Over recent decades, the Da Rang estuary in South-Central Vietnam has experienced significant morphological transformations. This study uses multi-temporal Landsat TM and OLI datasets to extract historical shoreline positions by coupling the Automated Water Extraction Index (AWEI) with unsupervised K-means clustering. Shoreline dynamics were quantified utilizing the EPR4Q plugin within QGIS. The findings demonstrate a pronounced seasonal cyclicity: the Southwest monsoon induces widespread accretion (averaging +18.9 m north and +16.3 m south), whereas the Northeast monsoon triggers severe erosion (averaging –14.5 m north and –12.0 m south). These seasonal patterns are driven by the dynamic interplay between monsoon-induced wave energy and riverine discharge. Long-term trajectories assessed via Linear Regression Rate (LRR) and End Point Rate (EPR) indicators indicate an overall progradation trend, with mean accretion rates of + 0.64 m/year and + 0.52 m/year for the northern and southern banks, respectively. Conversely, localized erosion hotspots along the southern spit closely align with the destructive wave impacts of Typhoon Damrey. Volumetric assessments of fluvial sand bars from 1989 to 2024 reveal a progressive depletion of downstream reserves. Total sand volume contracted from 89.1×106 m3 in 1989 to 82.6×106 m3 in 2024, yielding an annual loss rate of 185,700 m3. This sediment deficit and subsequent loss of alluvial supply are driven by the cumulative pressures of upstream damming and localized sand mining for urban development. Consequently, these insights highlight the critical need for integrated watershed management and regulated sediment extraction frameworks to counteract long-term coastal vulnerability.
The Tongyeong coastal region is a major aquaculture area in Korea, yet the relative importance of seasonal environmental variability and local spatial heterogeneity in structuring phytoplankton communities remains poorly understood. We conducted surveys from June 2016 to May 2017 across three contrasting zones, a plume zone (ZONE I), an oyster-farming zone (ZONE II), and a semi-enclosed fish-farming zone (ZONE III) to evaluate the relative importance of seasonal and spatial variability. Hydrographic conditions, nutrients, chlorophyll-a (Chl. a), and phytoplankton abundance varied significantly among the seasons (p < 0.05). Seasonal hydrographic conditions were characterized by elevated temperatures and stratification in summer, reduced salinity and nutrient enrichment associated with rainfall and typhoon-driven freshwater inputs in early autumn, and nutrient replenishment through cooling-induced water-column mixing in winter. Phytoplankton communities exhibited clear seasonal succession, with dinoflagellates Prorocentrum spp. dominating during summer while Margalefidinium polykrikoides occurred at low abundance, followed by diatoms Chaetoceros spp., Skeletonema spp., and Eucampia zodiacus during autumn, winter, and spring. Multivariate analyses revealed significant seasonal differences in phytoplankton community composition (PERMANOVA, p < 0.001), with seasonal variation accounting for a substantially greater proportion of community variability than zonal variation. Although localized environmental differences occurred among zones, including a significant variation in bottom-water NH4+ and dissolved oxygen, most environmental variables and Chl. a did not show significant zonal differences. Seasonal patterns were more pronounced than zonal patterns at the spatial scale examined, highlighting the importance of seasonal hydrographic conditions and nutrient availability in shaping phytoplankton succession in the Tongyeong coastal region
Ferromanganese (Fe–Mn) crusts are important archives of long-term oceanographic and redox conditions, but post-depositional phosphatization can alter their primary hydrogenetic geochemical signatures. This study investigates mineralogical and geochemical variations among representative stratigraphic layers in Fe–Mn crust cores recovered from western Pacific seamounts to better understand the effects of phosphatization on crust evolution. The crusts were divided into four layers (L1–L4) to compare non-phosphatized (L1–L2) and phosphatized (L3–L4) intervals and evaluate the effects of phosphatization on primary geochemical records. The crusts show predominantly hydrogenetic characteristics, including vernadite-dominated mineralogy, low Mn/Fe ratios, and seawater-like REY signatures. Phosphatized layers contain carbonate fluorapatite (CFA) and are enriched in REY, P, and Ca. Bulk REY concentrations show strong positive correlations with P and Ca, indicating incorporation into CFA during the phosphatization process. However, several individual REEs, including La, Nd, Sm, Gd, and Lu, are relatively enriched in the non-phosphatized layers, suggesting decoupling between bulk REY enrichment and primary hydrogenetic REE signatures. Variations in Ce anomalies are consistent with REY systematics being influenced not only by ambient redox conditions but also by post-depositional phosphatization. Within the context of previously published regional chronostratigraphic models, these results suggest a two-stage evolutionary history involving hydrogenetic precipitation under oxic seawater conditions followed by phosphatization under relatively suboxic diagenetic conditions. These findings provide new insights into the layer-specific mineralogical and geochemical evolution of hydrogenetic Fe–Mn crusts in the western Pacific and emphasize that REY-based paleo-redox interpretations should explicitly consider the effects of phosphatization and associated local redox variability.
Ship hull biofouling is an important vector for the introduction and spread of non-indigenous species (NIS) in marine ecosystems, yet hull-fouling assemblages in Korean ports remain poorly characterized. This study investigated marine fouling communities attached to nine ships to evaluate their role as vectors of non-indigenous species (NIS) and to analyze spatial heterogeneity in attachment locations. Surveys (Qualitative and quantitative) were conducted from 2021 to 2024 on structurally complex areas of the hull (bow and propeller) and relatively flat areas (hull and seabed). As a result, a total of 28 attached species were identified, including 13 NIS. Two barnacle species (Megabalanus coccopoma and Tetraclita rubescens) were recorded for the first time in Korean ports, and their taxonomic identities were confirmed through molecular analyses. Fouling assemblages differed among attachment locations, with structurally complex areas supporting higher species richness and density than flatter surfaces. The shell morphology of dominant barnacle species also varied with attachment location, suggesting responses to local hydrodynamic conditions. The results of this study indicate that ships contribute to the introduction of NIS into Korean coastal waters, and that monitoring of complex structures such as hull thrusters is necessary.
Zeaxanthin is a high-value xanthophyll carotenoid with broad applications in the pharmaceutical and nutraceutical industries, owing to its potent antioxidant properties and its efficacy in preventing age-related macular degeneration. In this study, we systematically optimized the culture conditions and medium composition for Lutimonas zeaxanthinifaciens YSD2104T, a recently isolated marine bacterium, to enhance biomass and zeaxanthin production. Initial optimization via the one-factor-at-a-time (OFAT) approach established the culture conditions at 30 °C, pH 7.0, and 2
