RESUMO
The aquatic ecosystem has been extensively investigated as a hotspot for the spread of antibiotic resistance genes (ARGs); yet, the evolution and distribution of ARGs profiles in submerged macrophytes biofilms and surrounding water remained unclear. In this study, the dynamic distribution and seasonal variations of microbial communities and ARGs profiles were investigated, alongside their assembly processes and mutual interactions. Bacitracin and multidrug resistance genes were predominant, constituting more than 60% of the total ARGs abundance. The deterministic processes (<65%), influenced by the physicochemical properties of the river environment, governed the assembly and composition of ARGs profiles, exhibiting significant seasonal variation. The peak diversity (21 types) and abundance (0.316 copy ratios) of ARGs were detected during the summer. Proteobacteria and Actinobacteria were the dominant bacterial phyla, accounting for 38.41-85.50% and 4.03-27.09% of the microbial community, respectively. Furthermore, Proteobacteria, especially genera such as Acinetobacter, Burkholderia, and Pseudomonas, with various resistance sequences, were the primary carriers of multiple ARGs. Notably, the genetic exchanges between biofilms and surrounding water facilitated the further propagation of high-risk ARGs, posing greater ecological risks. Redundancy analysis indicated that the total nitrogen and temperature in water determined the fate of pathogenic-resistant species. These findings provided theoretical support for the mitigation of ARGs contamination in aquatic environments.
Assuntos
Biofilmes , Resistência Microbiana a Medicamentos , Resistência Microbiana a Medicamentos/genética , Estações do Ano , Ecossistema , Proteobactérias/genética , Antibacterianos/farmacologia , Bactérias/genéticaRESUMO
Algal-bacterial symbiotic system is a biological purification system that combines sewage treatment with resource utilization and has the dual effects of carbon sequestration and pollution reduction. In this study, an immobilized algal-bacterial biofilm system was constructed for the treatment of natural sewage. Effects of exposure to microplastics (MPs) with different particle diameters (0.065 µm, 0.5 µm and 5 µm) were determined in terms of algal biomass recovery efficiency, the composition of extracellular polymeric substances (EPS) and morphologic characteristics. The impacts of MPs on the bacterial diversity and community structure of biofilms were also examined. The metagenomic analysis of key microorganisms and related metabolism pathways involved in system was further investigated. Results showed that following exposure to 5 µm MP, a maximum algal recovery efficiency of 80% was achieved, with a minimum PSII primary light energy conversion efficiency (Fv/Fm ratio) of 0.513. Furthermore, 5 µm MP caused the highest level of damage to the algal-bacterial biofilm, enhancing the secretion of protein-rich EPS. The biofilm morphology became rough and loose following exposure to 0.5 µm and 5 µm MP. Community diversity and richness were significantly high in biofilms exposed to 5 µm MP. Proteobacteria (15.3-24.1%), Firmicutes (5.0-7.8%) and Actinobacteria (4.2-4.9%) were dominant in all groups, with exposure to 5 µm MP resulting in the highest relative abundance for these species. The addition of MPs promoted the related metabolic functions while inhibited the degradation of harmful substances by algal-bacterial biofilms. The findings have environmental significance for the practical application of algal-bacterial biofilms for sewage treatment, providing novel insights into the potential effects of MPs on immobilized algal-bacterial biofilm systems.
Assuntos
Microbiota , Microplásticos , Bactérias/metabolismo , Biofilmes , Microplásticos/metabolismo , Microplásticos/farmacologia , Plásticos , EsgotosRESUMO
The microorganisms and functional predictions of leaf biofilms on submerged plants (Vallisneria natans (Val)) and in water samples (surface water (S) and bottom water (B)) in different seasons were evaluated in this study. S and B groups had 3249 identical operational taxonomic units (OTUs) (50.03%), while the Val group only had 1201 (18.49%) unique OTUs. There was significant overlap between microbial communities of S and B groups in the same season, while Val group showed the greater diversity. The dominant microbial clades were Proteobacteria (18.2-47.3%), Cyanobacteria (3.74-39.3%), Actinobacteria (1.64-29.3%), Bacteroidetes (1.31-21.7%), and Firmicutes (1.10-15.72%). Furthermore, there was a significant relationship between total organic carbon and the distribution of microbial taxa (p = 0.047), and TN may have altered the status of Cyanobacteria by affecting its biological nitrogen fixation capacity and reproductive capacity. The correlation network analysis results showed that the whole system consisted of 249 positive correlations and 111 negative correlations, indicating strong interactions between microbial communities. Functional predictions indicated that microbial functions were related to seasonal variation. These findings would guide the use of submerged plants to improve the diversity and stability of wetland microbial communities.
Assuntos
Cianobactérias , Hydrocharitaceae , Estações do Ano , Hydrocharitaceae/microbiologia , Biofilmes , Folhas de Planta , ÁguaRESUMO
Childhood maltreatment (CM) poses a serious risk to the physical, emotional and psychological well-being of children, and can advance the development of maladaptive behaviors, including conduct disorder (CD). CD involves repetitive, persistent violations of others' basic rights and societal norms. Little is known about whether and how CM influences the neural mechanisms underlying CD, and CD-characteristic neuroanatomical changes have not yet been defined in a structural magnetic resonance imaging (sMRI) study. Here, we used voxel-based morphometry (VBM) and surface-based morphometry (SBM) to investigate the influence of the CD diagnosis and CM on the brain in 96 boys diagnosed with CD (62 with CM) and 86 typically developing (TD) boys (46 with CM). The participants were 12-17 years of age. Compared to the CM- CD group, the CM+ CD group had structural gray matter (GM) alterations in the fronto-limbic regions, including the left amygdala, right posterior cingulate cortex (PCC), right putamen, right dorsolateral prefrontal cortex (dlPFC) and right anterior cingulate cortex (ACC). We also found boys with CD exhibited increased GM volume in bilateral dorsomedial prefrontal cortex (dmPFC), as well as decreased GM volume and decreased gyrification in the left superior temporal gyrus (STG) relative to TD boys. Regional GM volume correlated with aggression and conduct problem severity in the CD group, suggesting that the GM changes may contribute to increased aggression and conduct problems in boys with CD who have suffered CM. In conclusion, these results demonstrate previously unreported CM-associated distinct brain structural changes among CD-diagnosed boys.
Assuntos
Maus-Tratos Infantis , Transtorno da Conduta , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Córtex Cerebral/patologia , Criança , Transtorno da Conduta/diagnóstico por imagem , Transtorno da Conduta/patologia , Feminino , Substância Cinzenta/patologia , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Córtex Pré-Frontal/diagnóstico por imagem , Córtex Pré-Frontal/patologiaRESUMO
Ecological floating beds could enable roots to become suspended and this allowed submerged roots to harbour various types of microbes. But, there was a lack of systematic research on microbial community structure changes and the influencing mechanisms. In this study, the ecological floating beds were constructed using selected plants [Cyperus involucratus Rottboll (Cyp), Thalia dealbata Fraser (Tha) and Iris tectorum Maxim (Iri)] that was compared with a control group [static water (S)]. The results showed that the highest abundance and diversity of root microbial communities were found in autumn, with the dominant taxa being Proteobacteria, Actinobacteriota, Cyanobacteria, Chloroflexi, Firmicutes, Bacteroidota, and Acidobacteriota. The microbial communities of Tha and Cyp groups greatly overlapped, while the Iri and control groups exhibited distinctly diverse communities. The root microbial populations of the same plant also reflected a large change in different seasons. Conversely, photosynthetic autotrophs and specialized anaerobes were more inclined to thrive at higher temperatures and lower DO concentrations and then they gradually became the dominant species. Microbial co-occurrences of the Tha and control groups were complex and showed both cooperation and competition. In addition, TOC was an important environmental factor that shaped the microbial community structures and DO changed the microbial community by affecting the abundance of aerobic and anaerobic bacteria. Microorganisms showed potential for degradation and metabolism of non-food substances with low/no corresponding metabolic pathways.
Assuntos
Cianobactérias , Microbiota , Raízes de Plantas/microbiologia , Plantas , Rizosfera , Estações do Ano , Microbiologia do Solo , ÁguaRESUMO
BACKGROUND Many psychological problems arising from patients undergoing aesthetic repair of teeth should be considered. However, there are no published studies on the relationship between anxiety/depression and perfectionism in patients with aesthetic repair of anterior teeth. MATERIAL AND METHODS A total of 640 patients receiving aesthetic repair of anterior teeth were assessed using the Corah dental anxiety scale (CDAS), a self-rating anxiety scale (SAS), a self-rating depression scale (SDS), and the Chinese version of the Frost Multidimensional Perfectionism Psychological Scale (CFMPS). Statistical analyses included use of the independent-samples t test, correlation analysis, and multiple stepwise regression analysis. RESULTS We found that 156 patients with a high dental anxiety disorder had significantly greater SAS and SDS scores than those without a high dental anxiety disorder. There were significant differences between these patients and the non-high dental anxiety group, based on 3 dimensions of the CFMPS: concern over mistakes (CM), doubt about action (DA), and organization (OR). Patients with dental anxiety had a significant positive correlation with SAS in the categories CM and DA, with SDS in the categories CM and DA, and with personal standard (PS); OR was negatively correlated with SAS and SDS scores. Regression analysis showed that the CM and OR dimension scores of CFMPS and age had strong predictive effects on SAS scores, while CM, DA, PS dimension scores, and age were strong predictors of SDS scores. CONCLUSIONS The incidence of dental anxiety prior to anterior tooth repair treatment is high, and patients with dental anxiety have a significant tendency toward pursuing perfectionism.
Assuntos
Transtornos de Ansiedade/epidemiologia , Prótese Dentária/psicologia , Transtorno Depressivo/epidemiologia , Estética Dentária/psicologia , Perfeccionismo , Adolescente , Adulto , Idoso , Transtornos de Ansiedade/psicologia , Cerâmica , China/epidemiologia , Transtorno Depressivo/psicologia , Feminino , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
In this study, the influence of a static magnetic field (SMF) on a Chlorella vulgaris-Bacillus licheniformis consortium and the subsequent effect of this algal-bacterial consortium on sewage treatment were explored. Accordingly, the algal density, Fv/Fm, algal aggregation percentage, extracellular polymeric substances (EPS) content, dissolved organic matter distribution, enzymatic activity, metabolites, microbial community diversity and nutrient removal were investigated. For the treatment group exposed to an SMF of 150 mT, the total phosphorus removal rate reached 82.21%, which was 19.10% higher than the control group. On the last day, the algal density of the 150 mT group was the highest, being 56.01% greater than the control group. The high intensity SMF promoted the anti-oxidative stress response in C. vulgaris. It also affected EPS secretion, subsequently influencing the algal aggregation percentage and bacterial growth. Bacillus accounted for the largest proportion of the overall microbial community in the 150 mT group, which was conducive to rapid formation of the C. vulgaris-B. licheniformis consortium. In short, the SMF was conducive to the rapid formation of a C. vulgaris-B. licheniformis consortium. The use of an SMF can promote the efficiency of the algal-bacterial consortium, thereby shortening the processing time.
Assuntos
Bacillus licheniformis , Chlorella vulgaris , Campos Magnéticos , Fósforo , EsgotosRESUMO
The integrated effects of water flow on submerged macrophytes (Vallisneria natans) and leaf biofilms were comprehensively investigated in eutrophic microcosm. Changes in aquatic environmental factors were analyzed and water flow was found to elevate eutrophic water quality, especially in terms of TP removal. The removal efficiency of TP reached 78.95% in flowing water, which was more than 10-fold higher than in static water. Water flow altered the morphological and physiological characteristics of plants, decreasing the cell wall thickness and rate of photosynthesis, while promoting the accumulation of soluble sugar and protein in leaves. The starch content also increased with water flow, and significantly larger starch granules were observed in chloroplast. Furthermore, oxidative damage was evidenced by the consistently higher content of malondialdehyde in flowing water. Superoxide dismutase (SOD), peroxidase (POD) and Catalase (CAT) were induced in plants exposed to water flow, as an antioxidant stress response. The results of 16S rRNA high-throughput sequencing analysis showed that the structure of the biofilm microbial community changed in response to water flow. These results expand our understanding of the effects of water flow on submerged macrophytes and periphyton biofilms in eutrophic environments.
Assuntos
Hydrocharitaceae/fisiologia , Microbiota , Perifíton/fisiologia , Antioxidantes/metabolismo , Biofilmes , Hydrocharitaceae/metabolismo , Malondialdeído/análise , Malondialdeído/metabolismo , Fotossíntese , Folhas de Planta/metabolismo , RNA Ribossômico 16S/metabolismo , Água/química , Movimentos da ÁguaRESUMO
The study investigated the responses of the submerged macrophyte Vallisneria natans (V. natans) to snails (Bellamya aeruginosa) at different densities, with changes in physiological parameters, morphology, leaf-epiphytic bacteria community and water quality parameters examined. The changes of water quality parameters (pH, total nitrogen (TN), total phosphorus (TP) and total organic carbon (TOC)) indicated that snails secreted nutrients into water. Changes in morphological and physiological parameters (fresh weight, root length, shoot height, chlorophyll, malondialdehyde (MDA), activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD)) demonstrated that the presence of snails were beneficial to the growth of submerged macrophytes. Microbial diversity analyses indicated that snails could decrease microbial community richness and diversity. At medium densities (340 ind. m-2), an increase in snail density was beneficial to the growth of submerged macrophytes. The results of this study provide theoretical guidance and technical support for the maintenance and restoration of submerged macrophytes.
Assuntos
Hydrocharitaceae/fisiologia , Caramujos/fisiologia , Animais , Clorofila , Hydrocharitaceae/crescimento & desenvolvimento , Malondialdeído , Nitrogênio , Fósforo , Folhas de Planta , ÁguaRESUMO
A pilot-scale deep bed denitrification filter using quartz sand as the filter media was operated under filtration velocity of 5.23 m/h. Nitrate, nitrite, ammonia, and total nitrogen removal rates were relatively high at influent C/N ratios of 4:1 and 5:1. A model was developed using software to simulate the processes operating in the filter and improve the related parameters in the actual operations. The normalized sensitivity coefficient and the mean square sensitivity measure were used for the sensitivity analysis. Results showed that the stoichiometric parameters were the most sensitive, which were related to methylotrophs and biofilm. Measured data were consistent with the simulations. Moreover, the order of significance of factors affecting nitrate nitrogen removal was as follows: influent chemical oxygen demand, influent nitrate nitrogen, and hydraulic retention time. Last, the denitrification dynamic model was obtained at influent C/N ratio of 5:1.
Assuntos
Nitratos/química , Nitrogênio/química , Eliminação de Resíduos Líquidos/métodos , Biofilmes , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Calibragem , Simulação por Computador , Desnitrificação , Filtração/métodos , Metanol/química , Nitritos/química , Software , Águas Residuárias , Poluentes Químicos da Água/química , Purificação da Água/métodosRESUMO
In this study, algal growth potential tests were performed in water samples collected from six sampling sites in Meiliang Bay, Lake Taihu. The potential release of soluble reactive phosphorus (SRP) by enzymatic hydrolysis of enzymatically hydrolyzable phosphorus (EHP) was simultaneously evaluated. Results show that all studied regions were in highly eutrophic states, with additional nitrogen (N) or phosphorus (P) inputs, inducing negligible further increase in algal growth. EHP in water could be rapidly transformed into SRP, further supporting the proliferation of algal blooms. The shortest EHP mineralization time was calculated as 69 minutes; therefore, limiting specific nutrient inputs alone in extremely eutrophic lakes can have a limited effect on suppressing the proliferation of algal blooms. Methods to establish a suitable environmental fate for excessive nitrogen and phosphorus nutrients may be more effective and provide more significant results. PRACTITIONER POINTS: N and P were no longer serving as the limiting factors in Meiliang Bay. Enzymatically hydrolysable phosphorus could be hydrolyzed into soluble reactive phosphorus in a very short period during algal blooms. Both enzymatically hydrolysable phosphorus and soluble reactive phosphorus are required to be curbed in practical eutrophication control.
Assuntos
Fosfatase Alcalina/metabolismo , Baías , Monitoramento Ambiental , Eutrofização/efeitos dos fármacos , Lagos/química , Nutrientes/metabolismo , Fósforo/metabolismo , Sedimentos Geológicos/química , Hidrólise , Nitrogênio/metabolismo , Nitrogênio/farmacologia , Nutrientes/farmacologia , Fósforo/farmacologiaRESUMO
The Pacific oyster Crassostrea gigas belongs to one of the most species-rich but genomically poorly explored phyla, the Mollusca. Here we report the sequencing and assembly of the oyster genome using short reads and a fosmid-pooling strategy, along with transcriptomes of development and stress response and the proteome of the shell. The oyster genome is highly polymorphic and rich in repetitive sequences, with some transposable elements still actively shaping variation. Transcriptome studies reveal an extensive set of genes responding to environmental stress. The expansion of genes coding for heat shock protein 70 and inhibitors of apoptosis is probably central to the oyster's adaptation to sessile life in the highly stressful intertidal zone. Our analyses also show that shell formation in molluscs is more complex than currently understood and involves extensive participation of cells and their exosomes. The oyster genome sequence fills a void in our understanding of the Lophotrochozoa.
Assuntos
Adaptação Fisiológica/genética , Exoesqueleto/crescimento & desenvolvimento , Crassostrea/genética , Genoma/genética , Estresse Fisiológico/fisiologia , Exoesqueleto/química , Animais , Proteínas Reguladoras de Apoptose/genética , Elementos de DNA Transponíveis/genética , Evolução Molecular , Feminino , Regulação da Expressão Gênica no Desenvolvimento/genética , Genes Homeobox/genética , Genômica , Proteínas de Choque Térmico HSP70/genética , Humanos , Larva/genética , Larva/crescimento & desenvolvimento , Espectrometria de Massas , Anotação de Sequência Molecular , Dados de Sequência Molecular , Polimorfismo Genético/genética , Sequências Repetitivas de Ácido Nucleico/genética , Análise de Sequência de DNA , Estresse Fisiológico/genética , Transcriptoma/genéticaRESUMO
With the improvement of wastewater discharge standards, wastewater treatment plants (WWTPs) are continually undergoing technological improvements to meet the evolving standards. In this study, a quartz sand deep bed denitrification filter (DBDF) was used to purify WWTP secondary effluent, utilizing high nitrate nitrogen concentrations and a low C/N ratio. Results show that more than 90% of nitrate nitrogen (NO3-N) and 75% of chemical oxygen demand (COD) could be removed by the 20th day of filtration. When the filter layer depth was set to 1,600 mm and the additional carbon source CH3OH was maintained at 30 mg L-1 COD (20 mg L-1 methanol), the total nitrogen (TN) and COD concentrations of DBDF effluent were stabilized below 5 and 30 mg L-1, respectively. Analysis of fluorescence revealed that DBDF had a stronger effect on the removal of dissolved organic matter (DOM), especially of aromatic protein-like substances. High throughput sequencing and qPCR results indicate a distinctly stratified microbial distribution for the main functional species in DBDF, with quartz sand providing a good environment for microbes. The phyla Proteobacteria, Bacteroidetes, and Chloroflexi were found to be the dominant species in DBDF.
Assuntos
Nitrogênio/isolamento & purificação , Eliminação de Resíduos Líquidos/métodos , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos/microbiologia , Carbono/química , Desnitrificação , Filtração/instrumentação , Filtração/métodos , Metanol/química , Consórcios Microbianos/genética , Consórcios Microbianos/fisiologia , Nitratos/química , Nitrogênio/química , Eliminação de Resíduos Líquidos/instrumentação , Águas Residuárias/químicaRESUMO
This study was undertaken to develop an extraction method for seven acidic pharmaceuticals and five steroidal estrogens from wastewater, treated wastewater and sludge samples. The temperature and time of sample derivatization using N,O-bis(trimethylsilyl)trifluoroacetamide was optimized. Our results show that pretreatment combined with solid phase extraction (SPE) for wastewater samples (using an ENVI-C18 cartridge) and liquid-solid extraction combined with SPE (using an HLB cartridge) for sludge samples increased the analytical efficiency for acidic pharmaceuticals and estrogenic hormones using gas chromatography-mass spectrometry (GC-MS). The derivatization conditions were optimized at 40°C for 2 h. In addition, the derivatized samples were stable at ambient temperature. The new method was validated and applied to the analysis of real wastewater and discharged sludge samples from a local wastewater treatment plant. Except for 17α-ethinylestradiol, all acidic pharmaceuticals and estrogens were detected in the influent, effluent and discharged sludge samples. The concentrations of these compounds were particularly high in the discharged sludge samples.
Assuntos
Ácidos/análise , Estrogênios/análise , Preparações Farmacêuticas/análise , Esgotos/química , Águas Residuárias/química , Poluentes Químicos da Água/análise , Acetamidas/química , Cromatografia Gasosa-Espectrometria de Massas , Reprodutibilidade dos Testes , Extração em Fase Sólida , Compostos de Trimetilsilil/químicaRESUMO
In this study, we sought to identify influent carbon-to-nitrogen (C/N) ratios that yield relatively high nutrient removal efficiency with relatively low greenhouse gas (GHG) emissions. The earthworm eco-filter (EE) system, which is composed of earthworms and plants (EP group), was found to be optimal for maximizing nutrient removal while reducing GHG emissions. In this EE system, the optimal influent C/N ratio for nutrient removal and GHG emission under C2N treatment conditions. Nutrient removal efficiency under this condition was 85.19 ± 6.40% chemical oxygen demand, 71.99 ± 11.28% total nitrogen, and 77.91 ± 8.51% total phosphorus, while the CO2 emission rate was 678.89 ± 201.87 mg m(-2) h(-1). Moreover, the highest nutrient removal and GHG emission rates were both achieved in late summer (August). Thus, carbon variation, season, system variation, as well as synergistic interaction between system variations and seasons, significantly affect nutrient removal efficiencies and GHG emissions.
Assuntos
Carbono/metabolismo , Alimentos , Gases/metabolismo , Efeito Estufa , Nitrogênio/metabolismo , Oligoquetos/metabolismo , Plantas/metabolismo , Animais , Análise da Demanda Biológica de Oxigênio , EcossistemaRESUMO
Reactive oxygen species (ROS) play crucial roles in element cycling and pollutant dynamics, but their variations and mechanisms in the rhizosphere of submerged macrophytes are poorly investigated. This study investigated the light-dark cycle fluctuations and periodic variations in ROS, redox-active substances, and microbial communities in the rhizosphere of Vallisneria natans. The results showed sustained production and significant diurnal fluctuations in the O2â¢- and â¢OH from 27.6⯱â¯3.7 to 61.7⯱â¯3.0⯵mol/kg FW and 131.0⯱â¯6.8 to 195.4⯱â¯8.7⯵mol/kg FW, respectively, which simultaneously fluctuated with the redox-active substances. The ROS contents in the rhizosphere were higher than those observed in non-rhizosphere sediments over the V. natans growth period, exhibiting increasing-decreasing trends. According to the redundancy analysis results, water-soluble phenols, fungi, and bacteria were the main factors influencing ROS production in the rhizosphere, showing contribution rates of 74.0, 17.3, and 4.4â¯%, respectively. The results of partial least squares path modeling highlighted the coupled effects of redox-active substances and microbial metabolism. Our findings also demonstrated the degradation effect of ROS in rhizosphere sediments of submerged macrophytes. This study provides experimental evidence of ROS-related rhizosphere effects and further insights into submerged macrophytes-based ecological restoration.
RESUMO
Understanding the influence of terrestrial inputs on heavy metals in bays is crucial for the environmental protection of regional estuaries and coastal systems. In this study, the concentrations, temporal and regional distribution characteristics, and fluxes of heavy metals (Cr, Cu, Zn, Cd, Pb) in the surface seawater and terrestrial sewage of Zhanjiang Bay (ZJB) in four different seasons were investigated. The results identified the heavy metal concentrations in the sewage outlet around ZJB had significant seasonal variation. The heavy metals in the surface seawater of ZJB had significant spatiotemporal variations. Terrestrial input, biological activity and hydrodynamics affected the overall distribution. The heavy metal emission fluxes indicated that riverine input was the main influencing factor for heavy metals in ZJB (96.22 %). The fluxes of heavy metals into ZJB increased significantly after the typhoon (Cu: 127 %, Zn: 63 %, Pb: 136 %), it was possible to deteriorate the seawater quality.
Assuntos
Metais Pesados , Poluentes Químicos da Água , Baías , Esgotos , Chumbo , Poluentes Químicos da Água/análise , Monitoramento Ambiental/métodos , Metais Pesados/análise , China , Sedimentos Geológicos , Medição de RiscoRESUMO
Typhoons can induce variations in hydrodynamic conditions and biogeochemical processes, potentially escalating the risk of algal bloom occurrences impacting coastal ecosystems. However, the impacts of typhoons on instantaneous changes and the mechanisms behind typhoon-induced algal blooms remain poorly understood. This study utilized high-frequency in situ observation and machine learning model to track the dynamic variations in meteorological, hydrological, physicochemical, and Chlorophyll-a (Chl-a) levels through the complete Typhoon Talim landing in Zhanjiang Bay (ZJB) in July 2023. The results showed that a delayed onset of algal bloom occurring 10 days after typhoon's arrival. Subsequently, as temperatures reached a suitable range, with an ample supply of nutrients and water stability, Chl-a peaked at 121.49 µg L-1 in algal bloom period. Additionally, water temperature and air temperature decreased by 1.61 °C and 2.8 °C during the typhoon, respectively. In addition, wind speed and flow speed increased by 1.34 and 0.015 m s-1 h-1 to peak values, respectively. Moreover, the slow decline of 8.2 % in salinity suggested a substantial freshwater input, leading to an increase in nutrients. For instance, the mean DIN and DIP were 2.2 and 8.5 times higher than those of the pre-typhoon period, resulting in a decrease in DIN/DIP (closer to16) and the alleviation of P limitation. Furthermore, pH and dissolved oxygen (DO) were both low during the typhoon period and then peaked at 8.93 and 19.05 mg L-1 during the algal bloom period, respectively, but subsequently decreased, remaining lower than those of the pre-typhoon period. A preliminary learning machine model was established to predict Chl-a and exhibited good accuracy, with R2 of 0.73. This study revealed the mechanisms of eutrophication status formation and algal blooms occurrence in the coastal waters, providing insights into the effects of typhoon events on tropical coastal biogeochemistry and ecology.
Assuntos
Tempestades Ciclônicas , Ecossistema , Hidrologia , Baías , Eutrofização , Nutrientes , China , ÁguaRESUMO
Phosphorus (P) is a vital nutrient for the growth of marine organisms. Tidal cycle had major influence on various biogeochemical parameters of the bay and changed nutrients input with the ebb and flow of the tide. Seawater was collected by synchronous continuous observation during summer in 2021, to investigate tide drives total phosphorus (TP) variation on the concentration, speciation and exchange flux between Shuidong Bay (SDB) and South China Sea (SCS). Results indicated that there was significant tidal variation in exchange flux of TP between SDB and SCS. DIP and DOP were the main speciation of TDP in different tidal periods, accounting for 53.9 % and 46.1 %TP flowed from SCS to SDB, and monthly exchange flux was about 21.26 t. This study provides new insights in P tidal cycling across the semi-enclosed bay-coastal water continuum, which was implications for understanding P biogeochemical process and primary production dynamics in coastal water.
Assuntos
Baías , Monitoramento Ambiental , Fósforo , Estações do Ano , Água do Mar , Fósforo/análise , China , Água do Mar/química , Poluentes Químicos da Água/análise , Ondas de Maré , Movimentos da ÁguaRESUMO
Redox transformation of mercury (Hg) is critical for Hg exchange at the air-water interface. However, the superoxide radicals (O2â¢â) contribution of microalgal-fungal symbiotic systems in lake water to Hg(II) reduction is mainly unknown. Here, we studied the enhanced potential for O2â¢â production by the coupling effect between microalgae and fungi. The relationships between microenvironment, microorganisms, and O2â¢â production were also investigated. Furthermore, the implication of O2â¢â for Hg(II) reduction was explored. The results showed that the coupling effect of microalgae and fungi enhanced O2â¢â generation in the symbiotic systems, and the O2â¢â generation peaked on day 4 in the lake water at 160.51 ± 13.06-173.28 ± 18.21 µmol/kg FW (fresh weight). In addition, O2â¢- exhibited circadian fluctuations that correlated with changes in dissolved oxygen content and redox potential on the inter-spherical interface of microalgal-fungal consortia. Partial least squares path modeling (PLS-PM) indicates that O2â¢â formation was primarily associated with microenvironmental factors and microbial metabolic processes. The experimental results suggest that O2â¢â in the microalgal-fungal systems could mediate Hg(II) reduction, promoting Hg conversion and cycling. The findings highlight the importance of microalgae and fungal symbiotic systems in Hg transformation in aquatic environments.