Mozambique’s continental margin in East Africa was formed during the break-off stage of the east and west Gondwana lands. Studying the geological structure and division of continent-ocean boundary (COB) in Mozambique’s continental margin is considered of great significance to rebuild Gondwana land and understand its movement mode. Along these lines, in this work, the initial Moho was fit using the known Moho depth from reflection seismic profiles, and a 3D multi-point constrained gravity inversion was carried out. Thus, high-accuracy Moho depth and crustal thickness in the study area were acquired. According to the crustal structure distribution based on the inversion results, the continental crust at the narrowest position of the Mozambique Channel was detected. According to the analysis of the crustal thickness, the Mozambique ridge is generally oceanic crust and the COB of the whole Mozambique continental margin is divided.

The flexed frustules in pennate diatoms are usually associated with monoraphid diatoms. Interestingly, we found a biraphid diatom species with flexed frustules in an offshore intertidal beach environment on Weizhou Island, Beihai City, Guangxi Zhuang Autonomous Region, China. Therefore, based on morphological characteristics, we described a new genus of diatoms Yuzaoea sinensis gen. et sp. nov. CH Li, HH Liu, YH Gao & CP Chen. The frustule of this genus is characterized by heterogeneous frustule with one concave valve and one convex valve, complete raphe on both valves, straight and moderately eccentric raphe, uniseriate striae and girdle bands with a single row of areolae. The most identifying feature of this genus was the flexed frustule, which is rare in biraphid diatoms and common in monoraphid diatoms. We compared the morphometric characteristics of genus Yuzaoea with genus Rhoikoneis and several genera within the family Rhoicospheniaceae, including Rhoicosphenia, Campylopyxis, and Cuneolus. Phylogenetic analyses based on SSU rRNA and rbcL showed that the genus Yuzaoea was the sister group to the clade of Rhoicosphenia with a high support value (bootstrap values = 100%), and the clade “Yuzaoea+Rhoicosphenia” was sister to the clade of monoraphid diatoms, in which the genera Achnanthidium, Planothidium and some Cocconeis with high support values (bootstrap = 100%). Morphologically, the genus Yuzaoea shares many morphological features with monoraphid diatoms like genera Achnanthidium and Planothidium and the members within the Rhoicospheniaceae. Therefore, based on a combined morphological studies and phylogenetic results we suggested that this branch may represented the evolution of one kind monoraphid diatoms, from biraphid diatoms (e.g. genus Yuzaoea), to incompleted biraphid diatoms (e.g. genera Rhoicosphenia, Campylopyxis), to monoraphid diatoms (e.g. genera Achnanthidium and Planothidium).

Caenogastropoda is a highly diverse group, containing ~60% of all existing gastropods. Species in this subclass predominantly inhabit marine environments and have a high ecological and economic value. Owing to the increase in relevant phylogenetic studies, our understanding of between species relatedness in Caenogastropoda has improved. However, the biodiversity, taxonomic status, and phylogenetic relationships of this group remain unclear. In the present study, we performed next-generation sequencing of four complete mitochondrial genomes from three families (Buccinidae, Columbellidae, and Cypraeidae) and the four mitogenomes were classical circular structures, with a length of 16 177 bp in Volutharpa ampullacea, 16 244 bp in Mitrella albuginosa, 16 926 bp in Mauritia arabica asiatica and 15 422 bp in Erronea errones. Base composition analysis indicated that whole sequences were biased toward A and T. Then compared them with 171 complete mitochondrial genomes of Caenogastropoda. The phylogenetic relationship of Caenogastropoda derived from Maximum Likelihood (ML) and Bayesian Inference (BI) trees constructed based on CDS sequences was consistent with the results of traditional morphological analysis, with all three families showing close relationships. This study supported Caenogastropoda at the molecular level as a separate clade of Mollusca. According to our divergence time estimations, Caenogastropoda was formed during the middle Triassic period (~247.2–237 Ma). Our novel mitochondrial genomes provide evidence for the speciation of Caenogastropoda in addition to elucidating the mitochondrial genomic evolution of this subclass.

Acanthopagrus latus is an essential aquaculture species on the south coast of China. However, there is a lack of systematic breeding of A. latus, which considerably limits the sustainable development of A. latus. As a result, genetic improvements are urgently needed to breed new strains of A. latus with rapid growth and strong resistance to disease. During selective breeding, it is necessary to estimate the genetic parameters of the target trait, which in turn depends on an accurate disentangled pedigree for the selective population. Therefore, it is necessary to establish the parentage assignment technique for A. latus. In this study, 95 individuals selected from their parents and their 14 families were used as experimental material. SNPs were developed by genome re-sequencing, and highly polymorphic SNPs were screened on the basis of optimized filtering parameters. A total of 14 392 738 SNPs were discovered and 205 SNPs were selected for parentage assignment using the CERVUS software. In the model where the gender of the parents is known, the assignment success rate is 98.61% for the male parent, 97.22% for the female parent, and 95.83% for the parent pair. In the model where the gender of the parents is unknown, the assignment success rate is 100% for a single parent and 90.28% for the parent pair. The results of this study were expected to serve as a reference for the breeding of new varieties of A.latus.

The resource of Fenneropenaeus chinensis has declined sharply due to excessive fishing intensity, ecological changes and diseases. In order to supplement the fishing yield and restore resources of F. chinensis, the relevant authorities have carried out the activities of stock enhancement and releasing. It can increase biomass and recover resources. However, compared with increasing biomass, there were still few reports on its effect on the recovery of resources. Resource recovery is a process related to whether the released individuals can form a reproductive population. Up to now, there has been a lack of evidence whether the released F. chinensis can complete the entire life history, and form reproduction population. In this study, gravid female shrimp after spawning migration were captured from coastal waters of Haiyang, Qingdao, and Yellow Sea. After identifying parentage relationships using simple sequence repeat (SSR) and mtDNA haplotype, it was finally confirmed that there were eight released individuals in the recapture samples. It was confirmed for the first time that at least part of the released F. chinensis can complete overwintering and reproductive migration, and maintain the migration habits as their wild counterparts. Therefore, we infered that the released shrimp can reproduce under natural conditions, these F. chinensis can form reproductive populations theoretically if without human intervention. These results indicated that enhancenment and release activities have a positive effect on resource recovery.

With the development of ultra-wide coverage technology, multibeam echo-sounder (MBES) system has put forward higher requirements for localization accuracy and computational efficiency of ray tracing method. The classical equivalent sound speed profile (ESSP) method replaces the measured sound velocity profile (SVP) with a simple constant gradient SVP, reducing the computational workload of beam positioning. However, in deep-sea environment, the depth measurement error of this method rapidly increases from the central beam to the edge beam. By analyzing the positioning error of the ESSP method at edge beam, it is discovered that the positioning error increases monotonically with the incident angle, and the relationship between them could be expressed by polynomial function. Therefore, an error correction algorithm based on polynomial fitting is obtained. The simulation experiment conducted on an inclined seafloor shows that the proposed algorithm exhibits comparable efficiency to the original ESSP method, while significantly improving bathymetry accuracy by nearly eight times in the edge beam.

Upper ocean heat content (OHC) has been widely recognized as a crucial precursor to high-impact climate variability, especially for that being indispensable to the long-term memory of the ocean. Assessing the predictability of OHC using state-of-the-art climate models is invaluable for improving and advancing climate forecasts. Recently developed retrospective forecast experiments, based on a Community Earth System Model ensemble prediction system, offer a great opportunity to comprehensively explore OHC predictability. Our results indicate that the skill of actual OHC predictions varies across different oceans and diminishes as the lead time of prediction extends. The spatial distribution of the actual prediction skill closely resembles the corresponding persistence skill, indicating that the persistence of OHC serves as the primary predictive signal for its predictability. The decline in actual prediction skill is more pronounced in the Indian and Atlantic oceans than in the Pacific Ocean, particularly within tropical regions. Additionally, notable seasonal variations in the actual prediction skills across different oceans align well with the phase-locking features of OHC variability. The potential predictability of OHC generally surpasses the actual prediction skill at all lead times, highlighting significant room for improvement in current OHC predictions, especially for the North Indian Ocean and the Atlantic Ocean. Achieving such improvements necessitates a collaborative effort to enhance the quality of ocean observations, develop effective data assimilation methods, and reduce model bias.

An obvious trend shift in the annual mean and winter mixed layer depth (MLD) in the Antarctic Circumpolar Current (ACC) region was detected during the 1960–2021 period. Shallowing trends stopped in mid-1980s, followed by a period of weak trends. The MLD deepening trend difference between the two periods were mainly distributed in the western areas in the Drake Passage, the areas north to Victoria Land and Wilkes Land, and the central parts of the South Indian sector. The newly formed ocean current shear due to the meridional shift of the ACC flow axis between the two periods is the dominant driver for the MLD trends shift distributed in the western areas in the Drake Passage and the central parts of the South Indian sector. The saltier trends in the regions north to Victoria Land and Wilkes Land could be responsible for the strengthening mixing processes in this region.

In recent years, there has been a significant acceleration in the thinning, calving and retreat of the Pine Island Ice Shelf (PIIS). The basal channels, results of enhanced basal melting, have the potential to significantly impact the stability of the PIIS. In this study, we used a variety of remote sensing data, including Landsat, REMA DEM, ICESat-1 and ICESat-2 satellite altimetry observations, and IceBridge airborne measurements, to study the spatiotemporal changes in the basal channels from 2003 to 2020 and basal melt rate from 2010 to 2017 of the PIIS under the Eulerian framework. We found that the basal channels are highly developed in the PIIS, with a total length exceeding 450 km. Most of the basal channels are ocean-sourced or groundingline-sourced basal channels, caused by the rapid melting under the ice shelf or near the groundingline. A raised seabed prevented warm water intrusion into the eastern branch of the PIIS, resulting in a lower basal melt rate in that area. In contrast, a deep-sea trough facilitates warm seawater into the mainstream and the western branch of the PIIS, resulting in a higher basal melt rate in the main-stream, and the surface elevation changes above the basal channels of the mainstream and western branch are more significant. The El Niño event in 2015–2016 possibly slowed down the basal melting of the PIIS by modulating wind field, surface sea temperature and depth seawater temperature. Ocean and atmospheric changes were driven by El Niño, which can further explain and confirm the changes in the basal melting of the PIIS.

Antarctic coastal polynyas are biological hotspots in the Southern Ocean that support the abundance of high-trophic-level predators and are important for carbon cycling in the high-latitude oceans. In this study, we examined the interannual variation of summertime phytoplankton biomass in the Marguerite Bay polynya (MBP) in the western Antarctic Peninsula area, and linked such variability to the Southern Annular Mode (SAM) that dominated the southern hemisphere extratropical climate variability. Combining satellite data, atmosphere reanalysis products and numerical simulations, we found that the interannual variation of summer chlorophyll-a (Chl-a) concentration in the MBP is significantly and negatively correlated with the spring SAM index, and weakly correlated with the summer SAM index. The negative relation between summer Chl-a and spring SAM is due to weaker spring vertical mixing under a more positive SAM condition, which would inhibit the supply of iron from deep layers into the surface euphotic layer. The negative relation between spring mixing and spring SAM results from greater precipitation rate over the MBP region in positive SAM phase, which leads to lower salinity in the ocean surface layer. The coupled physical-biological mechanisms between SAM and phytoplankton biomass revealed in this study is important for us to predict the future variations of phytoplankton biomasses in Antarctic polynyas under climate change.