Search Results (307)

Eutrophication and its resultant cyanobacterial blooms are a severe environmental issue in global water bodies, and phosphate is regarded as one of the primary triggers. In this study, the in situ-synthesized heated kaolinite lanthanum hydroxide composite (HKL-LH) was used to treat cyanobacterial blooms through phosphate removal. A typical cyanobacteria species—Microcystis aeruginosa—was selected as the target organism. HKL-LH efficiently removed phosphate in the solution with the inoculation of M. aeruginosa over the course of one day. A good performance of HKL-LH on control cyanobacterial blooms with initial cell densities ranging from 10⁴ cells mL⁻¹ to 10⁵ cells mL⁻¹ was observed. Although the genetic expression relating to photosynthesis and cell division was upregulated under the stress of phosphorus deficiency, M. aeruginosa growth was significantly inhibited, i.e., the inhibition rate of up to 98% was achieved by 0.1g L⁻¹ of HKL-LH. In addition to cell growth, the photosynthetic activity and viability of M. aeruginosa cells were decreased by HKL-LH. Furthermore, the production of associated toxins (microcystins) and algal organic matters were effectively inhibited, which can reduce the ecological risk and challenges that follow water treatment. In this study, it is shown that HKL-LH has excellent application potential in the mitigation of cyanobacterial blooms in eutrophic water. Full article

The fragmentation of vessel tracks represents a significant challenge in the context of high-frequency surface wave radar (HFSWR) tracking. This paper proposes a new track segment association (TSA) algorithm that integrates optimal tracklet assignment, iterative discrimination, and multi-stage association. This paper reformulates the optimal tracklet assignment task as an optimal state search problem for modeling and solution purposes. To determine whether competing old and new tracklets can be associated, we assume the existence of a public state that represents the correlation between the tracklets. However, due to track fragmentation, this public state remains unknown. We need to search for the optimal public state of all candidate tracklet pairs within a feasible parameter space, using a fitness function value as the evaluation criterion. The old and new tracklets pairs that match the optimal public state are considered optimally associated. Since the solution process involves searching for the optimal state across multiple dimensions, it constitutes a high-dimensional optimization problem. To accomplish this task, the catch fish optimization algorithm (CFOA) is employed for its ability to escape local optima and handle high-dimensional optimization, enhancing the reliability of tracklet assignment. Furthermore, we achieve precise one-to-one associations by assigning new tracklet to old tracklet through the optimal tracklet assignment method we proposed, a process we abbreviate as AN2O, and its inverse process, which assigns old tracklet to new tracklet, abbreviated as AO2N. This dual approach is further complemented by an iterative discrimination mechanism that evaluates unselected tracklets to identify potential associations that may exist. The algorithm effectiveness of the proposed is validated using field experiment data from HFSWR in the Bohai Sea region, demonstrating its capability to accurately process complex tracklet data. Full article

The aquaculture industry of red swamp crayfish (RSC), Procambarus clarkii, has grown significantly in recent decades due to increasing market demand. In China, low water temperatures, particularly during overwintering, pose a challenge, hindering the development of the RSC aquaculture industry in northern regions. Understanding the molecular mechanism of RSCs’ responses to cold stress could be beneficial for its aquaculture practices. In this study, we exposed RSCs to 4 °C (T4) and 22 °C (T22: control) for 96 h. Transcriptomic and metabolomic analyses of hepatopancreas tissues were performed to identify key genes and metabolites that participate in cold stress response. A total of 787 differentially expressed genes (DEGs) and 198 differentially expressed metabolites (DEMs) were identified between T4 and T22. DEGs were significantly enriched in KEGG pathways related to carbohydrate, lipid, amino acid, and nucleotide metabolism, immunity, and signaling, while DEMs were significantly enriched in pathways associated with lipid and amino acid metabolism and membrane transport. The results indicated that cold stress altered RSCs’ metabolism and their innate immune system. This study provides valuable information to increase our understanding of cold stress responses in RSCs. Full article

The Yellow River (~5464 km) and the Yangtze River (~6300 km) are large rivers that originate from the Tibetan Plateau and flow into the western Pacific Ocean. The shelf seas of the western Pacific Ocean (e.g., Bohai, Yellow, and East China seas) serve as critical sites for investigating the evolution of these rivers. Distinguishing the material signals of the Yellow River from those of the Yangtze River is an essential step in this research. Therefore, we analyzed published zircon U-Pb ages (n = 1568 for the Yellow River and n = 1216 for the Yangtze River) and K-feldspar Pb isotopes (n = 380 for the Yellow River and n = 158 for the Yangtze River) from the middle and lower reaches of both rivers. The results indicate that the detrital material in the lower reaches of the Yellow River is primarily influenced by the western North China Craton and the Qinling Mountains, whereas the detrital material in the lower reaches of the Yangtze River mainly derives from the South China Block. The Qinling Mountains influence the material composition of the lower Yellow River, primarily due to the formation of overhanging rivers along the river’s course. These geological features inhibit the inflow of materials from the eastern North China Craton, thereby preventing the mixing from the Qinling Mountains. In contrast, the influence of the Qinling Mountains on the material composition of the lower Yangtze River is minimal. This limited impact is attributed to the influx of materials from the South China Block, which dilutes the contributions from the Qinling Mountains. Notably, substantial discrepancies exist in the U-Pb ages and Pb isotopic compositions of detrital zircons and K-feldspar from the lower Yellow River compared to those from the lower Yangtze River and the surrounding geological units. These disparities provide a robust foundation for investigating large river provenance tracing in the western Pacific Ocean shelf sea through the integration of these two analytical methods. However, the U-Pb age distributions of detrital zircons in the lower Yellow River have changed significantly over geological time. The U-Pb age data for detrital zircons collected from the eastern Sanmen Gorge of the middle Yellow River should be utilized to examine river evolution prior to the Quaternary period. Conversely, the U-Pb data from detrital zircons in the lower Yellow and the Yiluo rivers should be considered when discussing Quaternary river evolution. The zircon U-Pb age characteristics of the lower Yangtze River can be directly employed to analyze the evolution of large rivers in the western Pacific Ocean shelf sea during the Neogene. Full article

To meet the needs of marine disaster prevention and mitigation, this paper proposes a systematic methodological framework to describe the annual risk situation of Disastrous Sea Waves (DSWs) from four perspectives. Its application is demonstrated for the China Sea in 2023 as a case study. The systematic approach is reflected in the following: (1) a comprehensive description of DSW risks based on three dimensions: occurrence frequency, maximum intensity, and hazard index; (2) an overview of the DSW risk characteristics for the year through spatial and monthly distributions; (3) a comparative analysis of the year’s DSWs, with historical data based on anomalies and return periods used to assess the risk characteristics and extremities; and (4) an analysis of the causes of the year’s characteristics based on monthly anomalies and weather systems. Through its application to the China Sea in 2023, the analysis process is introduced as follows. (1) High-Frequency and Intensity Areas: DSWs frequently occurred in the northeastern South China Sea (SCS) and Taiwan Strait, exceeding 450 h. The maximum significant wave height (H_s), reaching 11.3 m, was recorded in the southern East China Sea (ECS) in August. (2) Extremity in Frequency and Attribution: The occurrence frequency was extremely high, with the cumulative hours exceeding the historical average by 159 h (9.1%). The southwestern SCS showed the most significant excess, up to 168 h (>120%). The reason for this was that DSWs in January caused by prolonged cold air lasted 236 h longer (121%). (3) Extremity in Intensity and Attribution: The maximum H_s in the southern ECS and Taiwan Strait was 2 m (30%) higher than the historical average. The intensified cold air waves caused the higher intensities. (4) Hazard Levels: Higher risk occurred in the southwestern SCS, southern ECS, and Taiwan Strait, while the highest extremity occurred in the Bohai Sea. Full article

This study addresses the local scour problem of monopile foundations in the central Bohai Sea. This study integrates numerical simulations with experimental validation to conduct an in-depth analysis of the tidal current background, sediment transport, sediment sources, and scour characteristics over the past two decades. The analysis of ocean currents and sediment dynamics revealed that the monthly average tidal current speed in the majority of the study region is below 0.6 m·s⁻¹, with annual seabed erosion and accretion changes within 0.02 m, exhibiting minimal variation. The annual erosion and accretion changes in the wind farm areas are less than 0.01 m. The analysis of local scour around monopile foundations indicates that approximately 80% of the scour occurs during the initial phase. A comparative analysis of collar protection effectiveness indicates that the collar can effectively reduce scour depth by 50%, thereby demonstrating significant protective effects. However, the prevailing trend of scouring remains unaltered, indicating that collar protection has inherent limitations in regulating early-stage scouring. The findings of this study provide a theoretical basis for the design and protection of monopile foundations in the central Bohai Sea and offer a valuable reference point for the scour protection of wind turbine foundations in similar regions. Full article

The estuarine area of Luanhe River is an important fisheries ground in China’s Bohai Sea. In 2016, Tangshan Marine Ranching Co., Ltd. constructed a 2 km² artificial oyster–macroalgae reef area by placing artificial reefs on the seabed adjacent to the Luanhe River Estuary. This action resulted in sustainable annual economic outputs through the fishing and sea cucumber put-and-take fishery. Although Luanhe River runoff and reef construction are important to the local phytoplankton community and fisheries’ production, little is known about how these factors affect phytoplankton community structure in the local coastal ecosystem. In this study, we conducted field surveys to investigate the spatiotemporal variations in species composition, abundance, dominant species, diversity indexes, niche width and overlap, and interspecific connection of the phytoplankton community in the ecosystem of oyster–macroalgal reefs. From July 2016 to August 2017, we collected data before and after reef construction in areas inside and outside of the benthic reefs in both the flood and dry seasons of Luanhe River runoff. We found a total of 79 species, with the majority represented by diatoms and dinoflagellates. The dominant species were Paralia sulcata and Coscinodiscus sp. The total species number and abundance increased from May to September. The species number in the reef area was greater than that outside the reef. Species abundance from August to September was greater in the reef area than in the control area, which was opposite the situation from May to June. We found more phytoplankton abundance in the flood season compared with that in the dry season. Our results suggest that reef construction can benefit the local phytoplankton community and that further studies of the relationship among oysters, macroalgae, and phytoplankton in the system are warranted. Moreover, we provide baseline data about variations in the phytoplankton community in a sea ranch area. Full article

China’s Yellow (Bohai) Sea bird habitat is an important ecological region. Its unique ecology and challenges provide rich resources for research and study. Our course design concept is supported by AI technology, and improves students’ abilities through innovative functions such as dynamic data support, personalized learning paths, immersive research and study experience, and diversified evaluation mechanisms. The course content revolves around the “human–land coordination concept”, including pre-trip thinking, research and study during the trip, and post-trip exhibition learning, covering regional cognition, remote sensing image analysis, field investigation, and protection plan display activities. ERNIE Bot participates in optimizing the learning path throughout the process. The course evaluation system starts from the three dimensions of “land to people”, “people to land”, and the “coordination of the human–land relationship”, adopts processes and final evaluation, and uses ERNIE Bot to achieve real-time monitoring, data analysis, personalized reports, and dynamic feedback, improving the objectivity and efficiency of evaluation, and helping students and teachers optimize learning and teaching. However, AI has limitations in geographical research and study, such as insufficient technical adaptability, the influence of students’ abilities and habits, and the adaptation of teachers’ role changes. To this end, optimization strategies such as improving data quality and technical platforms, strengthening student technical training, enhancing teachers’ AI application capabilities, and enriching AI functions and teaching scenarios are proposed to enhance the application effect of AI in geographical research and promote innovation in educational models and student capacity building. Full article

China has recently launched extensive marine ranching projects, highlighting the need for scientific evaluation of ecosystem structure and function to guide their development. This study established two energy flow models and an evaluation index system to assess the structure, function, carrying capacity, and ecological status of both a marine ranching ecosystem and a nearby control site in the Beibu Gulf. The results show that the ranching ecosystem outperformed the control ecosystem in terms of food chain length, system size, and ecological carrying capacity of economically important species. The ranching ecosystem was classified as “relatively good”, while the control ecosystem was deemed “relatively poor”, which may confirm the success of the ranching efforts. Mussels, large crabs, and scorpaenidae were identified as key species for stock enhancement based on their biomass potential. Scenario simulations using Ecosim, driven by biomass and fishing factors, indicate that stock enhancement strategies targeting MOB (mussels, oysters, and barnacles) significantly improved the ranching ecosystem, raising its status to “good”. However, the simulations also revealed that stock enhancement had limited effects on optimizing food web structure, system organization, and energy transfer efficiency, suggesting that a combination of strategies is necessary for further improvement. Full article

In order to improve the spatiotemporal coverage of satellite Chlorophyll-a (Chl-a) concentration products in marginal seas, a physically constrained deep learning model was established in this work to reconstruct sea surface Chl-a concentration in the Bohai and Yellow Seas using a Long Short-Term Memory (LSTM) neural network. Adopting the permutation feature importance method, time sequences of several geographical and physical variables, including longitude, latitude, time, sea surface temperature, salinity, sea level anomaly, wind field, etc., were selected and integrated to the reconstruction model as input parameters. Performance inter-comparisons between LSTM and other machine learning or deep learning models was conducted based on OC-CCI (Ocean Color Climate Change Initiative) Chl-a product. Compared with Gated Recurrent Unit, Random Forest, XGBoost, and Extra Trees models, the LSTM model exhibits the highest accuracy. The average unbiased percentage difference (UPD) of reconstructed Chl-a concentration is 11.7%, which is 2.9%, 7.6%, 10.6%, and 10.5% smaller than that of the other four models, respectively. Over the majority of the study area, the root mean square error is less than 0.05 mg/m³ and the UPD is below 10%, indicating that the LSTM model has considerable potential in accurately reconstructing sea surface Chl-a concentrations in shallow waters. Full article

The Yellow River Delta (YRD), as a key area for the economic development of the Bohai Rim region, significantly impacts soil fertility and plant growth through soil salinization content. Accurately determining the spatial distribution of soil salinization in the YRD is vital for regional salinity management and agricultural development. In this study, we constructed and evaluated three soil salinization indices—NDSI, SI, and S5—using measured soil conductivity data and three machine learning methods: Random Forest, Support Vector Machine, and XGBoost. The results indicate that the Support Vector Machine achieved the best inversion effect on regional salinization levels, with an Area Under Curve (AUC) value of 0.88. The salinization level in the YRD has shown an increasing trend over the years, decreasing spatially from north to south, from east to west, and from the coast inland. From 2003 to 2009, salinization was primarily concentrated in northern and eastern coastal areas, while from 2009 to 2021, it gradually expanded inland. The salinized area increased from 538.4 km² in 2003 to 761.5 km² in 2021, particularly between 2009 and 2015, with a 47.95% increase. The main factors influencing salinization in the YRD were distance from the Bohai Sea, seasonal average potential evapotranspiration, and seasonal average normalized vegetation index, with interaction-driven effects being stronger than single-factor effects. This study provides crucial scientific support for sustainable salinization management and ecological restoration in the Bohai Sea region. Full article

In the last decade, microplastics (MPs) have become a significant environmental pollutant with potential negative effects on aquatic biodiversity and ecosystems. This mesocosm study examined the effect of MPs on the growth and physiology of two common aquatic macrophytes (Myriophyllum spicatum and Phragmites australis), focusing on changes in biomass allocation and nutrient contents. We evaluated oxidative stress responses by measuring superoxide dismutase, malondialdehyde, soluble sugars, free amino acids, and glutamate synthetase activities for M. spicatum, and we assessed photosynthetic processes through metrics including Fv/Fm, electron transfer rate, and Y(II) for P. australis. Unlike most previous studies in plants, we found that the growth and all functional traits of these two plants were not significantly affected by the common MP type (polyethylene) at either low or high concentrations. Additionally, we have examined the impact of another type of MP (polystyrene) on P. australis, and no significant effect was observed. In conjunction with prior case studies, the majority of which demonstrated the toxic impacts of MPs, our research indicates that plants exhibit a species-specific response to MPs. In addition to the strong adaptation of widespread plants used in this study, the large experimental system and relative long-term treatment may also explain our negative results. Our study highlights the need to further investigate species-specific tolerances and adaptive responses to MPs to better understand their ecological impacts. Full article

Sea-level rise has important implications for the economic and infrastructure security of coastal cities. Land subsidence further exacerbates relative sea-level rise. The Beijing–Tianjin–Hebei region (BTHR) along the Bohai Bay is one of the areas most severely affected by ground subsidence in the world. This study applies the Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS InSAR) method to analyze 47 ALOS PALSAR-2 images with five frames, mapping subsidence across 21,677.7 km² and revealing spatial patterns and trends over time from 2015 to 2021. This is one of the few published research studies for large-scale and long-term analysis of its kind using ALOS-2 data in this region. The results reveal the existence of six major areas affected by severe subsidence in the study area, with the most pronounced in Jinzhan Town, Beijing, with the maximum subsiding velocity of −94.42 mm/y. Except for the two subsidence areas located in Chaoyang District of Beijing and Guangyang District of Langfang City, the other areas with serious subsidence detected are all located in suburban areas; this means that the strict regulations of controlling urban subsidence for downtown areas in the BTHR have worked. The accumulated subsidence is highly correlated with the time in the time series. Moreover, the subsidence of 161.4 km of the Beijing–Tianjin Inter-City High-Speed Railway (HSR) and 194.5 km of the Beijing–Shanghai HSR (out of a total length of 1318 km) were analyzed. It is the first time that PALSAR-2 data have been used to simultaneously investigate the subsidence along two important HSR lines in China and to analyze relatively long sections of the routes. The above two railways intersect five and seven subsiding areas, respectively. Within the range of the monitored railway line, the percentage of the section with subsidence velocity below −10 mm/y in the monitoring length range is 11.2% and 27.9%; this indicates that the Beijing–Shanghai HSR has suffered more serious subsidence than the Beijing–Tianjin Inter-City HSR within the monitoring period. This research is also beneficial for assessing the subsidence risk associated with different railways. In addition, this study further analyzed the potential reasons for the serious land subsidence of the identified areas. The results of the geological interpretation still indicate that the main cause of subsidence in the area is due to hydrogeological characteristics and underground water withdrawal. Full article

The severe water quality pollution of the Bohai Sea impacts both the ecosystem and the economy of the region. This study assesses the water quality of the Bohai Sea using a two-year (2020–2021) dataset to investigate the spatial distribution and sources of contamination. Multivariate statistical analysis methods, including principal component analysis (PCA), cluster analysis (CA), and discriminant analysis, are employed. Thirteen chemical indicators are analyzed through PCA, resulting in the extraction of three principal components that reflect different pollution sources related to domestic, industrial, and agricultural activities. Additionally, the corresponding water quality index (WQI) is calculated to categorize the water quality into three levels using CA. The PCA-based WQI method is feasible and shows similarities to the traditional WQI method. Higher pollution levels are observed in Panjin and Tianjin, while Huludao, Yantai, and Dalian exhibit relatively good water quality. The results indicate complex, multifactorial pollution causes in the Bohai Sea, including eutrophication, heavy metal contamination, and ammonia pollution. These findings can guide region-specific water quality management: Panjin should control heavy metal discharges from industry and transportation, while Tianjin requires improvements in runoff management of ammonia-based fertilizers. Together, these strategies support the ecological and sustainable development of the Bohai Sea. Full article

Many species of noctuid moths exhibit long-distance migratory behavior and have an important pollination service function in terrestrial ecosystems. Spodoptera litura (Fabricius) is a globally distributed insect; however, its role in pollination remains underexplored. In this study, the feeding preferences and inter regional pollination of S. litura adults were explored. We conducted pollen analysis on 1253 S. litura migrants captured from 2018 to 2021 on Beihuangcheng Island in the Bohai Strait of China, which is located in the East Asian insect migration path. The results show that an average of 51.1% of S. litura migrants carry plant pollen each year, and the carrying rate shows fluctuations based on sex, year, and season. By combining morphological identification and DNA barcoding, pollen species were identified from 40 species of plants, representing 21 families and 26 genera, mainly from angiosperms of Dicotyledoneae, with Asteraceae, Apocynaceae, and Amaranthaceae being the dominant taxa. The geographical distribution range of Chrysanthemum zawadskii and Adenophora trachelioides and a migration trajectory simulation analysis indicate that S. litura predominantly migrate from Liaoning Province in Northeast China to North China over the Bohai Sea in autumn. These findings indicate the potential pollination activities of S. litura in North China and Northeast China, enriching our understanding of the interaction between S. litura and the plants it pollinates. Full article