Jiaozhou Bay Research Articles

Phytoplankton biomass dynamics with diffuse terrestrial nutrients pollution discharge into bay

Diffuse terrestrial pollution in bay area has important ecological impacts on coastal ecosystems. This study investigated spatiotemporal changes in N, P, and chlorophyll a (Chla) in the Jiaozhou Bay (JZB) and phytoplankton biomass dynamics under terrestrial nutrients loading. The results from SWAT (Soil and Water Assessment Tool) model demonstrated that the annual average total N (TN) and total P (TP) loading from main rivers were 3626.3 t and 335.6 t, respectively, and were affected by land use type, precipitation, and temperature. Chla value interpreted by remote sensing showed a decrease from nearshore to the far shore. Changes in Chla concentration were usually “dual-cycle” in February and September, but explosive growth of Enteromorpha can cause multiple peaks. TN concentration in the bay was more susceptible to the impact of terrestrial input than TP. Phytoplankton biomass had a stronger correlation with P than with N in JZB. Enteromorpha contributing 4.05% of the phytoplankton biomass played a major role in phytoplankton biomass variability and responded most to nutrients loadings reduction. Under setting 5 m filter strip scenario, the Enteromorpha biomass removal efficiency could reach 35.25%. Furthermore, the findings of this study provide insights for sea-land integration and pollution prevention and control in urbanised bays.

Influence of a heavy rainfall event on nutrients and phytoplankton dynamics in a well-mixed semi-enclosed bay

With a warming climate, extreme precipitation events are projected to occur more frequently in future, which can lead to sediment and freshwater pulses to coastal waters that quickly affect water quality. Understanding how coastal systems respond to and recover from such acute events is becoming more and more important, particularly true in semi-enclosed bays with weak water exchange and purification capacities, such as Jiaozhou Bay (JZB). Based on the three cruises performed on 17 July, 5 and 22 August 2012, a coupled physical-biological model was used to examine ecosystem responses in JZB to Typhoon Damrey, an extreme precipitation event. In order to study the mechanism behind rainfall-induced changes, three groups of sensitivity experiments were set to furtherly analyze the contributions of rivers and atmospheric deposition, respectively. The results showed that typhoon-induced rainfall provided high concentration of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) to phytoplankton which caused a remarkable chlorophyll-a increase subsequently. During the heavy rainfall event, the nitrogen and phosphorus inputs from river runoff were 1.80 and 2.14 times than that from atmospheric deposition, respectively. River inputs supported 2.14 times the productivity than that supported by atmospheric deposition. Rainfall-induced nutrient input will lead to blooms in coastal areas, especially in semi-enclosed bays. Since increased rainfall would trigger higher river discharge, rivers became the main carriers of nutrients. Atmospheric deposition provided a low-level supply, and it was limited for alleviating phosphorus limitation in semi-enclosed bays. Enhancing ecological monitoring of rivers and atmospheric deposition is urgent and essential to predict the response of ecosystems to extreme rainfall events.

Effects of temperature and salinity on growth of Aurelia aurita

A three-stage (Medusa-Polyp-Ephyra) life history model of Aurelia aurita is formulated to investigate the role of ephyra and explore the ecological effects of sea surface temperature and seawater salinity on blooms. Both theoretical analyses and numerical simulations explain the mechanisms of A. aurita blooms in specific seasons. Sensitivity analyses (SAs) characterize the key factors that affect population sizes and provide a basis for feasible and effective control recommendations. In agreement with observational data, we then summarize the interannual variation patterns in the A. aurita population in Jiaozhou Bay and generalize its distribution in the Yellow Sea. This study shows that the occurrence of strobilation, ephyra development, and degree of asexual reproduction can significantly influence the steady states of A. aurita. Moreover, the population size of medusae is sensitive to medusa mortality and strobilation. The findings provide some valuable insights into revealing the mechanisms of A. aurita blooms and explain the connection between its population dynamics and environmental factors.

Coastline extraction based on multi-scale segmentation and multi-level inheritance classification

Detailed management of the coastline is critical to the development of coastal states. However, the current classification of the coastline is relatively weak. This study proposed an automatic method to detect coastlines with category attributes based on multi-scale segmentation and multi-level inheritance classification. Fully integrating the advantages of multi-scale segmentation and multi-level classification, it solved the problems that traditional methods could not solve, such as extracting coastlines with categorical attributes, cultivation ponds that are easily affected by tidal flats, and complex coastal terrain. The Chinese GF-2 satellite images are used to extract various types of coastlines in Jiaozhou Bay and its surrounding areas such as the harbor-wharf coastline, silt coastline, pond coastline, rocky coastline, and sandy coastline. Compared with the human interpretation, it is found that the coastline extracted by our proposed method is different by 10.104 km in the harbor-wharf coastline, 0.099 km in the silt coastline, 2.677 km in the pond coastline, 8.831 km in the rocky coastline, and 0.218 km in the sandy coastline. Furthermore, compared to the object-based region growing integrating edge detection (OBRGIE) method, it is increased by 13.52%, 2.16%, 14.48%, 52.57%, and 22.97%, respectively. The results show that our proposed method is algorithmically more reasonable, accurate, and powerful. It can provide data support for refined coastline management.

Capturing Secchi disk depth by using Sentinel-2 MSI imagery in Jiaozhou Bay, China from 2017 to 2021

Water clarity is a key parameter for assessing changes of aquatic environment. Coastal waters are complex and variable, remote sensing of water clarity for it is often limited by low spatial resolution. The Sentinel-2 Multi-Spectral Instrument (MSI) imagery with a resolution of up to 10 m are employed to solve the problem from 2017 to 2021. Distribution and characteristics of Secchi disk depth (SDD) in Jiaozhou Bay (JZB) are analyzed. Subtle changes in localized small areas are discovered, and main factors affecting the changes are explored. Among natural factors, precipitation and wind play dominant roles in variation in SDD. Human activities have a significant influence on transparency, among which fishery farming has the greatest impact. This is clearly evidenced by the significant improvement of SDD in JZB due to the sharp decrease in human activities caused by coronavirus disease 2019 (COVID-19).

Detection of marine oil spills from radar satellite images for the coastal ecological risk assessment

Coastal ecosystems offer substantial support and space for the sustainable development of human society, and hence the ecological risk evaluation of coastal ecosystems is of great significance. In this article, we propose an innovative framework for evaluating coastal ecological risk by considering oil spill risk information and environmental vulnerability information. Specifically, a deep learning based marine oil spill monitoring method is presented to obtain the oil spill risk information from Sentinel-1 polarimetric synthetic aperture radar (PolSAR) images. The environmental vulnerability information is then obtained from biological sample data and habitat information. Finally, a weighted probability model is introduced to utilize the oil spill risk and environmental vulnerability information, to evaluate the coastal ecological risk. In the experimental part, the proposed oil spill monitoring method shows its reliability in global ocean areas, and the proposed model is adopted to evaluate the ecological risk in Jiaozhou Bay, China. The results show that the ecological situation of more than half of the areas in Jiaozhou Bay is unstable, and the areas with high risk are mainly concentrated in the ports, shipping channels, and those areas with high biodiversity. This study provides some new perspectives on ecological risk assessment for coastal ecosystems, facilitating the planning process and the actions to be taken in response to the accidents that occur in the ocean, especially oil spill accidents.

Effects of Temperature and Food Concentration on the Population Recruitment of Acartia bifilosa (Copepoda, Calanoida): Implications for the Over-Summering Life History Strategy in Jiaozhou Bay

To obtain a clear understanding of the over-summering life history strategy of the dominant species A. bifilosa in the Jiaozhou Bay, the effects of high temperature and food concentration (represented by chlorophyll a, Chl a) simulating in situ summer conditions on the reproduction and post-embryonic development of A. bifilosa were studied. We found that the A. bifilosa population did not disappear from the seawater column in summer, and its abundance increased from June to July, and then sharply declined in August. Both temperature and food concentration had a significant influence on the reproduction of A. bifilosa. The results showed that 20 °C could not trigger the decline in population abundance and the resting egg strategy, and 28 °C was the upper threshold of A. bifilosa in the Jiaozhou Bay. Higher food concentration was essential for A. bifilosa to maintain population recruitment at a higher temperature. Nauplii could develop to adults in the higher-food-level treatments (10 and 15 μg/L Chl a). However, nauplii could not develop to copepodite at 28 °C with 5 μg/L Chl a. Neither temperature nor food concentration could induce resting eggs, and no resting eggs were detected in our study. A principal components analysis showed that temperature plays a more vital role than food concentration in determining the population recruitment of A. bifilosa. We suggest that A. bifilosa populations could sustain the high-temperature season independent of producing resting eggs in the Jiaozhou Bay, and implications for the over-summering life history strategy of A. bifilosa in the Jiaozhou Bay should be further discussed.

Establishing environmental background values of selected trace elements and environmental quality assessment of fine-grained sediments in the Jiaozhou Bay catchment, China

Establishing environmental background values of selected trace elements and environmental quality assessment of fine-grained sediments in the Jiaozhou Bay catchment, China

Occurrence, transport and environmental risk assessment of pharmaceuticals and personal care products (PPCPs) at the mouth of Jiaozhou Bay, China based on stir bar sorptive extraction.

In recent years, research on pharmaceuticals and personal care products (PPCPs) in the marine environment has attracted increasing attention worldwide. However, more work is needed to improve PPCPs detection methods, specifically for seawater environments. An analytical method based on stir bar sorptive extraction (SBSE) had been developed and fully optimized for the pretreatment and detection of ten widely used PPCPs that are commonly found in seawater samples. By optimizing several variables including the material of the stir bars, extraction temperature, extraction time, ionic strength, desorption solvent, and desorption time, the optimized method has achieved excellent results in the detection and quantification of target PPCPs with detection limits ranging from 0.03 to 1ng/L. The distribution of target PPCPs at the mouth of Jiaozhou Bay was successfully determined by this method, and the concentrations and detection frequencies of PPCPs varied greatly from N.D. to 449.36ng/L and from 9.1% to 100%, respectively. Moreover, the distributions of PPCPs were explained by the Lagrangian particle-tracking model, and the results showed that the Tuandao sewage treatment plant had the most significant impact on the study area. The environmental risk assessment results showed that several target PPCPs might pose risks to aquatic organisms. In particular, triclocarban should receive more attention and the risk quotients of the mixtures (MRQ) should not be ignored.

Effectiveness Evaluation of Optical Illusion Deceleration Markings for a V-Shaped Undersea Tunnel Based on the Set Pair Analysis Method and the Technique for Order Preference by Similarity to Ideal Solution Theory

To improve traffic safety in undersea tunnels, the speed control effect of optical illusion deceleration markings (OIDMs) in V-shaped undersea tunnels and their applicability to drivers were explored. In this study, UC-Win/Road software was used to build a simulation scenario, and the V-shaped Jiaozhou Bay undersea tunnel in Qingdao, China, was selected as the simulated road section. Four kinds of OIDMs were selected as the research objects. According to the physiological and psychological response characteristics of drivers to the visual recognition process of OIDMs and vehicle driving parameters, three primary and six secondary evaluation indices were identified. The analytic hierarchy process-entropy weight method was applied to assign weights to each evaluation index in combination, and a comprehensive evaluation model based on the set pair analysis method and the technique for order preference by similarity to ideal solution was constructed to comprehensively evaluate the effectiveness of the OIDMs based on the ternary coefficient and the comprehensive evaluation index. To verify the accuracy of the model, the data of the three secondary evaluation indicators with larger weight coefficients were statistically analyzed, and the results showed that the results of the statistical analysis of the data were consistent with the results of the model test. In the entrance section of the tunnel, the combination of white inverted fishbone deceleration markings and red warning pavement has the highest comprehensive evaluation index of γ A1 = 0.9611. In the downhill section of the tunnel, the white variable-spacing inverted fishbone deceleration markings have the highest comprehensive evaluation index, γ B1 = 0.9644.

Size-fractionated microbiome observed during an eight-month long sampling in Jiaozhou Bay and the Yellow Sea

Jiaozhou Bay is a typical semi-enclosed bay with a temperate climate imposed by strong anthropogenic influence. To investigate microbial biodiversity and ecosystem services in this highly dynamic coastal environment, we conducted a monthly microbial survey spanning eight months at two stations in the bay and the open Yellow Sea starting in April 2015. This report provides a comprehensive inventory of amplicon sequences and environmental microbial genomes from this survey. In total, 2,543 amplicon sequence variants were obtained with monthly relative abundance profiles in three size fractions (>2.7 μm, 2.7–0.7 μm, and 0.7–0.22 μm). Shotgun metagenomes yielded 915 high-quality metagenome-assembled genomes with ≥50% completeness and ≤5% contamination. These environmental genomes comprise 27 bacterial and 5 archaeal phyla. We expect this comprehensive dataset will facilitate a better understanding of coastal microbial ecology.

Belief-Propagation-Based Low-Complexity Channel Estimation and Detection for Underwater Acoustic Communications With Moving Transceivers

Achieving reliable communications with low complexity is challenging for underwater acoustic communications with moving transceivers, where the time-varying channels need to be estimated and tracked accurately and data detection needs to be performed with low complexity. In this article, with the use of a superimposed training (ST) scheme, we address this challenge by developing a low-complexity channel estimation and tracking algorithm, which is then integrated with low-complexity data detection in the frequency domain. ST is used to acquire improved channel-tracking capability. Based on belief propagation, we design a message-passing-based low-complexity bidirectional channel estimation (LCE-MP) algorithm, where all computational intensive parts are handled by the fast Fourier transform (FFT) algorithm, thereby achieving very efficient implementation with logarithmic complexity. Specifically, a message-passing-based fast information collection algorithm is presented to acquire “local” channel estimates, followed by the fusion of local channel estimates to achieve a “global” estimate of the channel. It is shown that the computational complexity per channel tap is only in a logarithmic level for the channel estimation and tracking. Moreover, the ST-scheme-based LCE-MP algorithm is combined with FFT-based data detection and decoding, which are performed in an iterative manner. The overall complexity of channel estimation and data detection is in a logarithmic level, and the system delivers excellent performance thanks to the joint processing. Field experiments were carried out in Jiaozhou Bay in 2019, and the experimental results verify the effectiveness of the proposed technique.

Evolution of polycyclic aromatic hydrocarbons in the surface sediment of southern Jiaozhou Bay in northern China after an accident of oil pipeline explosion.

The 2013 "Qingdao oil pipeline explosion" contaminated about 2.5km of shoreline in the Jiaozhou Bay area and aroused widespread concern because of the serious casualties even though it was not the most severe oil-spill contamination in China. To evaluate the long-term impact, we collected thirty-three surface sediment samples after 3years of the accident, with sixteen polycyclic aromatic hydrocarbons (PAHs) detected. Spatial-temporal variation in PAHs revealed that a minimal impact might still be present after 3years. Source analysis combined with a one-way ANOVA showed that pyrolytic sources were consistently predominant. The environmental impact was already minimal 3years later and negligible thereafter. Although the cancer risk has decreased over the years, there has always been a potential hazard to human for specific occupation, with all of the risk values exceeded 10-6. This study offers a reference for assessing the long-term impact of oil spills in similar bay areas.

Distinct distribution patterns of planktonic ciliate communities along environmental gradients in a semi-enclosed bay

Jiaozhou Bay is a representative temperate coastal ecosystem and connects with the Yellow Sea by a narrow mouth. The eastern part of the Bay is more polluted than the western and outer parts due to the combined effects of urban sewage and weak water exchange between different water masses. However, the previous results from microscopy analyses did not show any distinct distribution pattern of planktonic ciliates, which are generally considered good bioindicators along environmental gradients. We hypothesize that ciliates may respond to environmental stress by regulating the community of rare taxa, which was not uncovered by morphological methods. The diversity and distribution patterns of planktonic ciliate communities were investigated through high-throughput DNA sequencing from 13 stations in the eastern, western and outer parts of Jiaozhou Bay. The alpha diversity indices showed an increasing trend from the east Bay to the west Bay to the outer Bay. Significant differences in planktonic ciliate communities from different zones of the Bay were mainly attributed to rare rather than abundant taxa. Correlation network analysis revealed that the rare taxa generally have positive correlations with other rare ones, while more negative correlations were found among abundant taxa. We further revealed the distributions of three dominant genera (Stenosemella, Tintinnopsis, and Strombidium) were significantly correlated with environmental variables, suggesting that they might be used as ecological indicators. Our results elucidate the bioindicator potential of ciliate along environmental gradients in a semi-enclosed bay.

A dataset of trace elements in surface sediments from main rivers and intertidal zones in Jiaozhou Bay in 2015

A dataset of trace elements in surface sediments from main rivers and intertidal zones in Jiaozhou Bay in 2015

A transverse deceleration energy harvester based on a sliding plate for self-powered applications in near-zero energy road tunnels

Creating a near-zero energy environment is a hot research topic, and this concept can also be applied to road tunnels. By introducing cleaner energy for power generation, we can achieve the goal of sustainable cities and society. This paper proposes a sliding plate-based transverse deceleration energy harvester for near-zero energy road tunnels. The system comprises four modules. The sliding plate absorbs the kinetic energy lost as the vehicle slows down, and the transmission module converts it to electrical energy via the generator. A supercapacitor is used to store electrical energy from a generator. The average output power of 5.135 W is obtained at a peak conversion efficiency of 64.4% under 1.5 Hz frequency and 10 mm amplitude. At 1.5 Hz frequency and 8 mm amplitude, the harvester can supercharge a 5 F capacity to 4 V in 220 s. For example, the Jiaozhou Bay Tunnel's annual power generation capacity can reach 110 kW·h. The harvester can be installed at the tunnel's entrance and exit by recording the power ratings of tunnel lighting and common sensors, enabling self-powered applications in road tunnels.

Genetic Analysis of a Large-Scale Phaeocystis globosa Bloom Offshore Qingdao, China.

A sudden large-scale bloom event of the haptophyte Phaeocystis globosa that lasted over one month in the winter of 2021 was observed offshore Qingdao, China. This P. globosa bloom event was unusual as it was the first P. globosa bloom recorded in Qingdao offshore. Furthermore, the temperature at which this event occurred was much lower than that of previous P. globosa blooms in China. We hypothesize that the P. globosa strains that drove the development of this bloom offshore Qingdao were genetically unique and have a competitive advantage in the environmental conditions. To test this hypothesis, we analyzed P. globosa genetic diversity and the temporal dynamics of the bloom, using the high-resolution molecular markers pgcp1 and cox1 that we developed recently. The analysis revealed that the genetic compositions of P. globosa offshore Qingdao were rather limited, containing two dominant genotypes and other rare genotypes with low abundance, representing a small portion of the genetic diversities identified in coastal waters in China, and were rather different from the P. globosa genotypes outside of the Jiaozhou Bay before the P. globosa bloom in the winter of 2021. This suggested only certain strains contribute to the development of blooms under certain environmental conditions. The genetic composition may indicate the unusual timing and scale of this P. globosa event.

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.

Ecological risk assessment of metallic nanoparticles on the marine environments: Species sensitivity distributions analysis

Metallic nanoparticles (NPs) are increasingly being used and inevitably entering the marine environment. Therefore, the adverse effects of NPs on individual marine species have attracted increasing attentions. However, to date, the ecological risks of NPs on the marine ecosystem remain poorly understood. In this study, species sensitivity distributions (SSDs) were constructed for Ag, ZnO, CuO, and TiO2 NPs to understand their ecotoxicity to the marine ecosystem and the contribution of size effect and ion effect to the nanotoxicity. Furthermore, a case study on the assessment of marine ecological risk and marine environment carrying capacity of metallic NPs was performed in Jiaozhou Bay, China. The results showed the toxicity of metallic NPs to marine species following the order of Ag > ZnO > CuO > TiO2. Both size effect and ion effect contributed to the toxicity of NPs. Environmental concentrations of Ag, ZnO, CuO, and TiO2 NPs are much lower than the predicted no-effect concentrations, indicating that these metallic NPs have not yet posed risks to the marine ecosystem based on currently limited measured environmental concentrations of metallic NPs in seawater. And the marine environment carrying capacity of Ag, ZnO, CuO, and TiO2 NPs in Jiaozhou Bay seawater were determined to be 5.03, 8.72, 93.06, and 629.79 t, respectively. The results help us understand the ecological risk of NPs in marine environments and provide a scientific basis for the sustainable development of nanotechnology.

Effects of methyl halide flux characteristics following Spartina alterniflora invasion in a seaward direction in a temperate salt marsh, China

In this study, we explored the source-sink characteristics of methyl halide (CH3X; X = Cl, Br, I) in coastal wetlands located in temperate regions, and identified key factors affecting the spatio-temporal variation of CH3X during the invasion of Spartina alterniflora. We used static chamber-gas chromatography to monitor CH3X fluxes in the S. alterniflora area and bare flat area of the Jiaozhou Bay salt marsh for a long time from August 2015 to May 2017. Our results indicated that CH3X emissions showed obvious seasonal and diurnal variations. The S. alterniflora area was a source of CH3X, with higher fluxes in the spring and autumn seasons. CH3X fluxes were higher during the daytime than at night, and the diurnal difference in CH3Br was the most significant (4.51 times). The bare flat area was mainly a sink for CH3X, and the maximum absorption flux occurred in summer. At this time, the microbial activity was greater, and the consumption rate during the day was higher than that at night. Extreme linear correlations existed between the fluxes of CH3Cl, CH3Br, and CH3I (P < 0.01), indicating that the production and consumption of the three gases were likely to have similar mechanisms and were affected by the same factors. S. alterniflora invasion increased CH3X emissions and shifted the original bare flat area from a sink to a source of CH3X. The biomass of S. alterniflora, especially the leaf, significantly affects CH3X fluxes. Additionally, S. alterniflora increased the content of total organic carbon, total sulfur, available sulfur, and iron (III) in the soil, which were the main factors promoting the source-sink transformation of CH3X. Based on the current invasive area of S. alterniflora in China, we estimated that the annual emissions of CH3Cl, CH3Br, and CH3I from S. alterniflora into the troposphere were 9.04 × 106, 2.42 × 105 and 2.06 × 105 mol, respectively.