Based on wave data recorded in 2020 from 10 buoy stations in the northern part of the South China Sea, the synergistic effects of wave parameters such as wave steepness, spectral width, kurtosis, skewness and Benjamin-Feir index (BFI) on a rogue wave group in the northern waters of the South China Sea were investigated. The frequency and energy distributions of three types of rogue waves were recognized based on wavelet transform. Chaotic dynamics was introduced to study the chaotic phenomena in the wave series where rogue wave were located. Results show that wave steepening enhanced the nonlinear effect of waves, and a narrow spectrum could suppress the dispersion effect, which increased the BFI, triggered the modulation instability of waves, and promoted the generation of distorted waves. When kurtosis>3, the BFI increases as the degree of kurtosis deviation from the Gaussian distribution increases. In particular, when kurtosis>3 and H/H_s>2.2, the increase in kurtosis contributes significantly to the increase in the anomalous intensity of the rogue wave. Rogue waves induced by modulation instability and those induced by the superposition of wave clusters can be explained by phase and dispersion modulation as well as by energy distribution, whereas the generation mechanism of rogue waves that have not grown sufficiently is difficult to resolve from the time-domain waveform characteristics and the frequency-domain wavelet energy density. Qualitative analysis by the Poincaré cross section and quantitative analysis by the Lyapunov exponent verified that the nonlinear wave system, in which a rogue wave is located in the wave train, has weakly chaotic dynamic behavior.

Multibeam echosounder system (MBES) is an essential acoustic remote sensing technique for seabed topography surveys. The georeferenced model is crucial for the MBES when calculating the bathymetric soundings’ geolocation and depth. Existing models are complex and time-consuming, failing to meet the demands of large-scale or real-time data processing. To address these issues, we proposed a simplified and high-precision method. First, two regular sectors with the same vertex are assumed to represent the across-track and along-track beam patterns of the multibeam transmitter and receiver, respectively, instead of two cones in the conventional virtual concentric cone array (VCCA) model. Secondly, the beam vector representing the direction of sound ray tracing is derived by calculating the intersection point coordinates between the two sectors. Finally, an efficient progressive equivalent sound speed profile ray tracing progress is used to obtain the final depth of soundings. Experimental results demonstrate that the proposed method substantially reduces processing time, with reductions of approximately 52% for shallow water data and 84% for deep water data. The root mean square error of depth discrepancies is approximately 0.58% of water depth in overlapping regions of cross-survey lines. Furthermore, the proposed method achieves accuracy comparable to the VCCA algorithm.

Planktonic foraminifera in ocean sediments serve as unique paleoenvironmental recorders, and their distribution and diversity are affected by environmental factors. The northwest Indian Ocean, influenced by monsoons and ocean-basin-ridge systems, is a key research area in this regard. However, few studies have focused on the foraminiferal distribution in surface sediments. We analyzed 60 surface sediment samples in April 2023, from which 11 genera and 32 warm-water species were identified. The distribution was primarily controlled by depth-dependent carbonate dissolution, temperature-salinity gradients, and monsoon-driven hydrography. Four distinct assemblages were identified: the Arabian Basin assemblage (dominated by Globorotalia cultrata) demonstrates strong influence from the Arabian Sea high-salinity water and winter monsoon circulation; the Carlsberg Ridge assemblage (dominated by G. cultrata, Globorotalia tumida) exhibits depth-controlled productivity signatures; the Carlsberg Ridge Flanks assemblage (mainly including Globigerinita glutinata, G. cultrata, Globigerinoides ruber) reflects monsoon-induced mixing processes; and the Somali Basin assemblage (including mainly G. cultrata, Pulleniatina obliquiloculata, G. tumida) shows clear imprints of summer monsoon upwelling. Carbonate dissolution in the Somali Basin is strongest, followed by Arabian Basin, the Carlsberg Ridge showed the weakest dissolution. Based on planktonic foraminiferal abundance, fragmentation rate, CaCO₃ content, and dissolution susceptible/resistant species, the carbonate lysocline and compensation depth were estimated at ~3 700 and ~4 800 m, respectively.

Due to scarce in-situ research, little is known about planktonic biodiversity in deep sea and their environmental characteristics. The water masses in upper 3 000 m of the tropical Southeast Indian Ocean were sampled with the Maxi Multi Plankton Sampler and the containing Radiolaria species were identified, from which the vertical spectra of the species composition were clarified. Radiolarians displayed a classic shallow subsurface abundance maximum of 1 428–1 635 inds./m³ in 50–100 m, followed by a steep decline with increasing depth. Variance partitioning analysis indicated that temperature was the principal driver of vertical community structure, followed by silicate concentration. Nonetheless, water masses with different salinity modulated the vertical compression or expansion of radiolarian assemblages within a confined depth range. Cluster analysis and ordination analysis showed that radiolarian communities in two regions exhibited four depth-specific assemblages. In the euphotic layer, Dictyocoryne muelleri, Dictyocoryne truncatum, Didymocrytis tetrathalamus, Spongaster tetras, Tetrapyle spp., Acanthodesmia vinculata, Botryocyrtis scutum, and Zygocircus microporus were dominated and controlled by high temperature and adequate light. Anthosphaera minuta, Xiphatractus aff. trachyphloius, and Anthocyrtidium zanguebaricum were dominant species in Persian Gulf Water (200–500 m), while Amphisphaera umbilicata, Spongopyle aff. osculosa, Spongotrochus vitabilis, Lamprotripus hirundo, and Sethoconus sp. A were typical in the Red Sea Water (500–2 000 m) and could tolerate relatively lower dissolved oxygen (approx. 50 μmol/kg). The nutrient-rich Indonesian Intermediate Water could increase the growth of Actinomma eriosperma below 1 000 m. Amphisphaera aff. xiphydrion and Dictyophimus platycephalus reflecting rich silicate were probably influenced by the Circumpolar Deep Water.

Coral reefs are increasingly degraded due to anthropogenic disturbance and climate change, transforming them into structurally unstable rubble fields that impede natural recovery and resilience. Under these conditions, the likelihood of coral reef natural recovery declines significantly in the absence of human intervention. In 2017, we launched a restoration project by introducing 8 t of natural volcanic rock into a rubble field near Wuzhizhou Island, Sanya, Hainan Island, China. Comprehensive surveys were conducted in 2019 and 2023 to assess the long-term impacts of this intervention and verify the effectiveness of volcanic rocks in rubble field restoration. By 2023, the coral cover had increased to 27.4% in the restoration area, compared to just 10.2% in the control area. Additionally, the recruitment density of juvenile corals reached 8.33 inds./m², which was nearly 7 inds./m² higher than in the control area. The restoration area supported 28 fish species in density of 135.37 inds./100 m², while the control area supported only 9 fish species in density of 20.5 inds./100 m². Similarly, macroinvertebrate density was higher in the restoration area (0.59 inds./m²) than in the control area (0.29 inds./m²). These findings suggest that volcanic rocks offer an effective in situ substrate for coral larvae recruitment, enhancing the habitat structural complexity of rubble fields and promoting the aggregation of fish and macroinvertebrates.

Glucose homeostasis is a fundamental physiological process in both vertebrates and invertebrates, yet its regulatory mechanisms in molluscs remain largely unexplored. This study investigates temporal hemolymph glucose dynamics and associated molecular responses in the Pacific oyster Crassostrea gigas. Annual monitoring revealed significant seasonal variation in hemolymph glucose concentrations, with post-spawning oysters exhibiting the lowest levels. A glucose injection experiment demonstrated rapid uptake kinetics, followed by a return to baseline, suggesting the presence of efficient metabolic regulation. Transcriptomic analysis on hepatopancreas tissue identified cgHK2-2 as the dominant hexokinase isoform induced by hyperglycemia, while other HK genes (cgHK2 and cgHK2-like) showed tissue-specific but non-inducible expression profiles in the investigated tissue. Furthermore, upregulation of cgPPP1R3B and cgPCSK1 indicate possibly conserved glycogen metabolism and insulin-like signaling pathways. Phylogenetic analysis revealed divergent evolutionary trajectories of hexokinase in protostomes versus chordates, with oysters lacking a clear glucokinase orthologue. These findings highlight key molecular players in oyster glucose metabolism and suggest both conserved and lineage-specific regulatory strategies.

A strain of benthic dinoflagellate Prorocentrum formosum was isolated from the Anding Lianjiao (Contiguous Reef) (also known as Addington Shoal), Zhongsha Islands. Morphological observation using light and scanning electron microscopy revealed vegetative cells measuring 24–27 μm in length and 17–22 μm in width, which displayed an asymmetrical oval shape with smooth surfaces. The left and right valves contained two distinct types of radially arranged pores with differing diameters, characterized by sparsely distributed marginal pores and a seamless connection to the parallel horizontal intercalary band. The periflagellar area comprised 9 platelets arranged in a wide V-shape, containing both larger flagellar pores and smaller accessory pores. Phylogenetic analysis based on ITS and LSU rRNA gene sequences confirmed its classification within Prorocentrum, with strong bootstrap support (94% for ITS; 98% for LSU) and posterior probabilities (0.97 for ITS; 1.0 for LSU). Genetic distance analysis showed its closest relationship to Prorocentrum elegans (P=0.359 for ITS; P=0.118 for LSU). HPLC analysis detected chlorophyll a, chlorophyll c₂, peridinin, diadinoxanthin, and diatoxanthin. Although trace levels of okadaic acid (OA) were detected in the initial cultures, its production was no longer observed after prolonged cultivation of the strain. Toxicity tests demonstrated 72- and 96-h mortality rates of 18.75%±1.07% and 34.54%±2.71% in Brachionus plicatilis at 2 660 cells/mL, whereas Artemia salina exhibited no mortality after 96-h exposure. Hemolytic activity was not detected in algal extracts. This study provides the first molecular sequences of P. formosum.

Light is one of the important environmental factors on life activities of aquatic animals. Eyestalks are a multifunctional organ of crustaceans that conducts light signals, produces neurohormones, and regulates growth. However, the mechanism of growth regulation by light intensity remains poorly studied. We evaluated the growth performance of ridgetail white prawn (Exopalaemon carinicauda) under different light intensities (0, 100, 200, and 400 lx), and determined the regulatory mechanism of growth in response to light intensity through transcriptome analysis of eyestalks. Results show that light intensity at 100 lx significantly improved growth performance in growth rate, specific growth rate, and biomass increase rate, while 0-lx and 400-lx conditions inhibited the growth. A total of 931 DEGs were identified between the 100-lx and 0-lx groups, of which 411 were upregulated and 520 were downregulated. In addition, 456 DEGs were identified between groups of 100-lx and 400-lx, including 155 upregulated DEGs and 301 downregulated DEGs. The light intensity at 100 lx significantly improved the growth performance by upregulating the oxidative phosphorylation, Toll and Imd signaling pathway, and ribosome pathway, and downregulating the tyrosine metabolism, phagosome, lysosome, autophagy, and Hippo signaling pathway, whereas 0 lx and 400 lx inhibited growth in the opposite patterns. In total, eight growth-regulation-related candidate genes, i.e., hemocyanin, NADH dehydrogenase, cytochrome c oxidase, ATP synthase, cathepsin L, phenoloxidase activating factor, CLIP domain-containing serine protease, and 40S/60S ribosomal protein were identified. The optimal light intensity for improved growth of E. carinicauda was about 100 lx when reared indoor. These data shall provide key information for further understanding of the regulatory mechanism of light intensity on the growth performance of this species.

The circadian rhythms of gut bacterial community are essential for the health of the host. Although previous studies have shown that environmental light cycles synchronize circadian feeding patterns in animals and regulate microbial communities through environmental fluctuations, the role of light in regulating the circadian rhythms of gut bacterial community in crustaceans and the impact of dark environments on these rhythms remain unclear. To address this issue, we used the mud crab (Scylla paramamosain) as a model to evaluate the circadian rhythms of gut bacterial community in different photoperiods (12-h L꞉12-h D and 0-h L꞉24-h D), and identified the microbes exhibiting circadian rhythms influenced by light exposure and microbial circadian clocks. The study found that 12-h L꞉12-h D photoperiod optimally supports mud crab growth performance, animal welfare, and circadian microbial balance. While gut microbiota exhibited rhythmic fluctuations in different photoperiods, the community composition analysis revealed significant differences between light/dark and continuous dark conditions. The circadian rhythmic microbes regulated by light exposure were primarily dominated by Spirochaetes, while the dark environment significantly reduced the relative abundance of Alpha-proteobacteria and Bacteroidetes (P<0.05), with Fusobacteria serving as a representative microorganism. Additionally, the dark environment caused significant fluctuations in functional pathways related to environmental stress response (P<0.05), such as the FoxO signaling pathway, lysosome, and RNA transport, suggesting that a complete darkness environment disrupts the biological clock. These findings elucidated the regulatory mechanisms of circadian rhythms in the gut bacterial community of mud crabs and highlighted the significant role of light in shaping gut bacterial community.

Fish stock assessment is essential for ensuring the sustainable utilization of marine resources. We evaluated the stock status of the Pomadasys olivaceus along both the Balochistan and Sindh coasts of Pakistan using Catch-based Monte Carlo Maximum sustainable yield (CMSY), Bayesian Schaefer model (BSM), and a stock production model incorporating covariates (ASPIC) models based on catch and effort data from 2000 to 2022. Results from all models indicate the B/B_MSY (relative biomass) values were below 1.0 and F/F_MSY (fishery exploitation) values>1, indicating that the stock is severely overfished in both regions. The estimated maximum sustainable yield (MSY) from the CMSY and BSM methods ranged between 2 440–2 670 metric tons (mt) for Balochistan and 2 430–2 650 mt for Sindh. The ASPIC model (Fox and Logistic) also indicated overexploitation, with MSY estimates of 1 585 mt (Fox) and 1 379 mt (Logistic) for Balochistan, showing critical stock depletion. In contrast, MSY estimates from Sindh were 3 260 mt and 3 024 mt, suggesting stock condition was not over fished. These findings offer a scientific basis for the formulation of targeted management and conservation strategies by the government, particularly emphasizing urgent intervention for the Balochistan coast to ensure the long-term sustainability of the P. olivaceus fishery.