 16S rDNA sequencing and bioinformatics analysis.ResultsSerum IS and PCS levels were significantly elevated after administration of SFO (IS before 2.52 ± 1.60 mg/dl vs. after 3.13 ± 1.51 mg/dl, P = 0.008; PCS before 2.32 ± 2.44 mg/dl vs. after 3.45 ± 2.11 mg/dl, P = 0.002), while serum IS and PCS levels did not change in the control group. Microbiome analysis in the SFO group showed no significant change in diversity and major components in phylum, class, order, family, gene, and species.ConclusionAdministration of SFO increased the serum levels of IS and PCS with no change of major components of gastrointestinal microbiome.

The Japanese freshwater crab Geothelphusa dehaani species complex is distributed widely across the Japanese Archipelago. Despite its suggested high genetic and morphological diversity, key aspects such as nuclear DNA (nuDNA) population structure and relationship between body color patterns and genetic populations remain unclear. To address these gaps, this study analyzed genome-wide single nucleotide polymorphisms (SNPs) in nuDNA and mitochondrial DNA (mtDNA) cytochrome oxidase subunit 1 (COI) markers in samples from Hokkaido to the Tokara Islands, Japan. ADMIXTURE analysis identified five distinct populations with significant geographic boundaries. These populations exhibited unique geographical patterns, spanning across islands and enclave distribution, indicating that G . dehaani populations have been shaped by complex factors, including sea level changes and volcanic activity. Regional body color variations partially aligned with SNP clades. Further, combining body color with collection locality data could help identify the specimen populations. Contrasting patterns between mtDNA and nuDNA suggest historical gene flow and introgression, emphasizing the need for caution when interpreting earlier phylogenetic studies based on combined mtDNA and nuDNA sequences. Our findings provide a foundational baseline for future research into the taxonomy, phylogeny, and population dynamics of the G . dehaani species complex, advancing our understanding of its evolutionary history.

Drug screening tests are mandatory in the search for drugs in forensic biological samples, and immunological methods and mass spectrometry (e.g., gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry) are commonly used for that purpose. However, these methods have some drawbacks, and developing new screening methods is required. In this study, we develop a rapid-fire drug screening method by probe electrospray ionization tandem mass spectrometry (PESI-MS/MS), which is an ambient ionization mass spectrometry method, for human urine, named RaDPi-U. RaDPi-U is carried out in three steps: (1) mixing urine with internal standard (IS) solution and ethanol, followed by vortexing; (2) pipetting the mixture onto a sample plate for PESI; and (3) rapid-fire analysis by PESI-MS/MS. RaDPi-U targets 40 forensically important drugs, which include illegal drugs, hypnotics, and psychoactive substances. The analytical results were obtained within 3 min because of the above-mentioned simple workflow of RaDPi-U. The calibration curves of each analyte were constructed using the IS method, and they were quantitatively valid, resulting in good linearity (0.972–0.999) with a satisfactory lower limit of detection and lower limit of quantitation (0.01–7.1 ng/mL and 0.02–21 ng/mL, respectively). Further, both trueness and precisions were 28% or less, demonstrating the high reliability and repeatability of the method. Finally, we applied RaDPi-U to three postmortem urine specimens and successfully detected different drugs in each urine sample. The practicality of the method is proven, and RaDPi-U will be a strong tool as a rapid-fire drug screening method not only in forensic toxicology but also in clinical toxicology.