Oxygen Depletion in Central and Eastern Lake Erie: Relationship with Bacteria,Chlorophyll, POC,and Morphometry

Hypolimnion oxygen depletion in central and eastern Lake Erie was related to bacteria, particulate organic carbon, and chlorophyll concentrations during 1979. The central basin had the higher oxygen depletion rate and this was associated with more microbiota and particulate organic carbon. After compensation for temperature differences, the rate of oxygen depletion per unit bacteria, chlorophyll, and particulate organic carbon was found to be similar in each basin. These observations are consistent with the hypothesis that lake morphometry affects oxygen depletion through the control of hypolimnion particle concentrations. The implication that most of the hypolimnion oxygen metabolism occurs in the water column means that the role of sediments as a site of oxygen consumption should be reassessed.     

污染河道水质强化脱氮生化工艺研究

应用生化工艺对河道污染水体进行修复是目前最经济的一条途径,但其面临的一个突出问题是在生物脱氮过程中可利用碳源不足,从而影响其处理效果。本研究采用分段进水生物接触氧化工艺来强化受污染水脱氮性能,与传统单点进水方式相比,两段进水对有机物和总氮去除率有显著提升,CODMn平均去除率从50.6%提升到66.3%;总氮平均去除率从31.4%提升到60.9%。沿程统计硝化细菌和反硝化细菌数量,硝化细菌主要集中在曝气区,数量为5.58×106,反硝化细菌主要集中在非曝气区的中后段,数量为6.49×105。同时检测沿程溶解氧和各氮素浓度,溶解氧浓度沿程降低,最后出水仅为0.2 mg/L;氨氮在曝气区转化为硝态氮,在非曝气区硝态氮还原成氮气,其结果进一步证实了硝化细菌和反硝化细菌的分布特征。     

Sedimentation,Resuspension, and Oxygen Depletion in Lake Erie (1979)

Oxygen depletion in Lake Erie's central basin hypolimnion is ultimately sustained by the respiration rate of organisms using organic matter which is produced in the trophogenic zone. Although other transformations are certainly important, they are nevertheless driven by the decomposition of organic carbon both in the water column and in the sediments. Rates of transport of particulate organic carbon to the hypolimnion and sediments were estimated using sediment traps. Corrections for sediment resuspension were necessary even during the summer period when the lake is stratified. Particulate organic carbon concentrations in the hypolimnion were partially independent of short-term variations in chlorophyll concentration. The net downflux of carbon to the hypolimnion appeared less than that required to support the observed oxygen depletion. Sediment resuspension accounted for much of the particulate material caught by the sediment traps in the central basin. It is concluded that organic material stored in the surficial sediments is made available to the water column through frequent resuspension. Of total phosphorus in the trap samples, an average of 42% was potentially bioavailable (NaOH extraction).     

Estimation of bacterial production through the coupling of (methyl 3H) Thymidine incorporation and several parameters over a Microcystis aeruginosa bloom in a hypereutrophic reservoir

The coupling of the changes in bacterial quantitative and metabolic aspects during Microcystis aeruginosa bloom conditions together with several environmental parameters was studied in the hypereutrophic Villerest reservoir, France. Bacterial abundance varied from 5.20 to 21.28 × 10⁶ bacteria-mL^?1, while bacterial biomass ranged between 75 and 507 μg C mL^?1. These results confirmed the highly eutrophic status of the Villerest reservoir. The relative quantitative importance of attached bacteria increased as Microcystis proliferated. Methyl-³H incorporation and D-(U-¹⁴C) glucose uptake varied from 8.99 to 60.57 × 10⁶ cells-mL^?1, and 0.016 to 1.587 μg CL^?1 h^?1, respectively. Correlations between several abiotic and biotic parameters showed that phytoplankton regulated bacterial growth by releasing organic carbon which is directly uptaken by heterotrophic bacteria. In the hypolimnion, the sedimentation of decaying algae represented a substantial substrate for bacterial growth.     

Dissolved and particulate organic carbon concentrations in stream water and relationships with land use in multiple-use watersheds of the Han River (Korea)

This study examines temporal variation in dissolved organic carbon (DOC) and particulate organic carbon (POC) concentrations in streams in the Han River watershed, Korea. On days without significant antecedent rain, DOC and POC concentrations ranged from 0.87 to 3.23 mg C/L and 0.24 to 2.92 mg C/L, respectively. Following rain events, both DOC and POC concentrations were higher. Soil and compost had δ¹³C values similar to stream δ¹³C-DOC and δ¹³C-POC. These results demonstrate the importance of studies using tracer approaches and the value of research on sources of organic carbon transported in streams in multiple use monsoonal watersheds.     

Xenobiotic Perturbation of Microbial Growth as Measured by CO2 Uptake in Aquatic Heterotrophic Bacteria

A microbiological assay, based on the Wood and Werkman reaction (i.e., dark reaction carboxylation by heterotrophic bacteria), was developed to assess chemical-induced changes in aquatic heterotrophic bacterial populations in the laboratory and in natural waters. This simple, sensitive, reproducible ¹⁴C-radiometric assay was used to monitor changes in biosynthetic activity of naturally occurring heterotrophic bacteria stimulated with an organic nutrient and incubated with known or potential aquatic chemical contaminants. Kepone at water concentrations of ≥ 1.0 mg/L significantly inhibited bacterial carboxylation; inhibition tended to follow a linear dose-response. Simazine slightly stimulated bacterial carboxylation (≥ 10 μg/L); di-2-ethylhexyl phthalate, Dylox, and mirex produced no effects (≤ 10 mg/L).     

Microbial ecological characteristics in the Red Tide-Monitoring area of Bohai Bay

The abundance of bacterioplankton and benthic bacteria and their ecological characteristics in the Red Tide-Monitoring area of Bohai Bay was studied during five cruises from May to October in 2006 and May in 2011. A hydrodynamic-ecosystem model, coupled planktonic system and benthic system, was used to quantitatively study the effect of bacterioplankton and benthic bacteria on other ecological variables. The survey and simulation results showed that a) the abundance of bacterioplankton and benthic bacteria was 5.64 × 10⁸ to 1.03 × 10¹⁰ cells/L and 7.2 × 10⁷ to 6.89 × 10⁸ cells/g, respectively. Bacterioplanktonic abundance had a significant correlation with Chl-a and dissolved oxygen (DO); however, benthic bacterial abundance was not notably correlated with other environmental factors. The distribution characteristics of bacterioplankton in May 2011 were similar to those in May 2006, but the average and highest values were lower in 2011 than 2006. b) The main factors (determined by principal component analysis) that influence the growth of bacterioplankton were external organic pollution, phosphate concentration and the phytoplankton biomass. c) The average contribution rate from benthic bacteria to ammonia of the planktonic system was 41.4%, and the average contribution rates from phytoplankton, bacterioplankton, and detritus to zooplankton were 87.3%, 1.4% and 11.3%, respectively.     

Inorganic Chemistry of Particulate Matter from the Nearshore Zone of Lake Michigan

Particulate matter from a nearshore region of southeastern Lake Michigan serves as a sink for trace metals and a conveyor of trace metals to the sediments. Fe, K, Mg, and Mn are always more concentrated in the hypolimnion than in the epilimnion, and Ca, Cr, Cu, Na, Sr, Zn, and total P are generally more concentrated in the hypolimnion than in the epilimnion. Enrichment of these metals in the hypolimnion particulates is attributed to sediment resuspension. Comparison of trace metal concentrations in the particulates with those in phytoplankton and zooplankton indicates that the plankton are not a significant contributor to the trace metal particulate chemistry of this nearshore region. Significant fractions (33% to nearly 100%) of total Cr, Cu, Fe, Mn, and Zn concentrations in the water column are associated with particulates.During the warmer months, calcium carbonate precipitates. Particulate chemistry changes little with the CaCO₃ formation, with the exception of an increased amount of calcium. Variations in the concentrations of trace metals are controlled either by both dolomite and hydrated manganese oxides or by an unknown phase believed to be organic in nature.     

Influence of episodic wind events on thermal stratification and bottom water hypoxia in a Great Lakes estuary

Hypoxia formation and breakdown were tracked during 2015 in Muskegon Lake estuary at multiple locations, and five years (2011–2015) of time-series buoy observatory data were evaluated for the effect of episodic wind-events on lake mixing. Bi-weekly water temperature and dissolved oxygen (DO) profiles at four locations revealed that hypoxia occurred at all sites and persisted for 2–3 months during summer 2015. On one date in late-summer, up to 24% of the lake’s volume was estimated to be mildly hypoxic (DO < 4 mg L^?1) as defined by lake sturgeon requirements. Patterns of wind speed and water column stability in late spring indicated that high winds and low stability delayed the onset of hypoxia while in late summer low winds and high stability delayed degradation of hypoxia. Wind speeds appear to play a great role in the interannual variability of stratification and subsequent hypoxia. Water temperature and DO profiles taken before and after one mid-summer mixing event (wind speed >7.7 m s^?1 for 10 h), indicated that while the wind was unable to completely mix the entire water column, it deepened the epilimnion by ～1.5 m and sheared a thin layer from the upper hypolimnion. By entraining internally loaded nutrients, such episodic wind-events may initiate and sustain algal blooms in nutrient limited surface waters. Quantifying the variable role of wind and mixing events will be key to integrating limnological processes into climate models of the future.     

潘家口水库热分层期溶解氧垂向分布及影响因素

为探究水库热分层对溶解氧垂向分布的影响,2019年8月在潘家口水库设置监测平台,分别采用YSI-EXO2监测仪和NISKIN采样器进行监测和水样采集,测定库区水温、溶解氧、pH、浮游植物等水质指标的垂向分布,分析水体热分层期溶解氧垂向分布的影响因素及溶解氧极小值（MOM）的形成原因。结果表明：潘家口水库8月存在显著热分层现象,水温呈混合层-温跃层-滞温层结构。混合层溶解氧浓度大于6.5 mg/L;温跃层受热分层等影响显著,层内出现MOM,梯度明显增大,浓度显著减小;滞温层溶解氧逐渐恢复。相关性分析表明：溶解氧与水温和浮力频率显著相关,热分层是MOM形成的主要物理因素;溶解氧与浮游植物生物量和pH呈正相关,温跃层浮游植物的呼吸作用、营养物质的积累和有机物质的氧化分解等生物和化学因素在一定程度上促进了MOM的发展。     

不同条件对高效菌去除污水中氨氮效果影响研究

本文研究了pH值、温度、曝气时间、茵投入量（体积比）、溶解氧、水力停留时间、进水碳氮比、冲击负荷等影响因素对氨氮去除率的影响,对项目参数进行了优化。研究结果如下：在高效菌处理氨氮废水时,为了得到较好的去除效果,pH值应控制在7．0到8．O之间;温度应控制在25℃到35℃之间;曝气时间应保持在5h到6h之间;茵投入量（体积比）应保持在0．004到0．006之间;溶解氧浓度应保持在2mg／L到3mg／L之间：水力停留时间为16h．高效茵对污水中氨氮的去除效果最佳。     

Relationships between actinomycete populations and organic matter degradation in Lake Mulwala,southeastern Australia

This communication examines the proposal that actinomycete populations, and thus the occurrence of taste and odour problems in potable water supplies, are related to the input of organic matter to reservoirs. The number of actinomycetes in Lake Mulwala, a man-made lake in southeastern Australia, ranged from 2–80 ml^?1 in the water column, and 2.7–12 × 10⁴cm^?3 in the sediments. Population densities in the water column and sediments were greatest in winter and summer, respectively. They were not highly correlated with protein or polysaccharide degradation. The weak relationship between actinomycete numbers and the rate of organic-matter breakdown was probably due to metabolic inactivity of the bacteria, since actinomycetes in the sediments occurred mainly as spores rather than as vegetative cells. Limiting the input of organic matter, for instance by the removal of fringing vegetation, will have little effect on actinomycete populations in this reservoir.     

渤海湾浮游细菌分布特征及环境影响因素

于2011年5月、2012年5月和2012年11月分别对渤海湾33个站位表层水体中的浮游细菌及环境因子进行了调查,探讨渤海湾浮游细菌生态分布特征及其与环境影响因子的关系。结果表明:在渤海湾表层水体中,2011年5月的海洋浮游细菌丰度为(2. 51~28. 39)×108L-1,2012年5月的浮游细菌丰度为(2. 62~87. 26)×108L-1,2012年11月浮游细菌丰度为(2. 18~18. 15)×108L-1;浮游细菌数量在空间上都是近岸站位高于远岸站位; 2011年5月和2012年5月,浮游细菌生长所需有机碳分别来源于浮游植物胞外分泌的溶解有机碳和陆源输入有机碳,浮游细菌与氨氮都有极显著相关性关系,与磷酸盐均呈显著负相关关系; 2012年11月,浮游细菌除了与亚硝酸盐氮、水温呈正相关外,与其他环境因子都呈负相关关系。     

Distribution and Characterization of PCBs in Lake Michigan Water

Polychlorinated biphenyls (PCBs) were measured in the water column of Lake Michigan at 28 stations. Distributions between dissolved and particulate phases were used to evaluate the partitioning behavior of PCBs. The average PCB concentration in Lake Michigan was 1.8 ng/L, corresponding to a total PCB burden of 8,900 kg. The average PCB concentration was significantly lower in open lake (1.2 ng/L) than in nearshore zone samples (3.2 ng/L). Concentrations in Green Bay were elevated compared to the rest of the lake. Variations in concentration with depth were small. The average log of the water-particle partition coefficient (Kp) was 5.9. Little dependence of Kp on particulate organic carbon was observed. A relationship was found between log Kp and log SPM (suspended particulate matter) concentration, perhaps reflecting association of a non-filterable fraction of the SPM with the aqueous phase. Selected PCB congener Kp and Koc (Kp × organic carbon weight-fraction) values were measured and related to congener Kow (octanol-water partition coefficient), yielding the predictive relationship log Koc = 4.2 + 0.34 log Kow. Congener log Kp values are predicted to range from 4.8 to 6.1, indicating that congener fates in the water column differ and are partly controlled by their physical chemical properties.     

Diel variation of limnological parameters in a reservoir in northeastern Brazil (Boa Esperança, Maranhão/Piauí): Rainy period

The diel variation of limnological parameters, measured in Boa Esperança Reservoir, Brazil during the rainy period, exhibited small temperature gradients characterized by an increase in temperature by midday, followed by a partial homogenization of the water column in the night and the early morning. The result was an increase in the epilimnion to a depth of 17 m. The pH and dissolved oxygen concentrations showed higher values at the surface, with the occurrence of anomalies (concentrations higher than at the surface) of the latter variable in the epilimnion, probably as a result of the activity of primary producers and/or losses of oxygen to the atmosphere. The chemical forms of iron in the reservoir exhibited increasing concentrations with depth, as a result of an increase in the concentration of seston and/or accentuated reduction of the levels of oxygen in the bottom layers. The reduction of Fe³⁺ to Fe²⁺ in the bottom water layers in the reservoir, in addition to the primary production process in the epilimnion, could explain the increased phosphorus in the bottom water layer. The concentrations of nitrogen compounds did not exhibit relevant changes or a defined evolution profile, except for nitrate, which showed an outstanding increase in the bottom water layers, suggesting it could be an important nitrogen source for primary producers. Although not unequivocal, these data suggest that ecosystem instability in Boa Esperança Reservoir is the product of short diel thermal variations, and the reduced input of allochthonous materials and nutrients from local catchment. These conditions guarantee the oligotrophic status of Boa Esperança Reservoir for the present time.     

Characterizing natural dissolved organic matter in a freshly submerged catchment (Three Gorges Dam, China) using UV absorption, fluorescence spectroscopy and PARAFAC

This study applied parallel factor analysis (PARAFAC) to fluorescence excitation-emission matrices (EEMs) of natural water samples in a freshly submerged catchment in the upper reach of Three Gorges Dam (China). Two fluorescent natural dissolved organic matter (NDOM) components (humic/fulvic-like) were uncovered and were positively correlated with selected water quality parameters, i.e. dissolved oxygen concentration, dissolved organic carbon concentration, dissolved Kjeldahl nitrogen concentration and total (dissolved plus particulate) phosphorus concentration, respectively. To other water quality parameters (i.e. total nitrogen, particulate nitrogen, particulate phosphorus, dissolved phosphorus, dissolved nitrate, pH, and chemical oxygen demand), either the two components did not show any correlation or only one component showed correlation. In particular, particulate N correlated significantly to the fulvic acid, but not to the humic acid. Meanwhile, two conventional spectroscopic indices i.e. specific UV absorbance at 254 nm (SUVA254) and fluorescence index (FI) indicated that the whole NDOM in the waters were low in aromaticity and predominantly derived from aquatic microbial processes. Given together, it concludes that N and P did not function equally in the NDOM production, and the two components were not derived from the same microbial processes. The EEMs-PARAFAC has proven to be of potential as an effective tool in investigation of the interlink between NDOM and nutrients which may be utilized as an indicator of water environment.     

Variability in benthic respiration in three southeastern Australian lowland rivers

Benthic respiration is an important measure of decomposition processes occurring in streams, but our understanding of benthic respiration in lowland rivers is not well developed, particularly the factors that affect benthic respiration. In our study we measured benthic respiration at three sites in three contrasting lowland rivers in southeastern Australia. On most sampling occasions, rates of oxygen consumption in benthic chambers were linear. However, oxygen consumption rates fitted exponential decay curves during periods of highest microbial activity. Benthic community respiration ranged from 289 to 619 mg O₂ m² d^?1 in the Broken River, from 178 to 1438 mg O₂ m² d^?1 in the River Murray and from 127 to 2178 mg O₂ m² d^?1 in the Ovens River. Benthic respiration was closely correlated with water temperature, but not with sediment carbon content, sediment particle size, water column nutrients or water column dissolved organic carbon concentrations. Average carbon turnover periods were between 1.7 and 6 years for the three rivers, but were as low as 0.1 year immediately following an event that gave rise to mobilization of in‐stream dissolved organic carbon, sufficient to produce coloured water. The latter occurred in the Ovens River as a consequence of a rain event during a period of base‐flow. Flow regime as such did not have a major impact on benthic community respiration. Induced changes in respiration, by altering flows, would only occur by altering the quality and timing of carbon inputs, since temperature and carbon quality, rather than quantity, appear more important in determining lowland river benthic respiration. Copyright © 2005 John Wiley & Sons, Ltd.     

Scales of spatial variability in Lake Michigan glider-based limnological observations

This study quantified spatial variability in temperature, colored dissolved organic matter, and chlorophyll-α fluorescence in the epilimnion and hypolimnion of southern Lake Michigan using observations collected by an autonomous underwater vehicle (glider) deployed multiple times per year during 2012–2019. We also include similar analyses of the deep chlorophyll maximum during the summer of those years. Ranges based on semivariance analysis and decorrelation distances generally were 5–15 km, with greater differences observed among seasons in the epilimnion and less unresolved error found for the temperature calculations. Our analysis provides information on submesoscale variation in limnological conditions that may be useful for several applications, including planning field sampling, observation networks, and data assimilation.     

饮用水处理中不同滤料除氨氮效果及需氧量研究

对比研究了活性无烟煤、活性炭、石英砂以及无烟煤4种滤料过滤去除饮用水中氨氮的效果及其与需氧量的关系。试验结果表明,当氨氮低于2 mg/L时,4种滤料过滤都能够有效去除氨氮,水中溶解氧逐渐耗尽;当氨氮浓度高于2 mg/L时,4种滤料的去除率均有所下降,但相比石英砂和无烟煤而言,活性无烟煤和活性炭过滤能够更有效地去除氨氮。纯氧曝气能够将溶解氧浓度提高到25 mg/L,从而大幅度改善4种滤料对氨氮的去除效果;活性无烟煤和活性炭过滤可将大部分氨氮转化为硝酸盐,但石英砂和无烟煤过滤则会发生亚硝酸盐积累现象。在活性无烟煤和活性炭过滤去除氨氮过程中,氨氮去除量与溶解氧的平均比例为1∶4.25,略低于理论值。这种定量关系对于生物过滤去除氨氮工艺的设计和运行具有指导意义。     

于桥水库沉积物内源污染特性研究

通过对天津市于桥水库沉积物中污染物的释放实验研究,找出了于桥水库底泥中磷、有机质、氮、铁、锰等污染物释放的影响因素,得出了溶解氧、pH值、水温等影响因素对底泥污染物释放的影响程度,并对各污染物的释放机理进行了探讨。磷的释放条件:pH值≥8时,好氧条件下会缓慢释放,当ρ(DO)<2 mg/L时快速释放;在中酸性条件下,当ρ(DO)<1 mg/L时发生较快速释放;低溶解氧和高pH值协同作用强烈。有机物和氮的释放主要受溶解氧浓度影响,与pH值关系不大,在ρ(DO)<2 mg/L时发生了快速释放。溶解性铁、锰的释放取决于水体pH值,在酸性条件下,ρ(DO)<1 mg/L时释放。