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19 May 2022, Volume 2022 Issue 3 Previous Issue   
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Review
Research progress of microplastics and attached organisms in marine environment
Daoji LI, Xuri DONG
2022, 2022 (3):  1-7.  doi: 10.3969/j.issn.1000-5641.2022.03.001
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In recent years, white pollution caused by waste plastics has attracted widespread attention. Microplastics, which are smaller than 5 mm, are widely distributed in the marine environment. The organisms attached to microplastic surfaces include potential pathogenic bacteria that are harmful to marine life and even human health, as well as plastic-degrading bacteria that can reduce their pollution. Microplastics are difficult to degrade, so they can exist in the aquatic environment for a long time, and the microorganisms attached to their surface can also live stably. In addition, microplastics may pass through the food chain to organisms at higher nutritional levels, and may be eaten by fish and affect fish growth. This paper reviews the distribution of microplastics in the ocean and the potential effects of harmful substances contained or attached to the microplastic surface on organisms. The ecological effects of pathogenic microorganisms attached to the surface of microplastics and plastic decomposition microorganisms, as well as the potential of microplastic transmission to high nutritional levels through the food chain were discussed. The ecological risk of microplastic distribution and surface-attached organisms was analyzed. Furtherly, it is still necessary to understand the impact of plastic waste and microplastics on the marine ecosystem, so as to fully understand the ecological effects of marine microplastics and their attachments, and provide a scientific basis for marine plastic pollution control.

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Ecological and Environmental Sciences
Diversity of soil microbes in a vertical forest
Xianya XU, Stefano BOERI, Yibo XU
2022, 2022 (3):  8-16.  doi: 10.3969/j.issn.1000-5641.2022.03.002
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In this study, we analyzed the diversity of microbes across 45 collected soil samples using meta-barcoding. The analysis showed similar α diversity of soil microbes in a vertical forest (VF) building and the surrounding green area, but a high level of differentiation in the microbe community composition and β diversity between these two types of habitats. The results indicated that a VF can accommodate a large number of microbe species and provided evidence for the contribution of VFs to the conservation of urban biodiversity.

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Influence of habitat fragments on the richness of remnant natural forest species
Hong LIANG, Liangjun DA, Kun SONG, Chunling ZHOU, Zhiwen GAO, Kai WANG
2022, 2022 (3):  17-26.  doi: 10.3969/j.issn.1000-5641.2022.03.003
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Based on the classical theory of island biogeography, thirteen remnant forest patches of fragmented urban habitats were chosen as islands, and the Lao Mountain as the mainland. Then, canonical correspondence analysis (CCA) was used to analyze the relationship between species composition and four factors — namely, patch area, distance to species pool, human disturbance intensity, and isolation degree. The lengths of vectors in CCA biplots were used as weights for each influencing factor to calculate the overall sum, named the isolated island index (III); an isolated island index evaluation system of forest patches in fragmented urban habitats was subsequently designed. The results indicated that the relationship between III and richness was significantly negative for native species, but not significant for alien species richness. There was a significant relationship found for bird dispersal and wind dispersal species. The linear function was determined to be the best simulating model.

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Analysis and evaluation of the phytoplankton community structure in Luxun Park, Shanghai
Dan CUI, Ying LI, Tida CHEN, Minsheng HUANG
2022, 2022 (3):  27-38.  doi: 10.3969/j.issn.1000-5641.2022.03.004
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In this study, an ecological survey of the lake water in Luxun Park from January to October 2019 was conducted to determine the community structure characteristics and health of phytoplankton in the water. In particular, the community composition, density, biomass, diversity, uniformity, and dominant species of phytoplankton were analyzed. A total of 83 genera of 8 phyla of phytoplankton were identified; of these, Cyanophyta, Chlorophyta, and Diatoms had the largest number of species. The annual average cell density was 14.17×106 ind/L, and the annual average biomass was 3.57 mg/L. Density and biomass typically increase with seasonal changes. The dominant phyla were the Cyanophyta, Chlorophyta, and Diatom phylum; meanwhile, Pseudo-Anabaena, Platychophyta, Scenedesmus, and Cyclotella were the major dominant species. Redundant analysis was used to further analyze the environmental factors in the lake water of Luxun Park. The results showed that pH, nitrate nitrogen, nitrous nitrogen, and permanganate index are the key factors affecting the structure of the phytoplankton community.

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Application and analysis of the predominant trees in urban plots of the Yangtze River Delta Region
Long ZHANG, Geriletu , Jing YAN, Lingling WANG, Jiuxi SHI
2022, 2022 (3):  39-49.  doi: 10.3969/j.issn.1000-5641.2022.03.005
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Using a combination of mechanical and representative sampling, plots in 13 cities of the Yangtze River Delta Region were surveyed in 2015—2016; the survey consisted of 449 plots across 76 urban parks, roads, and waterfront greenbelt areas. As part of this study, we analyzed the factors and drivers for species composition, distribution, size, coverage, and growth vigor of the predominant trees located in the urban plots; the data provides a scientific basis for the future construction of forest cities and the improvement of urban human settlements. The results show that: ① In total, 157 tree species were recorded in the surveyed plots, which belonged to 115 genera and 54 families. The dominant families belonged to the Rosaceae group (20 species across 12 genera), with a high proportion of single families and relatively dispersed species composition. ② The plots were characterized by significant temperate features (73 genera), showing that the tree species have typical temperate properties in application. ③ The main tree species of the urban man-made forests were Cinnamomum camphora and Platanus × acerifolia, with coverage reaching 27.45%; specifically, Cinnamomum camphora was the dominant species. The utilization of trees across different types of urban plots varied considerably. ④ It was found that tree species with 10 cm ≤ D≤ 30 cm constituted the majority of tall trees in the urban plots, including many species of native trees such as Sapindus saponaria, Koelreuteria bipinnata 'Integrifoliola', and Liquidambar formosana. The quantity and distribution of the trees, however, was found to be extremely unbalanced. The coverage of Cinnamomum camphora and Platanus × acerifolia in the area was as high as 45.18%, and the relative species diversity and community stability were found to be weak. We recommend that the coverage of other tree species is gradually increased in the future construction of urban plots.

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Analysis of changes in water quality at the Qingcaosha Reservoir water intake over a period of 10 years
Yiping ZHU
2022, 2022 (3):  50-60.  doi: 10.3969/j.issn.1000-5641.2022.03.006
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Based on daily monitoring data of the Qingcaosha Reservoir water intake from 2010 to 2019, this paper analyzes the interannual and seasonal variation trends in the main physical and chemical water quality indicators, and explores the correlation between these indicators. The results show that: ① The dissolved oxygen at the intake of Qingcaosha Reservoir was consistently high, and the pH value was slightly alkaline. ② The concentration of ammonia nitrogen was low at the intake of Qingcaosha Reservoir, the concentration of nitrate-nitrogen was between 1.2 and 2.0 mg/L, the concentration of total phosphorus was between 0.1 and 0.2 mg/L, and the permanganate index was between 2.0 and 4.0 mg/L. These indexes, furthermore, all showed a downward trend after 2015, suggesting that the quality of incoming water subsequently improved. ③ Dissolved oxygen concentration, water temperature, and pH exhibited obvious seasonal variations, while total hardness, permanent hardness, conductivity, and chloride showed consistent variations under the influence of seawater intrusion. There was no significant seasonal variation in the other indicators. ④ The concentration of total phosphorus and the permanganate index increased with turbidity. The concentration of total phosphorus and nitrate nitrogen, moreover, decreased with an increase in water discharge at Datong.

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Study on ecological environmental effects of sediment dredging: A case study on river regulation in Shandong Province
Chunyi YANG, Guangxiang MA, Junjie GU, Jiayan GU, Guofu HE, Weixin KONG, Gensen YANG
2022, 2022 (3):  61-70.  doi: 10.3969/j.issn.1000-5641.2022.03.007
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In this study, follow-up monitoring over the course of two and a half years was carried out to analyze the long-term impact of sediment dredging on water quality, new sediments, benthos, and microorganisms of a river reach in Shandong Province. The results showed that the contents of CODCr and TP could be effectively removed by dredging, but little effect was observed on the contents of TN and NH4+-N. The C/N ratio in the new sediments decreased gradually over the observation period, which was beneficial to the recovery of microbial and benthic communities. Dredging can reduce the average biomass and density of tremididae in surface sediments to a certain extent, while Chironomidae density is less affected by dredging. Dredging did not change the microbial community structure significantly, which may be related to the depth of dredging. Exogenous pollutants and man-made drainage can affect the water quality and sediment pollutant content of the dredged river section; this effect, however, may recover in a short time after completion of the microbial community construction. In conclusion, the overall engineering effects of dredging were observed during the study period (2–4 years after dredging); in this time, the water quality and sediment pollution improved, which was conducive to the restoration of benthos and microbial diversity. However, with the passage of time and human interference, the net effect on water quality maintenance weakened.

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Soil respiration and its components across different land use types in the Dongtan reclamation area of Chongming Island
Jing HE, Qicheng ZHONG, Guilian ZHANG, Kaiyun WANG, Yueqi WU, Guishu HE, Dezhi LI, Nana PENG
2022, 2022 (3):  71-81.  doi: 10.3969/j.issn.1000-5641.2022.03.008
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In the Chongming Dongtan reclamation area, the soil carbon flux observation system (LI-8100A) and root removal method were used to continuously measure soil respiration (RS), heterotrophic respiration (RH), and autotrophic respiration (RA) of five land use types (Phragmites australis wetland, Imperata cylindrica wetland, young forest, middle-age forest, and cropland); the methods were also used to measure the soil temperature, volumetric water content, electrical conductivity, and other environmental factors in the 0-10 cm soil layer. In this study, the differences in soil respiration and its components among different land use types in the Chongming Dongtan reclamation area were systematically compared. The results showed that: ① RS in the young forest, middle-age forest, and cropland plot were significantly lower than those in the P. australis wetland and the I. cylindrica wetland plot; ② the proportion of RH found in the young forest, middle-age forest, and cropland was significantly higher than that observed in the P. australis wetland and the I. cylindrica wetland; ③ RS and its components showed a significant exponential relationship with soil temperature, but showed weak correlations with the soil volumetric water content and electrical conductivity. Compared with the residual wetlands, the different agroforestry utilization methods significantly reduced RS, but significantly increased RH, which may suggest that the soil organic carbon pool is still in a state of net loss after 20 years of reclamation. Thus, effective measures should be taken to improve the carbon sequestration capacity of the reclaimed soil in this area.

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Comparison of the fixation effect of formaldehyde and glutaraldehyde on the Ludox–QPS method
Miaoxun WANG, Yuan XU
2022, 2022 (3):  82-89.  doi: 10.3969/j.issn.1000-5641.2022.03.009
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Density gradient centrifugation in combination with quantitative protargol stain (Ludox–QPS) is an important research method for the separation, extraction, and staining of microbenthos. Glutaraldehyde solution is the most widely used fixative for this method; however, it is a hazardous chemical and transportation by civil aviation is forbidden. Hence, biogeography studies using glutaraldehyde solution on a large scale are greatly limited. In contrast, samples fixed with formaldehyde solution can be transported by air consignment under certain conditions. To test whether the results of a study on microbenthic communities fixed with formaldehyde and glutaraldehyde are comparable, we collected microbenthic samples from three natural habitats (bare mudflat, Scirpus mariqueter meadow, sandy beach) and fixed them with either formaldehyde (final concentration is 1%) or glutaraldehyde (final concentration is 2%). Then, we tested the significance of differences in species composition, diversity, and biomass of the communities using an ANOSIM two-way crossed analysis (fixative type and habitat type). The results of this study demonstrate that although significant differences exist in the community structures among the three habitats, the species composition, diversity indices (number of species, number of individuals, evenness, Shannon-Wiener diversity index), and biomass of the microbenthic communities between the two fixative types have no significant differences. NMDS analysis also shows similar results (stress = 0.11). In conclusion, the data indicates that the microbenthic communities fixed by the two fixatives are comparable. Therefore, formaldehyde is also suitable for ecological research of microbenthos as a fixative.

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Photosynthesis and fluorescence characteristics of mangrove Kandelia candel leaves in southern Zhejiang Province
Cheng ZHOU, Ying HUANG, Hualei YANG, Minghui DU, Ying ZHANG, Jianwu TANG
2022, 2022 (3):  90-100.  doi: 10.3969/j.issn.1000-5641.2022.03.010
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In this paper, we explore the dynamic changes in photosynthesis and chlorophyll fluorescence in Kandelia candel leaves from restored mangroves in southern Zhejiang Province to provide a scientific basis for the ecological restoration and northward migration of Kandelia candel. Using a LI-6800F portable, automatic photosynthesis-fluorescence measurement system, the diurnal variation of photosynthesis and chlorophyll fluorescence of Kandelia candel were measured for one day each month in 2019; the data was then used to analyze the relationship between the two parameters. The results showed that, except for water use efficiency (WUE) and non-photochemical quenching (NPQ), the diurnal variation curves of the parameters were generally u-shaped or inverted u-shaped; examples of these parameters included transpiration rate (E), stomatal conductance (Gsw), electron transfer rate (ETR), and maximum photochemical reaction quantum efficiency ( $F_{\rm {v}}' $ / $F_{\rm {m}}'$ ). Some parameters, such as net photosynthetic rate (A), E, Gsw, and ETR, were found to be significantly higher in July and August than in November and December. In addition, except for WUE, the correlation between photosynthetic factors and fluorescence factors was significant on a daily basis, and the correlation between A, E, Gsw, WUE, and ETR was significant on a monthly basis. The results also demonstrated that the photosynthetic capacity of Kandelia candel leaves was the strongest around noon on any given day; at the monthly level, the strongest capacity was observed in the summer, followed by spring and autumn, and lastly winter. The correlation between photosynthesis and chlorophyll fluorescence of Kandelia candel leaves on individual days was higher than that at the monthly level.

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Estuary and Coastal Research
Temperature sensitivity and controlling factors of nitrogen fixation processes in sediments of the Yangtze River Estuary
Zhiyong YOU, Bolin LIU, Cheng LIU, Dengzhou GAO
2022, 2022 (3):  101-108.  doi: 10.3969/j.issn.1000-5641.2022.03.011
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To understand the stability of the estuarine ecosystem and nitrogen balance in the context of global climate change, it is important to investigate the temperature sensitivity of the microbial nitrogen fixation process. Until now, there have been few studies in the literature on the response of the nitrogen fixation process to temperature changes and its influencing factors. We selected six sampling sites around the Yangtze River Estuary (including four sites inside and two sites outside the Yangtze River Estuary) for the scope of the study; in particular, we explored the temperature sensitivity and influencing factors of the nitrogen fixation process on sediments of the Yangtze River Estuary using slurry incubation experiments and the 15N2 isotope tracer technique. The results showed that the in-situ temperature nitrogen fixation rate in the sediments of the Yangtze River Estuary ranged from 0.72 to 2.85 nmol·g–1·h–1. At 5 ~ 10 ℃ and20 ~ 30 ℃, the nitrogen fixation rate was inhibited by an increase in temperature. However, in the range of 10 ~ 20 ℃, the nitrogen fixation rate was significantly promoted with an increase in temperature. The sensitivity of the nitrogen fixation rate to temperature is relatively consistent, although the physical and chemical properties of the sediments vary significantly. Correlation analysis showed that the contents of sulfide, ferrous iron, nitrate, and total organic carbon were the main environmental factors affecting nitrogen fixation.

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Numerical simulation of the North Branch regime change impact on saltwater intrusion in the Yangtze River Estuary from 2007 to 2016
Zhipeng LI, Jianrong ZHU
2022, 2022 (3):  109-124.  doi: 10.3969/j.issn.1000-5641.2022.03.012
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River regime changes have a substantial impact on estuary hydrodynamics and the incidence of saltwater intrusion. Based on measured water depth data in the North Branch of the Yangtze River Estuary from 2007 and 2016, we analyzed the river regime changes of the North Branch across a 10-year timespan; in addition, we numerically simulated and analyzed the influence of the river regime change on hydrodynamics and saltwater intrusion. The water volume increased by 4.4% in the upstream section, decreased by 8.8% in the midstream, and decreased by 20.5% in the downstream of the North Branch from 2007 to 2016. Overall, the data reflects an overall net erosion in the upstream section and deposition in the midstream and downstream sections of the North Branch. In fact, a new sand body with deposition thickness of 4 ~ 6 m appeared in the bifurcation of the North Brach and South Branch. The numerical simulation results, moreover, show that the new sand body caused a 15.0% increase in saltwater intrusion, a change in net water diversion ratio from –2.8% to –3.2% in the upstream section of the North Branch during spring tide, and clear enhancement of saltwater intrusion; if the new sand body continues to deposit up to 0.85 m, the saltwater intrusion will not increase further. At the water intakes of the three reservoirs in the South Branch, the new sand body caused the average salinity during spring tide to increase by 0.14 at Dongfengxisha reservoir, 0.12 at Chenhang reservoir, and 0.11 at Qingcaosha reservoir; similarly, the average salinity during the subsequent middle tide increased by 0.15 at Dongfengxisha, 0.11 at Chenhang, and 0.09 at Qingcaosha. The deposition in the downstream section of the North Branch led to tidal prisms cross section at the port of Lianxin during flood tide and ebb tide to decrease by 15.2% and 16.4%, respectively, in spring tide, and decrease by 21.2% and 19.0%, respectively, in neap tide. As we move further upstream along the North Branch: the amount of rising and falling tides decreases and shows a relative downward trend, the high tide level drops, the low tide level rises, and the tidal range decreases during spring tide. Moreover, the tidal prisms in the midstream and downstream sections of the North Branch decreased, and the saltwater spillover from the North Branch into the South Branch weakened. The deposition in the downstream section of the North Branch caused the salinity decrease at the water intakes of the three reservoirs of the South Branch. On the whole, the saltwater spillover from the North Branch to the South Branch weakened significantly due to the river regime changes in the North Branch from 2007 to 2016; the salinity decreased by 2 ~ 3 in the upstream section of the North Branch and 1 ~ 2 in the downstream section of the North Branch; the salinity decreased at the water intakes of the three reservoirs of the South Branch; and the average salinity during spring tide and the subsequent middle tide decreased by 0.41 and 0.21, respectively, at Dongfengxisha reservoir, decreased by 0.34 and 0.18, respectively, at Chenhang reservoir, and decreased by 0.28 and 0.17, respectively, at Qingcaosha reservoir.

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Inversion methods for typhoon wind fields using Sentinel-1
Peng YU, Xiaojing ZHONG, Xupu GENG
2022, 2022 (3):  125-136.  doi: 10.3969/j.issn.1000-5641.2022.03.013
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Under high-speed wind conditions, cross-polarization synthetic aperture radar (SAR) is not affected by signal saturation. Hence, SAR can be used to observe expansive, high-speed wind fields under all-weather, day- and night-time conditions and offers great potential for monitoring typhoons. Sentinel-1, which was launched by the European Space Agency (ESA), is one of the few available SAR satellites in orbit at present that can provide cross-polarization data. Based on Sentinel-1 cross-polarization data, seven different cross-polarization models, including the C-band cross polarization ocean model (C-2PO), C-band cross-polarization coupled-parameters ocean model (C-3PO), and quad-polarization stripmap cross-polarization model (QPS-CP), developed from 2011 to 2021 were used to estimate the typhoon wind fields of Higos and Molave. A denoising method was applied to remove the noise from extra wide (EW) mode SAR images. The results show that the denoising method can effectively reduce the noise and improve the retrieved wind fields. The C-3PO model performs well in monitoring high-speed winds, but does not obtain reliable results for low- to moderate-speed winds compared with the Sentinel-1 Level-2 Ocean (OCN) product. By merging results from the cross-polarization model and the OCN wind product, the combined wind field can effectively reproduce the inner high-speed winds and outer relative low-speed winds. This study is of significant value for forecasting, data assimilation, and research of typhoon disasters.

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Geography
Trends, challenges, and mitigation strategies for the use of sand and gravel resources in China
Shurong ZHUANG, Aurora TORRES, Ruishan CHEN, Chao YE
2022, 2022 (3):  137-147.  doi: 10.3969/j.issn.1000-5641.2022.03.014
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Sand, gravel, and crushed rock—together referred to as construction aggregates—are the world’s most extracted solid materials by mass. China’s annual consumption of construction aggregates reached over 20 billion tons in 2018, accounting for nearly half of global consumption. This article provides an overview of the use of sand and gravel in China, including current supply and demand conflicts and the impacts of mining, transportation, and use. We highlight that: ① the national demand for sand and gravel has continued to grow in the last two decades; crushed rock has become the main source of construction aggregates, whereas the supply of river sand has significantly declined; and ② there are significant environmental, economic, and social challenges associated with sand and gravel mining, transportation, and use, including the emergence of illicit supply networks. We then discuss opportunities to ensure sand and gravel supply, minimize mining impacts, and promote sustainable trajectories for the Chinese aggregates industry. First, the quantification of the material flows and stocks of construction aggregates that includes geological and anthropogenic stocks is crucial to identify supply bottlenecks and ensure more efficient use of resources. This requires establishing a reliable data monitoring system. Second, the government should increase investment and establish relevant institutions to optimize supply systems and minimize their impacts, strengthen the regulatory framework, promote the uptake of alternative materials, and establish standards and implement best practices in the aggregates industry. Finally, interdisciplinary integrated research is needed to analyze the existing challenges associated with the supply of sand and gravel resources as well as the potential and risks of adaptation strategies.

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