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Spatio-Temporal Projections of the Distribution of the Canopy-Forming Algae Sargassum in the Western North Pacific Under Climate Change Scenarios Using the MAXENT Model
No full textSargassum, canopy-forming algae, play a key role in coastal ecosystems by supporting marine organisms. This study projects how the habitats of four Sargassum species in the western North Pacific may change in the present and future (2030s, 2060s, and 2090s) under three climate scenarios (SSP1-1.9, SSP2-4.5, and SSP5-8.5). Seawater temperature and current velocity were major environmental factors influencing their distribution. Under the low-emission scenario (SSP1-1.9), three species (S. horneri, S. macrocarpum, and S. patens) are expected to maintain suitable habitats until the 2090s, whereas, under higher emissions, their habitats may shrink in the south and shift northward. Conversely, S. piluliferum may expand its range under SSP5-8.5. By the 2090s, the four Sargassum species are projected to shift northward from 0.8° N to 3.8° N. Although some marine protected areas overlap with these present and future suitable habitats, more conservation efforts are needed due to climate change.11Nsciescopu
A new aegisthid copepod (Copepoda, Harpacticoida, Aegisthidae) from the Northwest Pacific
No full textA new species of aegisthid harpacticoids was collected at a depth of 1,200 m in the Northwest Pacific Ocean with a Multiple Opening/Closing Net and Environmental Sampling System (MOCNESS) (200 μm mesh). The new species is placed in the genus Aegisthus based on the following characteristics: the P1-bearing somite not fused to cephalosome, the absent of long spinous processes on the cephalosome, the absent of a mandibular palp, the absent of an outer basal seta on P2, the absent of an inner seta on uniramous P5 in female, and the extreme elongation of caudal rami, which are more than twice the length of the body. The new aegisthid species closely resembles to A. mucronatus, sharing an elongated rostrum and a hook-like structure on the first segment of antennule. However, the new species can be distinguished by the seven-segmented antennule, a large spinous process on inner distal margin of the second segment of antennule, three setae on second and third endites of the maxilla, two proximal setae and two distal enlarged spines on the coxa of maxilliped, the relatively long proximal spine on P1 exp-2, and the relatively long apical seta on P5.2
Application of Neural Networks for Estimating Absorption Coefficients Using In-situ Data from Korean Coastal Waters
No full textThe accurate estimation of optical absorption coefficients in coastal waters is essential for understanding inherent optical properties. This study applies deep neural networks to predict ap(443nm), ad(443nm), and adom(443nm) using remote sensing reflectance (Rrs) at multiple wavelengths (380, 412, 443, 490, 510, 555, 620, 660, 680, 709, 745, 865nm) as input data. The dataset consists of 99 in-situ measurements collected from Korean coastal waters between 2020 and 2023. Data augmentation was performed using Gaussian noise addition and random scaling techniques to improve model generalization. The dataset was divided into training and test sets, and separate neural network models were trained for each absorption parameter. The models' performances were evaluated using R² (coefficient of determination) and RMSE (Root Mean Square Error). The models demonstrated high predictive accuracy for ap(443nm) (R²=0.9607, RMSE=0.1893) and ad(443nm) (R²=0.9867, RMSE=0.0697), indicating that neural networks effectively capture bio-optical relationships. However, the adom(443nm) model exhibited lower performance (R²=0.7148, RMSE=0.0187), suggesting potential challenges in modeling dissolved organic matter absorption due to environmental variability. These findings highlight the potential of deep neural networks in estimating absorption coefficients, contributing to ocean color remote sensing in Korean coastal waters. Future research will focus on refining data augmentation techniques, integrating additional in-situ data, and incorporating regional coastal characteristics to develop location-specific models. These improvements aim to enhance model robustness and applicability for diverse coastal environments.1
Heterogeneous density structure of seamounts: a sign count analysis of gravity anomalies
No full textAccurate characterization of seamount density structure is fundamental to modeling lithospheric flexure and understanding oceanic volcano evolution. Traditional gravity modeling approaches typically employ uniform density assumptions, which fail to capture the internal heterogeneity consistently revealed by seismic studies. We introduce sign count analysis—a novel method examining the spatial distribution of misfit polarities between observed and predicted gravity anomalies—to better constrain seamount density structure. While conventional root-mean-square (RMS) minimization produces compromise density values, sign count analysis identifies distinct transitions in residual polarity patterns that reveal edifice density independently from core contributions. We demonstrate this methodology through application to both synthetic models with known density contrasts and to Jasper Seamount in the eastern Pacific Ocean. For Jasper Seamount, sign count analysis yields an edifice density of 2250 kg m−3, significantly lower than the RMS-derived value (2475 kg m−3) and previous estimates (2380 kg m⁻3). When combined with a core density of 2750 kg m⁻3, our two-component model achieves closed agreement with observed gravity data. The discrepancy between RMS-optimal and sign count-derived densities provides quantitative evidence for significant density heterogeneity within seamounts, with important implications for flexural calculations and volcanic evolution models. This approach offers improved characterization of seamount internal structure applicable to submarine volcanoes worldwide, contributing to our understanding of oceanic lithosphere evolution and intraplate volcanism processes.11Nsciescopuskc
Interannual variability in the reproductive cycle of Manila clam (Ruditapes philippinarum) influenced by environmental and parasitic factors on the west coast of Korea
No full textExtensive studies have shown that geographic variation, primarily driven by environmental factors, affects the reproductive cycle duration, gametogenesis, and spawning periods of the Manila clam, Ruditapes philippinarum. From February 2008 to December 2010, we monitored the annual reproductive cycle of Manila clams on a tidal flat in Garorim Bay, located on Korea's west coast. In adult males, spermatogenesis began between December and February, reaching a peak (90 %) by March and April. Partial spawning in males occurred from May to July, coinciding with seawater temperatures rising from 11.2 to 20.0 °C. In females, oogenesis commenced between January and February, while spawning began in June, reaching a peak activity level of 36 %.A brief 3-month spawning period was recorded in 2009, while in other years, spawning extended for 4–5 months. The condition index (CI) of the clams ranged from 78 to 139, and fluctuations in CI during the spawning season indicated multiple spawning peaks in males, while females exhibited a single peak. The intensity of the protozoan parasite Perkinsus olseni infection ranged from 0 to 1.4x105 cells per gram of gill tissue, reflecting a low infection level compared to clams from other tidal flats on the west coast. Overall, variations in reproductive stages and CI at the study site appeared to be primarily influenced by seasonal fluctuations in water temperature and food availability, with negligible impact from parasite infection.11Nsciescopu
Isotope tracking of anthropogenic Cu and Zn in urbanized coastal environments: A review
No full textCopper (Cu) and zinc (Zn) are common trace metal contaminants in marine environments that, despite their importance for the health of marine organisms, can be toxic. Recently, the stable isotopes of these elements have emerged as powerful tracers for studying their cycles. Thus, this review aims to connect urban and marine interfaces under a “land-sea continuum” framework to understand the complex sources, pathways, and transformations of Cu and Zn in urbanized coastal environments, a perspective currently lacking in the literature. Here, we briefly establish the sampling and analytical aspects of isotope measurement of these elements in the natural matrices of marine realms, providing a recent compilation of reference materials for analytical control. The principles of isotope fractionation are introduced and contextualized within coastal ecosystems. We summarize the isotopic signatures of major anthropogenic sources—including road-deposited sediments, non-exhaust traffic-related emissions, industrial waste, and metallurgical byproducts—and highlight the challenges of distinguishing them when isotopic ranges overlap. In parallel, natural baselines such as ores, soils, suspended particulate matter (SPM), and riverine inputs are also reviewed to contextualize environmental variability. The review examines how source isotope signatures evolve with further isotope fractionation during estuarine transport and transfer processes in the water-sediment-biota interface. Finally, this review also identifies future research directions to trace the sources, pathways, and sinks of these contaminants along the land-sea continuum, as well as the legacy and ongoing impact of urban metal pollution at catchment-to-coastal scales.11Nsciescopu
Greenlandic water bears reveal a new morphological trait of external head sensory organs
No full textTardigrades are microscopic panarthropods renowned for their ability to undergo cryptobiosis. While integrative taxonomy of tardigrades has been intensively applied in the description of tardigrade species over the past two decades, many details of their external morphology remain poorly recognized and under-described. This limitation is largely due to their small size and the limited morphological features useful for classical taxonomy. In particular, compared to heterotardigrades, the external sensory structures of eutardigrades are less studied. In this study, we present a detailed morphological analysis using FE-SEM of two Greenlandic apochelan species, Milnesium grandicupula sp. nov. and M. cf. longiungue. We identified several previously unobserved anatomical structures in milnesiids, including minute sensory structures in the cephalic region. Detailed microphotographs revealed that apochelan tardigrades also possess a set of external sensory structures on the head sensory fields, similar to those observed in other major evolutionary lineages within tardigrades. This finding corroborates the hypothesis of the homology of head sensory organs between eutardigrades and heterotardigrades. Notably, these small sensory structures exhibit a distinctive pattern: a relatively large central organ surrounded by smaller pores, which may be comparable to the sensory dorsal organ (SDO) of crustaceans and the cephalic median organ (CMO) of trilobites.11Ysciescopu
A comprehensive analysis of the scrapping and abandonment of fiber-reinforced polymer vessels at sea
No full textFiber-reinforced polymer (FRP), also known as fiberglass, is a widely used composite material in marine, transportation, and construction industries because of its high strength, lightweight properties, and corrosion resistance. While FRPs are advantageous for these applications, the disposal and recycling of FRPs, especially in boats, remain challenging. The global FRP market valued at $3.9 billion USD in 2022. An increasing number of FRP vessels are reaching the end of their lifecycle, amounting to a global total of 250,000 to 500,000 tons of end-of-life vessels each year, contributing to environmental concerns. FRP boats, which have been popular since the 1950s, are often disposed of in landfills, as recycling methods are limited. Abandoned vessels pose hazards to navigation, ecosystems, and human health, releasing pollutants and breaking down into microplastics. Countries are exploring alternatives such as pyrolysis and recycling programs, although progress varies. An extended producer responsibility (EPR) system, which funds boat recycling, is an example of a proactive policy. However, broader efforts are needed to improve the recycling infrastructure and research sustainable materials. Addressing the environmental impact of FRP vessels requires collaborative research, policy development, and innovative solutions such as eco-design and improved recycling methods, especially as the global demand for boats and FRP materials continues to grow.11Nsciescopu