To study the hydrodynamic performance of an oscillating-water-column (OWC) wave energy converter in a real sea, a two-dimensional nonlinear numerical model of the interaction between irregular waves and a land-based OWC device is developed based on the potential flow theory and the high-order boundary element method (HOBEM) in this paper. The irregular waves are generated based on the JONSWAP spectrum. The viscous damping is introduced on the water surface boundary conditions inside the air chamber to consider the energy dissipation due to water viscosity. And physical modeling experiments are carried out in the wave-current flume at Dalian University of Technology to validate the numerical model. It is found that the OWC hydrodynamic efficiency under irregular waves is reduced in comparison with that under regular waves, especially in the low-frequency wave region where the efficiency difference is the largest. The frequency corresponding to the peak efficiency under the action of irregular waves is larger than that under regular waves. The dimensionless surface elevation inside the chamber decreases, while the dimensionless air pressure inside the chamber increases with the significant wave heights. The OWC hydrodynamic efficiency is less affected by the significant wave height. The frequency corresponding to the peak efficiency is not dependent on wave nonlinearity. This work can provide a reference for the design of OWCs.

The concept of ecosystem-based fisheries management has been widely recognized, but it’s application in the construction of marine ranch is still very rare. In this study, based on the data from a bottom trawl survey of fishery resources conducted in the waters of Wuzhizhou Island from 2020 to 2021, a marine ranch fish community size-spectrum model (SSM) was built, which reflects the complex structure of food webs and interspecies interactions in marine ranch, to assess the impacts of fishing on the fish community in marine ranch. The study analyzed the effects of changes in species-specific fishing death coefficient on fish community by simulating two management strategies (single-species management and multispecies management) and monitored the state of fish community characteristics using five community ecological indicators: the total biomass of the community, the slope of size spectrum, the mean maximum weight, the mean weight, and the large fish index. The results of the single-species management strategy showed that the marine ranch ecosystem of Wuzhizhou Island showed top-down control, and there was a strong regulatory effect of carnivorous fish on plankton-feeding fish. Complex interactions such as competitive predation among different species produce trophic cascade effects after changes in fishing death coefficient. The results of the multispecies management strategy showed that fishing death coefficient of Muraenesox cinereus had the greatest effect on the slope of size spectrum, and that fishing death coefficient of Trachiocephalus myops and Muraenesox cinereus had the greatest effect on fish community biomass and community structure and function. The results of this study have important implications for the conservation and stabilization of fish community, and can help managers to better understand the potential impacts of changes in fishing death coefficient rates on fish communities, so that viable and effective conservation and management strategies can be developed based on the importance of the species to the fishery.

The semienclosed pyloric caecum of Larimichthys crocea is an ideal organ to perform the host source tracking, as it containes several local bacteria colonized during early development. The alpha diversity, relative abundance of core bacteria and network relationship of the pyloric caecum microbiota in L. crocea from Sansha Bay were analyzed using the Illumina high-throughput sequencing. Furthermore, the random forest model was used to predict the population source (the wild population or the farmed population). The results showed that the farmed fish had more unique OUT and higher alpha diversity than the wild one. The wild and farmed fish significantly differed in the relative abundance of dominant bacteria (Proteobacteria, Firmicutes, Bacteroidota, Actinobacteria and Acidobacteria) (p < 0.05). The result of network analysis showed that the wild fish had higher ratio of negative to positive edges and modularity, but fewer nodes and edges than the farmed fish. Furthermore, a random forest classification prediction model with the accuracy of 92.31%, the Kappa coefficient of 0.8452, and an area under the ROC curve of 0.952 4 was constructed. Using this prediction model, the accuracy of source identification for the wild and farmed fish was 91.67% and 92.86%, respectively. Overall, the structure of microbial communities in the pyloric caecum of L. crocea was different between the wild and farmed populations, making it a potential marker for host source tracking. Our findings provide new insights into distinguishing wild and farmed L. crocea.

The ocean acidification effect is increasing with the large amount of CO₂ emissions. To investigate the effects of future seawater acidification on Ruditapes philippinarum, a control group (pH = 8.1) and acidification group (pH = 7.7, 7.1 and 6.4) were set up for 42 days. The changes in tissue structure, immune and antioxidant enzyme activities of Ruditapes philippinarum under acidification conditions were measured, as well as the effects produced at the molecular level. The results show that when Ruditapes philippinarum are placed in an acidified seawater environment, gill filament spacing expands with decreasing pH, gill filament cilia adhere, and the pipes and outer epidermal folds of the mantle gradually deepen. The activities of acid phosphatase (ACP) and superoxide dismutase (SOD) in gill tissues show a pattern of decreasing followed by increasing. Alkaline phosphatase (AKP) activities exhibit different trends in each group. Total antioxidant capacity (T-AOC), catalase (CAT), and lysozyme (LZM) activities show a pattern of increasing followed by decreasing. Glutathione peroxidase (GSH-Px) activities in gill and visceral masses show a continuous increase. LZM activity in the viscera group displays varying trends, while ACP activity shows a decreasing and then increasing pattern. AKP, SOD, and CAT activities exhibited an increasing and then decreasing pattern, while T-AOC activity shows a continuous decrease. Analysis of the transcriptome reveals that the GO functions in gill tissue are mainly enriched in DNA integration, integral components of the membrane, and RNA-directed DNA polymerase activity, among others. The KEGG pathway analysis shows enrichment in the phagosome pathway and pathways related to protein processing in the endoplasmic reticulum. The acidification of seawater caused varying degrees of damage to the tissues of Ruditapes philippinarum, disrupting its internal environmental homeostasis and altering metabolic levels and immune-related gene expression, and led to an increased risk of disease and even death in Ruditapes philippinarum.

Sediment source is a key issue in sedimentology. Although sediment geochemistry is an important tool in sedimentology, the explorations and applications of radionuclides in sediment geochemistry are still limited. In this study, naturally occurring radionuclides (²³⁸U, ²²⁶Ra, ²²⁸Ra, and ⁴⁰K) in sediments were simultaneously measured using a high-purity germanium γ-spectrometer in three typical ecosystems of mangrove, seagrass, and coral reefs. The distribution characteristics of radionuclides in sediments from the these ecosystems were discussed in one-dimensional view of activity level, two-dimensional view of radionuclide pairs and activity ratio, and three-dimensional view of ternary diagram of radionuclides to identify distinct sources of sediments. Ternary diagram of ²³⁸U-²³²Th(²²⁸Ra)-⁴⁰K/10 in sediments was applied in the China different seas for tracking distinct sediment sources. This study emphasized that the three-dimensional view of ternary diagram of ²³⁸U-²³²Th(²²⁸Ra)-⁴⁰K/10 comprehensively exhibited the information of activity level, composition, and spatial distribution area of radionuclides. In conclusion, ternary diagram of ²³⁸U-²³²Th(²²⁸Ra)-⁴⁰K/10 may be an optimized method for source identification in sediments and provide a supplement to the existing tools of geochemical proxies.

Research on the reconstruction of underwater three-dimensional temperature and salinity fields and the acquisition of acoustic field characteristics based on satellite sea surface observations has significant practical value in military oceans and other fields. However, its effectiveness not only depends on the reconstruction method but also changes with different sea surface observations used. Although there are few reports on related research, it has significant guiding value for the design of satellite sea surface observation schemes. In this study, based on the latest variational method applied by the US Navy, the influence of the vertical gradient of temperature and salinity and the sea surface height, sea surface temperature, and their joint use on the reconstruction of three-dimensional temperature and salinity and acoustic field characteristics were investigated. The results showed that the reconstruction scheme incorporating the three constraint items had the highest accuracy, with average reconstruction errors of 1.08℃ for temperature field and 0.11 for salinity field, and could better capture the spatial features of the temperature and salinity fields. By analyzing the spatial characteristics of different schemes, the sea surface temperature mainly plays a role in capturing the temperature and salinity characteristics of the shallow region of the mixing layer, which has a great influence on the Sound Layer Depth (SLD). Both the sea surface height and the vertical gradient of warm salt field can improve the inversion accuracy of mixed layer and deep area, which can affect the accuracy of the whole sound velocity profile. According to the analysis of acoustic characteristics, when SST, SSH, and the gradient were constrained simultaneously, the SLD had the smallest difference from HYCOM in the shallow sound speed, which was about 1 m/s. When there was no gradient constraint, the SLD differed significantly from HYCOM and failed to reflect the surface duct characteristics. It can be seen that the surface duct is more sensitive to sea surface temperature and gradient constraints.

The albedo of Antarctic sea-ice zone (ASZ) can affect the radiation budget and thus has essential influence on global climate change. Using the albedo product from satellite application facility on climate monitoring, the spatio-temporal variations of summer albedo in sea-ice zone from 1983 to 2022 in Antarctica and six sea sectors were analyzed, the relationships between ASZ albedo and sea ice concentration (SIC), air temperature and atmospheric circulation were also quantified. Results show that the albedo retrieved from satellite is consistent to that obtained from in situ observations and thus the satellite-based albedo is reliable. Among the six sea sectors, Weddell West has the highest multi-year averaged albedo of 0.61, whilst Ross Sea features the lowest one of 0.45. Albedo of ASZ in summer experienced gradual increases before 2015 followed by the rapid decline (2015–2022). All sea sectors have similar ASZ albedo variations to that of Antarctica, excepting for Bellingshausen-Amundsen Seas where decreases can be found in both two periods. ASZ albedo is positively correlated to SIC and negatively related to air temperature. From 1983 to 2015, the decreased summer air temperature weakened the sea ice ablation and the SIC increased slightly (0.03%/a), sea ice area increased by 2.07 × 10⁵ km² per decade on average, all of these led to the increase of reflected solar radiation and sea-ice zone albedo. During the summer from 2015 to 2022, as the increased temperature enhanced the sea ice ablation, more leads and open water appeared, and then decreased the SIC. The sea-ice zone thus absorbed more solar radiation and had less reflected radiation, which leads to a rapid decline of the albedo. In addition, the Antarctic annular mode is one of the driving factors changing the albedo in sea-ice zone in the Ross Sea and Weddell Sea.

Narrabeen Beach, located Sydney, Australia, has undergone frequent storm wave events. The beach form has an adaptive ability to evolve from storm profile to berm profile with little human intervention. In order to investigate the self-recovery capability of the headland bay after storm waves, this paper analyzes how beach evolves during the post-storm calm weathers and identify the main hydrodynamic factors that dominate the beach recovery based on the multi-year continuous measurement data of Narrabeen Beach. The results show that there are spatial differences along the shore in the recovery rates, with the fastest recovery rate in the middle of the beach. Besides, southeast breezes with small wave-height and long wave-period contribute most to the storm-profiles’ recovery, especially to the northern-to-central portion. Whilst for the southern part of the headland bay tidal force modulate the beach recovery efficiency more. Accordingly, a concept of cumulative wave energy considering tidal range is proposed by this study and found to well correlated with the self-recovery ability of the southern beach profile. Through investigation, variation of wave directions induced by topography, along with geological and geomorphological features all play a vital role on the spatial inhomogeneity of the recovery efficiency for the headland bay. In addition, from the secular time scale, the recovery ability of the storm profiles is also controlled by the Southern Oscillation Index. The analysis and findings of this paper can provide useful references for disaster prevention and mitigation, and post-disaster protection and restoration for a headland bay under extreme sea forces.

Tim (Timeless) is the second core circadian clock gene identified after the discovery of Per, which plays an important role in the regulation of animal reproduction. In order to explore the molecular mechanisms of Tim to regulate spawning in Sinonovacula constricta, the cDNA sequence of Tim was cloned and analyzed, the circadian expression patterns of Tim gene/protein in different tissues were analyzed by qRT-PCR and immunofluorescence technology, and the regulatory effects of Tim on sex hormone secretion were investigated by siRNA technology. The ORF sequence of Tim was 3 090 bp, encoding 1 029 amino acids and containing three conserved domains (TIMELESS superfamily、TIMELESS_C and FIil). Tim was expressed in test tissues, and showed higher expression levels in the hepatopancreas, siphon, ovary and testis. The expression levels of Tim were higher at 12:00–18:00 in the daytime and lower at 00:00–06:00 in the night time, which exhibited circadian rhythmic expression patterns in the ovary and testis. Tim protein was mainly expressed in hepatocytes of the hepatopancreas, epithelial cells of siphons, mature oocytes of the ovary, and spermatids of the testis. And protein fluorescence signals of Tim were slightly stronger at 12:00 during the day than at 00:00 during the night in the ovary and testis. After siRNA injection, the expression levels of Tim significantly decreased from the 3rd to 7th day in the siRNA treatment groups of the ovary and testis (P < 0.05). Meanwhile, the contents of testosterone in the testis and estradiol in the ovary decreased significantly from the 1st to 9th day after siRNA injection (P < 0.01). Consequently, it could be concluded that Tim gene/protein exhibited circadian rhythmic expression patterns in the ovary and testis, and the contents of sex hormones significantly decreased after Tim interference, which suggested that Tim might regulate the nocturnal spawning by mediating the secretion of sex hormones in S. constricta. These findings preliminarily explored the regulatory effects of circadian clock gene Tim on nocturnal spawning of S. constricta, which will provide important application value for in-depth analysis of spawning mechanism and optimizing industrialized seedling breeding technology in mollusks.

Previous research has conducted extensive work on sediment grain size testing, data analysis, and information extraction. However, studies on whether the collected sediment samples are representative are still relatively rare. Based on indicators such as the mode, median grain size, particle size distribution, sediment type, and grain size parameters, this study compared and analyzed the quantitative and qualitative results of the grain size distribution parameters of 30 parallel sediment samples collected from beaches in the southern part of Leizhou Peninsula, China. The study examined the differences, correlations, and consistencies of these parameters. The results showed that: (1) the mode, median grain size, and particle size distribution of parallel samples exhibited a certain degree of variability; (2) the skewness and kurtosis of parallel samples showed significant differences, with average values of P1 ranging from –2.90 to –1.53 and 11.23 to 21.59, P2 ranging from –2.55 to –1.52 and 11.23 to 21.59, and P3 ranging from –2.81 to –1.86 and 13.41 to 27.69; (3) about two-thirds of the combinations of grain size parameters had no correlation (R² ≤ 0.29); (4) qualitative results of sorting coefficients, skewness, and kurtosis showed differences in 1/3, 1/2, and 4/15 of the cases, respectively. The spatial heterogeneity of sediment grain size distribution information and the randomness of sample collection are the main reasons for these differences. To minimize the randomness of sample collection and characterize the spatiotemporal heterogeneity of grain size distribution information, parallel samples are recommended for future sample collection. This study provides a typical case of comparing the results of parallel sample grain size parameters for beach sediment, which can improve our understanding of effective sediment sample collection strategies.