Based on the investigation data of zooplankton in the sea area near the north operation area in the Lanshan Port of Rizhao Port in May (spring) and October (autumn) 2015, the community structure characteristics of zooplankton was analysed in this paper. The results showed that 20 species and 7 taxa of zooplankton were found in the two seasons, including 12 species and 4 taxa in spring and 19 species and 6 taxa in autumn, the average abundance of zooplankton were 128.1 ind./m³ in spring and 103.3 ind./m³ in autumn, the average biomass (wet weight) were 1 129.9 mg/m³ and 954.3 mg/m³, the average Shannon-Wiener diversity index (H'), Margalef’s species richness diversity (D) and Pielou’s evenness index (J) were 2.39, 0.85, 0.87 in spring, respectively, and 2.01, 1.21, 0.62 in autumn, respectively. In spring, the dominant species were Sagitta crassa, Calanus sinicus, Labibocera euchaeta, Acartia pacifica, Pleurobrachia globosa, while in autumn, the dominant species were Acartia pacifica, Doliolum denticulatum, Sagitta crassa, Labibocera euchaeta. Cluster analysis showed that the zooplankton in the investigation area could be divided into three groups. This study could provide important basic data for further study of zooplankton community structure in the coastal waters of Rizhao.

To examine the benthos food web structure in the Xiaoqing River Estuary adjacent sea area, four potential food sources, including sediment organic matter (SOM), suspended particulate organic matter (POM), zooplankton and phytoplankton, and 35 aquatic organisms are collected in October 2020. Carbon and nitrogen stable isotope technique and Bayesian mixing model (MixSIAR) are used to analyze the food web structure and the trophic relationship of benthos. The results show that the δ¹³C and δ¹⁵N values of potential food sources varies from −25.56‰ to −17.91‰ and 2.43‰ to 10.33‰, respectively. Moreover, the δ¹³C and δ¹⁵N values of benthos varies from −23.48‰ to −18.31‰ and 8.79‰ to 18.01‰, respectively. The trophic levels of the main consumers rang from 1.65 (Arcuatula senhousia) to 3.54 (Ctenotrypauchen chinensis). Trophic relationship analysis showes that there are two main energy transfer pathways in the Xiaoqing River Estuary adjacent sea area. One is the planktonic food chain with plankton as the major energy source, in which bivalves (except Solen brevissimus), small shrimps, and polychaetes are the main primary consumers. The other is the benthic food chain with SOM as the major energy source, in which Solen brevissimus and gastropods are the main primary consumers. On the whole, there is a certain degree of niche overlap and fierce competition among species in the Xiaoqing River Estuary adjacent sea area.

In order to study the relationship between daily increment of statolith and environment of neon flying squid (Ommastrephes bartramii) for different cohorts in the North Pacific during feeding ground, we explore the relationship between daily increment of statolith microstructure and environmental variables by gradient forest method (GFM) and generalized additive model (GAM) based on the samples collected in the North Pacific from 2010 to 2016. The results show that the life cycle of O. bartramii is about one year. The age of the autumn cohort ranges from 165 d to 345 d, and the age of winter-spring cohort ranges from 95 d to 271 d, respectively. Sea water temperature at the depth of 100 m (Temp_100), sea surface temperature (SST), sea surface salinity (SSS) and mixed layer depth (MLD) are the key environmental variables for the daily growth of autumn cohort. Temp_100, MLD, sea surface height (SSH) and chlorophyll a concentration (CHL) are the key environment variables for the daily growth of winter-spring cohort. GAM analysis shows that the daily increment width of statolith is significantly correlated with the key environmental variables selected by GFM (p<0.01). Key environmental variables of different cohorts suggest that the growth of O.bartrarnii is significantly affected by water temperature and prey abundance.

In order to mine single nucleotide polymorphism (SNP) sites relates to hypoxia stress and study the function of the gene SNP-Unigene from Rachycentron canadum. SOAPsnp software is mainly used to detect the SNP of the intestinal transcriptome sequencing results of cobia juveniles under hypoxia stress conditions, and then annotation of them in the databases of GO, KOG, and KEGG are compared. The results show that the transcriptome SNP locus are distributed on 26 120 SNP-Unigene, with a total of 431 845 SNP sites are detected, the average frequency of SNP occurrence is about 1/171 bp. SNP-Unigene functional annotation showes that the cobia is mainly involved in signal transduction, infectious disease, cancer and endocrine system under hypoxia stress. Further, 3 417 SNP-Unigene are annotated to 35 immune-related pathways including MAPK signaling pathway. Based on the transcriptome differential gene analysis, the distribution of SNP sites of 18 immune-related genes in 7 important immune pathways is examined. At the same time, the distribution of SNP sites of 8 differential genes such as PIK3CA in the HIF-1 signaling pathway is also detected. The research results will lay the foundation for further mining of the molecular genetic markers of immune and hypoxia-related SNPs, and provide a scientific reference for the in-depth study of cobia’s hypoxia adaptation mechanism.

The wetland vegetation is an important part of coastal wetlands, and its dynamic changes affect the structures and functions of wetland ecosystem. Therefore, it is of great significance to monitor and evaluate the long-term changes of wetland vegetation by remote sensing technology for the management of coastal resources and ecological protection. In this paper, we used multi-temporal Landsat satellite images as data sources, combined object-oriented method and random forest algorithm to achieve accurate classification of typical wetland vegetation in the Current Huanghe River Estuary Reserve, and revealed the spatiotemporal variation characteristics of Phragmites australis, Suaeda salsa and Spartina alterniflora in the study area from 2000 to 2020. It has been verified that the overall accuracy of wetland vegetation mapping is between 84.74% and 92.39%, and the Kappa coefficient is between 0.81 and 0.91. The results of long time series classification show that Phragmites australis is the dominant species in the Current Huanghe Estuary Reserve, and its distribution area is maintained at more than 6% and the overall growth is steady. The area of Suaeda salsa shows a decreasing trend since 2006. The dominance degree of Suaeda salsa is decreasing continuously and the degree of fragmentation is severe. The area of Spartina alterniflora increased year by year from 211.85 hm² in 2002 to 5267.79 hm² in 2020. The expansion process of Spartina alterniflora in the reserve could be divided into three stages: in the initial expansion period before 2008, the growth of Spartina alterniflora was unstable; from 2008 to 2014, there was a rapid expansion stage, with an average annual expansion rate of 54%, which showed that the seaward expansion invaded the plain and the landward expansion invaded the habitat of Suaeda salsa in space; since 2014, Spartina alterniflora has been growing slowly, entering a stable growth period, and the annual average expansion rate is only 9%.

Based on the investigations of surface sediments at six sampling stations of nine cruises carried out in the sea around the Yongxing Island of Xisha from 2009 to 2017, the background values of seven heavy metals are determined through the process of mathematical statistics, the contents and inter-annual variations of heavy metals are analyzed, and the contents of the heavy metals are evaluated by means of single factor standard index and potential ecological risk index. The results show that the background values of heavy metals in the sediments of the study area are low, the average level of them meet the first class of marine sediment quality, and the quality of sediment is excellent. The inter-annual variations of seven heavy metals in the sediments of the study area are slightly different and generally significant and affected obviously by the development activities on the Yongxing Island. From 2009 to 2017, the contents of Zn, Cd, Cu, Cr, As and Hg are to increase first and then decrease, while the content of Pb is to increase. The assessment by means of potential ecological risk index shows that the multi year average of potential ecological risk indexes are in the order of Cd, Hg, As, Cu, Pb, Cr, Zn, and Cd and Hg are the main potential ecological risk factors of the study area.

Dissimilatory nitrate reduction in marine sediment is one of the key nitrogen loss processes in the ocean. Dissimilatory nitrate reduction to ammonium (DNRA), unlike denitrification and anammox by which nitrate is reduced to N₂ and removed from the environment eventually, directly reduce nitrate to ammonium, could lead to eutrophication and water hypoxia afterwards. ¹⁵N labeled technique is the main method to investigate dissimilatory nitrate reduction processes in sediments. Accurate determination of ¹⁵${\rm {NH}}_4^+ $ in isotope enrichment samples is primarily required to evaluate the potential rate of DNRA. The commonly used method for the determination of ¹⁵${\rm {NH}}_4^+ $ at present is the hypobromite iodine oxidation-membrane inlet quadrupole mass spectrometer determination method. However, ³⁰N₂ as the final analyte of the method has two problems which lead to an analysis error: firstly, ³⁰N₂ determined can be significantly overestimated due to the O₂ interference; secondly, the low equilibrium rate of ³⁰N₂ in the detector could influence the precision of the method and low down the analysis speed. To solve the problems mentioned, a sodium hypobromite oxidation-sulfamic acid reduction method by which ¹⁵${\rm {NH}}_4^+ $ is transformed to ²⁹N₂ only and detected using membrane inlet quadrupole mass spectrometer afterwards (Redox-MIMS method) is reported in this article. The results indicate that the optical concentration of sulfamic acid is 80−100 mmol/L; the detection limit is 0.5 μmol/L and the precision (RSD) is 0.8%; the dynamic range of standard curve is 0−150 μmol/L. Comparing with the hypobromite iodine oxidation method, the Redox-MIMS method not only has the advantages of mild reaction conditions and easily obtained reagents, the memory effect of ³⁰N₂ in the detector can also be solved effectively for most of the produced ¹⁵N₂ is ²⁹N₂ which improves detection efficiency (2 min per sample) meanwhile. Determination results of rates of DNRA and the contribution of DNRA to all dissimilatory nitrate reduction processes in the Laizhou Bay sediments using both hypobromite iodine oxidation and Redox-MIMS methods shows no significant difference. These make the Redox-MIMS method an accurate and high-efficient method for determination of ¹⁵${\rm {NH}}_4^+ $ in isotope enrichment samples.

Black-hole eddy can be extracted based on elliptic Lagrangian Coherent Structures (eLCSs), which can transport material and maintain coherent under geostrophic for a long time. It was similar to the black hole in the ocean, so it was called black-hole eddy. In this paper, the boundary of black-hole eddy was extracted based on the data of the geostrophic flow velocity field. Using the method of eLCSs and choosing a targeted eddy (Eddy A) in the western Pacific to analyze. Sea surface temperature, sea surface salinity and chlorophyll concentration data are used to verify that the Eddy A is coherent in horizontal material transport. The temperature, salinity and dissolved oxygen data obtained by Argo in different depths are used to prove the coherence in vertical of Eddy A. The result demonstrates that the boundary of black-hole eddy is more coherent than Eulerian boundary in a long time scale and can describe the transport of material more objectively.

The significant wave height (SWH) is a key parameter for describing the ocean waves. In this paper, the SWH in the Taiwan Strait provided by the ERA-Interim reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) in March 2013 is compared with the buoy observations and the simulation results of the SWAN (Simulating Waves Nearshore) model. The results showed that the correlation coefficient of SWH between the buoy data and the ERA-Interim as well as the SWAN results is 0.94 and 0.98, respectively. The average SWH of the ERA-Interim data is about 51% of the buoy data and 70% of the SWAN results. The monthly averaged values of the spatial anomaly correlation coefficient (ACC) of the SWH between the ERA-Interim data and the SWAN results is 0.51. The ACC was minimal when the wind started, it boosted rapidly with increasing of the wind speed and reached the maximum before the wind speed reached the peak. Then the ACC turned to decrease at the peak wind speed. Integrated analysis imply that the ERA-Interim data can reflect the spatial distribution and the temporal variations trend of the SWH over the Taiwan Strait during this period, but it’s evidently smaller than the SWAN model data.

Interannual variability of meridional heat transport anomaly (MHTA) in the tropical Indian Ocean (IO) during monsoon transitions (boreal spring and autumn) is investigated based on SODA3.4.2 and POP2 results. There exist two leading interannual modes in spring, namely the consistent mode and the divergence and convergence (div/conv) mode. The consistent mode characterized by the northward MHTA in the upper IO, is controlled by the antisymmetric wind structures with northeasterlies anomalous northeasterlies (northwesterlies) to north (south) of the equator. However, the spring div/conv mode is featured by the meridional divergence in the surface layer and convergence in the subsurface layer on both side of the equator. Such a mode is modulated by the sea surface temperature anomaly (SSTA) dipole in the tropical southwestern IO and subtropical southeastern IO south of the equator. In autumn, the div/conv mode is dominated by the IOD-induced equatorial easterlies and associated anticyclonic wind stress anomalies in the off-equatorial regions. The POP2 model sensitivity experiments confirm the roles of anomalous winds induced by the Indian Ocean SSTA modes in modulating the MHTA, that is, the antisymmetric winds induce northward MHTA, while the anomalous easterly winds lead to the div/conv pattern. Therefore, the interannual variability of air-sea coupled modes in the IO plays a vital role in the basin-scale and hemispheric-scale heat exchanges.