Western Yellow Sea Research Articles

How do peak-water-levels respond to natural shoreline restoration projects with progressive tide parallel to shore

Facing strict control of natural shoreline retention and the urgent need for mitigation of oceanic hazards, amid climate change, challenges persist in the spatial allocation of nature-based and concrete-based measures in China's coastal protection and restoration plans. This study explores the feasibility of “Operational Landscape Units" (OLUs) and their impact on peak-water-levels (PWL) and tides on the western Yellow Sea inner shelf (WYS), considering the newly published “China Coastal Ecological Zoning on Land and Seas” in 2023. Numerical experiments with a single OLU of county-size operated along the WYS indicate the largest reduction of 10% (0.23m) in PWL on the coast happens when an OLU is set on the section closest to the tidal amphidrome and the shoreline is parallel to the tidal propagation direction. Furthermore, as the restoration section extends on both sides, the spatial scale of the changed PWL expands. Further investigation reveals that OLUs positioned upstream of the tidal propagational direction can more effectively mitigate coastal inundation risks. This is because local tidal damping through bottom friction inside the OLUs overweighs the tidal damping on the inner shelf outside the OLUs. Overall, this study provides insights into high-tidal-flooding mitigation through OLUs in China's coastal zones, offering references for future coastal plans and flood control deployments.

Two decades variations of nutrients in precipitation at the Qianliyan island, the western Yellow Sea

Precipitation is of great significance in the transport and removal of atmospheric nutrients. For the sake of the acquaintance of nutrient level, deposition flux and secular trend of marginal sea precipitation, two decades (1997–2019) atmospheric investigations were conducted at the Qianliyan island, the western Yellow Sea. Overall, the annual average wet deposition fluxes of nitrate (NO3−), ammonium (NH4+), phosphate (PO43−), silicate (SiO32−), dissolved organic nitrogen (DON) and organic phosphorus (DOP) ranged 9.17–42.80, 13.50–41.44, 0.06–1.88, 0.07–5.56, 14.20–42.14 and 0.09–0.62 mmol·m−2·a−1, respectively. The annual average concentrations of NO3− in precipitation showed a monotonic rising trend, while that of SiO32− showed a monotonic decreasing trend. From the long-term observation, it found an alleviation of acidic precipitation of the Yellow Sea under the policy controls of sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions. Meanwhile, effective control of sand-dust largely reduced precipitation SiO32− concentration. Source also effected precipitation nutrients. Average concentrations of NO3−, NH4+ and SiO32− in precipitation from the ocean were lower than those from the northern arid area, while average concentrations of PO43−, DON and DOP in precipitation from the ocean were higher than those from the northern arid area. Qianliyan precipitation brought rich dissolved inorganic nitrogen (DIN) over PO43− to the ocean surface, which might alter the phytoplankton community succession ultimately.

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.

Seasonal variability of phytoplankton community response to thermal discharge from nuclear power plant in temperate coastal area

Nuclear power plants (NPPs) developed rapidly worldwide in the last half-century and have become one of the most important electric power sources. Thermal discharge from NPPs increases the temperature of receiving waters, directly and indirectly affecting phytoplankton community. Seasonal and interannual variation in environmental factors in temperate areas makes it challenging to determine the effects of thermal effluents from NPPs on coastal phytoplankton. Here, a five-year study was performed around a NPP in the western Yellow Sea to determine how thermal effluents affect phytoplankton community during different seasons. A total of 106 phytoplankton species from 7 phyla were identified in 10 biological sites during the 19 cruises, among which diatoms dominated phytoplankton abundance in all seasons. Our results show that increased seawater temperature caused by thermal effluents (1) was not enough to cause a statistically significant effect on phytoplankton abundance composition from autumn through spring, (2) significantly stimulated phytoplankton population growth and changed phytoplankton composition in summer (3) increased the proportion of diatoms and decreased the proportion of dinoflagellate in summer, and (4) increased the abundance and dominance of Skeletonema costatum sensu lato, especially in summer. The findings of this study provide essential information on the ecological impact of thermal effluents from NPPs in temperate coastal areas.

Dimethylsulfoniopropionate, dimethylsulfide, and acrylic acid of a typical semi-enclosed bay in the western Yellow Sea: Spatiotemporal variations and influencing factors

As the degradation products of dimethylsulfoniopropionate (DMSP), dimethylsulfide (DMS) and acrylic acid (AA) are crucial to the sulfur cycle in the ocean. However, the biogeochemical processes of DMSP, DMS, and AA remain unclear. A monthly investigation was conducted to determine the DMSP, DMS, and AA concentrations and related parameters in the surface water of Jiaozhou Bay, a semi-enclosed bay in the western Yellow Sea, from December 2010 to November 2011. The monthly mean concentrations of DMSP, DMS, and AA were in the ranges of 5.02–27.25 nmol L−1, 0.41–3.14 nmol L−1, and below the detection limit–301.75 nmol L−1, respectively, showing significant seasonal variations with higher concentrations in summer than in autumn. The results were attributed to a combination of biogenic factors, including phytoplankton, zooplankton, and bacteria, as well as environmental factors, such as temperature and nutrients. The DMSP, DMS, and AA concentrations were not significantly correlated with chlorophyll a and bacterial abundance because of the influence of the community structure and anthropogenic activities. DMS was mainly produced by the enzymatic cleavage of DMSP, whereas AA was affected primarily by terrigenous input. The monthly mean sea-to-air fluxes of DMS ranged from 0.74 (in Apr) to 6.55 (in Jan) μmol m−2 d−1 with an average of 2.80 μmol m−2 d−1.

The patterns of trophic transfer of microplastic ingestion by fish in the artificial reef area and adjacent waters of Haizhou Bay

Plastic pollution has become a threat to the global marine environment. Many studies have shown that marine organisms are at risk of plastic ingestion, but there is still a lack of relevant research in the artificial reef area and adjacent waters of Haizhou Bay, located in the western Yellow Sea. The study of MPs will provide useful information for MPs pollution in the artificial reef food webs, as well as the understanding of MPs trophic transfer by reef fish. In this study, we quantified plastic ingestion by marine fish in artificial reef areas and adjacent waters (Natural area, NA; Aquaculture area, AA; Estuary area, EA; Artificial reefs area, AR and Comprehensive effective area, CEA) and analysed the related possible influencing factors. Of the 146 fish samples examined, 100% of fish ingested plastics, and 98.9% of these particles were microplastics (MPs) (<5 mm), with 3.00 ± 2.63 pieces/fish. The main types and colours of MPs were fibre (95.9%) and blue (84%). The MP quantity of AR and AA were significantly higher than that of CEA (P < 0.05) and there is no significant difference among other habitats. The MP ingestion by pelagic fishes was significantly lower than that of demersal fishes (P < 0.05). MP ingestion by omnivores was significantly higher than that by carnivores and planktivores (P < 0.05). The body length (body weight) of four species (Larimichthys polyactis: 17.7–16.7 cm (16.01–59.41 g); Collichthys lucidus: 8.1–14.3 cm (19.65–56.92 g); Tridentiger barbatus: 5.9–9.2 cm (3.37–19.1 g); Cynoglossus joyneri: 10.1–18.7 cm (5–45 g)) had no significant correlation with MP ingestion (P > 0.05). Our results showed that MPs in this region are ubiquitous (i.e., the MP ingestion rate was as high as 100%). We infer that there is a transfer mechanism in MPs from pelagic to benthic fish in this area, and there is weak biomagnification with the trophic transfer of the food chain (TMF = 1.62). However, more practical studies still need to verify whether MPs are actually transferred to humans through trophic transfer from the marine food web.

Dramatic temperature variations in the Yellow Sea during the passage of typhoon Lekima (2019)

During the passage of Typhoon Lekima over the stratified Yellow Sea (YS) in August 2019, dramatic bottom temperature cooling of 2–5 °C was observed in northern coastal oceans of the Shandong Peninsula. In the current study, satellite observations and high-resolution numerical simulations were combined to investigate three-dimensional temperature changes in the YS during Lekima's passage and the underlying dynamics. Results indicated that the YS showed spatially coherent surface cooling and subsurface warming, primarily due to enhanced vertical mixing. The strongest surface temperature cooling of 4–8 °C occurred just over the southern bottom slope in the North YS, for which tidal mixing and bottom slope were also important factors through maintaining strong thermal stratification and inducing locally enhanced upwelling. In contrast, bottom temperature changes were most significant in coastal oceans in the western YS, showing dramatic cooling in northern coastal oceans of the Shandong Peninsula but warming as high as 8 °C in southern coastal oceans of the Shandong and Liaodong Peninsulas. Surface winds drove northward/shoreward Ekman transports in the North/South YS. This resulted in surface water convergence and downwelling in southern coastal oceans of the Shandong and Liaodong Peninsulas but divergence and upwelling in northern coastal oceans of the Shandong Peninsula. Downwelling generated bottom warming through transporting downward surface warm water. In the bottom layer, southward pressure gradient force drove shoreward advection of cold water to induce temperature cooling in nearshore regions. The current study provides significantly more insights into oceanic responses to passages of typhoons in the YS, especially in coastal oceans, which are one of the most intensively maricultured areas in the world.

Coupling hydrochemistry and stable isotopes (δ2H and δ18O) to identify the major factors affecting the hydrochemical evolution of groundwater in the Western Yellow Sea Coast, China

Groundwater, as an invaluable freshwater resource, has a significant impact on the social and economic development of coastal areas. The Western Yellow Sea coast (WYSC), located in the eastern part of China, is considered one of the most prosperous areas in terms of economic development, with considerable demand for water. In this study, a total of 160 groundwater samples were collected in the field, for which the Ca2+, Mg2+, Na+, K+, Cl−, SO42−, HCO3−, F−, Br−, δ2H, and δ18O contents were determined. We studied the chemical characteristics, sources of dissolved substances, hydrogeochemical processes, and the difference between the chemical characteristics of groundwater in two areas of the WYSC, the Shandong part (SDP) and Jiangsu part (JSP). The results indicate that the major sources of dissolved substances in the groundwater of WYSC were mineral dissolution and seawater intrusion (SWI). SDP was mainly affected by mineral dissolution, whereas JSP was significantly affected by SWI. The major source of groundwater recharge in the WYSC was precipitation; moreover, the groundwater recharge was affected by seawater and evaporation. The groundwater in the SDP was affected by modern SWI, whereas that in JSP was affected by palaeo SWI. SWI not only directly changes the chemical composition of groundwater via mixing but also indirectly changes it by influencing the hydrogeochemical processes. SWI can also lead to the formation of high-fluoride groundwater. Therefore, feasible measures should be incorporated to prevent SWI and ensure drinking water safety for the inhabitants.

Semi-enclosed bays serve as hotspots for black carbon burial: A case study in Jiaozhou Bay, western Yellow Sea

The provenance of black carbon (BC) and its role in affecting contaminant cycling in both the atmosphere and aquatic environments have been extensively studied. However, the fate and cycling dynamics of BC, particularly in marine environments, are poorly understood. Herein, soot BC was determined in the semi-enclosed Jiaozhou Bay to examine the seasonal variability, residence timescale in seawater, and settling flux to sediments, together with particle-reactive 234Th. Soot BC ranged from 0.39 to 4.26 μmol-C L−1. On average, spring produced the highest value of 1.88 ± 0.31 μmol-C L−1, followed by winter (1.59 ± 0.18 μmol-C L−1), summer (0.94 ± 0.09 μmol-C L−1), and autumn (0.90 ± 0.09 μmol-C L−1). The seasonality of soot BC was similar to the activity concentration of particulate 234Th (i.e., 234ThP). The close relationships between soot BC and 234ThP (p < 0.01) provide the basis for the application of 234Th to trace the fate of soot BC. Based on the 234Th deficit with respect to 238U, the residence times of soot BC were estimated to be 41 ± 6 d and 36 ± 5 d for May–August and August–November, respectively. The shorter residence times of soot BC than that of seawater indicated that soot BC delivered to Jiaozhou Bay settled in the local sediments. Furthermore, soot BC concentrations were higher in the inflow seawater from the Yellow Sea than the outflow water from Jiaozhou Bay, implying a net input of soot BC from the Yellow Sea to Jiaozhou Bay. The soot BC fluxes were 0.266 ± 0.035 mmol-C m−2 d−1 and 0.0472 ± 0.0065 mmol-C m−2 d−1 for May–August and August–November, respectively. From the bay-scale perspective, Jiaozhou Bay had buried 0.101 ± 0.010 Gg of soot BC each year. These results indicate that the semi-enclosed Jiaozhou Bay acts as an effective trap for soot BC and particle-reactive contaminants.

Insights into spatiotemporal distributions of trace elements in kelp (Saccharina japonica) and seawater of the western Yellow Sea, northern China

China is the largest kelp (Saccharina japonica) producing country in the world. Kelp consumption is a tradition in many Asian countries. However, S. japonica accumulates trace elements that exhibit potential health risks upon ingestion. Here, we selected six sampling sites, from the shelf to offshore waters, in a maricultural area of Ailian Bay in Rongcheng City, northern China and investigated the spatiotemporal distributions of trace elements in kelp and seawater from 2016 to 2018. We then evaluated the bioremediation potential and food safety of S. japonica. Most trace elements in S. japonica and seawater demonstrated no marked spatial variations. The trace element concentrations in the tested kelp did not exceed the food safety standards, indicating that it is safe for human consumption. Moreover, S. japonica has a high bioremediation capability for trace elements, and the kelp in the coastal waters of Rongcheng (with annual yield of 1.7 × 104 t DW) removed 28.60 kg Cr, 165.51 kg Cu, 682.54 kg Zn, 34.00 kg Cd, 52.53 kg Pb, 3.60 kg Hg, and 1305.53 kg As from the seawater per year. Our results will be useful for evaluating the bioremediation potential of S. japonica and for food safety management.

Seasonal Physical Fronts and Associated Biogeochemical‐Ecological Effects off the Jiangsu Shoal in the Western Yellow Sea, China

AbstractThe Jiangsu Shoal and its adjacent area in the western Yellow Sea (YS) have become hotspots of ecological disasters in China and have attracted considerable attention. Based on remote sensing and field observations in this region, we investigated the physical fronts and their seasonal variations and clarified the spatiotemporal patterns of physical‐biogeochemical factors as well as their interactions and synergies. The results show that pronounced physical fronts were present in the study area. Specifically, arc‐ and “S”‐shaped thermal fronts existed off the shoal in summer and winter, respectively. The saline front largely expanded southeastward in spring, autumn, and winter, while it expanded northeastward in summer. The turbidity over the shoal was high year‐round, and a marked turbidity front was formed between the nearshore water and the offshore seawater. The seasonal patterns and variations of the physical fronts significantly influenced material transport. During cold seasons, the frontal system was responsible for the significant turbid water plume expanding in a southeastern direction from the Jiangsu Coast. In summer, the arc‐shaped thermal front confined the turbid water within the shoal. The expansion of excess dissolved inorganic nitrogen was consistent with the saline front, and the vertical transport of nutrients by upwelling occurred off the shoal in summer. Due to favorable conditions, the frontal region off the shoal is prone to high chlorophyll a (Chl‐a) and may act as oases in either summer or winter. A conceptual diagram is assembled to provide an overview of physical‐biogeochemical‐ecological interactions off the Jiangsu Shoal in the western YS.

Phenotypic plasticity and taxonomy of Cladophora gracilis (Griffiths) Kützing (Cladophorales, Chlorophyta) in the western Yellow Sea with the implication of its DNA barcode

Due to extensive morphological plasticity, the taxonomy of Cladophora species remains unclear. As one of the widely distributed species, C. gracilis was reported to hold many varieties, which make it difficult to identify the species. This study explored the morphology diversity of nine C. gracilis samples collected along the coast of western Yellow Sea. Some samples showed extremely varied characteristics, by which one cannot classify them correctly. Hence, 18S rDNA and nuclear ribosomal DNA internal transcribed spacer regions (ITS) sequences were employed to delimit species. For 18S rDNA, sequence similarity ranged from 99.6% to 100%. For ITS region, the similarity ranged from 98.7% to 100%. Molecular data strongly suggested that the morphologically heterogeneous samples were actually the same species. Characteristics comparison of the samples revealed that the taxonomy criteria including branching pattern and density, thallus color, height and texture varied widely, influenced by environmental conditions and age of alga. Besides, cell dimensions, as the relatively stable criterion, also exhibited intraspecific variance. Successful application of 18S rDNA and ITS sequences indicated that molecular method can be a powerful assistant as DNA barcodes to traditional morphology taxonomy.

Aeration-induced marine sediment acidification in the vicinity of Rizhao Port, western Yellow Sea

Two short-term summer cruises were performed in the vicinity of Rizhao Port, western Yellow Sea, to investigate summer water stratification and the phenomenon of marine sediment acidification. Results show that water stratification has formed as early as in May. The chemoclines of dissolved oxygen (DO) and pH usually occur deeper than the thermocline. Sometimes the chemoclines of DO and pH occur synchronously at the same depths, but sometimes they do not synchronize. Above the chemocline DO fluctuates markedly and maintains at a high level or even oversaturation in daytime, suggesting the far-field impact of vessel propulsion. Below the chemocline it invariably remains at a low and stable level and slowly drops downward. The pH values of surface sediments vary in the range of 6.3–7.6. A conspicuous sediment acidification is observed along the navigation region. This phenomenon is chiefly attributed to the intermittent disruption of summer stratification by shipping activity along the shipping channel and waterways. Water stratification precludes the penetration of DO down to the bottom sediments on fair ocean status, and maintains anoxia below the sediment–water interface, whereas the abrupt DO increase driven by propeller agitating is nearly restricted in the navigation area. Therefore, the aeration effect accelerating oxidation of reducing substances and organic matter is primarily responsible for enhanced acid accumulation in surface sediments. In addition, the suspension effect is identified by the negative offsets of zero point on pH–mV diagram. Most of the measured points are scattered correspondingly on three distinct regression lines, with similar slopes but different negative offsets of pH 6.53, 6.87, and 6.99, respectively. Their geographical distribution suggests that this effect has a positive relationship with the intensity of anthropogenic disturbance. Although the suspension effect is caused by the adsorption of charged particles at the pH glass electrode interface (Yang et al. in Part Sci Technol 7:139–152, 1989), its various intensity observed in practice may also reflect the inherent distinction of depositional environments in physicochemical conditions.

Heterotrophic diazotrophs in a eutrophic temperate bay (Jiaozhou Bay) broadens the domain of N2 fixation in China's coastal waters

N2 fixation in coastal waters represents an overlooked process in the global marine nitrogen cycle, yet the mechanisms and controls are still poorly understood. This study first conducted simultaneous measurements of N2 fixation rates, primary production, chlorophyll a (Chl a) concentration, organic carbon concentration, and the composition of nitrogen-fixing genes (nifH) in a eutrophic temperate bay (Jiaozhou Bay, the western Yellow Sea) from 2015 to 2017. The activity of N2 fixation (not detected–1.53 nmol N L −1 h −1) were observed at most sampling stations, suggesting that the N-replete conditions in Jiaozhou Bay did not prevent N2 fixation. The major N2 fixers in JB were heterotrophic, while N2 fixation were mainly contributed by > 10 μm fraction, indicating the possible active N2 fixation of heterotrophic diazotrophs on large particles or planktonic aggregates. Positive correlations between N2 fixation and organic carbon concentration were observed in spring. Further estimates of the level of phytoplankton-derived organic carbon and its potential relationship with N2 fixation suggest that phytoplankton processes may stimulate N2 fixation in Jiaozhou Bay by increasing the bioavailability of organic carbon or/and providing suitable environmental conditions for N2 fixation. Our results first infer the co-regulation of physical factors and biological processes on N2 fixation. As Jiaozhou Bay has been subject to anthropogenic pollution of inorganic nutrients, our results provide insights into the dominant controls on N2 fixation and relevant biogeochemical processes in coastal waters under anthropogenic disturbance.

Modeling the westward transversal current in the southern Yellow Sea entrance: a case study in winter 2007

The westward transversal current (TC) in the southern Yellow Sea entrance was investigated during winter 2007 using a numerical ocean model. The three-dimensional structures and dynamics of the westward TC were highlighted. The model-simulated monthly mean current fields showed that the strong westward TC was limited to the upper water column (shallower than 50 m) and extended westward from 126° E to 124° E. Momentum balance analysis indicated that the westward TC was mainly regulated by a quasi-geostrophic balance. Both the sea surface elevation–related barotropic pressure gradient force and the density-related baroclinic pressure gradient force controlled the intensity and direction of the westward TC. Sensitivity model experiments focusing on tide and wind demonstrated that the westward TC was intensified when tide was ignored and was greatly weakened when wind was excluded. Lagrangian particle tracking experiments were also performed, to investigate the relationship between the Yellow Sea Warm Current and the westward TC in the frontal region. The characteristics of the water in the Yellow Sea Warm Current were affected by the properties of the water in the frontal zone, especially in the sub-surface and lower layers. The westward TC might act as an important bridge, connecting the frontal zone with the Yellow Sea Warm Current flowing along the western Yellow Sea trough.

An anomalous bi-macroalgal bloom caused by Ulva and Sargassum seaweeds during spring to summer of 2017 in the western Yellow Sea, China

An unprecedented bi-macroalgal bloom caused by Ulva prolifera and Sargassum horneri occurred from spring to summer of 2017 in the western Yellow Sea (YS) of China, where annual large-scale green tides have prevailed for a decade. The distinct genesis and blooming dynamics of the two seaweed species were detected and described. Unlike the consistent raft-origin of the floating Ulva biomass, the massive pelagic S. horneri was derived from multiple sources (residual seaweeds from the previous winter bloom and those drifting from offshore water in the south). The scale of the green tide in 2017 was found smaller than the previous four years. We then discussed a number of hypotheses attributing to this reduction, including reduced epiphytic green algae from aquaculture rafts and the influences of the massive pelagic S. horneri. However, further research is needed to identify the origin of the pelagic S. horneri in the western YS and any affiliations with the benthic populations, and to elucidate the interactions of this species with the annual green tides and the ensuing consequences.

Provenance analysis of the Cretaceous Laiyang Group on Lingshan Island (western Yellow Sea, China) and its tectono-sedimentary implications

Longstanding debates on the tectonic setting and provenance of the Lower Cretaceous Lingshandao Formation have hindered basin analysis and tectonic studies of the collision of the Yangtze Craton and the North China Craton, and thus the evolution of the Sulu Orogen. Thin-section analysis, identification of rock particles, cathodoluminescence, heavy minerals and trace-element analysis have, in addition to field investigations, been applied to reconstruct the source area and transport pathways of the sediments that build the Lower Cretaceous Laiyang Group on the Lingshan Island, western Yellow Sea. These analyses indicate that the Laiyang Group consists mainly of material derived from a recycled orogen and from transitional continental sediments. The Laiyang Group on Lingshan Island has been sourced from igneous and metamorphic rocks. Comparing analyses of detrital minerals with rocks from surrounding areas leads to the conclusion that the main source area is the Sulu Orogen that supplied sediment to rift basin rather than a residual basin between the Yangtze Craton and the North China Craton.A recycled orogenic belt is the source area for the Laiyang Group on Linshan Island.Felsic metamorphic and igneous rocks form the most probable sources.The rift basin was filled by sediments supplied from the Sulu Orogen on both sides.

Spatial heterogeneity of seasonal phytoplankton blooms in a marginal sea: physical drivers and biological responses

Abstract Satellite and in situ observations are used in this study to examine spatial heterogeneity in the timing and magnitude of phytoplankton blooms in relation to local and remote physical processes in the Yellow Sea (YS), a marginal sea in the northwestern Pacific Ocean. Satellite ocean colour data reveal that annual chlorophyll maximums vary significantly in both timing and magnitude over different subregions of the YS. Strong summer blooms were found off estuary regions, and widespread spring blooms were found in the central trough. Localized autumn and winter peaks were found in small patches around Jeju Island and in nearshore regions. A statistical analysis of in situ measurements of the western YS suggests that variability in hydrographic properties could explain most of the spatial heterogeneity observed in both bloom timing and magnitude. The spatial heterogeneity of hydrographic properties, such as stratification and nutrient availability, are controlled by a suite of physical forcings, including the extent of the YS Cold Water Mass, river discharge, warm slope water intrusion, and seasonal warming/cooling. Our results imply that the spatial heterogeneity of marginal seas must be carefully considered when assessing phytoplankton responses in the context of climate change, because of the complexity of underlying mechanisms.

Long-Term Trend of Green and Golden Tides in the Eastern Yellow Sea

Kim, K.; Shin, J.; Kim, K.Y., and Ryu, J.H., 2019. Long-term trend of green and golden tide in the eastern Yellow Sea. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Remote Sensing and Geoscience Information Systems of Coastal Environments. Journal of Coastal Research, Special Issue No. 90, pp. 317-323. Coconut Creek (Florida), ISSN 0749-0208.Since 2008, floating green tides (Ulva sp.) have been occurring continuously in the Yellow Sea (YS), and after 2013 floating golden tides (Sargassum sp.) have also occurred. The distribution, areal coverage, and migration of floating green tides have been actively studied, but most research has focused only on the western YS. Little is known about the floating golden tides in the eastern YS. The purpose of this study was to determine the long-term distribution of floating green and golden tides in the eastern YS using Geostationary Ocean Color Imager (GOCI), Moderate Resolution Imaging Spectroradiometer (MODIS), and Landsat satellite images from 2008 to 2017. In addition, the migration of floating macroalgae with Global Hybrid Coordinate Ocean Model (HYCOM) surface current data were compared. Green tides were observed in 2008, 2009, 2011, 2015, and 2016 in the eastern YS. From a satellite image backtracking analysis, it was confirmed that the green tides observed in the eastern YS were supplied from the western YS. When the maximum areal coverage of green tide was compared between the eastern and western YS, the coverage in the eastern YS was found to be about 4 % of that of the western YS. However, in 2011, the largest amount of floating macroalgae was found in the eastern YS and it accounted for about 45 % of the amount in the western part of the YS. In the eastern YS, floating golden tides were found in 2013, 2015, 2016, and 2017, with the largest amount of floating macroalgae occurring in 2017. Although there were no long-term golden tide data for the western YS, such that it was not compared to the areal coverage of the eastern YS, it was confirmed that the amount of golden tide supplied to the eastern YS gradually increased. A comparison between the migration of floating macroalgae and HYCOM surface current data suggested that the migration and flow directions were not identical, and were considerably affected by surface ocean currents during their passage into the eastern YS. From this study, the long-term distribution and changes in areal coverage of green and golden tides in the eastern YS were obtained for the first time. This information will be useful for understanding the long-term patterns of green and golden tides, and provides basic data for predicting the occurrence and migration of floating macroalgae.

Atmospheric wet deposition of dissolved organic carbon to a typical anthropogenic-influenced semi-enclosed bay in the western Yellow Sea, China: Flux, sources and potential ecological environmental effects

Dissolved Organic Carbon (DOC) is a key organic compound in wet precipitation, but few data are available in China marginal seas. To probe the concentration, deposition flux, seasonality, source and potential ecological environmental effects of precipitation DOC, in this study, one-year precipitation samples were collected at Jiaozhou Bay (JZB), a typical anthropogenic-influenced semi-enclosed bay in the western Yellow Sea for the first time from June 2015 to May 2016. The concentrations of DOC in precipitation were highly variable with a volume-weighted mean (VWM) concentration of 3.63 mg C L−1, which was mostly higher than those in other areas. DOC concentrations were lower in wet season than that in dry season due to the dilution from more amount of rainfall. The wet deposition flux of DOC was calculated to be 3.15 g C m−2 yr−1 with 68.7% of which occurred in wet season mainly owing to the promoting of more rainfall amount. Besides, local emissions together with the long-range transport of pollutants were other factors controlling precipitation DOC. Fossil fuel combustion particularly coal burning was considered to be the leading source of precipitation DOC based on correlation analysis with some generally accepted indicators. Wet deposition dominates the external input of DOC at JZB by comparison with riverine input with a percentage of 54%. Heavy storm may exert enrichment effect on DOC levels in the surface water of JZB, and then promote the secondary productivity. This study emphasizes that wet deposition is an important process that should be seriously considered in the models of global/regional carbon biogeochemical cycling.