In this study, we used stable isotope technology to analyze different species (fish, crustaceans, cephalopods, benthos, etc.) collected in spring, summer and autumn in the coastal waters of Jiangsu Province. We used SIBER model to calculate the trophic niche of consumers, and calculated the quantitative indicators of six metrics in different seasons. The results showed that there were no significant differences in δ¹³C and nitrogen δ¹⁵N values among three seasons (p>0.05). In spring, the δ¹³C values ranged from −24.47‰ to −14.50‰, the δ¹⁵N values ranged from 6.86‰ to (14.98±0.49)‰, and the trophic level ranged from 1.52 to 4.28±0.17. In summer, the δ¹³C values ranged from −19.86‰ to −14.44‰, the δ¹⁵N values ranged from 5.79‰ to (12.54±3.50)‰, and the trophic level ranged from 1.25 to 3.52. In autumn, the δ¹³C values ranged from (−22.17±4.90)‰ to (−14.21±0.36)‰, the δ¹⁵N values ranged from 6.30‰ to (14.60±0.51)‰, and the trophic level ranged from 1.34 to 4.15±0.14. The structure of food web was stable in each season, and the trophic niche of some species overlaps in different degrees. In addition, the food sources are more extensive, and the trophic level and community diversity are higher in spring, the food sources of consumers are more abundant, but the degree of trophic niche differentiation is lower in summer, while in autumn, the structure of food web is relatively simple, but the distribution of trophic niche is wider.

Corals are one of the carriers for recording information about changes in the marine environment. For example, determining U/Ca to reconstruction of sea water temperature or measure the Th/U isotopic ratio for dating to reconstruction sea level etc. However, measuring the U and Th contents and isotopic ratio of corals is a prerequisite for extracting the recorded marine environmental change information, the difficulty lies in the separation of Ca matrix and enrichment and purification of trace U and Th. Based on this, this study modified the pretreatment method of separation and purification U and Th with single column stage of UTEVA resin, and then combined with high resolution inductively coupled plasma mass spectrometry to determine U and Th contents of corals. The results demonstrate that the HNO₃ medium concentration decrease from 3 mol/L to 2 mol/L will not affect the absorption efficiency of U and Th; 2 mL Milli-Q water can completely elute U, which significantly reduces the procedure blank value of the entire process of U; the improved method is used to determine the U and Th contents of three Hainan littoral corals (n=6, 1σ): U are (3.46±0.02)μg/g, (2.67±0.05)μg/g, (2.15±0.07)μg/g, respectively, Th are (10.12±0.24)ng/g, (4.82±0.10)ng/g, (5.65±0.12)ng/g, respectively; and the determination accuracy is below 3.3%, recovery rate of standard addition of U, Th are 97.9%–100.9%, 97.3%–99.7%, respectively. The method has high accuracy and good precision. This study provides a more accurate, convenient and rapid experimental method for the analysis of U and Th content and isotopic ratio in corals and other carbonate samples.

According to the bottom trawl survey data of fishery resources in the offshore waters of Shandong from 2016 to 2017, the spatial autocorrelation and spatial heterogeneity of demersal fish in the offshore waters of Shandong were examined by using spatial autocorrelation indices and variogram. The results showed that there were significant spatial aggregation patterns and spatial autocorrelation in the demersal fish in the offshore waters of Shandong. The spatial autocorrelations were strong in spring, summer and winter, and weak in autumn. From the perspective of spatial distribution, the areas of high relative abundance index of demersal fish were mainly located in the southern waters of Shandong in spring and summer, and areas of high relative abundance greatly decreased in autumn and winter, while the areas of low value were mainly in the Laizhou Bay and adjacent waters in four seasons. The parameters of variogram showed that there was a strong nugget effect in autumn, and the spatial heterogeneity of random part accounted for 76.0% of the total spatial heterogeneity. The spatial heterogeneity of random part in spring, summer and winter only accounted for 26.2%, 27.7% and 23.6% of the total spatial heterogeneity. In the spatial autocorrelation and spatial heterogeneity of demersal fish showed seasonal variation in the offshore waters of Shandong, which was to some extent related with changes in environmental factors such as water temperature.

According to the data collected in April (spring) and October (autumn) of 2018 in the eastern sea area of Zhoushan Islands (29°10′25.54′′−30°45′00′′N, 122°53′3.88′′−124°48′28.31′′E) based on the crab data obtained from bottom trawl survey of fishery resources, the community structure characteristics of crab resources such as species composition, dominant species and biodiversity were studied, and the relationship between crab quantity distribution and community structure and environmental factors such as temperature and salinity was analyzed. The results show that there are 40 species of crabs in spring and autumn, belonging to 23 genera and 12 families; among them, the dominant species in spring is Charybdis bimaculatus, and in autumn are C. bimaculatus and Portunus trituberculatus; the richness index (D) and Shannon Wiener-diversity index (H′) in autumn are higher than those in spring, while Pielou evenness index (J') is similar in spring and autumn; independent sample t-test show that there is significant difference between spring and autumn; according to cluster analysis and non metric multi-dimensional scaling analysis, spring can be divided into four communities, and autumn can be divided into four communities; canonical correspondence analysis show that bottom water temperature and surface salinity are the main environmental factors affecting the community structure and quantity distribution of crabs in the investigated sea area.

According to the seasonal fishery resource survey data from 2016 to 2017 in the adjacent waters of Changshan Islands, two-stage generalized additive model is used to examine the spatio-temporal distribution of Paralichthys olivaceus abundance and its relationships with relevant factors. The results show that the abundance of P. olivaceus exhibites obvious seasonal variation, and the abundances in spring and autumn is higher than those in winter and summer. In spring and autumn, it mainly distributes in the waters of 120.5°−122.5°E; and in summer and winter, it moves to the waters with suitable water temperature. The occurrence probability of P. olivacvacus is mainly affected by season, bottom salinity and bottom temperature. The probability of occurrence is relatively high at the salinity of 31. The relative abundance of P. olivaceus are mainly affected by bottom salinity and depth, and the relative resources is higher at the depth of 33 m. The spatio-temporal heterogeneity of the abundance distribution of P. olivaceus is affected by multiple factors in the adjacent waters of Changshan Islands.

This study aims to understand the characteristics and variability in the β diversity of fish community and its influencing environmental factors in the Haizhou Bay, which was rich in fishery resources in history but seriously declined in recent years due to overfishing and environmental pollution. The data were collected from fishery resource surveys conducted in the Haizhou Bay and its adjacent waters from 2013 to 2017 using bottom trawl in autumn. β diversity was measured by Sørensen dissimilarity index using pairwise and multiple-site methods. Additionally, β diversity was divided into turnover and nestedness components and the results were analyzed visually by violin plots. On this basis, the generalized dissimilarity modelling (GDM) was used to analyze the relationship between β diversity and its components with environmental factors. The results of this study showed that the β diversity of fish community and its components fluctuated remarkably among survey years, the fluctuation was larger in the shallow water, less for the deep water, and remained at a relatively stable level regarding the whole sea area. The proportion of the turnover component in β diversity was basically maintained at more than 80%. The component of turnover was significantly larger than that of nestedness, implying the changes of fish community in the Haizhou Bay were dominated by turnover. The salinity and chlorophyll concentration of seawater were the main factors influencing β diversity and its turnover component, and the accumulated deviance explained rate of salinity and chlorophyll were 28.05% and 23.33%, respectively, the influence of water temperature was weak. The environmental factors selected in this study had a low explanatory rate for the nestedness component, which was only 1.52%. Our results implied that the characteristics of fish community have been driven by the environment, and the community development can yield corresponding adaptive to environmental changes. The process of changes in β diversity of fish community may be complex. For instance, salinity and chlorophyll concentration affect the prey density of fish and thus affect β diversity, however, more influencing factors have not been evaluated. Further studies on β diversity and its components are necessary to understand the mechanism of changing characteristics of fish community, and to provide scientific reference for the establishment of marine reserves as well as the optimization of marine conservation strategies.

Cynoglossus semilaevis as a representative species of Pleuronectiformes, is an important marine economic fish in Chinese coastal areas. The abnormal body color of C. semilaevis has been perplexing the practitioners for a long time. There are many reasons leading to abnormal body color, among which the genetic factors are thought to be the most fundamental reasons. The present researches on hypermelanosis of the blind side of C. semilaevis mainly focus on environment, nutrition, physiology, cloning of known pigmental genes and so on, while the digging of new funtional genes is still lacking. In this study, skin samples with different colors of C. semilaevis are selected for transcriptome sequencing. Through GO and KEGG functional enrichment and comparative analysis of different genes, differential expressed genes are screened in six melanogenesis-related KEGG pathways and the top ten genes are verified by qPCR. In this study, we find five functional genes with significant changes in the hypermelanotic skin on the blind side of C. semilaevis, which refer to txndc, alox15b, ptgs2, ptgis, and atp1a2a (p<0.05). The expression levels of txndc, alox15b, ptgs2, and ptgis genes in the melanization group are higher than those in the control group. In terms of function, three of these five genes are related to arachidonic acid (AA) to some extent. This provides theoretical support for the hypothesis that nutritional regulation related to unsaturated fatty acids may be involved in the molecular mechanism of abnormal body color in C. semilaevis.

Picasso clownfish is named for its disorderly and abstract distribution of white patches in its skin. At the same time, due to the irregular and scarce formation of white patches, it belongs to a valuable clownfish. Therefore, analyzing the formation mechanism of skin white spots in Picasso clownfish can provide a theoretical basis for the artificial breeding of Picasso clownfish. In this study, we sequences the transcriptome of the skin of three color blocks (black, yellow and white） in the same part of the body between the dorsal fin and hip fin of Picasso clownfish. The results show that there are a large number of differentially expressed genes (DEGs） in white skin compared with yellow and black skin. Among them, the genes in the signal pathways related to melanin production (such as melanin production, hedgehog and Wnt signal pathways） show a downward trend in white skin tissue. The expression of upstream regulatory genes (such as ednrba and mitfa） decrease gradually from black to yellow to white skin tissue, but the expression of downstream core genes involved in melanin synthesis (including Tyr, tyrp1b and dct） decreases significantly in white skin assembly. Finally, the validity of transcriptome data is verified by fluorescence quantitative PCR. The results of this study will provide a theoretical basis for future people to interfere with gene expression to regulate clownfish body color.