Yellow Water Research Articles

Enhanced methane production from source-separated human feces (brown water) by single phase anaerobic co-digestion: Effects of different co-substrates

Based on the concept of source separation of brown water (BW, human feces with flushing water) and yellow water (urine) in rural area, anaerobic co-digestion of BW with agricultural waste is a promising and effective method for rural waste treatment and resource recovery. The purpose of this study was to investigate the performance of different agricultural wastes (peanut straw (PST), peanut shell (PSH), swine wastewater acting as co-substrate for anaerobic co-digestion with BW, and the relative mechanisms were explored. When the mixed ratio was uniformly set as 1:1 (mass ratio, measured by volatile solid (VS)) and initial VS load as 20 g/L, the maximum cumulative methane production obtained by co-digestion (21 days) of BW and PST was 688 mL/g-VS, which performed better than the individual substrates (341 mL/g-VS), as well as the average of the sole BW and sole PST groups (531.2 mL/g-VS). The most impactful advantage was ascribed to the promotion of hydrolytic and acidogenic enzyme activities. The addition of PST also reduced the production of endogenous humus, which is difficult for biodegradation. Microbial community analysis showed that different co-substrates would affect the microbial community composition in the reactor. The relative abundance of hydrolytic acidogens in the PST and PSH co-digestion groups were higher than that in the SW co-digestion and sole BW groups, and the methanogenic archaea were dominated by the acetate-trophic Methanotrichaceae. The overall results suggest that anaerobic co-digestion is a feasible method, and co-digestion of BW and PST can improve methane production potential.

Emission of CO2 and its related carbonate system dynamics in a hotspot area during winter and summer: the Changjiang River Estuary

The carbonate chemistry in river-dominated marginal seas is highly heterogeneous, and there is ongoing debate regarding the definition of atmospheric CO2 source or sink. On this basis, we investigated the carbonate chemistry and air-sea CO2 fluxes in a hotspot estuarine area: the Changjiang Estuary during winter and summer. The spatial characteristics of the carbonate system were influenced by water mixing of three end-members in winter, including the Changjiang freshwater with low total alkalinity (TA) concentration, the less saline Yellow Sea Surface Water with high TA, and the saline East China Sea (ECS) offshore water with moderate TA. While in summer with increased river discharge, the carbonate system was regulated by simplified two end-member mixing between the Changjiang freshwater and the ECS offshore water. By performing the end-member mixing model on DIC variations in the river plume region, significant biological addition of DIC was found in winter with an estimation of −120 ± 113 μmol kg−1 caused by wintertime organic matter remineralization from terrestrial source. While this biological addition of DIC shifted to DIC removal due to biological production in summer supported by the increased nutrient loading from Changjiang River. The pCO2 dynamics in the river plume and the ECS offshore were both subjected to physical mixing of freshwater and seawater, whether in winter and summer. In the inner estuary without horizontal mixing, the pCO2 dynamics were mainly influenced by biological uptake in winter and temperature in summer. The inner estuary, the river plume, and the ECS offshore were sources of atmospheric CO2, with their contributions varying seasonally. The Changjiang runoff enhanced the inner estuary's role as a CO2 source in summer, while intensive biological uptake reduced the river plume's contribution.

Interannual-decadal variations in the Yellow Sea Cold Water Mass in summer during 1958–2016 using an eddy-resolving hindcast simulation based on OFES2

In the Yellow Sea, a large volume of cold water with temperature below 10 °C exists in the bottom layer in summer and affects the regional circulation, climate and marine ecosystem. Here, we investigated in detail the interannual-decadal variations in the summer Yellow Sea Cold Water Mass (YSCWM) using six decades (1958–2016) of a quasi-global eddy-resolving hindcast simulation, which was validated with observations. Results indicated that volume and mean temperature of the YSCWM were 0.52 × 1012–4.10 × 1012 m3 (2.22 × 1012 m3 on average) and 8.53–9.32 °C (8.94 °C on average). The YSCWM was dominated by interannual-decadal variations with a weakly warming and shrinking trend. The YSCWM volume (mean temperature) had larger (smaller) average values and varied more significantly during the two periods of 1958–1988 and 2005–2016 than during 1989–2004. Interannual-decadal variations in the summer YSCWM agreed with those in February temperature in the Yellow Sea, which were primarily caused by net surface heat flux variations, with a minor but negative contribution from heat exchange with the East China Sea through the northward Yellow Sea warm current and southward coastal currents. Winter net surface heat flux variations were dominated by latent heat flux and sensible heat flux, both of which resulted from combined effects of the Siberia High, Western Pacific pattern and Arctic Oscillation through controlling sea surface wind speed and air temperature over the Yellow Sea. The current study provided a more complete picture and in-depth understanding of changes in the summer YSCWM responding to large-scale climate change and variabilities during the past six decades.

A novel biosorbent-based marine macroalgal biomass for efficient removal of toluidine blue and basic yellow 28 dyes-contaminated waters

Nowadays, the release of textile effluents has become a global environmental concern. Herein, Taonia atomaria macroalga was used for removing toluidine blue (TB) and basic yellow 28 (BY-28) dyes from water. The characterization results revealed that the Taonia atomaria surface exhibited an open morphology enriched with functional moieties. The maximum uptake capacity of Taonia atomaria biosorbent reached 104.16 and 140.84 mg.g−1 for BY-28 and TB dyes, respectively. The spent Taonia atomaria biosorbent was successfully reused up to 6 times. Overall, Taonia atomaria macroalgae might be consideredas an affordable, ecofriendly and reusable biosorbent for treating textile dyes-laden effluents.

The Critical Role of Thermal Stratification Associated With the Yellow Sea Cold Water Mass in Modulating Winter Sea Surface Temperature

AbstractThe Yellow Sea Cold Water Mass (YSCWM), a seasonal bottom‐layer water mass in the Yellow Sea (YS) most prominent in summer, has always been overlooked in previous studies investigating variations in the winter Sea Surface Temperature. Here, using observations and high‐resolution numerical modeling, we reveal for the first time the significant contribution of thermal stratification associated with the YSCWM to the sea surface cooling and the formation of the westward‐shifted Yellow Sea Warm Water Tongue (YSWT) in early winter. Heat budget analyses indicated that the impact of the YSCWM to surface cooling manifests in two aspects. First, the upward mixing of bottom cold water from the remnant YSCWM triggers cooling in the mixed layer. Second, the shallower local mixed layer above the YSCWM facilitates more pronounced cooling processes compared to the YSWT region under similar heat flux. The formation of the westward‐shifted YSWT is the result of intensified surface cooling in both the coastal shallow waters and the YSCWM region in the central YS. During the formation process of the YSWT, its main axis aligns with the western boundary of the YSCWM. As the YSCWM dissipates, the YSWT shows an eastward apparent displacement and eventually stabilizes near approximately 123°E. This study enriches our understanding of the transition from stratification to vertical homogeneity in the water temperature structure of the YS during early winter.

Climate change enables invasion of the portunid crab Charybdis bimaculata into the southern Bohai Sea

In May 2020, a bottom-trawl survey in the southern Bohai Sea collected the portunid crab Charybdis bimaculata, a species formerly found in the northern Yellow Sea. In subsequent surveys, C. bimaculata was found to be abundant and likely to occupy habitats and niches of native species. To study the suitability of habitat in the southern Bohai Sea for this crab, nine trawl surveys were conducted between 2020 and 2022 to monitor its dispersal. Using Biomod2 software and combining species occurrence and environmental data, a distribution model for C. bimaculata in the southern Bohai Sea is developed. We analyze relationships between this and other crustacean species by comparing niche widths and their overlap. A random forest model outperforms eight others, and has the highest evaluation indices among single algorithm species-distribution models. The evaluation index of an ensemble model is significantly higher than those of single algorithm models, indicating its greater accuracy and robustness. We report suitable habitat for C. bimaculata to occur mainly in central and northeastern Laizhou Bay, and for this habitat suitability to shift over years from the middle to northeastern waters. Niche width showed a negative trend from 2020 to 2022, and is greater in May than August for each year. Niche overlaps between C. bimaculata and other major crustaceans in the southern Bohai Sea exist. We consider that increased sea surface temperature caused by climate change enabled invasion of C. bimaculata from northern Yellow Sea waters into the southern Bohai Sea, where it can overwinter and complete its life cycle. These results provide a scientific basis upon which monitoring of C. bimaculata in the Bohai Sea can be strengthened to better cope with its invasion and any negative impact on local biodiversity.

Effects of extraction temperature on bioactive compounds and antioxidant activity of yellow velvetleaf (Limnocharis flava) and water lettuce (Pistia stratiotes) leaf extract

Oxidative stress is considered a source of metabolic disorders. It is caused by an imbalance between the body's antioxidant potential and free radical production. Therefore, the body needs exogenous antioxidants, such as the bioactive compounds of plants. The yellow velvetleaf (Limnocharis flava) and water lettuce (Pistia stratiotes) leaf showed potential antioxidant activity because of their polyphenol compounds. This study aimed to investigate the effects of extraction temperature on polyphenols and flavonoids as well as their antioxidant activity on yellow velvetleaf and water lettuce leaf. The plant was extracted by the maceration method in various processes using 70% ethanol. The results showed the total polyphenol (TPC) and flavonoid content (TFC), as well as the antioxidant content determined using the DPPH method. The highest TPC (512.5 mg GAE/g of dried sample; 273.7 mg GAE/g of the dried sample) and TFC (209.5 mg QE/g of dried sample; 641 mg QE/g of the dried sample) were observed in low-temperature extraction. Under these conditions, the highest antioxidant activity (IC50) of yellow velvetleaf and water lettuce was 0.207 mg/mL and 0.227 mg/mL, respectively. A low extraction temperature is optimal for extracting these bioactive compounds, primarily from yellow velvetleaf and water lettuce leaf.

Identifying the external N and Hg inputs to the estuary ecosystem based on the triple isotopic information (δ15NNO3, Δ17ONO3 and δ18ONO3)

The supply and sources of N and Hg in the Geum estuary of the western coast of Korea were evaluated. Triple isotope proxies (δ15NNO3, Δ17ONO3 and δ18ONO3) of NO3− combined with conservative mixing between river and ocean waters were used to improve isotope finger-printing methods. The N pool in the Geum estuary was primarily influenced by the Yellow Sea water, followed by riverine discharge (821 × 106 mol yr−1) and atmospheric deposition (51 × 106 mol yr−1). The influence of the river was found to be greater for Hg than that of the atmosphere. The triple isotope proxies revealed that the riverine and atmospheric inputs of N have been affected by septic wastes and fossil fuel burning, respectively. From the inner estuary towards offshore region, the influence of the river diminishes, thus increasing the relative impact of the atmosphere. Moreover, the isotope proxies showed a significant influence of N assimilation in February and nitrification in May.

Meiofauna community structure in the Yellow Sea Cold Water Mass and non‐Yellow Sea Cold Water Mass

This study investigated meiofaunal community structure over a large area of the Yellow Sea and East China Sea for 45 stations from 2021 to 2022. Meiofaunal densities were 34 ± 15–1610 ± 378 ind./10 cm2. Nematodes (67.3%) were the most dominant taxa, followed by benthic foraminifera (12.0%) and benthic harpacticoids (8.8%). The study was conducted in various sedimentary environments. Median grain size, water depth, and environmental characteristics (TOC, TN, Hg, Sr) were identified as influencing meiofauna community structure. The Yellow Sea and East China Sea, where this study was conducted, contain a variety of currents and the Yellow Sea Cold Water Mass (YSCWM) in the central waters. YSCWM and non-YSCWM areas differed in their meiofauna community structure. Even within the YSCWM region, we found differences in benthic community structure due to a variety of environmental factors. The meiofaunal taxon most affected by Sediment temperature was benthic foraminifera. Identifying foraminifera in paleo-oceanographic environments can indicate past expansion and contraction of YSCWM. Meiofauna have been used to monitor changes in marine ecosystems due to their sensitivity to changes in the surrounding environment. Meiofauna index (N/C ratio, MPI) were identified as appropriate for use in the study area.

Comparison of nutrients status in Liaodong Bay and Northern Yellow Sea, China: Controlling factors and nutrient budgets

Under the dual stress of global warming and human interaction, Liaodong Bay (LDB) and northern Yellow Sea (NYS) are undergoing significant ecological changes. Little is known about the driving nutrients characteristics supporting fishery resource output in these areas. We carried out three field observations in 2019 to investigate nutrient status. Results showed that dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved silica (DSi) concentrations changed seasonally, with lowest values in spring, and highest values in autumn. High DIN, DIP, and DSi concentrations were detected in LDB and NYS's estuary areas. The Yellow Sea Cold Water Mass plays a role in the distribution and seasonal variation of nutrients. Exchanges across the sediment-water interface, SFGD, atmospheric deposition, and the adjacent sea input dominated DIN dynamics of these areas. DIP primarily came from the adjacent sea input and DSi mainly originated from sediment release and the adjacent sea input. NYS seawater invasion accounted for 13.8% of DIN, 63.4% of DIP, and 35.1% of DSi in LDB. These results provide new insights to better facilitate the formulation of nitrogen and phosphorus reduction and control policies in these marginal seas.

АКТИВНОСТЬ ТЛЕЙ-ПЕРЕНОСЧИКОВ ВИРУСОВ КАРТОФЕЛЯ В АРХАНГЕЛЬСКОЙ ОБЛАСТИ

The research was carried out to study the activity of aphids that carry viruses on potato plantings in the southern part of Arkhangelsk region, to assess the degree of their prevalence and the need to apply plant protection measures. The work was carried out in 2018-2022. The catching of winged forms of aphids in potato plantings was carried out using yellow water traps. In total, over a five-year period, 834 aphids were caught visiting potato plantings, which belonged to 30 different species. The most effective carriers of potato viruses are 7 of them - Acyrthosiphum pisum Harr., Aphis fabae Scop., Aphis nasturtii Kalt., Aulacorthum solani Kalt., Hyperomyzus lactucae L., Macrosiphum euphorbiae Thomas and Rhopalosiphum padi L. These species were present on plantings annually (with the exception of M. euphorbiae Thomas), and their numbers varied from 82 (in 2020) to 181 (in 2021) individuals. At the same time, the share of aphids that carry viruses in their total number ranged from 56% (in 2022) to 82% (in 2018). Over the entire period of research, not a single individual of the aphid species Myzus persicae Sulz, the most harmful to potato plantings, was identified. The prevalence of virus-carrying aphids was insignificant; there were from 21 to 46 winged insects per 1 water trap during the growing season in different years. Aphids capable of transmitting potato viruses were present on the plantings throughout the entire growing season, which indicates the need for preventive and exterminatory measures to protect plants, based on systematic annual monitoring, which makes it possible to monitor changes in the species composition, numbers and flight dynamics of aphids.

Study on a new index for yellow water problem during source water switch and its application on one real project

The evaluation of yellow water problem in drinking water distribution systems (DWDSs) by Larson ratio, Langlier saturation index is associated with fairly large uncertainty. As the background, one city in East China plans to change its water source from the local River A and River B into a new Lake C. Real servicing pipes were excavated in this city and assembled into 12 pipe section reactors (PSRs). The objectives of this study were to develop a more accurate index to predict the iron release in DWDSs, to verify the validity by simulation experiments with PSRs and to develop the reconditioning measures for the forthcoming source water switching project. A new index called iron stability index (ISI) was proposed by dividing alkalinity with the Larson ratio. Its validity was verified by the data in this study and literatures. ISI present closer linear relationship than that of LR and LSI in the situation where the concentration of anions (chloride and sulfate), and alkalinity in raw water and the switched water change more drastically. The water source switching from the local River A to the new Lake C was predicted not able to bring yellow water problem while that for the local River B to the Lake C has the risk. The water quality reconditioning measures were evaluated to address that concern and applied successfully in this project.

Impact of environmental variables on the distribution of phytoplankton communities in the Southern Yellow Sea

To gain a comprehensive understanding of the seasonal variation in the structure of phytoplankton communities in the Southern Yellow Sea (SYS), two research expeditions were conducted from 12 to 24 in April 2019, and from 12 to 22 in October of 2019. During the spring season, the phytoplankton community within the SYS was primarily comprised of diatoms and dinoflagellates, while in autumn, diatoms and cyanobacteria dominated. Thalassiosira rotula and Paralia sulcata were the dominant species in both seasons. In spring, P. sulcata displayed no obvious correlation with any environmental parameter, while in autumn, it exhibited negative correlations with environmental factors. According to the cluster and multidimensional scaling analyses, the phytoplankton community was stratified into three distinct ecological provinces in the SYS: the Western Yellow Sea, the Yellow Sea basin, and the southern coastal region. The phytoplankton community composition was predominantly affected by seasonal fluctuations in temperature and nutrient levels. Notably, the Yellow Sea basin exhibited the lowest phytoplankton abundance, largely because of the impact of the Yellow Sea Cold Water Mass. Furthermore, the presence of cyanobacteria, particularly prevalent in the Yellow Sea basin, may have been facilitated by transport mechanisms associated with the Kuroshio current. Aggregated boosted tree (ABT) and Generalized Additive models (GAM) suggested that temperature, DIN, salinity, and DIP were significant parameters of phytoplankton abundance in SYS. Additionally, the N:P nutrient ratio was a key parameter in governing the structure of phytoplankton communities during both seasons.

Sticky traps and water pan traps to monitor Delia planipalpis (Diptera: Anthomyiidae), an emerging pest of broccoli in Mexico

The radish fly, Delia planipalpis (Meigen), is an emerging pest that infests broccoli in Mexico. Females oviposit near the stem of broccoli plants or in the inflorescence. Effective monitoring systems are necessary for the development of integrated pest management programs against this insect. Laboratory and field experiments were performed to determine the fly's responses to stick traps and water pan traps. Both yellow and blue sticky traps captured significantly more males than females. Yellow traps captured higher numbers of D. planipalpis than blue traps, but with a lower capture of Delia platura (Stein) and other non-target insects. Sticky traps or yellow water pan traps captured similar numbers of D. planipalpis in broccoli crops, but water pan traps captured significantly more females than sticky traps. The addition of the host attractant allyl isothiocyanate significantly increased the capture of flies when used in sticky traps but not in water pan traps. Sticky traps or water pan traps could be used for surveillance of D. planipalpis. Water pan traps require more servicing time as specimens need to be dried before identification. In contrast, sticky traps allow rapid identification of insects, but some insects become damaged on the sticky surface.

Aphid species populations and their seasonal fluctuation in Prunus orchards affected by Sharka disease within the quarantine areas of Argentina

Sharka is a disease of stone fruits, produced by the Plum Pox Virus and transmitted by aphids. It was detected for the first time in Argentina in 2004. In order to assess the aphid species that could act as a potential vector of this disease, we described the aphids community and seasonal fluctuation within two Prunus orchards affected by Sharka disease, located within two quarantine areas in Cuyo Region. Aphids were trapped weekly from October (spring) to April (autumn) during 2011-2012 and 2012-2013, by using yellow water traps (TAA), and identified using winged aphid’s taxonomic keys. In total, 27 aphid species were identified. The most dominant species collected was Myzus persicae (Sulzer). Orchard-trapped population of this dominant aphid showed seasonal fluctuation with two peaks, November (spring) and March (autumn).

Interannual Variability and Long-Term Trends in Intensity of the Yellow Sea Cold Water Mass during 1993–2019

The Yellow Sea Cold Water Mass (YSCWM) is an important component of the hydrodynamic system and it significantly impacts the primary production of the Yellow Sea. This study investigated the difference in the interannual variability and long-term trends between the northern YSCWM (NYSCWM) and southern YSCWM (SYSCWM), and explored the main physical environmental factors that led to their inconsistency using multiple wavelet coherence. On the interannual scale, the intensities of the NYSCWM and SYSCWM exhibited consistent variability, but the intensity of the SYSCWM had a larger standard deviation and longer periodic signal than that of the NYSCWM. The two-factor combination of surface air temperature (SAT)–Niño 3.4 in the NYSCWM and sea surface temperature (SST)–northward seawater velocity (Vgos) in the SYSCWM controlled the interannual variability, which meant the influencing intensity variability differed in the NYSCWM and SYSCWM. In the long-term trend, the intensities of the NYSCWM and SYSCWM both showed decreasing trends during the study period. However, the enhanced circulation provided more horizontal heat input into the SYSCWM, and the relatively higher increase in SST and decrease in the amplitude of variation in the thermocline depth promoted vertical heat exchange in the SYSCWM, thereby making the intensity of the SYSCWM decrease more quickly than that of the NYSCWM. These findings provide important references that facilitate a deeper understanding of the influence of hydrological processes on marine ecosystems in marginal seas.

Contrasting effects of temperature and biological processes on aragonite saturation state at the A4HDYD station in the North Yellow Sea

To explore the effects of seawater temperature and biological processes on aragonite saturation state (Ωarag), eight field surveys were conducted from December 2014 to November 2015 at A4HDYD station in the North Yellow Sea (NYS). Low regional yearly initial values of seawater Ωarag (1.26–1.76) were obtained in winter due to low seawater temperature. During spring to early autumn, surface-water Ωarag increased from 2.02 to 3.47 for the increasing seawater temperature and biological production, whereas bottom-water Ωarag remained as low as 1.44–1.79 due to low seawater temperature, net community respiration and the influence of the North Yellow Sea Cold Water Mass (NYSCWM). Following the collapse of stratification in late autumn, the seawater was well-mixed with an average Ωarag of 2.17. The annual cycle of seawater temperature dominated the seasonal variations of Ωarag, counteracted by biological production increasing Ωarag of 0.49 in surface water in March and strengthened by net community respiration decreasing Ωarag of 0.11–0.41 below the pycnocline during summer and autumn. It is, therefore, mid-to-high latitude coastal areas impacted by human activities are likely subject to ocean acidification due to the combined effects of low seawater temperature and net community respiration.

Factors controlling the distribution of dissolved organic carbon and nitrogen in the coastal waters off Jeju Island

The composition of dissolved organic matter (DOM) in the coastal waters off Jeju Island, Korea, originates from a complex mixture of organic sources. This study examined the dynamics and sources of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in the coastal waters off Jeju Island. Seasonal variation in the DOC and DON concentrations was observed, with significantly higher levels during summer (DOC: 82 ± 15 µM and DON: 6.8 ± 2.0 µM) than during the other seasons. In 2017, the Kuroshio Intermediate Water had a greater impact on the coastal waters off Jeju Island during winter (79%) and spring (69%) than during the other seasons, while the Changjiang Diluted Water (CDW) (12%) and the Kuroshio Surface Water (47%) had a stronger impact during summer and the Yellow Sea Cold Water (10%) had a stronger impact during autumn. Although water mass analysis provides valuable insights, certain aspects of the DOM distribution in coastal seawater remain unexplained. During summer, while the mixing of the CDW influenced the concentrations of DOC and DON, a distinct pulse in these concentrations was observed within a specific salinity range, suggesting microbial activity as a source. The relationship between dissolved inorganic nitrogen (DIN) and salinity also exhibited the opposite trend to that between DON and salinity, indicating the conversion of DON into DIN through microbial activity. These findings suggest that microbial activity plays a key role in the observed DOM pulse, transforming particulate organic matter into DOM and then converting it into DIN during the long transportation from Changjiang River to Jeju Island. This organic matter cycle could thus serve as a source of DIN in oligotrophic regions. However, further research on the sources and distribution of organic matter using biogeochemical parameters is required to gain a better understanding of the intricate processes involved.

Enhanced disinfection byproducts formation by fine iron particles intercepted in household point-of-use facilities.

To cope with the demand for good-quality potable water, household point-of-use (POU) facilities such as polypropylene cotton filters (PCFs) are widely used. However, the behaviors of new and used PCFs under discoloration are unclear. In this study, we found that new PCF did not effectively intercept particles under discoloration within the initial 5 d of inflow. In addition, the particles, especially the fine ones, accumulated in the long-used PCF exacerbated the risks of disinfection byproducts (DBPs) and microbes. The concentrations of trihalomethanes (THMs) and haloacetonitriles (HANs) in the effluent run through the PCF all increased over time; interestingly, all sharply increased after 5 d in accordance with the decrease in effluent iron particles. During this stage, maximum increases rate of 117.89% in THMs and 75.12% in HANs were observed. For haloacetic acids (HAAs), it served as the dominant contaminants, with concentrations approximately 10-fold greater than those of THMs and HANs. The increase showed that used PCFscould exacerbate the risks in DBPs exposure. Adenosine triphosphate (ATP) also showed a similar trend, with a maximum increase from 0.0033 to 0.0055 nmol/mL. Thus, PCFs can act only as pretreatment units and should be replaced after yellow water events. This study offers important guidance for PCF usage in drinking water purification, especially under discoloration.

The Influence of Ocean Processes on Fine-Scale Changes in the Yellow Sea Cold Water Mass Boundary Area Structure Based on Acoustic Observations

The boundary of Yellow Sea Cold Water Mass (YSCWM) is a key ocean frontal structure influencing the regional ecosystem. Complex oceanic processes such as tidal currents, upwelling, and internal waves influence fine-scale hydrological structures, comprehensively resulting in a significantly highly productive area for plankton and fisheries. However, detailed research requires inaccessible high-resolution data. To investigate the fine-scale and high-frequency effects of oceanic processes on the local hydrological and ecological environment, we conducted comprehensive cruise acoustic observations and intensive station surveys of the hydrological environment around the YSCWM boundary in summer 2021 and 2022, and found that: (1) fine-scale hydrological structures across the YSCWM boundary were directly captured through this specific intensive station observation design; (2) clear zooplankton diel vertical migration (DVM) phenomena match well with the thermocline variation, showing that acoustics are effective indicators that reflect the water mass layering structure in summer in the YS; and (3) the shear excited by internal waves during propagation and flood tides enhances the upward and downward mixing of the water mass near the thermocline, thus thickening and weakening the layer, an effect that will be more pronounced when both are present at the same time, with ebb tide having the opposite effect. Topographically influenced tidal upwelling also causes significant vertical fluctuations in isotherms. This represents a new way of studying the fine-scale hydrodynamic–hydrologic–ecological aspects of key regions through acoustic remote sensing.