The spatiotemporal variability of suspended particulate matter (SPM) in coastal seas is governed by complex interactions among such as tides, waves, riverine inputs, and other physical processes. This study investigates the physical transport mechanisms and source attribution of SPM in the Seto Inland Sea (SIS) using a three-dimensional hydrodynamic model coupled with a multi-layer sediment bed module. We conducted sensitivity experiments to quantify the relative contributions of riverine and sedimentary sources and found that sedimentary source dominates the SPM concentration throughout the year, while riverine source contributes relatively little to the SPM concentration but exhibit a distinct increase in the estuary areas during summer when the river discharges are large. The SPM in the surface layer is mainly composed of fine particles from riverine source, whereas the SPM in the bottom layer is predominantly derived from particles that resuspend from sedimentary source. In this semi-enclosed sea, the transport of riverine SPM is initially driven by the freshwater plume. However, due to gravitational settling, SPM gradually sinks from the surface layer and is entrained by mid-depth anticyclonic eddy, which ultimately redistributes the particles, dictating the widespread deposition and retention of riverine SPM across the bay basin. Furthermore, wave-induced bed shear stress enhances resuspension during winter along downwind southern coast.
The western Seto Inland Sea (WSIS) is surrounded by major industrial zones in Japan and receives substantial inputs of pollutants. However, per- and polyfluoroalkyl substances (PFAS) contamination in the WSIS remains poorly characterized. In this study, we investigated the occurrence and potential sources of PFAS in seawater samples from the WSIS, and conducted a preliminary ecological risk assessment. A total of 24 PFAS were identified and quantified, with total concentrations (Σ24PFAS) ranging from 519 to 916 ng/L. Trifluoroacetic acid (TFA) was the predominant compound (mean: 680 ± 156 ng/L), accounting for 96.9% of Σ24PFAS. After excluding TFA, perfluoroalkyl sulfonic acids (PFSAs) accounted for more than half of the remaining PFAS. Except for TFA, the remaining PFAS generally exhibited a spatial pattern suggestive of localized point-source inputs, with higher concentrations nearshore waters than in offshore waters. Principal component analysis-multiple linear regression (PCA-MLR) suggested that non-TFA PFAS were mainly associated with electroplating-related and surfactant-related sources, whereas correlation patterns and spatial distributions suggested that TFA was primarily associated with the atmospheric degradation of hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs). The results further suggest that the transition from legacy PFAS to emerging alternatives remains incomplete. Ecological risk assessment based on risk quotients (RQs) indicated that the estimated risk posed by TFA varied substantially depending on the toxicity data used. Under the worst-case scenario, TFA posed a high risk (RQ > 1), whereas perfluorooctane sulfonate (PFOS) exhibited a low risk (RQ < 0.01). These findings underscore the need for multi-compartment and seasonal monitoring in the WSIS, inclusion of TFA monitoring programs across other marine regions, and expanded toxicity testing in marine organisms.
Using James Webb Space Telescope /NIRCam data over a 0.28 deg(2 )area from COSMOS-Web survey, together with Hubble Space Telescope /Advanced Camera for Surveys data, we investigate early-type fraction of massive galaxies with M-star > 10(10.5) M-circle dot at 0.2 < z < 2.0, and explore the formation of their early-type morphology. We measure concentration index C (= R-80 /R-20 ) and asymmetry index A , and select early-type galaxies with C > C-n=2.5 and A(cor) < 0 . 2 . Here, C-n=2.5 is the concentration expected for a S & eacute;rsic profile with n = 2 . 5 under the spatial resolution and depth of the data, and A(cor) is the asymmetry corrected for resolution effects. The fraction of early-type galaxies with M-star > 10(11) M-circle dot (= 10(10.5)-10(11) M-circle dot) decreases with increasing redshift from similar to 70 per cent (similar to 40-60 per cent) at z similar to 0.3 to similar to 20-25 per cent (similar to 15-25 per cent) at z similar to 1.8. We also examine the evolution of their R-20 and R-80 , which enclose 20 per cent and 80 per cent of the total flux of the galaxy, respectively. The median R-80 shows strong mass dependence and significant redshift evolution, whereas the median R-20 shows little dependence on either stellar mass or redshift. In contrast, morphological differences are more pronounced in R-20 than in R-80 : the median R 20 of early-type galaxies is smaller than that of late-type and irregular galaxies by 0.25-0.45 and 0.3-0.6 dex, respectively. The median SSFR (specific star formation rate) of sample galaxies strongly correlates with R-20 , and early-type galaxies have lower SSFRs by similar to 1 dex. We further find that early-type galaxies at z greater than or similar to 1 . 3 have younger mass-weighted stellar ages of t(mw) less than or similar to 2 Gyr than late-type and irregular ones. Their SSFRs, t(mw), and morphological properties suggest that these high-z early-type galaxies experienced rapid formation of a dense stellar core through starburst, followed by quenching of star formation, and subsequently resumed star formation similar to 1-2 Gyr later.
Marine heatwaves (MHWs) are characterized by extremely high water temperatures persisting for at least several consecutive days, and their severe ecological and economic impacts have been increasing. In this study, the impacts of interannual-to-decadal sea surface temperature (SST) variability on MHWs in 10 areas around Japan were evaluated using daily satellite-based SST data from 1983 to 2022. To evaluate these impacts, MHWs were detected using SST without the interannual-to-decadal variability, while keeping the threshold for the MHW detection unchanged. As a result, the annual MHW days averaged for the 10 areas were reduced by 53
