Short-term changes in algal blooms and phytoplankton community after the passage of Super Typhoon Lekima in a temperate and inner sea (Bohai Sea) in China.

Extensive multi-species harmful algal blooms (HABs) were triggered by Super Typhoon Lekima in Laizhou Bay (Bohai Sea) in August 2019. After conducting two field cruises before and after the typhoon passage, we employed both high-performance liquid chromatography (HPLC)-pigment and microscopic methods to study the changes in the phytoplankton community and biomass. Following the passage of Lekima, the average surface salinity decreased, while dissolved inorganic nitrogen and dissolved silicate concentrations increased in the study area. The phytoplankton abundance and Chl a significantly increased after the typhoon event. Post-typhoon, the highest abundance values of Pseudo-nitzschia spp., Noctiluca scintillans, and Coscinodiscus spp. reached 106 cells/L and those of Bacillaria paxillifera, Ceratium spp., and Gymnodinium catenatum were in the order of 105 cells/L. HPLC-pigment CHEMTAX analysis showed that the biomass (Chl a) of dinoflagellates, diatoms, cryptophytes, chlorophytes, and haptophytes increased significantly after the typhoon. The increase in Chl a concentration was mainly attributable to large-sized phytoplankton, which are mostly diatoms and dinoflagellates. This study highlights that typhoons may cause HABs by introducing large amounts of freshwater and nutrients and change the phytoplankton community in a temperate and inner bay.

Alternative polyadenylation coordinates embryonic development, sexual dimorphism and longitudinal growth in Xenopus tropicalis.

RNA alternative polyadenylation contributes to the complexity of information transfer from genome to phenome, thus amplifying gene function. Here, we report the first X. tropicalis resource with 127,914 alternative polyadenylation (APA) sites derived from embryos and adults. Overall, APA networks play central roles in coordinating the maternal-zygotic transition (MZT) in embryos, sexual dimorphism in adults and longitudinal growth from embryos to adults. APA sites coordinate reprogramming in embryos before the MZT, but developmental events after the MZT due to zygotic genome activation. The APA transcriptomes of young adults are more variable than growing adults and male frog APA transcriptomes are more divergent than females. The APA profiles of young females were similar to embryos before the MZT. Enriched pathways in developing embryos were distinct across the MZT and noticeably segregated from adults. Briefly, our results suggest that the minimal functional units in genomes are alternative transcripts as opposed to genes.

A deep learning-based model for estimating pollution fluxes from rivers into the sea and its optimization.

Pollution fluxes from rivers into the sea are currently the main source of pollutants in nearshore areas. Based on the source-sink process of the basin-estuary-coastal waters system, the pollution fluxes into the sea and their spatiotemporal heterogeneity were estimated. A deep learning-based model was established to simplify the estimation of pollution fluxes into the sea, with socio-economic drivers and meteorological data as input variables. A method for estimating the contribution rate of pollution fluxes from different spatial gradient was proposed. In this study, we found that (1) the pollution fluxes into the sea of total nitrogen (TN) and total phosphorus (TP) from the Bohai Sea Rim Basin (BSRB) in 1980, 1990, 2000, 2010, and 2020 were 25.38 × 104, 26.12 × 104, 27.27 × 104, 29.82 × 104, 25.31 × 104 and 1.32 × 104, 2.14 × 104, 2.09 × 104, 1.87 × 104, 1.68 × 104 tons, respectively. (2) The proportion of rural life and livestock to the TN was the highest, accounting for 39.18 % and 21.19 %, respectively. The proportion of livestock to the TP was the highest, accounting for 39.20 %, followed by rural life, accounting for 24.72 %. The results indicated that the pollution fluxes in the BSRB were related to human economic activities and relevant environmental protection measures. (3) The deep learning-based model established to estimate runoff pollution fluxes into the sea had the accuracy of over 90 %. (4) As for contribution rate, in terms of the elevation, the range of 0-100 m had the highest proportion, accounting for 39.65 %. The range of 50-100 km from the coastline had the highest proportion, accounting for 18.11 %. In terms of the district, coastal area has the highest proportion, accounting for 38.00 %. This study revealed the changing trends and driving mechanisms of pollution fluxes into the sea over the past 40 years and established a simplified deep learning-based model for estimating pollution fluxes into the sea. Then, we identified regions with high pollution contribution rate. The results can provide scientific references for the adaptive management of the nearshore areas based on the ecosystem.

Degeneration of foundation cushion species induced by ecological constraints can cause massive changes in alpine plant communities.

Foundational cushion plants can re-organize community structures and sustain a prominent proportion of alpine biodiversity, but they are sensitive to climate change. The loss of cushion species can have broad consequences for associated biota. The potential plant community changes with the population dynamics of cushion plants remain, however, unclear. Using eight plant communities along a climatic and community successional gradient, we assessed cushion population dynamics, the underlying ecological constraints and hence associated plant community changes in alpine communities dominated by the foundational cushion plant Arenaria polytrichoides. The population dynamics of Arenaria are attributed to ecological constraints at a series of life history stages. Reproductive functions are constrained by increasing associated beneficiary plants; subsequent seedling establishment is constrained by temperature, water and light availability, extreme climate events, and interspecific competition; strong competitive exclusion may accelerate mortality and degeneration of cushion populations. Along with cushion dynamics, species composition, abundance and community structure gradually change. Once cushion plants completely degenerate, previously cushion-dominated communities shift to relatively stable communities that are overwhelmingly dominated by sedges. Climate warming may accelerate the degeneration process of A. polytrichoides. Degeneration of this foundational cushion plant will possibly induce massive changes in alpine plant communities and hence ecosystem functions in alpine ecosystems. The assessment of the population dynamics of foundation species is critical for an effective conservation of alpine biodiversity.

Three-dimensional spatial interpolation for chlorophyll-a and its application in the Bohai Sea.

Assessing the health of coastal ecosystems is crucial for maintaining ecological balance. One significant indicator of water eutrophication is the distribution of chlorophyll-a (Chl-a), which makes obtaining a complete three-dimensional spatial distribution of Chl-a essential for assessment. This study utilized the linear radial basis function (RBF-Linear) method to obtain a comprehensive and reasonable spatial distribution of Chl-a. The method was applied to obtain the three-dimensional spatial field of Chl-a concentration in the Bohai Sea in March, May, August, and October from 2016 to 2018. The distribution pattern of Chl-a concentration in the Bohai Sea displayed characteristic spatial and temporal variations. Spatially, high Chl-a concentration was most concentrated in coastal waters, particularly in estuaries and mariculture areas. Temporally, there were two peaks in March and August. The total Chl-a and areas with high Chl-a concentration in four sub-regions of the Bohai Sea were also calculated to enable a comprehensive assessment of the marine ecological environment. By analyzing the temporal and spatial variation of Chl-a in the Bohai Sea and evaluating the marine ecological environment, we confirmed the feasibility and rationality of RBF-Linear. Our findings have the potential to contribute to improve the accuracy of ecological models and assessment of the satellite products.

Elevational patterns of functional diversity and trait of Delphinium (Ranunculaceae) in Hengduan Mountains, China.

Elevational patterns of trait occurrence and functional diversity provide an important perspective for understanding biodiversity. However, previous studies have mostly examined functional diversity at the community scale. Here, we examined large-scale patterns of trait occurrence and functional diversity in Delphinium along an elevational gradient from 1000 to 5700 m in the Hengduan Mountains, SW China. Elevational distribution and trait data of 102 Delphinium species were compiled to evaluate the patterns of interspecific traits, species richness, and functional diversity. We found that the distribution of species richness showed a unimodal curve that peaked between 3500 and 4000 m; functional diversity and traits showed different patterns along an elevational gradient. The functional diversity increased at a lower rate along an elevation gradient, whereas species richness continued to increase. Species with large ranges and non-endemic species were most affected by geometric constraints. Richness of species endemic to the Hengduan Mountains peaked at higher elevations, likely due to increased speciation and restricted dispersion under alpine conditions. We conclude that the middle elevation region is not only the functionally richest but also the most functionally stable region for Delphinium, which could be insurance against environmental change. Extreme conditions and strong environmental filters in an alpine environment may cause the convergence of species traits, which could relate to reducing nutrient trait investment and increasing reproductive trait investment. We conclude that large-scale studies are consistent with previous studies at the community scale. This may indicate that the relationship between functional diversity and species richness across different scales is the same.

Heavy metals in the sediments of Laoshan Bay, China: Distribution and contamination assessment.

We analyzed total organic carbon (TOC), total nitrogen (TN), and heavy metals in 58 sediment samples from the Laoshan Bay, China. TOC and TN results identified marine primary production as the dominant source for organic matter, and the weak correlations between TOC, TN, and heavy metals indicated the terrestrial origin of heavy metals. Cd showed insignificant correlations with other metals, which suggests that agriculture production is the main anthropogenic activity affecting the distribution of Cd. Pb contamination in past 50 years was likely to have occurred because of fossil fuel combustion. Despite 210Pb dating, it was still difficult to trace the contamination condition over interannual variations. Nonetheless, these results provide data for monitoring Pb contamination. As Laoshan Bay is an important economic area, it would be beneficial to conduct further studies to determine the sources and degree of contamination for each heavy metal.

Spatiotemporal evolution of nutrients and the influencing factors in Laizhou Bay over the past 40 years.

The nutrient status in Laizhou Bay has changed in composition and structure as a result of anthropogenic activities and climate change, which has led to several environmental problems (e.g., eutrophication, organic pollution and red tides). To better understand the spatiotemporal variations in dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and eutrophication in the Laizhou Bay, we collected historical research data and conducted four cruises in 2021. The highest surface DIN was found to occur in autumn and predominantly concentrated in the southwestern bay. The highest surface DIP content was found in winter and distributed in the northwestern bay. Surface organic pollution showed estuaries as the most polluted areas. In the past 40-60 years, the DIN, DIP, and eutrophication have shown an inverted U-shaped trend, and the bay has changed from N limitation to P limitation. Economic development, phytoplankton absorption, and bottom mineral release are factors influencing the content and distribution of nutrient in the bay.

Alpine community recruitment potential is determined by habitat attributes in the alpine ecosystems of the Himalaya-Hengduan Mountains, SW China.

The fragility and sensitivity to climate change of alpine ecosystems make it difficult to maintain the stability of their plant communities. Thus, it is important to determine which plant propagules are stored in the soils in order to understand community recruitment potential, especially under different environmental conditions. Based on a soil seed germination and seedling cultivation experiment, we aimed to identify differences in the soil seed attributes between three typical habitat types in the alpine subnival ecosystems of the Himalaya-Hengduan Mountains and hence to predict the community recruitment potential of each of these different communities. We found that the seed assemblages in the soils differed between habitats. The most abundant taxa were from the genera Saxifraga, Kobresia, Arenaria, Polygonum, Draba, and Viola, while the taxa with lowest abundance were Apiaceae, Campanulaceae, Circaea, Crassulaceae, and Gentiana. Different habitats exhibited variable soil seed richness, diversity, and density. However, the patterns differed between study sites. Specifically, at Baima (BM) and Shika (SK) snow mountains, soil seed richness, diversity, and density were generally highest in grassland, followed by rock bed and bare ground. In contrast, on Jiaozi (JZ) snow mountain, the rock bed supported the highest soil seed richness and density, followed by grassland and bare ground. These results suggest that the attributes of habitats and communities can both affect the accumulation of soil seeds. Bare ground supports the lowest seed diversity and density but also harbors the most empty niches. We, therefore, predict that, once the thermal conditions become suitable as a result of global warming, this habitat has the potential to see greater changes than grassland and rock bed in terms of community recruitment.

[Distribution of Micro-plastics in the Soil Covered by Different Vegetation in Yellow River Delta Wetland].

Micro-plastics (MPs) pollution has been a hotspot in soil environment. To explore the correlation of the vegetation cover and the distribution of MPs in Yellow River Delta wetland, the characters of MPs in the soil sampled at 16 sites where reed (Phragmites communis, a low-salt dominant species) and Suaeda salsa (a high-salt dominant species) covered were investigated. The abundance of MPs here ranged to 80-4640 n·kg-1, and the particle size ranged to 13 µm-5 mm. The main components of MPs with large size were polyethylene (PE), polyethylene terephthalate (PET) and polystyrene (PS), and the content of PET ranged to 0.22-1.16 µg·kg-1. The barrier effect of reed on MPs was higher than that of Suaeda salsa. The average abundance of MPs and PET contents at the sites where reed covered were 1423 n·kg-1 and 0.62 µg·kg-1, and they mainly consisted of small particles with a size less than 50 µm. The average abundance of MPs and PET contents at the site Suaeda salsa covered were 584 n·kg-1 and 0.33 µg·kg-1, and they mainly consisted of fragments and fibers with a size ranged to 100-1000 µm. The abundance of MPs in the soil was significantly correlated with the growth statues of the vegetations (P=0.001). Therefore, the distribution of MPs in the soil in the same area covered by different vegetation might be spatial different.

Safety and Immunogenicity of a Shigella Bivalent Conjugate Vaccine (ZF0901) in 3-Month- to 5-Year-Old Children in China.

No licensed Shigella vaccine is presently available globally. A double-blinded, randomized, placebo-controlled, age descending phase II clinical trial of a bivalent conjugate vaccine was studied in China. The vaccine ZF0901 consisted of O-specific polysaccharides purified and detoxified from lipopolysaccharide (LPS) of S. flexneri 2a and S. sonnei and covalently bonded to tetanus toxoid. A total of 224, 310, and 434 children, consented by parents or guardians, aged 3 to 6 and 6 to 12 months and 1 to 5 years old, respectively, were injected with half or full doses, with or without adjuvant or control Hib vaccine. There were no serious adverse reactions in all recipients of ZF0901 vaccine independent of age, dosage, number of injections, or the adjuvant status. Thirty days after the last injection, ZF0901 induced robust immune responses with significantly higher levels of type-specific serum antibodies (geometric mean concentrations (GMCs) of IgG anti-LPS) against both serotypes in all age groups compared with the pre-immune or the Hib control (p < 0.0001). Here, we demonstrated that ZF0901 bivalent Shigella conjugate vaccine is safe and immunogenic in infants and young children and is likely suitable for routine immunization.

Evaluation system of coastal wetland ecological vulnerability under the synergetic influence of land and sea: A case study in the Yellow River Delta, China.

A comprehensive evaluation system and model of Coastal Wetland Ecological Vulnerability (CWEV) was constructed and applied to reveal spatial heterogeneity of the ecological vulnerability of the Yellow River Delta Wetland (YRDW). The results showed that the score of the ecological vulnerability (EVS) of the YRDW was 0.49, which was generally at a medium vulnerability level. The wetland area of high vulnerability was up to 943km2, accounting for 35.2% of the total area, followed by the medium vulnerable area with an area of 750km2, accounting for 28.1% of the total area. From the coastline perpendicularly to the land, the "seaward" gradient effect gradually decreased, the vulnerability-increasing "hydrologic connectivity" effect increased with the distance from the river channel, and the "land source influence" effect gradually decayed along with the vulnerability of population and economy gathering areas.

Simulating spatial distribution of coastal soil carbon content using a comprehensive land surface factor system based on remote sensing.

Surface soil carbon content (SCC) in coastal area is affected by complex factors, and revealing the SCC spatial distribution is considerably significant for judging the quantity of stored carbon and identifying the driving factors of SCC variation. A comprehensive land surface factor system (CLSFS) was established; it utilized the ecological significances of remote sensing data and included four-class factors, namely, spectrum information, ecological indices, spatial location, and land cover. Different simulation algorithms, including single-factor regression (SFR), multiple-factor regression (MFR), partial least squares regression (PLSR), and back propagation neural network (BPNN), were adopted to conduct the surface (0-30cm) SCC mapping in the Yellow River Delta in China, and a 10-fold cross validation approach was used to validate the uncertainty and accuracy of the algorithms. The results indicated that the mean simulated standard deviations were all <0.5g/kg and thus showed a low uncertainty; the mean root mean squared errors based on the simulated and measured SCC were 3.88g/kg (SFR), 3.85g/kg (PLSR), 3.67g/kg (MFR), and 2.78g/kg (BPNN) with the BPNN exhibiting a high accuracy compared to similar studies. The mean SCC was 17.40g/kg in the Yellow River Delta with distinct spatial heterogeneity; in general, the SCC in the alongshore regions, except for estuaries, was low, and that in the west of the study area was high. The mean SCCs in farmland (18.31g/kg) and wetland vegetation (17.98g/kg) were higher than those in water area (16.07g/kg), saltern (15.61g/kg), and bare land (14.71g/kg). Land-sea interaction and human activity jointly affected the SCC spatial distribution. The CLSFS was proven to have good applicability, and can be widely used in simulating the SCC spatial distribution in coastal areas.

Spatial heterogeneity of estuarine wetland ecosystem health influenced by complex natural and anthropogenic factors.

The evaluation of estuarine wetland ecosystem health (EWEH) is vital and difficult due to complex influencing factors and their spatial heterogeneities. An EWEH evaluation model was established in this study on the basis of the typical features of estuarine wetland ecosystems with focus on spatial heterogeneity. The index system comprises external factors, internal factors, and ecological state, and covers all aspects of the natural and anthropogenic factors, with each index possessing its own spatial heterogeneity. The Yellow River Delta, a typical estuarine wetland in China, was selected as the study area to demonstrate the model. Results indicated that the present EWEH in the entire study area was in good status with distinct spatial heterogeneity. Ecosystem productivity, seawater intrusion, human interference, and Yellow River input were the most relevant indexes of EWEH. The temporal variations of EWEH fluctuated from 1987 to 2016. The decrease in the Yellow River input and the increase in human activity intensity deteriorated EWEH, whereas the alongshore embankment and nature reserve construction improved EWEH in certain parts. The influence of natural factors continuously decreased, and human activity became the main driving factor of the EWEH spatial variation. Our model was proven to possess comprehensive reflections of estuarine wetland ecological characteristics, full exhibitions of spatial heterogeneity, and high applicability; therefore, it can be widely used to evaluate EWEH in different areas.

Evaluation on island ecological vulnerability and its spatial heterogeneity.

The evaluation on island ecological vulnerability (IEV) can help reveal the comprehensive characteristics of the island ecosystem and provide reference for controlling human activities on islands. An IEV evaluation model which reflects the land-sea dual features, natural and anthropogenic attributes, and spatial heterogeneity of the island ecosystem was established, and the southern islands of Miaodao Archipelago in North China were taken as the study area. The IEV, its spatial heterogeneity, and its sensitivities to the evaluation elements were analyzed. Results indicated that the IEV was in status of mild vulnerability in the archipelago scale, and population pressure, ecosystem productivity, environmental quality, landscape pattern, and economic development were the sensitive elements. The IEV showed significant spatial heterogeneities both in land and surrounding waters sub-ecosystems. Construction scale control, optimization of development allocation, improvement of exploitation methods, and reasonable ecological construction are important measures to control the IEV.

Study on the cumulative impact of reclamation activities on ecosystem health in coastal waters.

The purpose of this study is to develop feasible tools to investigate the cumulative impact of reclamations on coastal ecosystem health, so that the strategies of ecosystem-based management can be applied in the coastal zone. An indicator system and model were proposed to assess the cumulative impact synthetically. Two coastal water bodies, namely Laizhou Bay (LZB) and Tianjin coastal waters (TCW), in the Bohai Sea of China were studied and compared, each in a different phase of reclamations. Case studies showed that the indicator scores of coastal ecosystem health in LZB and TCW were 0.75 and 0.68 out of 1.0, respectively. It can be concluded that coastal reclamations have a historically cumulative effect on benthic environment, whose degree is larger than that on aquatic environment. The ecosystem-based management of coastal reclamations should emphasize the spatially and industrially intensive layout.

Tracing the origin of green macroalgal blooms based on the large scale spatio-temporal distribution of Ulva microscopic propagules and settled mature Ulva vegetative thalli in coastal regions of the Yellow Sea, China.

From 2008 to 2016, massive floating green macroalgal blooms occurred annually during the summer months in the Yellow Sea. The original source of these blooms was traced based on the spatio-temporal distribution and species composition of Ulva microscopic propagules and settled Ulva vegetative thalli monthly from December 2012 to May 2013 in the Yellow Sea. High quantities of Ulva microscopic propagules in both the water column and sediments were found in the Pyropia aquaculture area along the Jiangsu coast before a green macroalgal bloom appeared in the Yellow Sea. The abundance of Ulva microscopic propagules was significantly lower in outer areas compared to in Pyropia aquaculture areas. A molecular phylogenetic analysis suggested that Ulva prolifera microscopic propagules were the dominant microscopic propagules present during the study period. The extremely low biomass of settled Ulva vegetative thalli along the coast indicated that somatic cells of settled Ulva vegetative thalli did not provide a propagule bank for the green macroalgal blooms in the Yellow Sea. The results of this study provide further supporting evidence that the floating green macroalgal blooms originate from green macroalgae attached to Pyropia aquaculture rafts along the Jiangsu coastline of the southern Yellow Sea.

Changes to the biomass and species composition of Ulva sp. on Porphyra aquaculture rafts, along the coastal radial sandbank of the Southern Yellow Sea.

Compositions, changes and biomass of attached Ulva species on Porphyra rafts along the radial sandbank in the Yellow Sea were investigated, and potential contributions to green tides was analyzed. Ulva prolifera, Ulva flexuosa and Ulva linza were all appeared throughout the investigated period. U. prolifera and U. flexuosa dominated attached Ulva population on Porphyra rafts. Attached Ulva species biomass showed obviously spatial and temporal variations. Temperature, Ulva microscopic propagules and human activities were main factors to influence attached Ulva species biomass. The total attached Ulva species biomass was more than 20,000 fresh weight tons in April, and the green tide causative species U. prolifera accounted 51.03% in April 2013 before green tides occurred. The high biomass of attached Ulva species would contribute most to green tides in the Yellow Sea. But how attached Ulva species on Porphyra rafts contributing to green tides in the Yellow Sea should be further studied.

Application of macrobenthos functional groups to estimate the ecosystem health in a semi-enclosed bay.

In this study, the functional group concept was first applied to evaluate the ecosystem health of Bohai Bay. Macrobenthos functional groups were defined according to feeding types and divided into five groups: a carnivorous group (CA), omnivorous group (OM), planktivorous group (PL), herbivorous group (HE), and detritivorous group (DE). Groups CA, DE, OM, and PL were identified, but the HE group was absent from Bohai Bay. Group DE was dominant during the study periods. The ecosystem health was assessed using a functional group evenness index. The functional group evenness values of most sampling stations were less than 0.40, indicating that the ecosystem health was deteriorated in Bohai Bay. Such deterioration could be attributed to land reclamation, industrial and sewage effluents, oil pollution, and hypersaline water discharge. This study demonstrates that the functional group concept can be applied to ecosystem health assessment in a semi-enclosed bay.