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.

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.

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.