In real ocean environments, natural reefs typically exhibit complex topography, with reef platforms presenting non-uniform characteristics. Previous extensive research has mainly focused on simplified stepped reef models and has not conducted in-depth studies on the impact of non-uniform reef platforms on the propagation and evolution characteristics of waves. To address the shortcomings of previous research, this paper conducted physical model experiments to systematically study the propagation and evolution characteristics of tsunami-like waves over complex reef platforms. Previous studies did not consider the impact of the non-uniformity of reef platform topography on solitary waves, therefore, this paper also analyzed the effects of incident wave height and reef platform water depth. To investigate the impact of non-uniform reef platform geometric characteristics on the propagation and evolution of tsunami-like waves and the load characteristics of sea walls under different incident wave conditions, this paper further carried out a series of high-resolution numerical calculations. First, physical experiments were used to verify the accuracy of the numerical simulation method, and then numerical calculations were used to study the effects of two wave parameters, incident wave height and reef platform submergence depth, and three complex reef topography factors—the height of the second reef platform, the position of the reef platform steps, and the slope of the reef front slope—on the maximum wave height along the path, reflection coefficient, maximum run-up height, distribution of the maximum impact pressure on the sea wall, and the variation of the maximum total force and total moment on the sea wall. The research results indicate that the reflection coefficient of solitary waves decreases with increasing incident wave height and increases with increasing reef platform water depth. The maximum run-up height increases with increasing incident wave height and decreases with increasing cot α of the reef front slope. The maximum total force and maximum total moment on the sea wall increase with increasing incident wave height and reef platform water depth, and decrease with increasing height of the second reef platform. The position of the maximum impact pressure on the sea wall rises with increasing incident wave height, increasing reef platform water depth, and decreasing distance between the reef platform steps and the sea wall. The research results can provide a reference for further protecting coastal facilities from the impact of extreme marine environments.

In recent decades, the beaches on both sides of the Jiehe River (hereinafter referred to as Jiehe Beach) in the northeastern part of Laizhou Bay have suffered severe erosion due to reduced riverine sediment input to the sea. Additionally, the construction of coastal engineering projects such as Yulong Island (a large artificial offshore island) has made the evolution of the Jiehe Beach shoreline exceptionally complex. This paper utilizes 1186 satellite images from 1984 to 2024, employing a transect-focused method and sub-pixel shoreline recognition technology to study the evolution of the Jiehe Beach shoreline and assess the impacts of river sediment discharge and coastal engineering. The results show that the early evolution (1984−2004) of Jiehe Beach was primarily controlled by the closure and opening of the Jiehe River estuary, the alongshore movement of sand spits, and the onshore movement of sandbars, with overall erosion occurring. The later evolution (2004−2024) of Jiehe Beach was mainly influenced by the construction of coastal engineering projects such as Yulong Island, with overall accretion occurring. In today’s era of intensifying coastal development, the rational layout of coastal engineering is expected to mitigate beach erosion.

Submarine fans developed in the middle Miocene Meishan Formation possess significant potential for natural gas exploration. Most of scholars believed that these Miocene submarine fans were formed primarily by turbidity currents. However, drilling cores revealed the presence of pebbles with a particle size of up to 5 cm in the sandy conglomerates. These sandy conglomerates exhibited good roundness and poor sorting, indicating that the traditional turbidity formation mechanism cannot fully explain the origin of this type of sandy conglomerates. Furthermore, the classic submarine fan model has limitations in predicting the distribution of sand bodies. Through a comprehensive study involving core, thin section observation, and grain size analysis, we have conducted a systematic investigation of the petrological characteristics and sedimentary structures of submarine fan in the study area. Our findings suggest that submarine fans in the study area resulted from the interaction of turbidity and hyperpycnal flow deposits. We have identified distinct sequences of turbidites and hyperpycnalites within the submarine fan. Based on the paleogeomorphlogy of the study area, we have established a genetic evolution model for the submarine fan in Meishan Formation. This model reveals that the hyperpycnites dominated by feldspathic litharenite, exhibit low compositional maturity. Poor sorting and subangular-circular of the rocks indicate middle-to-high structural maturity. Typical features of hyperpycnal flow include orientated gravel within block sandy conglomerates, reverse-to-normal grain order bedding, parallel bedding, carbonaceous debris, and biological fossil fragments. Multi stage superimposed turbidite sequence and hyperpycnites sequence developed in submarine fan in the study area. The early Meishan period is primarily composed of turbidite submarine fan lobes, while the middle Meishan period is dominated by hyperpycnites submarine fan channels. The late Meishan period, on the other hand, is mainly composed of turbidite submarine fan channels. We predict that more favorable submarine fan sand bodies could be found in the southern part of the study area. The results can serve as a basis for predicting the distribution of favorable submarine fan reservoirs of the Qiongdongnan Basin, and they hold significance for selecting exploration and development targets for hydrocarbon exploration.

Seagrass meadows play a vital role in protecting marine biodiversity, mitigating ocean acidification, and preventing soil erosion in the coastal ecosystem. However, global climate change and human activities seriously affect the life of seagrass, which cause the widespread degradation of the seagrass and threaten the safety of coastal ecosystems. Recently, the vital value of microorganisms in promoting the energy flow of seagrass meadows and their growth and development has gradually gained attention. Plant growth-promoting microorganisms(PGPM) will play their value in seedling cultivation, plant transplantation, seed planting and other techniques of seagrass meadow restoration. This paper reviewed the research on how microorganisms interacts with seagrass to promote the growth of plants and increase the resistance to abiotic stress. We introduced the mechanism of PGPM to enhance plant stress tolerance under high temperature, high salt, and low light. We propsoed that modern molecular biological technique should be used to screen seagrass PGPM, clarify the colonization site of PGPM, and explore the molecular interaction mechanism between PGPM and seagrass in different environmental conditions. This paper is some advice for promoting the application of PGPM in seagrass meadow restoration and seagrass protection.

The phenomenon of marine phytoplankton bloom in ocean refers to the annual cycle increase in biomass caused by rapid reproduction, which plays an important role in the biochemical cycles of marine organisms. However, the spatiotemporal variation characteristics of global phytoplankton blooms and their response mechanisms to the environment still require further exploration. Based on the chlorophyll a products of the MODIS-Aqua (Moderate Resolution Imaging Spectroradiometer) from 2003 to 2022, we extracted the bloom indexes of global ocean phytoplankton (the ratio of bloom duration and bloom intensity). Then, we analyzed their spatiotemporal characteristics, trends, and correlations with environmental factors. The results indicated that there are significant seasonal and latitudinal difference in the distribution of the bloom indexes. Blooms in high latitudes of the Northern Hemisphere mainly occur from April to October, while in mid-low latitudes, blooms mainly occur from November to March of the following year. In the Southern Hemisphere, blooms develop in the month of November and persist until March of the following year in high latitudes, while those in low and middle latitudes occur from May to September. The ratio of bloom duration and bloom intensity show decreasing trends mainly in the mid-low latitude regions of the North Pacific, while increasing trends are observed in mid-high latitude regions of the Southern Hemisphere. The distribution and trends of bloom indices are both regulated by environmental factors. Sea surface temperature and photosynthetically active radiation promote blooms intensity in high latitude waters, but inhibit them in low latitude waters. Meanwhile, the wind speed plays a restraining role in the high latitude sea area and a promoting role in the low latitude sea area.

Sargassum horneri has good economic traits and value, and its culture is gradually being emphasized. However, the suitable water depth for culture is still unclear, and the physiological characteristics and ecological functions of S. horneri in different water depths are also unclear. In this paper, we compared the primary productivity, nutrient uptake capacity, and algal trophic composition of S. horneri at different water depths (0.5 m and 2 m) based on light intensity in different water depths. The results showed that light intensity varied significantly (P < 0.05) with water depths and that the difference in light intensity due to water depth was significantly correlated with the primary productivity of S. horneri. The total productivity of S. horneri grown at 0.5 m water depth (upper layer) was significantly higher than that of S. horneri grown at 2 m water depth (lower layer) (P < 0.05), and S. horneri in the upper layer showed higher primary productivity and carbon sequestration capacity. The uptake of ${{\rm {NH}}_4^+} $ and ${{\rm {PO}}_4^{3-}} $ by the upper layer of S. horneri was significantly better than that of the lower layer of S. horneri under the light conditions (P<0.05), which has good potential in purifying the eutrophic water and regulating the ecological balance of the waters. However, the uptake of ${{\rm {NO}}_3^-} $ and ${{\rm {NO}}_2^-} $ by the upper layer of S. horneri is significantly lower than the lower layer of S. horneri (P>0.05), and it indicates that some strong light inhibition phenomenon occurs in S. horneri which affects the uptake of ${{\rm {NO}}_3^-} $ and ${{\rm {NO}}_2^-} $ by S. horneri. The moisture content of S. horneri at different water depths ranged from 71% to 75%, the ash content from 20% to 23%, the total lipids content from 6% to 8%, and the crude protein content from 8% to 10%. Nutrient composition did not differ significantly (P > 0.05) between the two water depth treatment groups. Studies have shown that by appropriately raising the culture layer, S. horneri can achieve higher productivity and nutrient uptake capacity, while the nutrient composition of S. horneri in the different water layers would remain relatively stable. This study has great significance for the technological development and upgrading of the artificial culture of S. horneri in natural sea areas as well as for the ecological environmental protection of sea areas.

The stratospheric sulfate aerosol layer formed after large volcanic eruptions can inhibit the formation and development of tropical cyclones. But relevant studies mainly focus on the Atlantic Ocean, and few involve other sea areas. The Northwest Pacific Ocean is the area where most tropical cyclones are generated. Exploring the climate influencing factors is helpful for us to deeply understand the generation and development mechanism of tropical cyclones. Based on the data of tropical cyclones in the Northwest Pacific Ocean recorded in the International Optimum Orbit Database and the China Meteorological Administration database, the changes of sea surface temperature and the number of tropical cyclones in the Northwest Pacific Ocean before and after major volcanic eruptions during 1900−2023 are compared, and the effects of major volcanic eruptions on tropical cyclones in the Northwest Pacific Ocean are discussed. By comparing the number of tropical cyclones two years before the eruption and two years after the eruption, we found that the number of tropical cyclones in the Northwest Pacific decreased significantly after a major eruption. The sea surface temperature significantly responds to low-latitude volcanic eruptions, but does not significantly respond to high-latitude volcanic eruptions. Our study shows that the increase of aerosol forcing after large volcanic eruptions is closely related to the frequency of tropical cyclones, but the decrease of sea surface temperature caused by it may not be the direct cause of the decrease of tropical cyclones, and its mechanism may be related to the migration of the intertropical convergence zone caused by aerosol forcing, which still needs further investigation.

To analysis the suitability of using wind field data for forecasting Pacific saury habitat in the northwest Pacific, this paper use the generalized additive model to fit the habitat suitability index (HSI) for Pacific saury in summer and autumn, based on the Chinese fishery data, environmental data and four types of wind field data included the China-France oceanography satellite (CFOSAT) during June to November in 2019−2020. The result indicates that: (1) Weighted analysis shows distinct seasonal variation of environmental variables on catch per unit effort, with chlorophyll concentration and sea surface temperature having the highest weights in summer and autumn respectively, while wind speed had the lowest weight and direct proportionality to the weight. (2) The average accuracy of the four data in summer and autumn is 68.37% and 76.65% respectively, and CFOSAT reaching the highest accuracy of 80.94% in autumn. (3) The high-HSI areas are consistent with the fishing grounds of Pacific saury, while the HSI high-value regions of scatter meter in autumn seems more robust. There are advantages of using wind speed on the forecast model in autumn, as this model can reflect the influence of transient variation factors on the migration and aggregation of Pacific saury.

The tidal creek system is an active geomorphic unit in coastal wetlands, and the water environment of different level tidal creeks changes significantly, leading to spatial distribution differences of biological communities. This study selected a typical tidal creek unit in the Huanghe River Delta and used environmental DNA metabarcoding (eDNA) technique to detect the diversity of invertebrates. The biological co-occurrence network analysis and redundancy analysis (RDA) were respectively used to reveal the keystone species and driving factors of the invertebrate community in the typical tidal creek. The results showed that a total of 127 operational taxonomic units (OTUs) of invertebrates were detected in the tidal creek unit, belonging to 9 phyla, 24 classes, 53 orders, 103 families, 87 genera, and 90 species; among them, the class level was dominated by the Arthropoda (43.9%), and the genus level was dominated by the Perinereis (25.2%). The comprehensive diversity index (CD) analysis showed that the comprehensive diversity of invertebrates in the third-level tidal creek was the highest, and the comprehensive diversity of invertebrates in the first-level tidal creek was the lowest. The biological co-occurrence network analysis showed that the Perinereis linea and the Obelia dichotoma were the keystone species, which played a key role in maintaining the stability of the invertebrate community structure in the tidal creek. The RDA showed that the silicate content of the water body, temperature, and the proportion of fine sand and clay in the sediment were the main environmental factors affecting the invertebrate community characteristics in the tidal creek. Correlation network analysis showed that the keystone species were significantly affected by silicate content, clay, and nitrogen content in water (P < 0.05). The research results are helpful for understanding the community structure of typical tidal creek invertebrates, revealing the keystone species of typical tidal ditch invertebrates, and providing data support and theoretical reference for the monitoring and protection of invertebrate diversity.

During June 9th to 15th in 2017, the dynamic of Gymnodinium catenatum bloom along the coast of Hui’an County Fujian Province, were investigated. Six monitoring stations were established for marine environmental factors assessment over seven sampling trips. The water quality data from June 6th, along with the phytoplankton data collected in March and November 2017, was selected for comparative analysis. Furthermore, the survey results of dinoflagellate cysts and paralytic shellfish poison (PSP) in cultured shellfish were integrated to explore the relationship between dormant cysts and the bloom dynamics, as well as the patterns of PSP accumulation and elimination in cultured shellfish. The results revealed that during the bloom, conditions were characterized by sunny weather and favorable sea states, with water temperature ranging from 24.2℃ to 26.8℃ and the salinity between 30.4 and 33.2. The concentrations of nutrients were low, indicating oligotrophic conditions, while the density of G. catenatum peaked at 1.79×10⁶ cells/L during the bloom period. The interplay of favorable hydro-meteorological conditions, N/P ratio and the trophic pattern of G. catenatum provided a basis for the evolution of the bloom, whereas adverse weather conditions primarily contributed to its decline. The average density of G. catenatum cysts in the surveyed sea area was 33.2 cysts/g, suggesting potential for these cysts to germinate into trophic cells, which could lead to the reemergence of the bloom and therefore it necessitates further attention. During the bloom period, both oysters and mussels rapidly accumulated high concentrations of PSP toxins, with levels directly proportional to G. catenatum density. Additionally, even low densities of G. catenatum posed a risk for PSP exceedances. Mussels exhibited a rapid accumulation and slow elimination of PSP, with a significantly greater capacity for toxin accumulation compared to oysters, while their elimination rate was significantly slower.