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Objectives: This study aims to describe the experience and practice of an intervention process for mental health crisis with 14,093 students living in a suddenly quarantined campus during the COVID‐19 pandemic. Methods: An expert committee of psychiatrists, psychologists and student counsellors was formed to manage the psychological crisis experienced by students. The committee provided online and onsite support, disclosed timely information, attended various online courses and facilitated various activities. Using the PHQ‐9, GAD‐7 and ISI scales, psychological weekly reports, student files and emergencies, students who were likely to have a crisis event were screened, and their degree of crisis was evaluated. A "one person–one case–one team" intervention was conducted for high‐risk students. Results: Of the 14,093 students, 11,121 finished all three online questionnaires. Based on the results of the screening tests, 732 students were placed in the prioritised attention group, 293 in the crisis group and 33 (10 [3.41%] male and 23 [7.85%] female) showed severe suicidal intentions. In total, 186 (3.26%) students declared poor sleep quality, while 610 (10.05%) students were found to have depression. The number of students affected with generalised anxiety was 650 (10.77%). Clinical intervention was successful with no untoward incidents. Conclusions: With strong support from the government, and the cooperation between multidisciplinary experts and the comprehensive intervention programme, the study obtained positive results. However, the limitations include the partial online survey responses and incomplete records of intervention. Nevertheless, the findings of this study could provide a foundation for further research. [ABSTRACT FROM AUTHOR]

Terrestrial inputs of dissolved organic matter (DOM) stimulate microbial growth by supplying organic carbon and DOM‐associated nutrients, and thus increase food availability for zooplankton. Terrestrial inputs of DOM might decrease the content of eicosapentaenoic acid (EPA) in particular organic matter (POM) due to an increase in biomass of EPA‐poor microbes, for example, heterotrophic bacteria and autotrophic cyanobacteria, thereby reducing food quality and filter‐feeding zooplankton's biomass. We performed a 26‐d mesocosm experiment where terrestrial DOM was manipulated by adding (treatments) and kept without adding (controls) 13C‐labeled maize leachate to evaluate the effect of food quality changes induced by terrestrial DOM inputs on zooplankton. DOM addition treatments had significantly higher concentrations of POM and Chlorophyll a relative to controls, but significant lower EPA content of POM, responding to increased biomass of bacteria and chlorophytes. Biomass and EPA content of filter‐feeding cladoceran Chydorus sphaericus was significantly reduced by terrestrial DOM addition. Stable isotope analyses showed 13C enrichments in bacteria and cryptophytes in the treatment of 13C‐labeled maize leachate, indicating a growth stimulation of heterotrophic microbes by organic carbon addition. Although the 13C enrichment in Chydorus evidenced the extensive use of terrestrial DOM by this cladoceran, positive relationships between Chydorus biomass and EPA content of POM suggest that terrestrial DOM inputs increase food quality constrains on filter‐feeding zooplankton. Our study suggests that the response of filter‐feeding zooplankton to inputs of terrestrial DOM depends on how the terrestrial inputs change the microbial communities and thus the food quality in the receiving aquatic ecosystems. [ABSTRACT FROM AUTHOR]

A mesocosm study illuminated possible transfer pathways for dissolved organic carbon from the water column to zooplankton. Organic carbon was added as 13C enriched glucose to 15 mesocosms filled with natural lake water. Stable isotope analysis and phospholipid fatty acids-based stable isotope probing were used to trace the incorporation of 13C into the cladoceran Bosmina and its potential food items. Glucose-C was shown to be assimilated into phytoplankton (including fungi and heterotrophic protists), bacteria and Bosmina, all of which became enriched with 13C during the experiment. The study suggests that bacteria play an important role in the transfer of glucose-C to Bosmina. Furthermore, osmotic algae, fungi and heterotrophic protists might also contribute to the isotopic signature changes observed in Bosmina. These findings help to clarify the contribution of dissolved organic carbon to zooplankton and its potential pathways.

Carbon with a radiocarbon age above 200 years before present (bp) generally is referred to as ancient carbon. Ancient organic carbon (OC) stored in glaciers, permafrost and unperturbed soil has been released with increasing temperatures resulting from climate warming and anthropogenic activities. Evidence suggests that ancient terrestrial OC can be incorporated by heterotrophic bacteria and consumers in many aquatic systems. However, it remains unknown whether ancient terrestrial OC promotes growth and reproduction of consumers.Ancient dissolved organic carbon (DOC) was extracted from frozen soils in the catchments of Lakes Tsochuolong (−216.9‰, 1,960 years bp) and Zhangnaitso (−384.1‰, 3,895 years bp) on the Tibetan Plateau, and was further degraded by heterotrophic bacteria. Degraded ancient DOC (containing bacteria) and Auxenochlorella (−161.6‰) were used exclusively or in combination as food (total 6 mg C/L) for Daphnia magna (D. magna) to compare their body length, mortality rate and offspring production. The mixed diets consisted of ancient DOC converted by bacteria at 4 mg C/L and Auxenochlorella at 2 mg C/L.The radiocarbon isotope (∆14C) value of D. magna fed on mixed diets was −293.0‰ for Lake Tsochuolong (group CA) and −265.9‰ for Lake Zhangnaitso (group CB), which was depleted than those fed exclusively on Auxenochlorella (−187.3‰, group 6C). This result suggests that 14C‐depleted DOC can be assimilated by zooplankton. Daphnia magna in group CB had the highest intrinsic rate of population increase (0.33/day) and number of neonates per individual (15.97/ind). The higher growth rate and offspring production in group CB than in CA (0.21/day and 7.68/ind) probably were because D. magna utilised more Auxenochlorella and phosphorus from diets in CB. However, there was no significant difference in the two indicators between CA and 6C (0.24/day and 12.30/ind) or between CB and 6C. Daphnia magna fed exclusively on degraded DOC plus bacteria had the lowest growth rate and offspring production.The results demonstrate that in the presence of algae with high nutritional value, degraded ancient DOC could support the growth and reproduction of zooplankton. Our findings extend the understanding of carbon sources and carbon cycling in food webs in lakes, particularly in high‐altitude and polar lakes in the context of climatic and environmental changes. [ABSTRACT FROM AUTHOR]

Submerged macrophytes cannot be utilized directly by zooplankton. However, vegetation can serve as an organic carbon resource for heterotrophic bacteria, which are themselves accessible to zooplankton. We therefore hypothesize that submerged macrophytes supply a carbon source to zooplankton by increasing the availability of food such as heterotrophic bacteria. Here, we used stable carbon isotope (13C) labeling to trace the carbon flow from submerged macrophytes to zooplankton with a mesocosm experiment. The carbon stable isotope ratios of zooplankton and their potential food sources were analyzed in mesocosms planted with 13C-labeled Hydrilla verticillata (L. f.) Royle in comparison with the control in which plastic plants were planted. We found that all potential food resources of zooplankton, including phytoplankton, bacterioplankton, macrophyte-associated epiphyton and epibacteria, were significantly enriched with 13C in the presence of 13C-enriched H. verticillata. Zooplankton were significantly more enriched with 13C than phytoplankton, epiphyton and bacterioplankton but significantly less enriched with 13C than epibacteria. Based on a stable isotopic mixing model, we found a macrophyte carbon contribution of 30.5% to epibacteria and 14.7% to zooplankton. Our results indicated that macrophytes might be used by zooplankton as a carbon resource, mainly via a pathway involving epibacteria attached to macrophytes. [ABSTRACT FROM AUTHOR]

Biologically configured ββ-hopanes, geologically configured αβ-hopanes and the biogenic hopenes were determined in dated sediment cores from Lake Fuxian in SW China and Lake Changdang in Eastern China in order to investigate anthropogenic influences on the abundance, composition and provenance of hopanoid hydrocarbons in lake sediments. Based on the results, hopenes were prevalent, with maximum values reaching 148.9 μg g−1 TOC in sediments of Lake Fuxian, an oligotrophic deep lake (average depth 89.6 m), where the long water column provided ample potential for the growth of hopene-producing bacteria especially the cyanobacteria. Sediment hopenes have diminished in abundance to values of 13.4–78.5 μg g−1 TOC in Lake Changdang, a eutrophic shallow (average 0.8–1.2 m) body, reflecting comparatively reduced importance of nutrient level on hopene production. Historical trends in hopenes input to the sediments of each lake are strongly dependent on nutrient status. During the last few decades, human-induced eutrophication has greatly boosted bacterial production, enhancing the accumulation of hopenes in sediments. Inputs of petroleum-derived αβ-hopanes were exceptionally high (average 71.2 μg g−1 TOC) in post-1968 sediments from Lake Changdang, their increase coinciding with the advent and acceleration of petroleum product use around the lake, in particular by fishing boats. Lake Fuxian on the other hand, has undergone slower economic development and the appearance of petroleum-derived αβ-hopanes in sediments was delayed to 1990 since when the average value has been 27.1 μg g−1 TOC. The abundance of αβ-hopanes in Lake Changdang has created a marked decrease in the relative contribution of hopenes to total hopanoids since 1968. Conversely, the amounts of αβ-hopanes introduced to Lake Fuxian since 1990 has yet to yield a clear change in the overall proportion of hopenes, but the abundance of ββ-hopanes has declined relative to total hopanoid levels for the period. [ABSTRACT FROM AUTHOR]

Highlights • Fatty acids and alcohols were analyzed in surface sediments of lakes in Eastern China. • Abundances of fatty acids were dependent on the type of organisms within the lakes. • Variation of trophic status in lakes exerted influence on some alcohols in sediments. • (C26 + C28)/(C22 + C24) n -alkanoic acids or n -alkanols can indicate transition of lake ecosystems. Abstract During the past hundred years, the majority of lakes along the middle and lower reaches of the Yangtze River (MLRYZ) have been greatly impacted by human intervention, resulting in a significant spatial heterogeneity in water and ecosystem quality. We quantified the fatty acid (FA), n -alkanol, sterol and long-chain alkyl diol content of surface sediments of MLRYZ lakes in order to determine how ecological differences (algae versus macrophyte-dominated state) and trophic status influence the composition, origin and abundance of lipid biomarkers in the sediments. Based on the results, variation in FAs appears to be mainly controlled by the type of organisms within the lakes. Short-chain n -alkanoic acids, monounsaturated FAs (MUFAs) and polyunsaturated FAs (PUFAs) were generally more abundant in sediments of algal lakes (lacking macrophyte growth) than in lakes with macrophyte growth. The opposite trend was apparent for long-chain n -alkanoic acids. Ratios of (C26 + C28)/(C22 + C24) n -alkanoic acids differed significantly between macrophyte and algal lakes. In the alcohol fraction, lipid biomarker abundance appeared to be controlled by trophic status of the lake, with the exception of cholesterol and long-chain n -alkanols whose abundances were closely related to the present organisms and exhibiting greater abundances in algal lakes. Enhanced levels of total phosphorus (TP) and total nitrogen (TN) in a lake create greater concentrations of C32 1,15 alkyl diol and brassicasterol respectively, while the abundance of dinosterol and the ratio of dinosterol/brassicasterol decline in line with increase in TP and TN, respectively. Ratios of (C26 + C28)/(C22 + C24) n -alkanol were also greatly influenced by the type of organisms present, exhibiting higher values in algal lakes. The sensitivity of these sediment lipid biomarker responses points to a potentially useful role as proxies for biological community types and trophic status in paleolimnology studies. [ABSTRACT FROM AUTHOR]

Aliphatic hydrocarbon biomarkers from the surface sediments of lakes along the lower reaches of the Yangtze River (Eastern China) were analyzed in order to determine the origin and composition of organic matter (OM) in the sediment. This is necessary to understand how anthropogenic environmental change in the region is impacting on OM dynamics and carbon cycles. The results indicate that OM in lake sediments is derived from biogenic sources, including phytoplankton, aquatic macrophytes, bacteria and terrestrial plants and abiotic sources of petroleum hydrocarbon contamination. The significance of each source varies greatly between lakes. Inputs of autochthonous OM to sediments were closely dependent on nutrient levels and the organisms present in the lake water column. Cyanobacterial OM input, signified by the distribution of short-chain n -alkanes, was most abundant in sediments from the most severely polluted lake, West Lake Chaohu. OM derived from diatoms, indicated by C 25 highly branched isoprenoids (HBIs), was relatively abundant in sediments from lakes Gucheng and Shijiu, the two studied lakes with the lowest nutrient levels. Growth of macrophytes in lakes Gucheng, Shijiu, Gehu and Yangcheng resulted in a significant accumulation of OM from these organisms in the sediments. In contrast, the input of allochthonous OM was controlled mainly by natural and anthropogenic activities around the lakes. For example, terrestrial plant OM input, deduced from the abundance and proportion of long-chain n -alkanes, was exceptionally high in the sediment of Lake Nanyi, perhaps stemmed from frequent severe flooding in the catchment. Input of fossil fuel OM reflected direct petroleum contamination of the water or anthropogenic petroleum burning in the catchment. In addition, the allochthonous refractory OM tended to be enriched in sediments of lakes with strong hydrodynamic process. The results of this study provided a lot of detail in explaining the variation of terrestrial OM dynamics and carbon cycle in response to anthropogenic activities. [ABSTRACT FROM AUTHOR]

During the past hundred years, the Lake Taihu basin has been greatly impacted by human interventions. The undesirable changes in water quality of lakes, presumably caused by the human activities, remain relatively undescribed in this area. In order to investigate these anthropogenic effects, a 210 Pb dated sediment core from a relatively small lake in the upper reaches of Lake Taihu known as Lake Changdang was subject to a detailed lipid biomarker study and other geochemical analyses including quantification of biogenic silica (BSi), nutrients and heavy metals. Based on the results, the recent environmental history of Lake Changdang can be divided into three periods. The first period from approximately 1906 to 1950, represents a natural state, with minimal anthropogenic impact on the lake. Human induced environmental change is recorded in the following stage, ca. 1950–1982, during which the trophic status of the lake increased slightly in response to inputs of agricultural waste and nitrogen (N) and phosphorus (P) based fertilizers. In particular, the signs of eutrophication during this phase accelerated from ca. 1973, perhaps owing to large-scale using phosphate based chemical fertilizer around the lake at the time. A second phase of nutrient input in the most recent stage, ca. from 1982 to 2016, initiated by wastewater discharge from rapid urbanization and industrialization of the catchment, greatly enhanced the nutrient level in the lake. However, the central zone of the lake has yet to reach a phytoplankton-dominated stable state, with both algae and aquatic macrophytes tracking an increased trend in productivity driven by intermediate nutrient levels in the water of this zone. [ABSTRACT FROM AUTHOR]

Increased phosphorus (P) export from sediments to the overlying water column is a significant factor driving the variation of phytoplankton in productivity and community structure in lakes. However, the lack of long-term instrumental data often impeded analyses attempting to associate dynamics of phytoplankton with variation of internal P loading. Here, elements and lipid biomarkers were analyzed in a sediment core from Lake Heihai, a small, deep, and ultraoligotrophic alpine lake in Haba Mountain, Yunnan Province, SW China. The data document incredible enrichment of element iron (Fe) in the sediment, whose concentrations are much higher than those of other common major elements including titanium (Ti), aluminum (Al), calcium (Ca), and magnesium (Mg). This finding, together with the abundance correlation between P and Fe ( n = 30, R = 0.783) suggested that P was probably retained in sediments through sorption with micro-layer of FeOOH at the sediment-water interface. The P/Ti ratios, P/Fe ratios, and P/total organic carbon (TOC) ratios all declined in the sediment since 1980, perhaps indicating increased P release from sediments to the overlying water column initiated by hypolimnion anoxia and sulfidic, which is presumably triggered by regional climate warming since the 1980s. The P-rich bottom water can be injected into photic zone during wind-driven mixing and overturn of the water column, although its frequency and intensity might decline due to stronger water column stratification in warming climate. In response, diatoms exhibited a rapid increase of productivity at this time, because diatoms have a storage vacuole and thereby nutrients such as P can be concentrated and used for cell division long after they are depleted in the bulk fluid. Elevated diatom biomass produced shading of light penetration, allowing for a low productivity for dinoflagellates. This study deepens our understanding of the impact of climate warming on lake systems and highlights the element biogeochemical cycle contributing to the variation of nutrients in the lake water column. [ABSTRACT FROM AUTHOR]

Terrestrial chromophoric dissolved organic matter (CDOM) could subsidize lake food webs. Trophic state and altitude have a pronounced influence on the CDOM concentration and composition of a lake. The impact of future changes in solar radiation on high-altitude lakes is particularly alarming because these aquatic ecosystems experience the most pronounced radiation variation worldwide. Photodegradation experiments were conducted on terrestrial CDOM samples from oligotrophic alpine Lake Tiancai and low-altitude eutrophic Lake Xiaohu to investigate the response of bacterial growth to photodegraded CDOM. During the photo-irradiation process, the fluorescent CDOM intensity evidently decreased in an inflowing stream of Lake Tiancai, with the predominance of humic-like fluorescence. By contrast, minimal changes were observed in the riverine CDOM of Lake Xiaohu, with the predominance of protein-like fluorescence. The kinetic constants of photodegradation indicated that the degradation rate of terrestrial (soil) humic acid in Lake Tiancai was significantly higher than that in Lake Xiaohu ( p < 0.001). Soil humic and fulvic acids irradiated in the simulated experiment were applied to incubated bacteria. The specific growth rate of bacteria incubated with soil humic substances was significantly higher in Lake Tiancai than in Lake Xiaohu ( p < 0.05). Furthermore, the utilizing rate of dissolved oxygen (DO) confirmed that the DO consumption by bacteria incubated with terrestrial CDOM in Lake Tiancai was significantly greater than that in Lake Xiaohu ( p < 0.05). In summary, the exposure of terrestrial CDOM to light significantly enhances its availability to heterotrophic bacteria in Lake Tiancai, an oligotrophic alpine lake, which is of importance in understanding bacterial growth in response to photodegraded terrestrial CDOM for different types of lakes. [ABSTRACT FROM AUTHOR]

In order to elucidate the effect of recent warming, we studied lipid biomarkers and trace elements in a dated sediment core from Lake Heihai, a small, deep, and ultraoligotrophic alpine lake in Yunnan Province (SW China), being only marginally affected by anthropogenic activities. The variation in lipid biomarkers (such as 10-methyl-C16:0 fatty acid (FA), iso-branched C15 (i-C15) and anteiso-branched C15 (ai-C15) FA, and tetrahymanol) suggests a rapid productivity increase in sulfate reducing bacteria and ciliates since 1980, likely reflecting expansion of the hypolimnion anoxia and a prolonged duration of an oxic–anoxic chemocline in the water column. The concentrations of element molybdenum (Mo) in pre-1980 sediments approach the values in average crust. After 1980, the concentration increased, reaching levels approximately sixfold higher than the initial abundances. This likely reflects a high authigenic Mo deposition when the bottom water was more anoxic and enrichment in H2S. The suggested spatial and temporal expansion of the anoxic bottom water since 1980 was probably a response to the regional climate warming, resulting in stronger water column stratification and terrestrial grass inputs to the lake, and thus higher dissolved oxygen (DO) loss in hypolimnion. [ABSTRACT FROM AUTHOR]

The reliability of Δ7/Δ5 sterol ratios as an indicator of trophic status in Lake Fuxian was tested with in situ nutrient enrichment incubation experiment and a comparison of Δ7/Δ5 values in the strata of a sediment core with the known chronology of nutrient enrichment in the lake. The results indicated that the Δ7/Δ5 sterol ratios (including sum of Δ7/sum of Δ5 sterol ratios and C27-C29 Δ7/C27-C29 Δ5 sterol ratios) in the incubation water increased consistently with total phosphorus (TP) and total nitrogen (TN) concentration across the full experimental range from 0.012 to 0.130 mg/L and from 0.068 to 1.351 mg/L, respectively. The covariation between Δ7/Δ5 sterol ratios and TP and TN concentration could be explained by enhanced productivity of Δ7 sterol-producing green algae (e.g., Scenedesmus sp.) under the prevailing nutrient conditions. A sediment core from Lake Fuxian showed a two-stage increase in C27-C29 Δ7/C27-C29 Δ5 sterol ratios over time, including a small rise from 1951 to 1986, and a much greater increase since 1986. These results coincide with the two-stage eutrophication previously documented in Lake Fuxian using geochemical evidence and water quality monitoring data. This study therefore demonstrates Δ7/Δ5 sterol ratio as a credible descriptor of trophic status in Lake Fuxian. [ABSTRACT FROM AUTHOR]

Organic geochemical analysis of a sediment core from Lake Fuxian was carried out to reconstruct the progression of eutrophication in this lake from ca. 1857 to 2012. The results indicate that two episodes can be identified during the eutrophication of the lake water. Both bulk geochemical proxies and sediment lipid biomarkers recorded an enhanced eutrophication in this lake since 1986. Total organic carbon (TOC), total nitrogen (TN) and phytoplankton biomarkers were most abundant in this period, indicating high phytoplankton productivity. Phytoplankton composition showed an elevated proportion of dinoflagellate and green algae relative to diatoms, in response to the anthropogenic nutrient inputs (e.g., sewage, fertilizers) since the 1980s. On the other hand, only the sediment lipid biomarker detected a minor eutrophication of the lake water between 1951 and 1986. During this period, phytoplankton biomarkers, regardless of their labile or refractory nature, exhibited a little enhanced concentration in the sediment, indicating a minor increase of phytoplankton productivity. Phytoplankton composition was characterized by a slight increase of diatoms relative to dinoflagellates and green algae. Variations of algal productivity and community structure in this period could be attributed to the nutrients (e.g., soil Si) input from catchment erosion. A causal relationship might be present between the eutrophication process of Lake Fuxian and the anthropogenic activities within the catchment. [ABSTRACT FROM AUTHOR]

Highlights: [•] TiO2 nanotubes showed high photocatalytic activity for microcystin-LR degradation. [•] Conjugated system and methoxy group in Adda chain are liable to be attacked by OH. [•] Conjugated system in Mdha amino acid is susceptible to be attacked by OH. [•] Carboxyl and amino groups of the peptides are inferred to be hydrolyzed. [•] Adda is proposed to be separated from heptapeptides, leaving alkyl derivatives. [Copyright &y& Elsevier]

Abstract: Highly ordered TiO2 nanotubes with different tube length were fabricated by anodization using C2H2O4·2H2O containing 0.5wt.% NH4F (electrolyte A) and anhydrous dimethyl sulfoxide containing 1% HF (electrolyte B), respectively. Then cathodic reduction method was used to dope Pt in TiO2 nanotubes in chloroplatinic acid. The results indicated that cathodic reduction could efficiently platinize TiO2 nanotubes. Pt-doped TiO2 nanotubes with the longer length had the higher photocatalytic activity for degrading methyl orange under UV and visible irradiation. The longer tube length has a positive effect on the photocatalytic activity of Pt-doped TiO2 nanotubes. Besides, as the content of anatase further decreases, the photocatalytic activity drops gradually due to the reduction reaction in the surface area. [Copyright &y& Elsevier]

In order to obtain TiO2 with high photocatalytic activity, a cathode reduction was used to dope I7+ and I5+ into TiO2 nanotubes of anodized Ti in C2H2O4⋅2H2O + NH4F electrolyte. SEM images show that the anodization method integrated the preparation with the doping process, which for nonmetals-doping is advantageous to maintain the morphological integrity of TiO2 nanotubes. I7-I5+-doping enhances the UV response of TiO2 and result in a red-shift. Under UV/visible irradiation, a I7+-I5+-doped sample (400°C) showed the highest Iph and photocatalytic efficiency. A part of I- in the I7+-I5+-doped sample is involved in the UV response, the red-shift and the higher Iph. [ABSTRACT FROM AUTHOR]