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.

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.

The distribution of wave energy in enclosure aquaculture areas not only significantly influences nutrient transport but also constitutes a critical hydrological factor in validating the design of structures in inner aquaculture area. Investigating the changes in wave field energy influenced by these structures is crucial. The FUNWAVE 2.0 numerical model was employed to simulate irregular wave propagation in aquaculture areas with varying pile-net enclosure structures. The effects of pile spacing and incident wave angles in the evolution of wave energy was examined. The results indicate that if the internal facilities are positioned close to the outer pile-net enclosure structure, the pile spacing should be less than 10 m, provided that structural stability is ensured. Conversely, if the internal facilities are located farther from the outer pile-net enclosure, a pile spacing greater than 10 m should be selected. Additionally, oblique wave incidents may pose greater structural challenges at certain locations compared to normally incident waves, which should also be considered during design.

In November 2020, sediment samples were collected from the Yalong Bay Qingmei Port mangrove nature reserve and the Sanya River mangrove nature reserve in Hainan Province. The present study focused on the community characteristics of marine nematodes and their influencing factors in these two mangroves. The results of the present study showed that the average abundance of marine nematodes was (80.4 ± 40.3) ind./cm² in the Qingmei Port mangrove, while it was (96.7 ± 55.6) ind./cm² in the Sanya River mangrove. In this study, the average abundance of marine nematodes in the two study mangrove wetlands was (88.5 ± 47.1) ind./cm². There were significant differences in the abundance of marine nematodes between the two mangrove wetlands. A total of 77 species of marine nematodes were identified, belonging to 56 genera, 21 families and 7 orders. The dominant genera in the Qingmei Port mangrove were Neochromadora, Terschellingia, Paramonohystera, Daptonema and Desmodora, and epigrowth feeders were the dominant feeding type. The dominant genera in the Sanya River mangrove were Terschellingia, Sabatieria, Eleutherolaimus, Parodontophora and Ptycholaimellus, and the selective deposit feeders dominated. Terschellingia dominated in both mangroves. There were spatial differences in the community structure of marine nematodes in study mangroves. Although the marine nematode communities differentiated between the two mangroves, the difference was not significant. Organic matter content and phaeophorbide content in sediments were important factors affecting the abundance and community structure of marine nematodes in Sanya River mangrove. The differences in mangrove vegetation types may affect the abundance and community structure of marine nematodes in Qingmei Port mangrove to some extent. The differences of sediment granularity characteristics, seawater pH and salinity could explain the differentiation of marine nematode communities at selected sites of the two mangrove. In addition, there are sewage project, port construction and tourism development in Qingmei Port mangrove. And there are felling, dike construction, salt pan development and wastewater discharge from shrimp ponds in Sanya River mangrove. The different pollution status in these two mangroves may also be the reason for the differences in the abundance and community structure of marine nematodes in this study.

Against the backdrop of global warming, the Arctic has experienced a series of changes, including permafrost degradation, reduced summer sea ice, increased land runoff, and intensified coastal erosion. With global warming, organic carbon (OC) stored in permafrost is accelerating its migration and release to the sea, which will affect the pattern of carbon cycling in the Arctic Ocean. However, there is currently little evidence to directly confirm this inference. This article analyzes the lignin and carbon isotopes of two hundred year scale sedimentary cores in the Chukchi Sea, and discusses the sources and profile changes of the buried organic matter. The results showed that the organic carbon in the columnar sediments of the Chukchi Sea came from a mixed contribution of herbaceous tissue of terrestrial C3 plants and marine source production. The absolute content of lignin Σ8 in sediment shows an overall upward trend, indicating that with global warming, more terrestrial materials are being transported to the Chukchi Sea. This study indicates that global warming caused by human activities has indeed increased the migration of organic carbon from permafrost to the sea, and the increase in lignin content due to enhanced terrestrial inputs is direct evidence of the enhanced melting of permafrost caused by global warming on a century scale.

Oil spill is one of the critical target of marine environmental monitoring. Synthetic Aperture Radar (SAR), thermal infrared remote sensing, and optical remote sensing for monitoring of marine oil spills have been elucidated, and it is crucial for marine environmental protection to utilize the features and advantages of multi-source remote sensing to achieve accurate monitoring and quantitative assessment of marine oil spills. On April 27, 2021, the collision between the Panamanian vessel Sea Justice and the Liberian oil tanker A Symphony resulted in an estimated 9400 t of cargo oil seeping into the yellow sea. Here, we used multi-source satellite remote sensing data to monitor and analyze the coverage of oil spill and the distribution of emulsified oil in this accident. Based on the response mechanism and characteristics of oil spill multi-source remote sensing, the processing of multi-source data is optimized to realize the identification of oil spills and the classification of multiple oil types. The findings indicate that from May 1 to May 22, 2021, the cumulative pixel area of oil spills from A Symphony tanker was 2368.7 km², of which the emulsified oil pixel area was 1019.3 km², accounting for 43.0%. The maximum daily oil spill pixel area reached 734 km². The results of multi-remote sensing monitoring validated each other, and optical remote sensing is more capable of identifying different oil types, in which the emulsified oil represents the key of pollution hazards. It improves the accuracy of monitoring and assessment of marine oil spills, and provides reliable technical and methodological references for the hazard assessment and refined monitoring of oil pollution events.

Based on analyses of solid-phase and porewater chemistry of sediment cores at four sites collected from Laizhou Bay of the Bohai Sea, we revealed diagenetic cycles of iron, manganese and sulfur and their responses to terrestrial inputs and anthropogenic perturbations. Results suggest that water eutrophication of the bay has not given rise to organic carbon (OC) enrichment in the sediments. Actually, contents and lability of sediment OC are generally low, largely due to the inputs of terrestrial refractory OC and intense sediment resuspension induced by natural processes and anthropogenic perturbations in the river-dominated area. This feature greatly dampens sulfate reduction, resulting in low accumulation of total reduced inorganic sulfide (0.28−88 μmol/g). Porewater Mn²⁺ is mainly from reductive dissolution of amorphous and poorly crystalline Mn oxides, while precipitation of MnCO₃ is mainly responsible for Mn²⁺ consumption in sediment below 10 cm depth. Intense sediment resuspension and refractory nature of sediment OC encourage dissimilatory iron reduction, with relative contribution of this pathway to total anaerobic OC mineralization of about 51%, on average. At the site (S6) heavily influenced by the Huanghe River input, dynamic depositional regime facilitates reductive dissolution of manganese oxides, but dampens reduction of iron oxides and sulfate to some extent. Upward diffusive fluxes of porewater Mn²⁺ and Fe²⁺ in the sediments are at the lower end for sediments of other areas dominated by major river inputs, which is attributable to overall low lability of sediment OC.

The seasonal variations of zooplankton communities in the nearby seas of the Island was investigated to know the relationship between the structure of zooplankton communities and environmental factors in the sea areas around Weizhou Island in Guangxi. Collecting samples of zooplankton communities were conducted in January (winter), April (spring), August (summer), and November (autumn) of 2022. The study examines the variations in zooplankton species composition, abundance, biomass, and dominant species across the four seasons, while also investigating their primary environmental influencing factors. A total of 224 species (classes) of zooplankton were identified throughout the four seasons of the year, including 25 species (classes) planktonic larvae, belonging to 18 groups. Copepods were the most abundant (78 species), followed by hydrozoan jellyfish (35 species). The number of zooplankton species shows a seasonal variation pattern of spring > autumn > winter > summer, and the composition of species shows a seasonal variation pattern of spring > winter > autumn > summer. The dominant species group exhibits a seasonal replacement phenomenon of copepods, red tide organisms, and glial organisms, as well as hairy jawbones and copepods. The seasonal variation characteristics of the zooplankton community structure are obvious. The annual average abundance and biomass of zooplankton are (246.50 ± 158.75) ind./m³ and (126.08 ± 192.27) mg/m³, respectively. The abundance and biomass in spring are the highest (712.80 ± 630.28) ind./m³ and (367.79 ± 264.33) mg/m³, while the abundance in winter is the lowest (62.09 ± 29.61) ind./m³ and the biomass in summer is the lowest (35.48 ± 19.88) mg/m³. The results of redundancy analysis indicate that water temperature, salinity, nutrients and chlorophyll a are the main environmental factors affecting the seasonal changes of zooplankton community structure in the sea area of Weizhou Island, Guangxi. The seasonal changes in water masses cause by the ocean monsoon drive the succession of dominant species of zooplankton. The seasonal variation characteristics of the abundance of copepods, an important group of zooplankton in the sea area, are consistent with the migration patterns of the Balaenoptera edeni in the waters of Weizhou Island, indicating that the basic feed organisms of the fishing industry affect the migration activities of the B. edeni. In addition, the ecological impact of the decreased dominant group of copepods caused by the proliferation and growth of protozoa and glial organisms in spring on the waters of Weizhou Island deserves attention and exploration.

Recognition of reef-building corals is important for protecting and monitoring coral reef ecosystems. Deep learning, as an advanced technology in image recognition, has been increasingly applied in coral recognition. However, its performance is still challenged by several issues, such as the imbalance of samples among different coral categories within a dataset and the limitation of data diversity. The former makes the deep learning model more likely to extract features from classes with a large number of samples and, therefore, decreases its ability to recognize small-sample-size corals, which often refer to endangered ones needing to be protected. The latter further reduces the performance of deep learning in recognizing corals with different appearances and are captured in variant environments. To solve these two problems, this study develops a reef-building coral recognition method by integrating a category-quantity adaptive deep data augmentation algorithm and transfer learning. To address the first problem, a category-quantity adaptive deep data augmentation algorithm named DeepSMOTE-F₁ is proposed. This algorithm improves the existing DeepSMOTE by introducing a sample-size determination stagey using an F1-score based evaluation metric. It can adaptively augment the number of samples of each category of corals according to its recognition performance so that the deep learning model can fully learn features from each class of corals. For the second problem, transfer learning is used to further enhance the model's ability to extract features. The experimental results on three widely used public coral recognition datasets, RSMAS, EILAT, and EILAT2 show that the recognition accuracy of the proposed DeepSMOTE-F₁ is improved by 2.88%, 0.39%, and 1.54%, respectively, compared with the traditional DeepSMOTE; and the accuracy of the integrated method is improved by 0.76%, 1.40% and 1.30% compared with the existing deep learning methods for coral recognition.

In order to understand the long−term variations in the nutritional environment and the key influencing factors of Bohai Bay, sediment cores from the mouth of the bay (BH15) and the outer area of the bay (BH47) were collected in April and June 2018 separately. The contents of total organic carbon (TOC), total nitrogen (TN), phosphorus (P), biogenic silica (BSi), and stable isotopes of carbon and nitrogen (δ¹³C, δ¹⁵N) were analyzed, and the causes of the changes of the above parameters were discussed in combination with the changes of climate and surrounding human activities. The results showed that the TN content in both sediment cores exhibited an increasing trend since the 1980s, which is consistent with the long-term variations in dissolved inorganic nitrogen (DIN) in the sea water. Sewage discharge, fertilizer application and mariculture are the main sources of nitrogen in the Bohai Bay, among which the input of agricultural fertilizer has decreased since 2007, while the discharge of mariculture and domestic sewage into the sea has shown a continuous upward trend. Inorganic Phosphorus (IP) was the main form of phosphorus in sediments. The IP in BH15 in the bay has shown a decreasing trend since the mid-1990s, while the IP in BH47 from the mouth of the bay has shown a decreasing trend after 1970s and a slow increasing trend since 1990s. All of them show obvious terrigenous input characteristics. The results of TOC/TN ratio、δ¹³C value and δ¹³C two-endmember mixing model indicated that the sediment organic matter in the mouth of Bohai Bay and adjacent sea area was influenced by both terrestrial input and marine autochthonous sources, with marine organic matter being the dominant source, the contribution of marine organic matter has decreased Since the 1990s. Compared with the BH47 core from the mouth of the bay, the BH15 core is closer to the coastal area, more significantly affected by terrestrial input, with higher TN content and contribution of terrestrial organic matter. This study shows that in order to effectively manage the water environment of Bohai Bay, it is necessary to strengthen the control of mariculture and domestic sewage discharge into the sea while controlling the use of agricultural fertilizers in the future.