Around the world, green tides are happening with increasing frequency because of the dual effects of increasingly intense human activity and climate change; this leads to significant impacts on marine ecology and economies. In the last decade, the world's largest green tide, which is formed by Ulva/Enteromorpha porifera, has become a recurrent phenomenon every year in the southern Yellow Sea (China), and it has been getting worse. To alleviate the impacts of such green tide outbreaks, multiple measures need to be developed. Among these approaches, biotechnology plays important roles in revealing the outbreak mechanism (e.g., molecular identification technology for algal genotypes), controlling and preventing outbreaks at the origin sites (e.g., technology to inhibit propagation), and utilizing valuable algal biomass. This review focuses on the various previously used biotechnological approaches that may be applicable to worldwide seaweed blooms that result from global climate change and environmental degradation.

Copper has become one of the most important heavy metal pollutants in the environment because of its wide application and high toxicity, but research on water quality criteria (WQCs) on copper is limited, especially the derivation of seawater WQC. In addition, the toxicity of copper in the seawater system is affected by various environmental factors. Therefore, establishing a WQC that meets the characteristics of the regional environment is a top priority. The correlations between four factors of temperature, salinity, pH, dissolved organic carbon (DOC) and the toxic effect values of copper were analyzed in this study, and the temperature was determined as the most influential factor among the four factors in the Bohai Sea. A specific correlation between temperature and the toxic effects of copper was identified, and WQCs were derived based on the identified correlation and the variations of the Bohai Sea's temperature in different seasons by species sensitivity distribution (SSD) method. Under the condition of the winter, spring, autumn, and summer with an average water temperature of 0.09, 15.96, 17.83, and 24.87 °C, the obtained short-term water quality criteria (SWQCs) were 44.29, 4.70, 4.31, and 3.33 μg/L; the long-term water quality criteria (LWQCs) were 18.14, 1.93, 1.77 and 1.36 μg/L. The findings indicated the importance of introducing specific environmental conditions during the derivation process. This work could provide valuable information for pollution prevention and aquatic life protection in the Bohai Sea and provide a valuable reference for the derivation of criteria in other regions alike.

High demands for but strict regulatory measures on Organophosphorus Flame Retardants (OPFRs) have resulted in mainland China transitioning from the region that imports OPRFs to one that exports these substances. Simultaneously, large quantities of terrigenous OPFRs have been exported to adjacent seas by the major river systems, particularly the Yangtze River. This study examined the presence of ten OPFRs in China's adjacent seas. High levels of OPFRs were observed in seas south of mainland China, with Tris (2-chloroethyl) phosphate (TCEP) and Tris (1,3-dichloro-2-propyl) phosphate (TDCPP) dominant. The terrigenous OPFRs were redistributed by the ocean surface currents, with OPFRs tending to accumulate in regions with lower current speed. The producers of OPFRs are mainly distributed along the Haihe, Yellow, and Yangtze river systems. The application of OPFRs to electric vehicle charging stations, charging connectors, and 5G infrastructure in the Chinese mainland will likely drive rapid growth in OPFR related industry in the future. The diffusion trend map of OPFR indicated that the Bohai Sea and the central northern Yellow Sea are at high risk of ecological damage in the spring. The offshore region of the north of the South China Sea tended to aggregate more OPFRs in summer. Regions of the OPFR aggregation effect were at a higher risk of ecological damage.

Airborne fine particles can affect climate change and human health; moreover, they can be transported over significant distances. However, studies on characteristics of individual particles and their morphology, elemental composition, aging processes, and spatial distribution after long-range transport over the Yellow Sea are limited. Therefore, in this study, we conducted shipborne measurements of fine particulate matter of less than 2.5 μm in diameter (PM₂.₅) over the Yellow Sea and classified the individual particles into seven types based on their morphology and composition. Overall, the percentage of organic-rich particles was the highest, followed by that of sea spray, sulfur-rich, dust, metals, fly ash, soot, and other particles. Near Shandong, China, the percentage of fly ash and sulfur-rich particles increased, while an increased percentage of only sulfur-rich particles was observed near the Korean Peninsula. In the open sea, the PM₂.₅ concentrations were the lowest, and sea spray particles predominated. During the cruises, three types (Types 1, 2, and 3) of events with substantially increased PM₂.₅ concentrations occurred, each with different dominant particles. Type 1 events frequently featured air masses from northern China and Mongolia with high wind speeds and increased dust particles. Type 2 events involved air masses from China with high wind speeds; fly ash, soot, organic-rich particles, and the sulfate percentage in PM₂.₅ increased. Type 3 events displayed stagnant conditions and local transport (from Korea); soot, dust particles, and the secondary sulfate and nitrate percentages in PM₂.₅ increased. Thus, different types of transport affected concentrations and dominant types of fine particles over the Yellow Sea during spring.

Organophosphates (OPEs) are manmade organic pollutants that are widely used as flame retardants, plasticizers, and antifoaming and hydraulic agents. In this study, seven OPEs in seawater and sediment from the Yellow Sea and East China Sea were determined to study the distribution and diffusion behavior, and to evaluate the environmental risks. The ΣOPEs in the seawater and sediments ranged from below the method detection limit (<MDL) to 497.40 ng/L and from < MDL to 66.50 ng/g dw, respectively. Tri-n-butyl phosphate (TnBP), tris-(1, 3-Dichloro-2-Propyl) phosphate (TDCPP), and tri-meta-cresyl phosphate (TmCP) were the dominant OPEs in the seawater and sediments. OPEs were mainly distributed in coastal areas and the South Yellow Sea, indicating that they are mainly affected by land-based pollution and ocean currents. Fugacity analysis shows that tri-para-cresyl phosphate (TpCP) was in a state of equilibrium, while TDCPP, TnBP, and TmCP other OPEs tended to diffuse from sediment to water. The diffusion behavior of OPEs is mainly affected by their chemical properties. Hazard quotient (HQ) values of TmCP and TpCP in sediment samples were >1.0, indicating high ecological risks to aquatic organisms.

This paper reports trends in the input of underwater noise source energy emission from global shipping, based on bottom-up modeling of individual ships. In terms of energy, we predict the doubling of global shipping noise emissions every 11.5 years, on average, but there are large regional differences. Shipping noise emissions increase rapidly in Arctic areas and the Norwegian Sea. The largest contributors are the containerships, dry bulk and liquid tanker vessels which emit 75% of the underwater shipping noise source energy. The COVID-19 pandemic changed vessel traffic patterns and our modeling indicates a reduction of −6% in global shipping noise source energy in the 63 Hz ⅓ octave band. This reduction was largest in the Greenland Sea, the Coastal Waters of Southeast Alaska and British Columbia as well as the Gulf of California, temporarily disrupting the increasing pre-pandemic noise emission trend. However, in some sea areas, such as the Indian Ocean, Yellow Sea and Eastern China Sea the emitted noise source energy was only slightly reduced. In global scale, COVID-19 pandemic reduced the underwater shipping noise emissions close to 2017 levels, but it is expected that the increasing trend of underwater noise emissions will continue when the global economy recovers.

The marine environment of coastal Shandong Peninsula has been significantly influenced by anthropogenic activities due to the rapid industrialization and economic development in the past decades. However, the sedimentary records of PTEs in the North Yellow Sea have rarely been reported. In this study, a 209-cm-long sediment core was collected off the northern coast of Shandong Peninsula, analyzed for grain size and elemental compositions, and assessed using EF, Igₑₒ and several numerical Sediment Quality Guidelines (SQGs). The EF and Igₑₒ results suggested that sediment profile could be slightly to moderately polluted with As and Sb, while ecological risk assessment using SQGs showed that As, Cr, Sb and Ni in the sediment profile may have a moderate incidence of toxicity. Our results highlighted the nonnegligible ecological risk of Sb in sediments of North Yellow Sea, and great importance should be attached to the fact that many PTEs may also pose a potential ecological risk to the aquatic organisms, even though their concentrations meet the standards of the Marine Sediments Quality (MSQ). Moreover, the reconstructed PTEs record showed a dramatic increase over the past 250 years, which could be related to the intense anthropogenic activities since the Industrial Revolution. The multivariate statistical analysis results indicated that Co, Cr, Cu, Pb, Ni and Zn may be mainly related to the natural origin, while As and Sb could be influenced by both natural weathering sources and anthropogenic activities. This study provides more insights into the historical record of PTEs in the North Yellow Sea, and lays foundation for future comparison of PTEs sedimentary records.

Rapid urbanization and industrialization in the eastern seaboard region of China enhance the widespread use of organophosphorus flame retardants (OPFRs). The present study set up a coupled WRF-CMAQ-SMOKE and multi-compartment exchange modeling framework to assess the environmental fate and cycling of OPFRs and their contamination in the Bohai and Yellow Seas' marine food web. The framework predicts meteorological conditions, optimized air emissions, and concentrations of OPFRs in air, seawaters, marine sediment, and the food web. The model was implemented to simulate the temporal and spatial fluctuations of Tris (2-chloroisopropyl) phosphate (TCPP), the most dominant congener of OPFRs in China, in the Bohai and the Yellow Sea ecosystems on a spatial resolution of 10 km. Results revealed the effects of source proximity, atmospheric transport and deposition, and the changes in meteorology on TCPP's temporal-spatial distribution across different areas of coastal waters. The model also captures TCPP levels in commercial fish species in the Bohai Sea. The detailed temporal-spatial characteristics of TCPP with the mesoscale resolution provide useful information and a new tool for the environmental and health consequences of mariculture, urban and industrial emission mitigation in coastal regions for emerging chemicals, and fishery industry development.

As reservoirs for pollutants transported via the Yangtze and Yellow Rivers, the Bohai Sea (BS) and Yellow Sea (YS) play an important role in transporting microplastics (MPs) to the Pacific Ocean. The fate, sources and mass budget of MPs in the BS and the YS were investigated by Pearson correlation, principal component analysis-multilinear regression analysis (PCA-MRLA) and a mass balance model to sedimentary MPs data. Average MP abundances were 137 and 119 items kg⁻¹ in the Bohai and Yellow Seas, respectively. MPs <1000 μm exhibited similar distribution patterns to total organic carbon and fine-grained sediments, while MPs >1000 μm were confined in the BS and exhibited a strong positive correlation with chlorophyll-a and polyethylene terephthalate, suggesting that larger MPs might deposit faster due to biofouling or when comprised of high density polymers. PCA-MLRA analysis indicated land-based inputs (packing materials, textile material and daily commodities) were dominant in the BS, while maritime activities (fishing and mariculture) were the main source of MPs in the YS. The mass balance model revealed that the total MP input and output to the BS and the YS was 3396.92 t yr⁻¹ and 3814.81 t yr⁻¹, respectively. The major input pathway of MPs to the BS and the YS were river discharge and air deposition, respectively. Notably, 94% of MPs in the BS and the YS were deposited to sediments. This study revealed that BS and YS sediments play an important role in preventing MPs from being further transported to the Pacific Ocean, thus more attention should be paid to local ecological risk assessment.

Green tide outbreaks caused by overgrowth of Ulva prolifera in the Yellow Sea of China can cause serious ecological stress with concomitant economic hardships, especially to marine fisheries. In this study, short-term effects (14 days) were evaluated using fresh algae U. prolifera (FU), and a 7-day assessment of the effects of decomposing U. prolifera (DU) algal effluent was conducted to determine the effects on the environmental and intestinal microbiota, intestinal transcriptome and mortality of the commercial marine benthic fish, Japanese flounder (Paralichthys olivaceus). The results revealed that algal degradation altered the microbial community structure of fish farm water and fish intestines and increased the relative abundance of the pathogens Flavobacteriaceae in water and Vibrio in fish intestines. Fish intestinal tissue structure appeared to be damaged, as indicated in pathological sections, and transcriptome analysis showed intestinal inflammation after exposure, which may have caused an increase in fish mortality. The degradation of U. prolifera led to a bloom of potential pathogenic bacteria and the inflammation of fish intestines, which resulted in disease in the flounder population that reduced fish harvests and might pose a potential health threat.