This article is focus on the distribution and source of organic matter in tidal flat in the Jiulong River Estuary, and to seek effective organic geochemistry proxies for recognize sedimentary microfacies, and thus to help that organic carbon is better applied to identify sedimentary microfacies and paleo-environment. Forty one surficial sediment samples were obtained and measured their grain size, total organic carbon (TOC), total nitrogen (TN), and organic carbon stable isotopes (δ¹³C) in the tidal flat from three sedimentary environments: upper tidal flat, middle tidal flat and lower tidal flat in summer and winter. The results show that, from upper tidal flat to lower tidal flat, the grain size of sediments becomes coarser gradually with decreasing TOC, TN and C/N, and the increase of δ¹³C. The sources of organic matter in the upper tidal flat are dominated by terrestrial organic matter and mangrove, marine organic matter and Spartina alterniflora in middle tidal, and marine organic matter in lower tidal flat. The distribution and sources of organic carbon in tidal flat from the Jiulong River Estuary are controlled by the seasonal changes of land-ocean interaction, sedimentary hydrodynamic sorting, and plants. There is a significant difference in TOC, and a highly significant difference in TN and δ¹³C in sediments of the tidal flat. We thus proposed that organic geochemistry properties TOC, TN and δ¹³C are the effective indicators to identify upper tidal flat and middle-lower tidal flat in the Jiulong River Estuary.

In order to understand the characteristics of food web structure in Zhongjieshan Islands, consumer samples of fish, shrimp and crabs, cephalopods, shellfish and zooplankton were collected from Zhongjieshan Islands in July 2020. Based on the carbon and nitrogen stable isotope techniques, the contributions of the four potential carbon sources (macroalgae, phytoplankton, suspended particulate organic matter (POM) and substrate organic matter (SOM)) to consumers, as well as the food web structure and nutritional relationship of the Zhongjieshan Islands were analyzed. The results revealed that the δ¹³C values of carbon sources ranged from −22.93‰ to −9.73‰, and the δ¹⁵N values ranged from 1.72‰ to 7.68‰. The δ¹³C values of consumers ranged from −21.95‰ to −12.55‰, and the δ¹⁵N values of consumers ranged from 4.13‰ to 12.92‰. One-way analysis of variance showed that there were significant differences in carbon and nitrogen stable isotopes among different carbon sources and different groups of consumers (p<0.01). SIBER model was used to analyze the trophic structure indexes of the regional ecosystem of Zhongjieshan Islands. Compared with the research results of other sea areas, it was found that the level of food source diversity (CR), trophic level length (NR) and total niche area (TA) were relatively high. SIAR model was used to calculate the carbon source contribution rate. The results showed that phytoplankton and POM were important carbon sources, with an average contribution rate of 29.63% and 28.72%. The maximum contribution rate of phytoplankton to zooplankton was 80.58%, and the maximum contribution rate of POM to fish was 79.74%; the maximum contribution rate of SOM to shrimp and crab was 49.94%; the carbon source contribution of macroalgae to consumers was the lowest, with an average of 18.37%. The mean trophic level range of the main consumers in Zhongjieshan Islands was 1.58 to 3.63, and the trophic level was 3. The average trophic level from big to small was as follows of cephalopods (3.09), fish (3.00), shrimps and crabs (2.70), shellfish (1.82). The consumers in the waters of Zhongjieshan Islands were mainly low and intermediate carnivores, and there were few omnivores and high carnivores. This study initially constructed the ecosystem food web of Zhongjieshan Islands, which provided reference data for understanding the trophic structure in this area, and also provided theoretical information for further study of the ecosystem.

As potential mineral resources, rare earth elements and yttrium (REY)-rich sediments in deep-sea, have attracted a lot of attention in recent years. It is generally believed that the main source of REY should come from overlying seawater, but studies are in general lacking on the REY in overlying seawater in REY-enriched areas. In this paper, the dissolved concentrations and vertical distributions of 15 REY were studied in three stations located in the South Pacific Ocean, where enriched REY concentrations were found in sediments. Data obtained from this study were compared with data reported in adjacent waters and other ocean basins. The REY concentration in surface water of the study area was mainly controlled by wind-driven dust input, while the middle and deep waters were controlled by water masses. After the normalization of Post Achaean Australian Shale (PAAS) and North Pacific deep water (NPDW), the fractionation characteristics of REY can be clearly identified, and different water mass characteristics can be distinguished. When compared to data reported in other ocean basins and adjacent waters, more differences are found in surface waters due to dust and terrestrial inputs, while the REY concentrations in Indian Ocean are similar to the study region; the REY concentrations in deep water show a positive correlation with the age of water mass, i.e. the concentrations of REY from small to large are Atlantic, Indian Ocean, South Pacific, North Pacific.

In order to identify the functional diversity of the adjacent waters of the Changshan Islands in the ecotone between the Yellow Sea and the Bohai Sea, based on the quarterly survey of fish biological resources and environment factors from October 2016 to August 2017, combined with 13 functional traits such as feeding habit, trophic level, migration type, thermophily, resilience and fish eggs type, the spatio-temporal pattern of functional diversity and its relationship with environmental factors were studied by using community weighted mean index (CWM), functional diversity index and Spearman rank correlation analysis. The results showed that the dominant species of fish community in spring and winter were depressiform, warm temperate and demersal species with the characteristics of anterior or upper mouth, low growth coefficient, high vulnerability, low resilience and non-migration or short distance migration. The dominant species in summer and autumn showed more functional traits, such as long distance migration, pelagic, fusiform and compressiform. FRic in summer and autumn was significantly higher than that in spring and winter, FEve was the highest in spring, and FDiv was the lowest in autumn and was significantly lower than other seasons. FEve in spring and season and FDiv in spring and autumn showed a trend of high in the west and low in the east, while FRic in summer and winter and FEve in autumn showed a trend of high in the east and low in the west. There was a certain correlation between environmental factors and functional diversity index. As an ecotone between the Yellow Sea and the Bohai Sea, the functional traits of the dominant species and functional diversity show seasonal variations made by the fish migration, and the spatial pattern of functional diversity shows complexity and heterogeneity made by environment changing in the adjacent waters of the Changshan Islands.

To study the spatial distribution patterns of meiofauna in the southern Yellow Sea and the influencing environmental factors, two cruises were conducted in the southern Yellow Sea in August (summer) and November (autumn) 2020 to analyze the taxa composition, abundance, biomass, vertical distribution, community structure of meiofauna and their relationship with environmental factors. The results showed that a total of 15 taxa of meiofauna were identified, among which free-living marine nematode was the most dominant group, accounting for 75.6% and 84.6% of the total abundance of meiofauna in the two cruises, respectively. Other important groups were benthic copepods, rotifers and cladocerans. The average abundance of meiofauna in summer and autumn was (514.9±32.1) ind./(10 cm²) and (350.8±30.7) ind./(10 cm²), and the average biomass (dry weight) was (651.7±98.0) μg/(10 cm²) and (589.2±37.1) μg/(10 cm²), respectively. There were differences both in the spatial and temporal distribution of meiofauna. In terms of seasonal distribution, highly significant differences were found in the abundance and taxa composition of meiofauna. Combined with the analysis results of environmental factors, the sediment median diameter was the main environmental factor causing the differences. In terms of spatial distribution, the abundance of meiofauna and community structure differed significantly along the water depth gradient in summer, while no significant differences were found along the water depth gradient in autumn. The Yellow Sea Cold Water Mass was supposed to be the main factor affecting the spatial distribution of meiofauna in summer. The abundance and taxa diversity of meiofauna in this study were lower compared with other studies on meiofauna in the southern Yellow Sea. The sediment chlorophyll a and organic matter contents were the important factors causing the change in abundance of meiofauna in the southern Yellow Sea. The assessment of the abundance ratio of marine nematodes to copepods (N/C ratio) showed the presence of organic pollution in the area in autumn, while this result was not consistent with that of the macrofaunal assemblages in the environmental quality evaluation of the same area, and further studies are needed for the application of N/C ratio to evaluate the environmental quality.

According to the Pholis fangi otoliths collected from bottom-trawl surveys in Haizhou Bay during from 2015 to 2019, linear mixed-effects model (LMEM) was used to study the interannual variation of growth rate of P. fangi from 2013 to 2018 and assess the response of the growth of P. fangi at different ages to external environmental factors such as bottom temperature, chlorophyll content and population density. The results showed that the otolith increment of P. fangi differed significantly between ages, with the mean otolith increment of 0.327 mm at 0 year old, significantly higher than that at another ages. The random-effects showed that the growth rate of P. fangi showed an increasing trend from 2013 to 2015, with a fluctuating trend from 2016 to 2018. The main factors affecting the growth of P. fangi at 0 year old were bottom temperature and population density. The growth rate increased and then decreased with the increase of bottom temperature, and decreased with the increase of population density. The effect of environmental factors on the growth rate of P. fangi at 1 year old were not significant, reflecting the ability of adults to adapt to the environment. This study provided insight into the growth dynamics of fish in response to biotic and abiotic factors, which will help to cope with the impact of climate change on fishery ecosystems.

As a typical dwelled tidal shellfish, Sinonovacula constricta is often exposed to sulfide-rich environment and shows strong sulfide tolerance. The cytosolic sulfotransferase 1B1 (SULT1B1) is located at downstream of the sulfur metabolism pathway, while it is a key enzyme catalyzing the sulfation reaction and plays an important role in the biotransformation of endogenous substances such as thyroid hormones (THs). In order to study the role of ScSULT1B1-12 in sulfur resistance, the sequence characteristics were analyzed by bioinformatics method. Combined with the changes of blood ${\rm {SO}} _4^{2-} $ concentration, the spatial expression and temporal expression profiles during 72 h sulfide stress (50 μmol/L, 150 μmol/L, 300 μmol/L) were studied. The full-length cDNA of ScSULT1B1-12 gene was 1 100 bp, containing an open reading frame of 897 bp, and encoding 298 amino acids. Sequence analysis showed that ScSULT1B1-12 contains four catalytic active sites (₅₆K, ₁₀₄N, ₁₀₆H, and ₁₃₄A), one PAPS binding domain (YPKSGTXW) at N terminal, and one PAPS binding and dimerization domain (RKGXXGDWKNXFTVXXE) at C terminal, indicating that it was structurally able to catalyze the sulfation reaction. Spatial expression showed that ScSULT1B1-12 was highly expressed in gills, followed by the adductor muscle and hepatopancreas. Blood ${\rm {SO}} _4^{2-} $ concentration decreased, and the expression patterns of ScSULT1B1-12 also declined with fluctuation after sulfide stress, indicating that sulfate can be further transformed to sulfated donors, and ScSULT1B1-12-mediated sulfation may be inhibited to keep THs at a certain level in S. constricta, in order to strengthen the metabolic and immune functions, and make the organism adapt the adverse environment of high sulfide.

In this study, the harmonic constants of the 5 global vertical displacement loading tide models FES2014, EOT11a, GOT4.10c, GOT4.8 and NAO.99b are validated evaluated to the observed data of 21 GPS stations in Bohai Sea, Yellow Sea, East China Sea and surrounding areas. The results show that the accuracy of the M₂ constituents of FES2014 and EOT11a models are relatively high, S₂ constituents of NAO.99b and EOT11a models are relatively high, K₁ constituents of EOT11a and FES2014 models are relatively high, O₁ constituents of EOT11a and GOT4.8 models are relatively high, N₂ constituents of EOT11a and FES2014 models are relatively high, K₂ constituents of NAO.99b and FES2014 models are relatively high, P₁ constituents of EOT11a and GOT4.8 models are relatively high, Q₁ constituents of FES2014 and EOT11a models are relatively high. The distribution features of the eight vertical displacement loading tides in Bohai Sea, Yellow Sea, East China Sea and surrounding areas.

The South Kunsong area is a negative tectonic unit in the western part of the Wan’an Basin, in which the N−S trending faults run through the north and the south. The unique tectonic characteristics make it a window for studying the tectonic evolution and regional fault strike-slip activities in the western part of the Wan’an Basin. The sedimentary strata in the study area are divided into three sets of structural layers, the structure-sedimentary filling section in the South Kunsong area is drawn by the back stripping method, and the tectonic subsidence and tectonic subsidence rate in the South Kunsong area are calculated. Settlement process and controlling factors. The research results show that the fault combination styles in the lower and middle structural layers are mainly core-type faults, "Y"-type faults, stepped faults and high-angle flower-shaped structures. W−E trending and NE−SW trending; the upper tectonic layer is not developed with faults and is stable deposition; under the control of regional strike-slip faults and the South China Sea spreading movement, the tectonic evolution of the South Kunsong area has experienced four stages since the Eocene: the initial stage. During the rifting period, extensional fault-deflection period, strike-slip reformation period and thermal subsidence period, the stratigraphic structure properties of the Cenozoic also showed a three-stage transformation of extension and strike-slip, control of strike-slip faults, and thermal subsidence.

How to study the response process of wetland system under the influence of extreme weather events such as typhoon, and then put forward effective ecological integrity maintenance and management schemes is of great significance to wetland management and ecological security maintenance in key areas. In this paper, during the process of “Chanthu” Typhoon in September 2021, hydrodynamic observation points were set up on the South Bank of Nanhui east tidal flat, surface sediments were collected, tidal flat surface elevation was measured, and vegetation images were obtained by unmanned aerial vehicle. Using ArcGIS spatial analysis, the hydrodynamic and sedimentary changes of Nanhui east tidal flat and the response of tidal flat surface elevation, surface sediments and vegetation distribution area were discussed. The results show that the average effective wave height and wave energy at the edge of the vegetation are 1.54 times and 2.14 times in the typhoon, the average current velocity near the bottom layer is 0.23 m/s, and a “high suspended sediment concentration layer” (>10 g/L) with a thickness of more than 1 m appears on the tidal flat for 8.13 h. After the typhoon, the tidal flat surface of Scirpus mariqueter and Spartina alterniflora distributed sparsely below 4 m eroded 0−4.8 cm, and the tidal flat surface with lush growth of Spartina alterniflora and Phragmites australis above 4 m deposited 0−14.7 cm. The distribution area of vegetation in the study area decreased by 1827.67 m², accounting for 1.63% of the total vegetation before the typhoon, including 31.9% of the eroded tidal flat vegetation and 68.1% of the deposited tidal flat vegetation. The wetland management after the typhoon process can be summarized as follows: (1) The wetland basically shows the characteristics of coexistence of erosion and accretion areas after the typhoon process; (2) For the tidal flat surface with an elevation lower than 4 m, it is suggested to determine the elevation suitable for vegetation growth, combine the erosion and deposition changes during the typhoon process, and use the “microbial film” and vegetation patch transplantation to dissipate waves, consolidate the tidal flat and promote accretion, so as to accelerate the rapid restoration of the wetland after the impact of the typhoon process.