Based on tropical cyclone (TC) disaster data and the best-track database from Shanghai Typhoon Institute of China Meteorological Administration (CMA-STI) during 1984 to 2017, this study analyzed the spatial-temporal characteristics of TC disaster in China and their differences for the three prevailing tracks, along with the discussion of the overland duration and its potential risk. Main results of this study were summarized as follows: (1) There was a significant upward trend with direct TC-associated economic losses, while the proportion of losses to Gross Domestic Product (GDP) and the deaths showed a downward trend. (2) TC-associated economic losses accompanied with the three prevailing TC tracks showed a substantial difference. The recurving TCs tended to be less and lower impact, while westward and west-northward TCs appeared to be more and higher impact in China. Particularly, more frequent TCs with westward movement affected the Guangdong, Guangxi and Hainan provinces. TCs tending to west-northward tracks mainly caused a serious TC-associated disaster in Guangdong, Fujian, and Zhejiang provinces. (3) The average overland duration, as a potential index for TC-associated disaster, showed an upward trend. Note that the reasons on the changes of TC overland duration for the three prevailing tracks appeared to be different. The increased average overland duration for recurving TCs were likely to relate to the decreased in TC average overland translation speed. In contrast, the increased average overland duration of westward and west-northward moving TCs were possibly due to the increased average distance that TCs traveled over land.

This study aimed to investigate the allelopathic effects of Sesuvium portulacastrum (Aizoaceae) on typical red tide algae and identify the sources of the active compounds. Three red tide algae species, Prorocentrum micans, Karenia mikimotoi, and Alexandrium catenella, were selected as test subjects. The planting water of the coastal salt-tolerant plant Sesuvium portulacastrum served as the research material. Root exudates from the plant were adsorbed using a C₁₈ solid-phase extraction column and then extracted with methanol, ethyl acetate, dichloromethane, and n-hexane. The four extracts exhibited varying degrees of inhibition on the growth of the algae, with the dichloromethane extract showing the most significant inhibitory effect. At a concentration of 10 g/L, the inhibition rates for the three algae species were 50.83%, 97.30%, and 81.41%, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis identified 19 fatty acids and their derivatives. Among these, stearic acid, oleamide, and docosanol exhibited algicidal activity, with docosanol showing the strongest effect. At a concentration of 2 mg/L, the inhibition rates for the three algae species were 90%, 100%, and 81.04%, respectively. These results indicate that Sesuvium portulacastrum can release fatty acids and their derivatives to inhibit the growth of red tide algae, demonstrating its potential as a plant-based tool for red tide control and environmental remediation.

The Zhujiang River Estuary is located in the northern South China Sea. It has a wide intertidal zone and a high diversity of intertidal macrobenthos. However, most of the previous intertidal-related studies and intertidal species records were carried out on the east coast of the Zhujiang River Estuary, while studies on the west coast of the Zhujiang River Estuary were relatively scarce. From 2021 to 2023, a comprehensive survey focus on Brachyura (crabs), one of the main groups of intertidal macrobenthos, was conducted in the intertidal zone of Qi’ao Island, Zhuhai City, western Zhujiang River Estuary. Combined with the collection and revision of species recorded in previous studies, an updated checklist of intertidal crabs in Qi’ao Island was created, and the ecological and geographical distribution of these crab species were described. A total of 90 specimens were colleted and 31 species from 10 families and 21 genera were identified. Seventeen species (e.g. Orisarma patshuni and Anomalifrons lightana) were new to the Qi’ao Island, and one species (Hemigrapsus takanoi) were new to the Zhujiang River Estuary. The updated checklist includes 48 intertidal crab species belonging to 13 families and 29 genera, among which Sesarmidae (10 species), Varunidae (10) and Ocypodidae (8) are the three most species-rich families. The crab fauna composition of the island is mainly composed of East Asian endemic taxa and Indo-West Pacific/West Pacific widespread taxa, showing overwhelming East Asian warm water characteristics. Mudflats and mangroves are the most abundant habitat types for crab species on the island. Our results has increased the number of intertidal crab species on the west coast of the Zhujiang River Estuary from 31 to 55 species, which is the same as the number of species recorded in Shenzhen Bay on the east coast of the Zhujiang River Estuary. The total number of intertidal crab species recorded in the Zhujiang River Estuary has reached 77 species in 14 families and 38 genera, of which 33 species (42.9%) has been reported on both the east and west coasts.

Using tide gauge observation, satellite altimeter data, and the result of 10 CMIP6 Earth System Models with good simulation performance, the long-term trend of sea level change in China, and predicts the range of sea level rise in the future are analyzed in this study. The results show that: (1) from 1960 to 2021, the sea level in China’s coastal areas showed an accelerated rising trend, with a rise rate of 2.5 mm/a and an acceleration of 0.06 mm/a². From 1993 to 2021, the rise rate was 4.0 mm/a, higher than the global rate of 3.3 mm/a in the same period. (2) From 1980 to 2021, the sea level rise rates of the Bohai Sea and the Yellow Sea, the East China Sea and the South China Sea were 3.5 mm/a, 3.3 mm/a and 3.6 mm/a, respectively. The sea level rise rates of the Bohai Sea and the Yellow Sea, the South China Sea were relatively fast, while the sea level rise rates of East China Sea was slow. The coastal sea level rose slowly from 1960s to 1970s, and accelerated after 1980s in the Bohai Sea and the Yellow Sea. (3) Under the medium (SSP2-4.5) and high (SSP5-8.5) scenarios, China’s offshore sea level will rise by 0.22 m (0.19−0.28 m) and 0.24 m (0.21−0.33 m) respectively in 2050, and will rise by 0.59 m (0.47−0.80 m) and 0.83 m (0.64−1.09 m) respectively in 2100. (4) During 2021−2040, the median value of sea level rise predicted by statistics is close to the predicted value under the low, medium and high scenarios of the numerical model. During 2041−2060, the predicted values of the low, medium and high scenarios of the numerical model are between the middle and high values of the statistical prediction. During 2081−2100, the high value of sea level rise predicted by statistics is close to that predicted by the medium scenario of the numerical model, the absolute deviation is 0.017 m, and the relative deviation is 3.4%. (5) Under the high scenario, the existing once-in-a-century extreme high sea level in 2100 will become less than 10 year return period, in which more than 50% of the stations will become less than 2 year return period, the defense capacity of coastal protection works and other infrastructure will be reduced, and the risk of flood and other disaster events in complex coastal cities will increase.

Phytoplankton blooms in polar regions with seasonal sea ice cover show a unimodal seasonality. However, the bloom processes are controlled by multiple physical and biogeochemical factors, including sea ice, light availability, mixed layer depth, and nutrients; those may result in great uncertainties in simulating phytoplankton bloom by the Earth System Models (ESMs). In this study, the results of 11 Coupled Model Intercomparison Phase-6 (CMIP6) ESMs were analyzed and evaluated with various types of observational products in order to determine whether those ESMs can correctly model the phytoplankton blooms in three Arctic shelf seas, Barents Sea, Chukchi Sea, and Bering Sea. By calculating multiple indices that represent light and nutrient limitations, the error sources of simulated surface chlorophyll a concentrations were comprehensively analyzed. Our results show that the 11 ESMs can be divided into three groups based on ice-adjusted photoperiod, rate of change of mixed layer depth, and surface nitrate concentration. Some groups are characterized by the smallest bias between modeled indices and observation-based reference, and those ESMs perform best in simulating phytoplankton bloom characteristics. The other groups of ESMs differ significantly from the reference values in terms of surface nitrate and/or rate of change of mixed layer depth, resulting in delayed occurrences of annual chlorophyll a peak concentration and greater differences in corresponding peak values. In general, in addition to the two primary constraints of light and nutrients, the ESMs should also well represent the upper mixed layer controlled by temperature and salinity distributions, so as to accurately simulate the seasonal variation of surface chlorophyll a concentration. The above analyses indicate ESMs can be used in assessing polar planktonic ecosystems, and there is room for improving ecosystem-related parametrization in future ESM development.

In order to identify the functional diversity of the adjacent waters of the Changshan Islands in the ecotone between the Yellow Sea and the Bohai Sea, based on the quarterly survey of fish biological resources and environment factors from October 2016 to August 2017, combined with 13 functional traits such as feeding habit, trophic level, migration type, thermophily, resilience and fish eggs type, the spatio-temporal pattern of functional diversity and its relationship with environmental factors were studied by using community weighted mean index (CWM), functional diversity index and Spearman rank correlation analysis. The results showed that the dominant species of fish community in spring and winter were depressiform, warm temperate and demersal species with the characteristics of anterior or upper mouth, low growth coefficient, high vulnerability, low resilience and non-migration or short distance migration. The dominant species in summer and autumn showed more functional traits, such as long distance migration, pelagic, fusiform and compressiform. FRic in summer and autumn was significantly higher than that in spring and winter, FEve was the highest in spring, and FDiv was the lowest in autumn and was significantly lower than other seasons. FEve in spring and season and FDiv in spring and autumn showed a trend of high in the west and low in the east, while FRic in summer and winter and FEve in autumn showed a trend of high in the east and low in the west. There was a certain correlation between environmental factors and functional diversity index. As an ecotone between the Yellow Sea and the Bohai Sea, the functional traits of the dominant species and functional diversity show seasonal variations made by the fish migration, and the spatial pattern of functional diversity shows complexity and heterogeneity made by environment changing in the adjacent waters of the Changshan Islands.

Due to the limitations of the Rayleigh criterion, classical harmonic analysis (CHA) model requires half a year of data records to analyze the eight main tidal constituents, namely, M₂, S₂, N₂, K₂, K₁, O₁, P₁, Q₁. For short-term tidal records, the unresolved constituents typically rely on the ratio differences from nearby long-term tidal stations for estimation. However, there is a scarcity of publicly available long-term tidal data in the coastal areas of Zhejiang, which currently prevents the accurate extraction of the main constituents from short-term records. This paper introduces a modified harmonic analysis model, referred to as the Modified Harmonic Analysis model based on the Credo of Smoothness (MHACS). Based on the smooth functions established by the intrinsic connections between major constituents, it breaks through the Rayleigh criterion, significantly reducing the length of tidal records required, especially suitable for coastal areas with abundant short-term data. This algorithm was applied to the multi-island area of Zhejiang offshore, using tidal records shorter than 15 days. The results show that the harmonic constants of the eight main constituents at the Shipu station are very close to the results obtained by the CHA method, and the required data length is reduced from 8760 hours to 336 hours, which can be used to calculate characteristic parameters such as the theoretical depth datum. For analyzing the eight main constituents along the Zhejiang coast using MHACS, a minimum data length of 5 days is recommended.

Mangroves represent the most productive ecosystem along the coastline. The mangrove forest is a source of diverse organic carbon, which contributes to the complexity of the trophic structure of the benthic food web. This study employed the benthic animals in the mangroves along Yanpu Bay as the research object, analysing the community trophic structure and determining the potential food sources through the utilisation of the stable isotope technique in conjunction with the Stable Isotope Bayesian Ellipses (SIBER) model and the Stable Isotope Mixing Models (Simmr). The study demonstrated that the carbon stable isotope (δ¹³C) values of benthic animals ranged from −22.04‰ to −11.27‰, while the nitrogen stable isotope (δ¹⁵N) values ranged the trophic levels ranged from 1.33 (Cerithidea rhizophorarum) to 3.95 (Periophthalmus cantonensis), with carbon stable isotope (δ¹³C) values from 5.86‰ to 16.21‰. The trophic level of fish is relatively high, ranging from 2.38 to 3.95, while that of crustaceans is 2.61 to 3.52. In contrast, the trophic level of mollusc is relatively low, ranging from 1.33 to 3.15. These differences are related to the feeding preferences of the different groups. The analysis of the nutritional structure indicates that the length of the food chain and the nutritional diversity of fish are greater than those of crustaceans and mollusc. The diversity of food sources and nutritional uniformity of crustaceans are the highest, while the nutritional diversity and similarity of mollusc are the highest. Overall, there is a varying degree of overlap between the core nutritional niches of fish, crustaceans and mollusc. An analysis of the potential food sources of benthic animals based on a Simmr mixed model revealed that SOM was the primary carbon source, accounting for 78.2% of the total, followed by phytoplankton, which constituted 21.6% of the total, while litter and POM represented the lowest proportions, at 3.7% and 3.3%, respectively. The findings of this study enhance our comprehension of the trophic relationships of benthic animals in mangrove ecosystems along the northern coast of China. They will facilitate more effective conservation and restoration of mangrove biodiversity from a trophic regulation perspective.

The annual, seasonal, monthly and diurnal variations of sea surface wind field over the Taiwan Strait were analyzed based on the new version of Cross-Calibrated Multi-Platform Version 3.1 (CCMP V3.1) wind data from 1993 to 2022. The results showed that the wind field in the Taiwan Strait and the water around Taiwan Island had obvious spatial distribution characteristics, the topographic effect leads to the maximum and minimum wind speed regions in different sea areas. Because the central Taiwan Strait was affected by the “narrow tube effect”, the wind speed was the highest and the wind direction was basically parallel to the strait in winter; the wind speed in summer was lower than the speed outside the channel, and there was no “narrow tube effect”. In addition, the sea surface wind field also had obvious seasonal and monthly variation characteristics. The northeast wind prevailed in winter, and in this season the wind speed was the highest in the whole year; the southwest wind prevailed in summer with the lowest wind speed; the characteristics of spring and autumn monsoon fields were similar, both prevailing northeast wind; winter monsoon last longer than summer monsoon, accounting for about three quarters of the year. The analysis of the inter-annual variation of wind field showed that the wind direction tended to deflect at a large angle in summer. The annual mean wind speed maintained a basically flat linear trend, and the abnormal high or low in some years was related to the occurrence of El Niño-Southern Oscillation (ENSO). When the diurnal variation characteristics were studied, it was found that the wind speed and direction fluctuated most at 20 PM. The wind speed varied periodically within a day. The diurnal variation of wind direction deflection was most obvious in summer.

The crown-of-thorns starfish (CoTS) outbreak has caused severe damage to coral reefs in China and the Indo-Pacific region. Fish predators have been considered as an important factor in controlling the population outbreak, but there is a lack of research on the fish that can prey on crown-of-thorns starfish in China. By collecting coral reef fish from five outbreak areas of crown-of-thorns starfish in the Xisha Islands, CoTS DNA was detectedin the intestinal contents of the reef fish using PCR technology, and which compared with reported CoTS larval predators. The results showed that a total of 62 fish belonging to 23 families, 36 genera and 50 species were captured in this survey. CoTS DNA was detected in the gut contents of four fish species, namely Naso lituratus, Dascyllus reticulatus, Chelilinus trilobatus and Lethrinus erythropterus. Among them, N. lituratus, C. trilobatus and L. erythropterusare reported for the first time as potential predators of CoTS. This study has identified the potential predators of CoTS for the first time in China, providing important references for the development of early prevention and control techniques for crown-of-thorns starfish.