To better understand the influence of sea surface temperature (SST) on tropical cyclones rapidly intensifying, the characteristics of rapid changes in sea surface temperature and intensity of tropical cyclones in the western North Pacific during 1979−2019 were statistically analyzed using the tropical cyclones best track data compiled by the Shanghai Typhoon Research Institute of the China Meteorological Administration and the sea surface temperature data provided by European Centre for Medium-Range Weather Forecasts. The results indicate the following: (1) About 90% of the rapid intensification of tropical cyclones occurred in summer and autumn, accounting for 32.8% and 56.4% of the total number of rapid intensification respectively. Most tropical cyclones are dominated by rapid intensification across one intensity level, rapid intensification from a severe tropical storm to a typhoon and rapid intensification from a typhoon to a severe typhoon are the two conditions that occur more frequently. (2) The SST conditions greater than 28℃ in summer and 27.5℃ in autumn are conducive to the rapid intensification of tropical cyclones. Lower intensity of tropical cyclones require higher SST (> 29℃) for rapid intensification. The faster translation speed of tropical cyclones is conducive to maintaining high SST environment at its center. (3) When the time variation of SST is within ±0.2℃/(6 h), the horizontal spatial gradient is less than 0.4℃/(°), which is the favorable condition for the rapid intensification of tropical cyclone; the stronger the tropical cyclone is, the more stable the SST environment is needed. (4) When tropical cyclone is a severe tropical storm or above, it is better to judge whether rapid intensification occurs by using only the SST conditions. This work quantifies the SST environment conducive to tropical cyclone intensification and provides a technical reference for quantitative prediction of tropical cyclone intensity evolution based on SST.

Early melt onset (EMO) is a crucial time index for sea ice melting and has a significant impact on the thermal balance of sea ice. In this paper, EMO remote sensing, ERA5 reanalysis, and sea ice concentration data have been used to reveal the relative contribution of surface air temperature and liquid precipitation. Our research indicates that, the most significant advancement of EMO is observed in the southern Atlantic sector among the five study sea areas from 1979−2021, with the rate of −3.3 d/(10 a). For the atmospheric factors affecting EMO, surface air temperature has a considerable correlation period lasting 1−2 months with EMO in all Arctic sea areas. In addition, surface air temperature in the southern Pacific sector and northern and southern Atlantic sectors have a longer duration and stronger correlation with EMO than liquid precipitation. However, for the northern Pacific sector and the central Arctic, liquid precipitation has a higher contribution only in the 2−3 weeks prior to EMO. For the northern Pacific sector, atmospheric circulation provides strong water vapor transport channel extends into this sea area, increasing saturated water vapor in the lower troposphere. Meanwhile, the trend of the 500 hPa potential height shows a three-wave strengthening atmospheric circulation structure around the pole, allowing meridional heat exchange and enhancing the vertical gradient of specific humidity, which promotes the advancement of EMO. For the central Arctic, in years when EMO is advanced, the liquid precipitation is 33% higher than climatology. Additionally, not only the Pacific water vapor transport in the climatology is enhanced, but also the converges with water vapor channel over Eurasia continent, contributing to the formation of cyclonic water vapor transport mode in the eastern Arctic, providing conditions for the advancement of EMO.

Based on the nonhydrostatic single-phase flow numerical wave model (NHWAVE), the propagation of random waves on a permeable fringing reef is simulated numerically, and the effects of incident wave height, water depth on reef flat, spectrum peak period, thickness of permeable layer, porosity and median diameters the hydrodynamic characteristics of waves on the fringing reef are considered comprehensively, focusing on the variation of sea-swell wave height, infragravity wave height and mean water level along the reef, and comparing with that of the fringing reef without permeable layer. The study shows that the existence of the permeable layer has a significant impact on the hydrodynamic characteristics of waves on the fringing reef. The study shows that the existence of the permeable layer reduces the shallow water deformation of waves on the slope in front of the reef and the wave breaking near the reef edge, and significantly decreases the sea-swell wave height, infragravity wave height, and wave setup near the shoreline, in addition to that, the existence of the permeable layer reduces the maximum wave runup on the shoreline. The greater the incident wave height and spectrum peak period, the more significant the effect of the permeable layer on the sea-swell wave, infragravity wave and wave setup on the fringing reef; when the water depth of the reef is increased, the effect of the permeable layer on wave attenuation is weakened; as the thickness of the permeable layer increases, the values of sea-swell wave height, infragravity wave height and wave setup near the shoreline decrease.

Typhoons are one of the major global environmental disasters, and their variability is of great concern to modern society. However, the variability of typhoon activity and its climate drivers on centennial-millennial scales are less clear due to the lack of atmospheric instrumental records before the mid-19th century. Coastal sedimentary archives provide a means to extend our knowledge of typhoon dynamics, of which the effective identification of typhoon event layers is an important foundation. Although many studies have attempted to reconstruct typhoon activity on long time scales using various indicators and methods, there is still a lack of evaluation of the effectiveness of these indicators and methods for the identification of typhoon event layer. In this study, a high-resolution sedimentary record (Core ZM02) from the muddy belt of inner shelf of the East China Sea was used, and its dating framework was determined using ²¹⁰Pb and ¹³⁷Cs dating methods. The instrumental and sedimentary records were then coupled to analyze the correspondence between typhoon intensity and frequency and sensitivity indicators of typhoon deposits (i.e., sand content and D₉₀ in this study). The results show that the upper 4.5−100 cm of the core dates between 1917 and 2011 AD at a sedimentation rate of 0.97 cm/a. Among the three technical solutions, the threshold method was found to have the best identification and highest stability. Both sand content and D₉₀ were found to be effective indicators for the identification of typhoon deposits in the study area. Sand content may be a potential indicator of typhoon intensity variation along the Zhejiang coast, and D₉₀ contains information on typhoon frequency. The knowledge obtained here will not only contribute to the more accurate use of the sedimentary record to extend the time span of the typhoon record, but also to improve the ability to decipher information from the sedimentary record.

In this paper, we analyze the variation of local dense shelf water around the Cape Darnley fast ice by using a landfast ice dataset and in-situ observation data of Antarctic elephant seals. The results show that: firstly, there are significant seasonal variations of Cape Darnley fast ice, which has a vital impact on the formation of the Cape Darnley polynya and the local dense shelf water. Secondly, the interannual variation of Cape Darnley fast ice is minimal from 2000 to 2014, with no significant trend of increasing or decreasing. Thirdly, we identify two significant sources of local dense shelf water near the Cape Darnley fast ice area: (1) dense shelf water produced by the strong brine rejection process during the rapid generation of Cape Darnley fast ice from March to April; (2) Cape Darnley fast ice reaching its maximum extent and local brine rejection being reduced to a minimum in May. After the weakening of the inhibition of ice shelf water, the formation of dense shelf water in the upstream MacKenzie Bay polynya is enhanced and transported northwest to the vicinity of the Cape Darnley fast ice. In this study, we preliminarily demonstrates that, in addition to maintaining Cape Darnley polynya, Cape Darnley fast ice probably has an important influence on the generation of local dense shelf water, and points out an important water mass transport path. These would help improve the comprehension of ice-sea interaction near Cape Darnley and point out the need for more observations or modeling studies in this area.

In recent years, large yellow croaker (LYC) has been caught with high abundance in the East China Sea (ECS), which raises concerns about the conservation of LYC resources. We collected LYC samples from spawning grounds and wintering grounds in the offshore Zhejiang from 2020 to 2022. In order to find out the migration route of LYC in the ECS, we made use of otolith microchemical elements by LA-ICP-MS analysis, combined with the clustering analysis and PCA of trace elements such as Ba/Ca, to classify different LYC groups. With the age characteristics of otolith, the habitat patterns of LYC group was studied, and the updated migration route of LYC was speculated. The results showed that groups with Ba/Ca $\leqslant$ 0.004 2 was inhabited in the marine region. That with Ba/Ca $\geqslant$ 0.008 1 was inhabited in the estuary region, and that with 0.004 2 < Ba/Ca < 0.008 1 was inhabited in the mixed (estuary and oceanic) habitat. The five group types of LYC were: (1) offshore spawning, short-term mixed waters inhabited (accounting for 22.2%); (2) offshore spawning, periodically back and forth with mixed water inhabited (accounting for 15.6%); (3) offshore spawning, feeding and nursering in estuary waters, and wintering inhabited in the open sea (31.1%); (4) estuary spawning, nursering in the mixed waters, overwintering inhabited in the open sea (6.7%); (5) shortly spawning in the mixed waters, most of the time inhabited in the open ocean (24.4%). PCA was performed with Ba/Ca core, peak and edge values of all samples, and the results showed that samples from five groups were evenly distributed on both sides of the first axis: G1, G2 and G5 groups, which spent most of their time in the ocean, and G3 and G4 groups, which were heavily influenced by terrestrial sources. At the same time, the PCA results also showed that all the samples appeared nearly synchronously near the island or reefs, indicating that populations in the open sea, offshore and estuary waters may mix due to factors such as migration, indicating the importance of Zhoushan offshore waters for LYC nursering and spawning. This study provides a certain basis for the migration history of the LYC in the ECS between its coastal spawning, feeding grounds and its overwintering grounds in the open sea, as well as for the speculation of its migration routes.

Diaphus is one of the genera with the highest species abundance and the most abundant population in the family Myctophidae, and it is also the dominant group of deep sea fishes in the ocean. However, due to the high similarity of external morphology, it is difficult to identify the lanternfish species. In order to explore the feasibility of otoliths morphological analysis in identifying the otolith differences between Diaphus species with similar otoliths and large overlapping distribution areas, the otoliths of three Diaphus species were collected from the Indian Ocean and the South China Sea for morphometrics analysis with landmark method. The results showed that the morphological variation of sagittal otoliths in three lanternfishes were mainly in the internal main sulcus, and the internal punctuation contribution rate reached 62%. The grid difference visualization showed that the wing length of sagittal otoliths in D. thiollierei was longer than that of the other two species, while the width was slightly narrower. The Bayes function was used for classification and discrimination, and the results showed that the success rate of D. thiollierei was 100%, while the other two species had a few misjudgments. In addition, taking into account the habitat environment and the genetic relationship between these three species, we supposed that the main reason for the morphological differences in the main sulcus of the three spescies was the huge salinity difference in the habitat sea area. However, the impact and physiological mechanism of salinity on the morphology of the main sulcus of sagittal otoliths needs to be further studied.

The Huanghe River Delta is an important ecological function area in China. It is of guiding significance to explore the distribution of suspended sediment concentration (SSC) at the estuary and its influencing factors for sediment erosion and re-suspension, and the ecological process in the estuary and coastal zone. Based on the relationship between chromaticity angle and SSC, an SSC inversion model (R² = 0.80, MRE = 11.0%, RMSE = 1.35 mg/L) suitable for the Huanghe River Estuary and its adjacent sea areas is established in this paper. With the help of the GEE (Google Earth Engine) platform, the spatial and temporal distribution characteristics and changing rules of SSC in the Huanghe River Estuary and its adjacent sea area during the 22 years from 2000 to 2021 were studied, and the influencing factors were analyzed from two aspects of nature and human activities. The annual average value of SSC in the study area showed a downward trend (−1.83 mg/(L·a)). The spatial distribution shows that SSC gradually decreases from near shore to far shore; the diffusion interval (SSC > 20 mg/(L·a)) is only 4.8−14.6 km away from the estuary, and the influence of sediment from the Yellow River on the current sediment diffusion at the estuary is limited. The wave and suspended sediment concentration have the same seasonal characteristics. During the non-water and sediment regulation period, there is a positive correlation between the effective wave height and the SSC interdecadal monthly average (r = 0.66, p < 0.01). During the period of water and sediment regulation, the current SSC at the mouth of the Huanghe River and Laizhou Bay is limited by wind speed and effective wave height, and water and sediment regulation is dominant. During the period of water and sediment regulation, there is a positive correlation between the incoming sediment coefficient and the area change rate of high-concentration areas. After the water and sediment regulation (within 16 days), the boundary of the high concentration area (SSC > 200 mg/L) is expanded from about 1.3 km to about 2.5 km from the coast.

Accurate extraction of marine raft aquaculture area information is of great significance for marine resource management and environmental monitoring. But the raft culture area is often submerged in water with weak data signal areas, resulting in low extraction accuracy based on optical images alone. Therefore, this paper takes Weihai Rongcheng Bay as the research area, and improves the U-Net neural network by adding channel attention mechanism to combine the spectral information of GF-2 optical image and the texture information of GF-3 radar image, trying to improve the extraction accuracy of raft aquaculture area. The results show that: （1) Whether it is a single optical image or a fusion image of optical and radar images, the overall accuracy of the prediction results of the U-Net neural network with channel attention mechanism will be improved, with an increase of 2.21%−4.12%. （2) Using the improved U-Net neural network to process the fusion data, the overall accuracy is 95.75%, which is 4.3% higher than that of only using GF-2 image. （3) For weak signal region, the overall accuracy and Kappa coefficient of extraction based on improved network and data fusion are 91.61% and 0.827 7, respectively. This method can effectively extract the weak signal area of marine raft aquaculture area, and can provide technical support for marine aquaculture area statistics and marine environment detection.

In order to clarify the effects of litter decomposition of Gracilaria lemaneiformis segments on environment and the succession of bacterial community, the characteristics of nutrient content in seaweed, water and sediment, and succession characteristics of bacterial community attached to the seaweed, water and sediment were carried out by the simulation experiment. The results showed that its decomposition rate reached 83.5% after 50 d. The content of total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) in water increased by 241.2%, 229.8% and 101.3%, respectively, compared with the initial period. The content of dissolved oxygen (DO) in water decreased by 82.9%, which from 1.87 mg/L to 0.32 mg/L. In addition, the number of bacteria attached to G. lemanei-formis remained at 10⁷ copy/g, while the richness and diversity of bacteria continued to increase during the decomposition processes. The bacteria community structure was significantly affected by total organic carbon, total nitrogen, total phosphorus and DO in water. The relative abundances of Planctomycetes, Spirochaetae, Firmicutes and δ-Proteobacteria increased, while that of Bacteroidetes, α-Proteobacteria and γ-Proteobacteria decreased. During the process of decomposition, the functional gene abundance of metabolism attached to G. lemaneiformis continued to decline. Briefly, the results indicated that decomposition of G. lemaneiformis segments would lead to the increasing of nutrient concentration in water. And Planctomycetes, Spirochaetae, Firmicutes and δ-Proteobacteria played important roles in the process of decomposing of G. lemaneiformis.