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Using multisource sea ice fusion data, the spatiotemporal characteristics of sea ice cover were analyzed for the marginal seas of East Asia for the period 2005–2021. The results show that there were obvious differences in the beginning and end dates of the sea ice in the different sea areas. The northern Sea of Japan had the longest ice period, and Laizhou Bay and Bohai Bay in the Bohai Sea had the shortest ice period. The time when the largest sea ice extent appeared was relatively stable and mostly concentrated in late January to mid-February. There were obvious spatial differences in the duration of the sea ice cover in the marginal seas of East Asia. The duration of the sea ice cover gradually decreased from high latitude to low latitude and from nearshore to open seas. The annual average duration of the sea ice cover was more than 100 days in most of the Sea of Japan and approximately 20 days in most of Laizhou Bay and Bohai Bay. The melting speed was significantly faster than the freezing speed in the Bohai Sea and Yellow Sea, resulting in asymmetric changes in the daily sea ice extent in the two seas. The increasing trends in the maximum sea ice extent and total sea ice extent were 0.912 × 105 km2/10 yr and 0.722 × 107 km2/10 yr, respectively, from 2005 to 2013, both of which passed the significance test at the 0.05 level.

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are components of bacterial membranes in terrestrial soils, which are widely used in paleoenvironmental reconstruction in global terrestrial soils and marine sediments. In marine sediments, the mixed sources of brGDGTs complicate the applications of brGDGT-related indicators in reconstructing terrestrial environments. In this study, we reported the spatial distribution of brGDGT-related indicators (MBTʹ 5ME, CBTʹ 5ME, #Ringstetra, and IIIa/IIa) in surface sediments from the East China Sea (ECS). MBTʹ 5ME and CBTʹ 5ME showed a stepped trend from the inner shelf to the outer shelf, and #Ringstetra and ∑IIIa/∑IIa values in sediments of the ECS are distinct compared with those in the catchment soils, suggesting marine in situ production of brGDGTs. We also examined the existence of marine in situ brGDGTs and quantitatively determined the contributions of terrestrial and in situ production of brGDGTs. This study reported mixed sources of soil-derived brGDGTs were dominant, and marine in situ brGDGTs were overprinted. Our results indicate that there were predominantly marine in situ brGDGTs (avg. 60.5 ± 5.5%) in the outer shelf due to the weak riverine transportation and were characterized by high #Ringstetra and IIIa/IIa.

Through photosynthesis, phytoplankton initiate material cycling and the flow of energy through marine ecosystems. The structure of marine ecosystems is sensitive to the size of primary producers, and size-specific photosynthesis-irradiance (P-I) parameters are required for modeling the size-specific primary production. We defined a phytoplankton type to be a group of phytoplankton communities with similar compositions and hypothesized that a function of phytoplankton types might be used to quantify systematic differences of P-I parameters between size classes (structural effects) and variations of the magnitudes of those parameters if the overlap between habitats was small (environmental effects). To test this hypothesis, we conducted a study to measure the size-specific P-I parameters of two size classes ( 2 μm) and pigment-based phytoplankton community structure in a marginal sea, the Taiwan Strait. Three phytoplankton types were classified, and type-based and size-specific P-I parameters were derived. The results demonstrated the potential of a type-based model to estimate P-I parameters for two phytoplankton size classes as well as different habitats.

Iodirne-129 is useful for tracking water mass movement in the ocean. In this study, the concentration of iodine isotopes in seawater of the East China Sea (ECS) in October 2013 were analyzed to investigate the spatial and vertical distribution of 129I and 127I to understand water mass exchange. Results showed that the 129I/127I atomic ratios varied with the water mass, with higher values of (10-20) × 10-11 in the coastal regions and lower values of b8 × 10−11 offshore. Inventories of 129I were estimated to be (0.23–1.7) × 1012 atoms m−2 (n = 18) in upper 100 m waters, which is comparable to those of other regions without being contaminated by the nuclear accidents or nuclear reprocessing facilities. The total amount of 129I in the ECS water column was estimated to be 88 g in which over 90% is attributed to the oceanic input (e.g., West Pacific) via the Kuroshio Current (KC). The contributions of 129I from Changjiang (Yangtze River) terrestrial watershed (b7.5%) and atmospheric fallout (b2.7%) were small. Those from the Fukushima accident were negligible during this investigation. The 129I/127I ratios versus salinity distribution showed the range and stratification of the Changjiang, Yellow Sea, and KC waters in the ECS. Our study shows that the Changjiang fresh water could be transported to the North Jiangsu coast in October; the Taiwan Warm Current water could intrude to Northern part of the Changjiang Estuary (32°N). Besides, our results suggest that the 129I/127I profile is useful to indicate the seawater mixing process in ocean marginal systems.

The repeated transgression and regression of coastlines mediated by the late Quaternary glacial-interglacial cycles make the northwest Pacific to become a hotspot to study marine speciation and population diversity. The red alga Agarophyton vermiculophyllum is an ecologically important foundation species native to the northwest Pacific, capturing considerable research interest due to its range-wide invasiveness in Europe and North America. However, the knowledge of phylogeographic structure and intraspecific genetic diversity across the entire native range are still scarce. Here, we used 1214-bp of mitochondrial cytochrome c oxidase subunit 1 (cox1) to explore phylogeographic patterns, lineage structure and population genetic differentiation of 47 A. vermiculophyllum populations in the northwest Pacific. Our DNA data revealed overall high haplotype diversity and low nucleotide diversity, and five phylogeographically structured genetic lineages that diverged significantly from each other. S-DIVA analyses showed the ancestors of A. vermiculophyllum originating from multiple areas encompassing the Japan-Pacific coast, the Sea of Japan, East and South China Seas. These combined evidence indicate that A. vermiculophyllum might have survived in multiple scattered glacial refugia during the late Quaternary climate oscillations in the northwest Pacific. This knowledge may help to better understand how climate shifts interacted with contemporary environments to contribute to intraspecific genetic variation and adaptation capability of seaweed under current global climate warming.

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Ecological evidence suggests that heterotrophic diazotrophs fueled by organic carbon respiration in sediments play an important role in marine nitrogen fixation. However, fundamental knowledge about the identities, abundance, diversity, biogeography, and controlling environmental factors of nitrogen-fixing communities in open ocean sediments is still elusive. Surprisingly, little is known also about nitrogen-fixing communities in sediments of the more research-accessible marginal seas. Here we report on an investigation of the environmental geochemistry and putative diazotrophic microbiota in the sediments of Bohai Sea, an eutrophic marginal sea of the western Pacific Ocean. Diverse and abundant nifH gene sequences were identified and sulfate-reducing bacteria (SRB) were found to be the dominant putative nitrogen-fixing microbes. Community statistical analyses suggested bottom water temperature, bottom water chlorophyll a content (or the covarying turbidity) and sediment porewater Eh (or the covarying pH) as the most significant environmental factors controlling the structure and spatial distribution of the putative diazotrophic communities, while sediment Hg content, sulfide content, and porewater [Formula: see text]-Si content were identified as the key environmental factors correlated positively with the nifH gene abundance in Bohai Sea sediments. Comparative analyses between the Bohai Sea and the northern South China Sea (nSCS) identified a significant composition difference of the putative diazotrophic communities in sediments between the shallow-water (estuarine and nearshore) and deep-water (offshore and deep-sea) environments, and sediment porewater dissolved oxygen content, water depth and in situ temperature as the key environmental factors tentatively controlling the species composition, community structure, and spatial distribution of the marginal sea sediment nifH-harboring microbiota. This confirms the ecophysiological specialization and niche differentiation between the shallow-water and deep-water sediment diazotrophic communities and suggests that the in situ physical and geochemical conditions play a more important role than geographical contiguity in determining the community similarity of the diazotrophic microbiota in marginal sea sediments.

Based on the interpretations of three seismic profiles and one wide-angle seismic profile across the Northwest Sub-basin, South China Sea, stratigraphic sequences, deformation characteristics and an extension model for this sub-basin have been worked out. Three tectonic-stratigraphic units are determined. Detailed analyses of extension show that the event occurred mainly during the Paleogene and resulted in the formation of half-grabens or grabens distributed symmetrically around the spreading center. Sediments are characterized by chaotic and discontinuous reflectors, indicating clastic sediments. Farther to the southwest, the sub-basin features mainly continental rifting instead of sea-floor spreading. The rifting would have been controlled by the shape of the massif and developed just along the northern edge of the Zhongsha-Xisha Block, rather than joined the Xisha Trough. After 25 Ma, a southward ridge jump triggered the opening of the Southwest Sub-basin. The NW-directed stress caused by the sea-floor spreading of the Northwest Sub-basin may have prevented the continuous opening of the sub-basin. After that the Northwest Sub-basin experienced thermal cooling and exhibited broad subsidence. The deep crustal structure shown by the velocity model from a wide-angle seismic profile is also symmetrical around the spreading center, which indicates that the Northwest Sub-basin might have opened in a pure shear model.

This paper describes the concentrations of selenite, selenate and organic selenide in pore water, and selenium in sediment cores in the marginal seas. The selenium accumulation rates for the Sulu Sea and the South China Sea were 1.16 and 0.21 mg cm^yr^. The upward diffusive fluxes of dissolved selenium were estimated by using Fick’s first law. The calculated fluxes od dissolved selenium as selenate in the Sulu and South China Seas were estimated to be 0.17 and 0.88 μg cm^yr^, respectively., 本文データは一部CiNiiから複製したものである。

Temperature, salinity, chlorophyll a, and surface CO2 fugacity (fCO2) were extensively investigated in the Ulleung Basin of the East/Japan Sea during four seasonal cruises. In spring, surface fCO2 showed large variations ranging from 260 to 356 μatm, which were considerably lower than the atmospheric CO2 levels. Surface fCO2 was highest (316 to 409 μatm) in summer. The central part of the study area was undersaturated with respect to atmospheric CO2, while the coastal and easternmost regions were oversaturated. In autumn, the entire study area was fairly undersaturated with respect to atmospheric CO2. In winter, surface fCO2 ranged from 303 to 371 μatm, similar to that in autumn, despite the much lower sea surface temperature. The seasonal variation in surface fCO2 could not be explained solely by seasonal changes in sea surface temperature and salinity. The vertical mixing, lateral transport, and sea-air CO2 exchange considerably influenced the seasonal variation in surface fCO2. The Ulleung Basin of the East/Japan Sea was a sink of atmospheric CO2 in spring, autumn, and winter, but a weak source of CO2 to the atmosphere in summer. The annual integrated sea-air CO2 flux in the Ulleung Basin of the East/ Japan Sea was -2.47 ± 1.26 mol m^(-2) yr^(-1), quite similar to a previous estimate (-2.2 mol m^(-2) yr^(-1)) in the south East/Japan Sea. This indicates that the Ulleung Basin of the East/Japan Sea acts as a strong sink of atmospheric CO2.

Two ultrabasic-basic rocks-bearing units occur in the Vizcaino Peninsula of Southern Baja California (Mexico) : the Vizcaino Layered Complex (VLC) and the San Hipolito Zone (SHZ). The VLC consists of two sequences : the lower Puerto Nuevo Sequence (serpentinite breccia, harzburgite, dunite, cyclic units), and the upper La Pintada Sequence (cyclic units, gabbros, diorites). The SHZ consists of serpentinite, actinote schists. microgabbros, spilitic pillow lavas, ophicalcites, radiolarites, tuffs, greywackes, interbedded limestone and dolomite, siliceous sandstones, and volcanosedimentary strata). The VLC is an autochtonous complex generated by a magma underplating, which is intrusive into the San Pablo Metamorphic Complex (SPMC) (amphibole-biotite gneiss with lenses of granite, migmatitic amphibolitic gneiss, orthoamphibolites). Originally, together with its metamorphic roof, the SPMC, it constituted a continental magmatic arc .The SHZ, a former Late Triassic marginal sea, is an allochthonous Carnian (?)-Norian ophiolitic unit, emplaced as a nappe upon the VLC during the Liassic. During the Late Triassic (starting at ±220 Ma) this zone underwent a long lived extensional event, during which plagiogranite dykes and dolerite/albitite dykes were emplaced into it, whereas the San Hipolito Basin opened behind it. Then, different units of the VLC were exhumed and exposed by low angle normal listric faults. It seems that the upper part of the VLC, La Pintada Sequence and the SPMC were then displaced to their present position of San Pablo-La Pintada. During the Liassic compressional phase the plagiogranite dykes were boudinaged, and slices of the SHZ Nappe came to rest upon every one of the units of the Puerto Nuevo Sequence, including the serpentinite breccia (which gave way to the erroneous notion of the so-called Puerto Nuevo Mélange of previous literature). En la Península del Vizcaino, Baja California Sur (México), se encuentran dos unidades de rocas básicas-ultrabásicas.: el Complejo Estratificado del Vizcaino (CEV) y la Zona San Hipólito (ZSH). El CEV consiste de dos secuencias actualmente separadas, de abajo hacia arriba: la Secuencia de Puerto Nuevo (brecha de serpentinita, harzburgíta, dunita, unidades cíclicas), y la Secuencia de La Pintada (unidades cíclicas, gabros, dioritas). La ZSH consiste de serpentinitas, esquistos actinolíticos, microgabros, pillow lavas espilíticas, oficalcitas, radiolaritas, tobas, grauvacas, intercalaciones de calizas y dolomías, areniscas silíceas, y depósitos volcáno-sedimentarios). El CEV, producto de una acreción magmática sub-cortical, es intrusivo en el Complejo Metamórfico San Pablo (CMSP) (gneises anphibolíticos y biotíticos con lentes de granito, gneises migmatítico-anfibolíticos, orto-anfibolitas). El CEV y su techo metamórfico, el CMSP, constituyen un arco magmático continental. La ZSH, depósitos de un mar marginal del Triásico Superior (Cárnico?-Nórico), es una unidad ofiolítica alóctona, una cobijadura emplazada durante el Liásico arriba del CEV. Durante el Triásico Superior el CEV fue sometido a un largo evento distensivo durante el cual se emplazaron diques de plagiogranito y de dolerita/albitita, mientras que atrás de él se abría la cuenca San Hipólito. Las diferentes unidades del VLC fueron entonces exhumadas y expuestas por fallas normales lístricas, por las cuales la Secuencia de La Pintada y el SPMC fueron desplazados y llevados a su posición actual de San Pablo-La Pintada. Durante la fase compresiva del Liasico los diques de plagiogranito sufrieron budinaje, y la Cobijadura de la SHZ, frecuentemente desmembrada, llegó a descansar sobre las diferentes unidades de la Secuencia de Puerto Nuevo, incluyendo la brecha de serpentina - lo que dió lugar a la noción errónea del Mélange de Puerto Nuevo de la literatura.