In 1988, the tropical Pacific experienced a strong La Niña event, during which significant equatorial Pacific easterly wind surges were observed. Analysis based on reanalysis data indicates that the intensity of the 1988 surges reached the highest level during 1982-2020. Linear regression results show that the equatorial Pacific SST gradient contributed 70.59% to the surge intensity index in 1988. Further examination of wind field characteristics after removing the influence of the SST gradient reveals that, apart from the enhanced spatial extent of the surge event in late February, both the frequency and magnitude of surges decreased significantly from mid-March onward. To gain deeper insight into the specific causes of the easterly wind surges, a typical case analysis was then conducted to investigate the triggering mechanism of a representative event. Composite analysis confirms that the strong easterly wind surge at the end of March 1988 was closely linked to the convectively active phase of a Madden-Julian Oscillation (MJO) event over the Maritime Continent, which contributed approximately 42.96% to the surge’s formation.

Ocean waves are a fundamental component of marine dynamics, exerting significant impacts on maritime navigation and offshore operations. The wave spectrum provides an effective representation of the statistical distribution of wave energy across the frequency domain. In this study, observational data from 70 NDBC buoy stations were used to retrieve significant wave heights based on both the JONSWAP spectrum and the third-order Stokes nonlinear spectrum. Results show that, compared with the JONSWAP-based retrievals, the nonlinear spectrum achieves average improvements degree exceeding 10% in both absolute and relative errors, with maximum improvements degree of 28.54% and 22.29%, respectively, demonstrating the nonlinear spectrum’s clear advantages. Further analysis indicates that the performance degrees of the nonlinear spectrum are closely related to significant wave height, wind speed, the angle between wind and wave directions, and water depth. Specifically, the improvement degree increases with larger wave heights and stronger winds; smaller directional angle between wind and waves yields greater benefits, though wind speed exerts a much stronger influence than directional angle. In water depths shallower than 500 m, the inversion accuracies of both wave spectras are higher than those in depths deeper than 500 m. However, within the depth range of 500-5 500 m, the improvement degree in the nonlinear spectrum exceeds that in the shallow-water region, showing a linear increasing trend.

To assess the potential impact of plumes generated by deep-sea mining on the midwater ocean, this study systematically analyzed the flow field characteristics of the intermediate currents at the 1 000 m and 2 000 m in deep-sea mining areas of the Pacific Ocean (Western Pacific: Block C, Block M, Block CW, Block WJ; Eastern Pacific: Block A5, Block KW, Block EK, Block A12678, Block A3, Block A4) and predicted the zonal movement trend of midwater plumes. The analysis was based on the global Argo float trajectory and mid-depth current dataset from the China Argo Real-Time Data Center covering the period from August 1997 to October 2024, combined with data from 3 moored observation stations. The results show that: (1)The currents at the 1 000 m layer in the Pacific mining areas are mainly controlled by zonal currents, with the velocity of eastward jets being greater than that of westward jets. The velocity and direction of currents in the mining areas are sensitive to changes in latitude. (2)The eastward jets that affect the 1 000 m flow field in the Western Pacific mining area have the center located at 14°N (weak) and 18°N (strong). Under their influence, in the southern part of the Block M, the midwater plumes move eastward. In other areas, the midwater plumes move slowly westward.(3) The eastward jets that affect the 1 000 m layer of the Eastern Pacific mining areas have the centers located at 7°N and 9°N. They are stronger in summer and autumn, and weaker in winter and spring. (4)The flow field directional characteristics in the 2 000 m area of Block M, Block A5, Block KW and Block EK are the same as those in the 1 000 m layer, indicating that the depth affected by jets can reach 2 000 m.

Optical survey and evaluation of deep-sea polymetallic nodules face challenges such as low contrast, small object detection, and boundary ambiguity. This study proposes an improved Mask R-CNN model incorporating dynamic sparse convolution (DSConv) and simple parameter-free attention module (SimAM) for nodule image segmentation. SimAM effectively suppresses sediment background interference, while DSConv alleviates boundary blurring. The combined model achieves an accuracy of 91.5%, precision of 78.0%, recall of 75.1%, and IoU of 69.4%. When applying the improved model and the original model to the actual survey lines, it was found that in the identification results of the seabed nodules coverage rate, the proportion of data with an error less than 5%, increased from 57% of the original model to 77% of the improved model. This research can provide a reliable technical solution for the calculation of deep-sea polymetallic nodule coverage rate, and its modular design can also be extended to other fields of target recognition and image segmentation.

Accurate assessment of tidal flat erosion and deposition dynamics is very important for coastal zone resource management and disaster prevention and mitigation. However, due to the solidification of artificial shorelines and the time-lag effect of tidal flat profile evolution, the methods based on shoreline transition often have great uncertainty in evaluating tidal flat morphology and dynamics, and the analysis of the internal mechanism is also relatively insufficient. In this study, synchronous hydrological-sedimentary-geomorphological dynamic measurements were carried out for 19 consecutive tidal cycles in the upper, middle and lower intertidal zones on the Dafeng tidal flat on the coast of Jiangsu in May 2021. A sediment conservation model was constructed to quantitatively analyze the transport process of sediments during the observation period and its relationship with the dynamic changes of tidal flat landforms. The results show that the erosion and deposition changes estimated based on sediment budget are basically consistent with the measured elevation changes, which verifies the effectiveness of this method in describing the tidal flat landform dynamics. In addition, the analysis also shows that high energy dynamics (such as spring tide and strong wind wave) are the main driving forces of tidal flat erosion. This study can provide a new empirical basis and method support for the research and scientific management of tidal flat landform process.

The new seawall ecological armour block is a type of face protection structure with both excellent wave dissipation performance and ecological function. In order to systematically evaluate its wave dissipation performance, this study carried out a two-dimensional wave flume physical modeling test using Zhoujiayuanshan Island in Zhoushan as the engineering background. The test systematically investigated the effects of wave period, wave height, relative water depth, wave steepness, breaking parameter, and block geometry (outer diameter and height), as well as model materials on the reflection coefficients under the action of regular waves. The results show that: firstly, the feasibility of using polypropylene random copolymer (PP-R) instead of foamed concrete in the physical modeling test is verified through the comparison experiments of nine working conditions, and the average difference in their reflection coefficient is only 1.17%. Secondly, for its wave dissipation performance, the reflection coefficient increases with increasing wave period, relative water depth and breaking parameter, and decreases with increasing wave height and wave steepness. Among all the tested conditions, the two types of blocks with outer diameter 7.5 cm-height 10 cm and outer diameter 10 cm-height 6.5 cm have the best wave dissipation performance, with average reflection coefficients of 0.395 and 0.382, respectively. Finally, the reflection coefficient formula for the six types of blocks is fitted based on the experimental data in this study. The formula has a root mean square error (RMSE) of 0.106 9, which is of high accuracy and our study can provide a certain reference for related engineering design.

Given the underutilization of elemental geochemistry in paleoenvironmental and sea-level studies during the Late Pleistocene in southern Hangzhou Bay, this research employs an integrated approach using core NZD01. Combining sedimentological analysis, grain-size distributions, and key geochemical proxies (Sr/Cu, CIA, CIW, Sr/Ba, 100×(MgO/Al₂O₃), U/Th, Ni/Co) with AMS ¹⁴C dating and correlation of magnetic susceptibility with speleothem δ¹⁸O records, we aim to reconstruct the sedimentary evolution sequence and its responses to climate-sea level interactions. Five sedimentary facies were identified: fluvial channel, floodplain, estuarine, shallow marine and modern estuary. Grain-size characteristics indicate a hydrodynamic evolution process: from strong to relatively weak, then to stronger and more complex, followed by weak and stable, and finally to moderate conditions. Geochemical indicators reveal: (1) Sr/Cu ratios document a distinct paleoclimatic transition from arid to warm-humid and finally to semi-arid conditions with frequent humidity-aridity oscillations since the Late Pleistocene; (2)CIA and CIW values indicate weathering intensity variations: moderate weathering phase, moderate-dominated phase with localized intense weathering,moderate weathering recurrence, generally moderate phase with intermittent primary weathering, and transition from moderate to primary weathering(frequent fluctuations); (3) Sr/Ba and 100×(MgO/Al₂O₃) demonstrate rising paleosalinity responding to Last Deglaciation transgression; (4) U/Th and Ni/Co ratios suggest overall oxidizing conditions, with Ni/Co peaks in Unit I potentially marking extreme marine events. This study demonstrates that element geochemical approaches effectively reveal the evolutionary sequence from continental to marginal marine environments and their responses to climate-sea level fluctuations in this region.

Oyster reefs are one of the important coastal habitats. Over the past century, oyster reefs have been severely degraded worldwide. However, with the gradual recognition of the irreplaceable ecosystem service functions of oyster reefs, the significance of oyster reef conservation and restoration has become prominent in the global efforts to restore and protect degraded coastal ecosystems. This study systematically collects and collates the distribution information of natural oyster reefs and artificially restored oyster reefs in China, summarizes the main work and achievements in the field of oyster reef conservation and restoration in China since the beginning of this century. Combined with the author’s practical experience in the Wenzhou coastal zone protection and restoration project (oyster reef), the technical process of restoration is described in detail, with emphasis on the design and structure of the inclined support composite oyster reef and the artificial seedling attachment technology used in the restoration project. Corresponding suggestions are put forward, which can provide references for future oyster reef conservation and restoration work.

Deep-sea seamounts are known as hot spots of marine biodiversity, supporting a high richness of deep-sea biological communities. However, a key question in deep-sea ecology remains: how do benthic communities on these seamounts thrive despite the limited availability of food sources? To explore the food sources of the megabenthic communities from a deep seamount (the Weijia Guyot) in the oligotrophic open ocean, we measured the stable isotope values (δ¹³C and δ¹⁵N) of eight representative benthic groups (Porifera, Anthozoa, Gammaridea, Asteroidea, Crinoidea, Ophiuroidea, Holothuroidea and Tunicate) as well as two potential food sources (zooplankton and surface sediments). The results showed that the δ¹⁵N values of zooplankton increased with water depth. The δ¹⁵N value of surface sediments were 7.7‰. The δ¹³C and δ¹⁵N values of benthos exhibited a wide range of variation (δ¹³C: -22.9‰ to -15.1‰, δ¹⁵N: 8.3‰ to 19.2‰). The differences in δ¹⁵N values between zooplankton, surface sediments, and some benthic species were approximately equivalent to one trophic level, suggesting that they might serve as direct food sources for some megabenthos. However, the substantial variation in δ¹³C and δ¹⁵N values among different megabenthic species indicated that additional, unidentified food sources also likely contribute to their diets. This study provides a preliminary analysis of carbon and nitrogen isotope variations among the major benthic communities of deep-sea seamounts and explores their possible food sources. Our findings offer valuable insights into the food web and trophic structure of deep-sea seamount ecosystems, make contributions to a better understanding of the function of this unique environment.

The Western Pacific is characterised by high species diversity. However, limited studies have been carried out in the past, particularly in terms of biology in the Western Pacific seamount region owing to its unique geography. Therefore, it is important and necessary to carry out zooplankton species diversity study in this region. In this study, 15 dominant zooplankton species (Pleuromamma robusta, Nannocalanus minor, Haloptilus longicornis, Corycaeus speciosus, Scolecithrix danae, Euchaeta rimana, Chelophyes appendiculata, Bassia bassensis, Eudoxoides mitra, Abylopsis eschscholtzi, Abylopsis tetragona, Sagitta enflata, Sagitta pacifica, Paraconchoecia oblonga, Thalia democratica) collected by macroplankton net from eight stations in the Western Pacific seamount region were microscopically photographed, morphologically described, and their geographical distribution and ecological habits were analysed. This study provides a scientific basis and reference for more in-depth future studies on the composition, distribution, origin, dispersal, zonation and geographic characteristics of marine zooplankton species in the Western Pacific.

Coastal wetland ecosystems have important carbon sink function. Human life, industrial and agricultural production will input heavy metals into wetlands, however, the impacts of heavy metals on various soil carbon components are still unclear. Based on the comparison of the soil carbon component content in the different types of coastal wetlands in Yueqing Bay of southern Zhejiang Province, it was found that the contents of soil organic carbon (SOC), easily oxidizing organic carbon (EOC) and dissolved organic carbon (DOC) in the adult mangroves, young mangroves, Spartina alterniflora salt marshes and mudflats presented the significant regional and inter-habitat differences. Soil total carbon (STC) and microbial biomass carbon (MBC) presented the significant regional differences. By monitoring the spatial distribution of heavy metals, the results showed that the contents of Cd, Pb and Hg in the coastal wetlands adjacent to industrial/agricultural lands and residential area were higher than those in the non-disturbed areas. Correspondingly, the contents of STC, SOC and EOC of the high-disturbed wetlands were lower than those of the non-disturbed wetlands. Furthermore, the results of redundancy analyses (RDA) showed that the STC, SOC and EOC contents were significantly negatively correlated with the Hg and Cd content in the S. alterniflora salt marshes; the SOC and EOC contents were significantly negatively correlated with the Pb and Zn contents in the adult mangroves; the STC, SOC and EOC contents were significantly negatively correlated with the Pb and Cr contents in the young mangroves; and the STC, SOC and EOC contents were significantly negatively correlated with the Cd and Cr contents in the mudflats. This reflects that the increased heavy metals might cause a negative impact on the soil carbon pool. However, the RDA analysis indicated that the MBC content was positively correlated with some heavy metals, probably reflecting the adaptability of the microbial community in the coastal wetland to the low content of heavy metals. The results of this study can provide scientific basis and data support for the environmental quality assessment and natural carbon sink management of coastal wetlands in Zhejiang Province.