Spatial distribution of lipophilic shellfish toxins in seawater and sediment in the Bohai Sea and the Yellow Sea, China.

Lipophilic shellfish toxins (LSTs) are widely distributed in marine environments worldwide, potentially threatening marine ecosystem health and aquaculture safety. In this study, two large-scale cruises were conducted in the Bohai Sea and the Yellow Sea, China, in spring and summer 2023 to clarify the composition, concentration, and spatial distribution of LSTs in the water columns and sediments. Results showed that okadaic acid (OA), dinophysistoxin-1 (DTX1) and/or pectenotoxin-2 (PTX2) were detected in 249 seawater samples collected in spring and summer. The concentrations of ∑LSTs in seawater were ranging of ND (not detected) -13.86, 1.60-17.03, 2.73-17.39, and 1.26-30.21 pmol L-1 in the spring surface, intermediate, bottom water columns and summer surface water layers, respectively. The detection rates of LSTs in spring and summer seawater samples were 97% and 100%, respectively. The high concentrations of ∑LSTs were mainly distributed in the north Yellow Sea and the northeast Bohai Sea in spring, and in the northeast Yellow Sea, the waters around Laizhou Bay and Rongcheng Bay in summer. Similarly, only OA, DTX1 and PTX2 were detected in the surface sediments. Overall, the concentration of ∑LSTs in the surface sediments of the northern Yellow Sea was higher than that in other regions. In sediment cores, PTX2 was mainly detected in the upper sediment samples, whereas OA and DTX1 were detected in deeper sediments, and LSTs can persist in the sediments for a long time. Overall, OA, DTX1 and PTX2 were widely distributed in the water column and surface sediments in the Bohai Sea and the Yellow Sea, China. The results of this study contribute to the understanding of spatial distribution of LSTs in seawater and sediment environmental media and provide basic information for health risk assessment of phycotoxins.

Accumulation of trace metal elements in ophiuroids with different feeding types in the North Yellow Sea.

Ophiuroids, as an important group of echinoderms, are widely distributed in marine benthic habitats. Previous studies have identified two primary feeding types of ophiuroids in the Yellow Sea, including carnivorous (Ophiura sarsii vadicola and Stegophiura sladeni) and suspension feeders (Ophiopholis mirabilis). Despite their ecological role in the benthic food webs, little is known about their accumulation of trace metal elements (TMEs). In this study, the content of TMEs (Pb, As, Cd, Hg, Cr, Cu, Zn), methylmercury (MeHg) and δ15N value of three ophiuroids species from the North Yellow Sea were determined. Our results showed that the contents of some TMEs (As, Cd, Cr, Cu and Zn) and MeHg were significantly different in three species of ophiuroid (p < 0.05). There were significant correlations between the accumulations of trace metal elements (Pb, Cd and Zn) and the δ15N value of the ophiuroids (p < 0.05). Additionally, As and Zn exhibited opposite correlations in ophiuroid with two feeding types, which may be related to their host species and different feeding habits. This study provided fundamental data for understanding the distribution of trace metal elements in echinoderms.

Spatial-temporal impacts of invasive Spartina anglica on the rates and pathways of organic carbon mineralization and resulting C-Fe-S cycles in the intertidal wetland of the Han River Estuary, Yellow Sea.

To elucidate the spatial-temporal impact of invasive saltmarsh plant Spartina anglica on the biogeochemical processes in coastal wetlands, we investigated the rates and partitioning of organic carbon (Corg) mineralization in three representative benthic habitats: (1) vegetated sediments inhabited by invasive S. anglica (SA); vegetated sediments by indigenous Suaeda japonica; and (3) unvegetated mud flats. Microbial metabolic rates were greatly stimulated at the SA site during the active growing seasons of Spartina, indicating that a substantial amount of organic substrates was supplied from the high below-ground biomass of Spartina. At the SA site, sulfate reduction dominated the Corg mineralization pathways during the plant growing season, whereas iron reduction dominated during the non-growing season. Overall, due to its greater biomass and longer growing season than native Suaeda, the expansion of invasive Spartina is likely to greatly alter the Corg-Fe-S cycles and carbon storage capacity in the coastal wetlands.

Anthropocene 129I Record in the Yellow Sea Sediments and Its Indication for River-Delivered Radioactive Pollution to Marginal Seas.

As the number of coastal nuclear facilities rapidly increases and the wastewater from the Fukushima Nuclear Plant has been discharged into the Pacific Ocean, the nuclear environmental safety of China's marginal seas is gaining increased attention along with the heightened potential risk of nuclear accidents. However, insufficient work limits our understanding of the impact of human nuclear activities on the Yellow Sea (YS) and the assessment of their environmental process. This study first reports the 129I and 127I records of posthuman nuclear activities in the two YS sediments. Source identification of anthropogenic 129I reveals that, in addition to the gaseous 129I release and re-emission of oceanic 129I discharged from the European Nuclear Fuel Reprocessing Plants (NFRPs), the Chinese nuclear weapons testing fallout along with the global fallout is an additional 129I input for the continental shelf of the YS. The 129I/127I atomic ratios in the North YS (NYS) sediment are significantly higher than those in the other adjacent coastal areas, attributed to the significant riverine input of particulate 129I by the Yellow River. Furthermore, we found a remarkable 129I latitudinal disparity in the sediments than those in the seawaters in the various China seas, revealing that sediments in China's marginal seas already received a huge anthropogenic 129I from terrigenous sources via rivers and thus became a significant sink of anthropogenic 129I. This study broadens an insight into the potential impacts of terrigenous anthropogenic pollution on the Chinese coastal marine radioactive ecosystem.

Characteristics of sub-micron aerosols in the Yellow Sea and its environmental implications.

The Yellow Sea, characterized by an influx of both natural marine and anthropogenic pollutants, coupled with favorable photochemical conditions, serve as key sites for potential interactions between atmospheric gases and aerosols. A recent air monitoring campaign in the Yellow Sea revealed aerosol contributions from four sources, with the highest mass concentrations and dominance of NO3- (38.1 ± 0.37 %) during winds from China. Indications of potential secondary aerosol formation were observed through the presence of hydrolysis and oxidation products of nitrate and volatile organic compounds. Correlations between time series distributions of biomass burning organic aerosols and particle number counts (Dp 100-500 nm, R2 = 0.94) further suggest potential size growth through adsorption and scavenging processes. The results from this study provide observational evidence of a shift in atmospheric compositions from sulfate to nitrate, leading to an increased atmospheric nitrogen deposition in the Yellow Sea.

Deciphering and quantifying nitrate sources and processes in the central Yellow Sea using dual isotopes of nitrate.

Anthropogenic activities pose significant challenges to the accumulation of coastal nitrogen (N). Accurate identification of nitrate (NO3-) sources is thus essential for mitigating excessive N in many marginal seas. We investigated the dual isotopes of NO3- in the central Yellow Sea to elucidate the sources and cycling processes of NO3-. The results revealed significant spatial variability in NO3- concentrations among the Yellow Sea Surface Water (YSSW), Changjiang Diluted Water (CDW), Yellow Sea Cold Water Mass (YSCWM), and Taiwan Warm Current Water (TWCW). Stratification played a crucial role in restricting vertical nutrient transport, leading to distinct nutrient sources and concentrations in different water masses. The dual NO3- isotopic signature indicated that atmospheric deposition was the primary source of surface NO3-, contributing approximately 30 % to the NO3- in the YSSW. In the NO3--rich CDW, the heavier δ15N-NO3- and δ18O-NO3- suggested incomplete NO3- assimilation. Organic matter mineralization and water stratification played crucial roles in the accumulation of nutrients within the YSCWM and TWCW. Notably, regenerated NO3- accounted for approximately half of the NO3- stored in the YSCWM. A synthesis of NO3- dual isotope data across the coastal China seas revealed significant spatial and seasonal variations in the N source. The study emphasized the dynamics of coastal NO3- supply, which are shaped by the complex interconnections among marine, terrestrial, and atmospheric processes. Our approach is a feasible method for exploring the origins of N amidst the escalating pressures of anthropogenic nutrient pollution in coastal waters.

Compound- and element-specific accumulation characteristics of persistent toxic substances and metals in sediments of the Yellow Sea.

This study investigated the large-scale distributions of persistent toxic substances (PTSs) and heavy metals in sediments of the Yellow Sea, collected from six transects between latitudes 32 and 37 degrees north (n = 35). Elevated concentrations of polychlorinated biphenyls (PCBs) were detected near the mainland, with a predominance of low-chlorinated congeners (di to tetra, ∼60%), indicative of atmospheric deposition. Analysis of traditional and emerging polycyclic aromatic hydrocarbons (t-PAHs and e-PAHs) revealed notable enrichment in the Central Yellow Sea Mud Zone (CYSM), attributing fossil fuel combustion as the significant source. Styrene oligomers and alkylphenols exhibited notable accumulation near the Han River Estuary in South Korea and the Yangtze River Estuary in China, respectively. The accumulation of heavy metals was predominantly observed in the CYSM, with element-specific distribution patterns. Cluster analysis revealed distinct distribution patterns for PTSs and metals, highlighting their source-dependent and grain size-dependent behaviors. In addition, the distribution and accumulation of PTSs tended to depend on their partitioning coefficients, such as the octanol-air partition coefficient (log KOA) and octanol-water partition coefficient (log KOW). This study offers valuable insights into the sources, transport, and fate of hazardous substances in the Yellow Sea, emphasizing the necessity for targeted environmental management strategies.

Seasonal patterns and bloom dynamics of phytoplankton based on satellite-derived chlorophyll-a in the eastern yellow sea.

Satellite-derived chlorophyll-a concentration (Chl-a) is essential for assessing environmental conditions, yet its application in the optically complex waters of the eastern Yellow Sea (EYS) is challenged. This study refines the Chl-a algorithm for the EYS employing a switching approach based on normalized water-leaving radiance at 555 nm wavelength according to turbidity conditions to investigate phytoplankton bloom patterns in the EYS. The refined Chl-a algorithm (EYS algorithm) outperforms prior algorithms, exhibiting a strong alignment with in situ Chl-a. Employing the EYS algorithm, seasonal and bloom patterns of Chl-a are detailed for the offshore and nearshore EYS areas. Distinct seasonal Chl-a patterns and factors influencing bloom initiation differed between the areas, and the peak Chl-a during the bloom period from 2018 to 2020 was significantly lower than the average year in both areas. Specifically, bimodal and unimodal peak patterns in Chl-a were observed in the offshore and nearshore areas, respectively. By investigating the relationships between environmental factors and bloom parameters, we identified that major controlling factors governing bloom initiation were mixed layer depth (MLD) and suspended particulate matter (SPM) in the offshore and nearshore areas, respectively. Additionally, this study proposed that the recent decrease in the peak Chl-a might be caused by rapid environmental changes such as the warming trend of sea surface temperature (SST) and the limitation of nutrients. For example, external forcing, phytoplankton growth, and nutrient dynamics can change due to increased SST and limitation of nutrients, which can lead to a decrease in Chl-a. This study contributes to understanding phytoplankton dynamics in the EYS, highlighting the importance of region-specific considerations in comprehending Chl-a patterns and bloom dynamics.

Benzotriazole ultraviolet absorbents in surface waters and sediments of the Bohai Sea and North Yellow Sea: Spatial trends and influencing factors.

Benzotriazole ultraviolet absorbents (BUAs) of emerging concern were recently monitored in seawater and sediments from the Bohai Sea (BS) and North Yellow Sea (NYS), which are impacted by human activities, to elucidate their regional occurrence patterns, phase distributions, and contamination profiles. Although environmental variables such as sedimentary organic carbon, particle size, and salinity, as well as hydrological conditions, affected the environmental occurrence of BUAs in the BS and NYS, the source dependence of BUA distributions associated with urban impacts and riverine inputs was highlighted. Substantial spatial variability in the composition patterns and contamination profiles of BUAs identified through correlation and principal component analyses were likely caused by region-specific sources and characteristics. The distribution of target BUAs between the sediment and seawater phases showed no dependence on the octanol-water partition coefficient (KOW) but exhibited marked spatial variations. The diversity of BUA sorption behaviors was further explained by the total organic carbon (TOC)-normalized distribution coefficient (KTOC). Classic logKTOC-logKOW linear relationships accurately predicted the phase distributions of UV-326, UV-328, and UV-234, but deviations were found for lighter and heavier BUAs, possibly due to the influences of physical disturbance and microparticle binding.

Dynamics of green macroalgal micro-propagules and the influencing factors in the southern Yellow Sea, China.

Micro-propagules (banks of microscopic forms) play important roles in the expansion of green tides, which are spreading on eutrophic coasts worldwide. In particular, large-scale green tides (Yellow Sea Green Tide, YSGTs) have persisted in the Yellow Sea for over 15 years, but the dynamics and functions of micro-propagules in their development remain unclear. In the present study, year-round field surveys were conducted to identify the reservoirs and investigate the persistence mechanisms and associated biotic and abiotic factors driving the temporal and spatial variations of micro-propagules. Micro-propagules in the southern Yellow Sea (SYS) showed evident spatial heterogeneity in terms of seasonal patterns and major influencing factors. Offshore of the SYS, the micro-propagule population underwent ephemeral expansion along with a large-scale bloom of floating Ulva algae in late spring and early summer. The Subei Shoal, particularly the sediments in the central raft region, had the highest micro-propagule abundance (MA) and was a major reservoir. The pronounced seasonal variation of MA in the Subei Shoal was primarily associated with the attached Ulva algae on Neopyropia aquaculture rafts. Vast aquaculture rafts provided essential substrates for micro-propagules to complete their life cycle and replenish the seed bank, thereby sustaining persistent YSGTs. It implied that habitat modification has pronounced ecological impacts on this intertidal muddy flat. The unique environmental conditions (enriched nutrients, esp. nitrate, favourable seawater temperatures in spring, and strong tidal mixing) facilitated the abundance, seasonal variation and recruitment of micro-propagules in the Subei Shoal. Given the current mitigation measures implemented in the raft region, further research is required to monitor and investigate the physiological and ecological responses of micro-propagule populations to the complex hydrobiological, geochemical, and physical matrices.

Methylmercury cycling in the Bohai Sea and Yellow Sea: Reasons for the low system efficiency of methylmercury production.

Coastal seas contribute the majority of human methylmercury (MeHg) exposure via marine fisheries. The terrestrial area surrounding the Bohai Sea and Yellow Sea (BS and YS) is one of the mercury (Hg) emission "hot spots" in the world, resulting in high concentrations of Hg in BS and YS seawater in comparison to other marine systems. However, comparable or even lower Hg levels were detected in seafood from the BS and YS than other coastal regions around the word, suggesting a low system bioaccumulation of Hg. Reasoning a low system efficiency of MeHg production (represented by MeHg/THg (total Hg) in seawater) may be present in these two systems, seven cruises were conducted in the BS and YS to test this hypothesis. MeHg/THg ratios in BS and YS seawater were found to be lower than that in most coastal systems, indicating that the system efficiency of MeHg production is relatively lower in the BS and YS. The low system efficiency of MeHg production reduces the risk of Hg in the BS and YS with high Hg discharge intensity. By measuring in situ production and degradation of MeHg using double stable isotope addition method, and MeHg discharge flux from various sources and its exchange at various interfaces, the budgets of MeHg in the BS and YS were estimated. The results indicate that in situ methylation and demethylation are the major source and sink of MeHg in the BS and YS. By comparing the potential controlling processes and environmental parameters for MeHg/THg in the BS and YS with the other coastal seas, estuaries and bays, lower transport efficiency of inorganic Hg from water column to the sediment, slower methylation of Hg, and rapid demethylation of MeHg were identified to be major reasons for the low system efficiency of MeHg production in the BS and YS. This study highlights the necessity of monitoring the system efficiency of MeHg production, associated processes, and controlling parameters to evaluate the efficiency of reducing Hg emissions in China as well as the other countries.

Environmental controls on the seasonal variations of diatoms and dinoflagellates in the Qingdao coastal region, the Yellow Sea.

Diatoms and dinoflagellates are two typical functional groups of phytoplankton assemblages, which play a crucial role in the structure and functioning of most marine ecosystems. To date, a novel challenge in ecology and biogeochemistry is to address the influences of environmental changes associated with climate change and human activities on the dynamics of diatoms and dinoflagellates. However, the knowledge of the key environmental factors controlling the diatom-dinoflagellate dynamics remains to be improved, particularly in the coastal ecosystems. Therefore, we conducted four cruises along the Qingdao coastline in spring, summer, autumn, and winter 2022 to explore how diatoms and dinoflagellates varied in response to regional environmental changes. The results showed that the phytoplankton communities were dominated by diatoms and dinoflagellates in terms of abundance and species diversity throughout the year in the study region. Yet, there were significant seasonal variability of diatoms and dinoflagellates across the four seasons. For example, diatom species was the most diverse during autumn, and the higher average abundance was observed in the fall and winter. In contrast, the average abundance of dinoflagellates was maximum during the summer and minimum in the autumn season. Moreover, the abundance and species ratios of diatoms/dinoflagellates (dia/dino) also showed significant seasonal variations in the region. The dia/dino abundance ratio was lowest in summer, while the dia/dino species ratio showed an increasing trend from spring to fall and a slight descending trend during winter. Based on the redundancy analysis, we revealed that diatoms and dinoflagellates responded differently to various environmental variables in different seasons, of which temperature and nutrients (especially dissolved inorganic nitrogen, DIN) had highly significant correlations with both the dia/dino abundance and species ratios. Thus, we suggested that temperature and DIN were the key factors controlling the seasonal dynamics of diatoms and dinoflagellates in the Qingdao coastal area.

Evolutionary trends and analysis of the driving factors of Ulva prolifera green tides: A study based on the random forest algorithm and multisource remote sensing images.

Understanding the prolonged spatiotemporal evolution and identifying the underlying causes of Ulva prolifera green tides play pivotal roles in managing such occurrences, restoring water ecology, and fostering sustainable development in marine ecosystems. Satellite remote sensing represents the primary choice for monitoring Ulva prolifera green tides due to its capability for extensive, long-term ocean monitoring. Based on multi-source remote sensing images, ecological and environmental datasets, and machine learning algorithms, therefore, this study focused on "remote sensing modelling - evolution history - change trends - mechanism analysis" to elucidate both the remote sensing monitoring models and the underlying driving factors governing the spatiotemporal evolution of Ulva prolifera green tides in the highly impacted South Yellow Sea of China. With the use of GOCI Ⅰ/Ⅱ images, an hybrid remote sensing extraction model merging the robustness of the random forest (RF) model and the optical algae cloud index (ACI) was established to map Ulva prolifera distribution patterns. The ACI-RF method exhibited exceptional performance, with an F1 score surpassing 0.95, outperforming alternative methods such as the support vector machine (SVM) and K-nearest neighbour (KNN) methods. On the basis, we analysed the evolutionary trends and the driving factors determining these distribution patterns using meteorological data, runoff data, and data on various water quality parameters (SST, ocean current speed, wind speed, precipitation, DO, PAR, Si, NO3-, PO43-and N/P). Over the period from 2011 to 2022, excluding 2021, there was a notable decline in the area of Ulva prolifera green tides, varying between 397 and 2689.9 km2, with an average annual reduction rate of 3%. The maximum annual biomass varied between 0.12 and 15.9 kt. Notably, more than 75% of the area of Ulva prolifera green tides exhibited northward drift, which was significantly influenced by northern currents and wind fields. The analysis of driving factors indicates that factors such as average sea surface temperature, eastward wind speed, northward wind speed, precipitation, PO43- and N/P/Si significantly influence the biological growth rate of Ulva prolifera. Furthermore, coastal land use change and surface runoff, particularly surface runoff in June, significantly impacted the growth rate of Ulva prolifera, with Pearson correlation coefficients of 0.74 and 0.67, respectively. Against the background of global warming and severe deterioration in the marine environment, Ulva prolifera blooms persist. Consequently, two distinct management strategies were proposed based on the distribution patterns and cause analysis results for addressing Ulva prolifera green tides: establishing a continuous protection framework for rivers, lakes, and nearshore areas to mitigate pollutant inputs and implementing precise environmental monitoring measures in urban expansion areas and farmlands to combat overgrowth-induced green tides. This methodology could be applied in other regions affected by marine ecological disasters, and the criteria for selecting influencing factors offer a valuable reference for designing tailored and proactive measures aimed at controlling Ulva prolifera green tides.

Two new diatom species of the genus Gomphonemopsis (Bacillariophyceae) from the coast of China and two new combinations for the genus.

Two new diatom species belonging to the genus Gomphonemopsis are described, Gomphonemopsisnanasp. nov. and Gomphonemopsisgaoisp. nov. These two species were compared in detail with congeners. Gomphonemopsisnana is distinguished by its high stria density and small size. This species was found so far to be epiphytic only on the eelgrass collected from Qingdao Bay (Yellow Sea). Gomphonemopsisgaoi is characterized by its isopolar valves, simple proximal raphe endings and acutely rounded apices. This taxon was separated from the exoskeleton of marine copepods sampled from the Futian Mangrove Nature Reserve (South China Sea). In addition, two new combinations, Gomphonemopsisoahuensis (Hustedt) Lang Li, Yuhang Li & Changping Chen, comb. nov. and Gomphonemopsisplatypus (Østrup) Lang Li, Yuhang Li & Junxiang Lai, comb. nov. are proposed. This study increases the records and knowledge of Gomphonemopsis along the coast of China.

Back-trajectory analyses for evaluating the transboundary transport effect to the aerosol pollution in South Korea.

This study performed a back-trajectory analysis to determine the influence of transboundary transport on the extent of aerosol pollution in South Korea, based on 5-year PM2.5 measurements (2015-2019) in five cities covering South Korea. A transboundary transport case was selected if a back trajectory passed over a dedicated region (BOX 1 and BOX 2) in the Yellow Sea. First, we found that the frequency of transboundary transport largely increases in the high pollution case, and this pattern is almost consistent for all months and all five cities, indicating the importance of investigating the horizontal direction of air mass movement associated with PM2.5, which has been discussed extensively in previous studies. In this study, we also examined the altitude change and straight moving distance (defined as travel distance) of back trajectories regarding the extent of local PM2.5. Consequently, we found that back trajectories in high aerosol pollution showed much lower altitudes and shorter travel differences, implying a significant contribution of surface emissions and stagnant air conditions to severe aerosol pollution. As a result, the local PM2.5 level was not significantly enhanced when the air mass passed over the Yellow Sea if transboundary transport occurred at high altitudes with rapid movement (i.e., high altitude and long travel distance back-trajectory). Based on these results, we suggest utilizing the combined information of the horizontal direction, altitude variation, and length of back trajectories to better evaluate transboundary transport.

Significant CO2 emission in the shallow inshore waters of the southeastern Yellow Sea in 2020.

This study investigated the carbonate system and air-sea CO2 exchange in the inshore waters along South Korea's western coastline in 2020. Overlooking these waters might introduce significant errors in estimating air-sea CO2 fluxes of the southeastern Yellow Sea, given their interaction with land, offshore regions, and sediments. During periods other than summer, seasonal variations in seawater CO2 partial pressure (pCO2) could be generally explained by thermal effects. Tidal mixing and shallow depths resulted in weaker stratification-induced carbon export compared to offshore regions. However, during summer, inshore waters exhibited high spatial variability in pCO2, ranging from approximately 185 to 1000 µatm. In contrast to offshore waters that modestly absorbed CO2, inshore waters shallower than 20 m emitted ∼100 Gg C yr-1 to the atmosphere. However, considering the high heterogeneity of the study area, additional observations with high spatial and temporal resolution are required to refine estimates of air-sea CO2 exchange.

Competition between ocean thermal structure and tropical cyclone characteristics modulates ocean environmental responses in the Yellow and Bohai Seas.

To study the environmental responses of tropical cyclones (TCs) in continental shelf regions, TCs passing over the Yellow Sea and Bohai Sea (YBS) during 2002-2020 were investigated, with a special focus on how competition between ocean thermal structure and TC characteristics modulates ocean surface changes. The spatial distributions of the climatic mixed layer depth (MLD), accumulated wind forcing power index (WPi), accumulated sea surface temperature (SST) changes and accumulated chlorophyll (Chl-a) changes in the YBS were calculated. The linear regressions indicate that both the TC-induced SST cooling and TC-induced Chl-a increase are correlated with the TC wind speed rather than the translation speed, especially when the TC forcing depth (Zmixing) is greater than the MLD. Otherwise, both the changes in SST and Chl-a are correlated with the TC translation speed when Zmixing is shallower than the MLD. Further study has shown that whether TCs can break the MLD is also a key condition for oceanic responses. In the southern YBS, which has a deep-sea basin and MLD, the TC wind speed is the major factor affecting SST cooling and Chl-a increase, as TCs need more strength to reach the MLD. However, in the northern YBS, which has the shallowest sea basin and MLD, even weak TCs can easily break the MLD and reach the seabed; thus, ocean surface changes are associated mainly with the TC translation speed. The composite results reveal that both the maximum SST cooling center (1.64 °C) and the maximum Chl-a increasing center (0.14 log10(mg/m3)) are located on the right and behind the TC center, respectively. In addition, TC-induced SST cooling and Chl-a increase were initiated two days prior to TC passage and then reached their maximum values after 1 day. It takes approximately 7-8 days for the Chl-a concentration to recover, but it takes a much longer time (>15 days) for the SST to recover.

Projections of climate-driven biogeographical changes of benthic mollusks in the Yellow Sea and East China Sea.

Climate change influences the distribution of many marine species. To project the biogeographical changes of benthic mollusks in response to climate change in the Yellow Sea and East China Sea, ensemble species distribution models (SDMs) were applied. Ensemble SDMs performed well for ten of the thirteen selected benthic mollusks with environmental variables including temperature, salinity, current velocity, and depth. Six cold water mollusks, including bivalves Acila mirabilis, Ennucula niponica, Ennucula tenuis, Nuculana yokoyamai, Pendaloma otohimeae and Megayoldia japonica, were projected to contract their habitats and move northward in 2050s and 2100s under all of the RCP2.6, 4.5, 6.0 and 8.5 climate scenarios, with temperature being the most important environmental variable. Two warm water mollusks (bivalves Nucula tokyoensis and Leptomya minuta) were projected to lose their suitable habitats under future climate scenarios (all RCP scenarios), while two (the gastropod Cylichna biplicata and the bivalve Moerella hilaris) were projected to expand their habitats to the deeper water area. The most important environmental variable varied among warm water species between temperature, salinity and depth. This study will contribute to better understanding the marine species biogeographical changes under climate change, and thus we can better protect their biodiversity.

Characteristics, distribution patterns and sources of atmospheric microplastics in the Bohai and Yellow Seas, China.

Although the prevalence of microplastics in the atmosphere has recently received considerable attention, there is little information available regarding the distribution of atmospheric microplastics over oceanic regions. In this study, during the summer and autumn months of 2022, we investigated atmospheric microplastics in four marine regions off the eastern coast of mainland China, namely, the southern, middle, and northern regions of the Yellow Sea, and the Bohai Sea. The abundance of atmospheric microplastics in these regions ranged from 1.65 to 16.80 items/100 m3 during summer and from 0.38 to 14.58 items/100 m3 during autumn, although we detected no significant differences in abundance among these regions. Polyamide, chlorinated polyethylene, and polyethylene terephthalate were identified as the main types of plastic polymer. On the basis of meteorological data and backward trajectory model analyses, we established that the atmospheric microplastics detected during summer were mainly derived from the adjacent marine atmosphere and that over the continental landmass in the vicinity of the sampling area, whereas microplastics detected during autumn appear to have originated mainly from the northeast of China. By influencing the settlement and migration of microplastics, meteorological factors, such as relative humidity and wind speed, were identified as potential factors determining the distribution and characteristics of the detected microplastics. Our findings in this study, revealing the origin and fate of marine atmospheric microplastics, make an important contribution to our current understanding of the distribution and transmission of microplastics within the surveyed region and potentially worldwide.

Unveiling the evolution of phytoplankton communities: Decades-long insights into the southern Yellow Sea, China (1959-2023).

We obtained historical and observational data on phytoplankton communities from 1959 to 2023 to explore the responses of the phytoplankton community structure to long-term environmental changes in the southern Yellow Sea (SYS), China. The results revealed a decrease in the proportions of diatom cell abundance within the phytoplankton community by 8 %, accompanied by a corresponding increase in that of dinoflagellates. Dominant phytoplankton species were mainly chain-forming diatoms before 2000, and large dinoflagellate species from the genera Tripos and Noctiluca increased their dominance after 2000. Warm-water phytoplankton species have increased in dominance over the study period. Correlation analysis revealed that the ocean warming and alterations in nutrient structure (N/P and Si/N ratios) were mostly responsible for the long-term evolution trend, and these changes may result in an increase in dinoflagellate harmful algal blooms, reduced efficiency of the biological carbon pump, and heightened hypoxia in the future, which should draw our attention.