There is a great deal of uncertainty in hydrogeological modeling. Overparametrized models increase uncertainty since the information of the observations is distributed through all of the parameters. The present study proposes a new option to reduce this uncertainty. A way to achieve this goal is to select a model which provides good performance with as few calibrated parameters as possible (parsimonious model) and to calibrate it using many sources of information. Akaike’s Information Criterion (AIC), proposed by Hirotugu Akaike in 1973, is a statistic-probabilistic criterion based on the Information Theory, which allows us to select a parsimonious model. AIC formulates the problem of parsimonious model selection as an optimization problem across a set of proposed conceptual models. The AIC assessment is relatively new in groundwater modeling and it presents a challenge to apply it with different sources of observations. In this dissertation, important findings in the application of AIC in hydrogeological modeling using different sources of observations are discussed. AIC is tested on ground-water models using three sets of synthetic data: hydraulic pressure, horizontal hydraulic conductivity, and tracer concentration. In the present study, the impact of the following factors is analyzed: number of observations, types of observations and order of calibrated parameters. These analyses reveal not only that the number of observations determine how complex a model can be but also that its diversity allows for further complexity in the parsimonious model. However, a truly parsimonious model was only achieved when the order of calibrated parameters was properly considered. This means that parameters which provide bigger improvements in model fit should be considered first. The approach to obtain a parsimonious model applying AIC with different types of information was successfully applied to an unbiased lysimeter model using two different types of real data: evapotranspiration and seepage water. With this additional independent model assessment it was possible to underpin the general validity of this AIC approach. / Hydrogeologische Modellierung ist von erheblicher Unsicherheit geprägt. Überparametrisierte Modelle erhöhen die Unsicherheit, da gemessene Informationen auf alle Parameter verteilt sind. Die vorliegende Arbeit schlägt einen neuen Ansatz vor, um diese Unsicherheit zu reduzieren. Eine Möglichkeit, um dieses Ziel zu erreichen, besteht darin, ein Modell auszuwählen, das ein gutes Ergebnis mit möglichst wenigen Parametern liefert („parsimonious model“), und es zu kalibrieren, indem viele Informationsquellen genutzt werden. Das 1973 von Hirotugu Akaike vorgeschlagene Informationskriterium, bekannt als Akaike-Informationskriterium (engl. Akaike’s Information Criterion; AIC), ist ein statistisches Wahrscheinlichkeitskriterium basierend auf der Informationstheorie, welches die Auswahl eines Modells mit möglichst wenigen Parametern erlaubt. AIC formuliert das Problem der Entscheidung für ein gering parametrisiertes Modell als ein modellübergreifendes Optimierungsproblem. Die Anwendung von AIC in der Grundwassermodellierung ist relativ neu und stellt eine Herausforderung in der Anwendung verschiedener Messquellen dar. In der vorliegenden Dissertation werden maßgebliche Forschungsergebnisse in der Anwendung des AIC in hydrogeologischer Modellierung unter Anwendung unterschiedlicher Messquellen diskutiert. AIC wird an Grundwassermodellen getestet, bei denen drei synthetische Datensätze angewendet werden: Wasserstand, horizontale hydraulische Leitfähigkeit und Tracer-Konzentration. Die vorliegende Arbeit analysiert den Einfluss folgender Faktoren: Anzahl der Messungen, Arten der Messungen und Reihenfolge der kalibrierten Parameter. Diese Analysen machen nicht nur deutlich, dass die Anzahl der gemessenen Parameter die Komplexität eines Modells bestimmt, sondern auch, dass seine Diversität weitere Komplexität für gering parametrisierte Modelle erlaubt. Allerdings konnte ein solches Modell nur erreicht werden, wenn eine bestimmte Reihenfolge der kalibrierten Parameter berücksichtigt wurde. Folglich sollten zuerst jene Parameter in Betracht gezogen werden, die deutliche Verbesserungen in der Modellanpassung liefern. Der Ansatz, ein gering parametrisiertes Modell durch die Anwendung des AIC mit unterschiedlichen Informationsarten zu erhalten, wurde erfolgreich auf einen Lysimeterstandort übertragen. Dabei wurden zwei unterschiedliche reale Messwertarten genutzt: Evapotranspiration und Sickerwasser. Mit Hilfe dieser weiteren, unabhängigen Modellbewertung konnte die Gültigkeit dieses AIC-Ansatzes gezeigt werden.

Current research concentrates on ways to investigate and improve water productivity (WP), as agriculture is today’s predominant freshwater consumer, averaging at 70% and reaching up to 93% in some regions. A growing world population will require more food and thus more water for cultivation. Regions that are already affected by physical water scarcity and which depend on irrigation for growing crops will face even greater challenges regarding their water supply. Other problems in such regions are a variable water supply, inefficient irrigation practices, and over-pumping of available groundwater resources with other adverse effects on the ecosystem. To face those challenges, strategies are needed that use the available water resources more efficiently and allow farming in a more sustainable way. This work focused on the management of sensor-based deficit irrigation (DI) systems and improvements of WP through a combined approach of simulation-optimization and irrigation experiments. In order to improve irrigation control, a new sensor called pF-meter was employed, which extended the measurement range of the commonly used tensiometers from pF 2.9 to pF 7. The following research questions were raised: (i) Is this approach a suitable strategy to improve WP; (ii) Is the sensor for irrigation control suitable; (iii) Which crop growth models are suitable to be part of that approach; and (iv) Can the combined application with experiments prove an increase of WP? The stochastic simulation-optimization approach allowed deriving parameter values for an optimal irrigation control for sensor-based full and deficit irrigation strategies. Objective was to achieve high WP with high reliability. Parameters for irrigation control included irrigation thresholds of soil-water potentials because of the working principle behind plant transpiration where pressure gradients are transmitted from the air through the plant and into the root zone. Optimal parameter values for full and deficit irrigation strategies were tested in irrigation experiments in containers in a vegetation hall with drip irrigated maize and compared to schedule-based irrigation strategies with regard to WP and water consumption. Observation data from one of the treatments was used afterwards in a simulation study to systematically investigate the parameters for implementing effective setups of DI systems. The combination of simulation-optimization and irrigation experiments proved to be a suitable approach for investigating and improving WP, as well as for deriving optimal parameter values of different irrigation strategies. This was verified in the irrigation experiment and shown through overall high WP, equally high WP between deficit and full irrigation strategies, and achieved water savings. Irrigation thresholds beyond the measurement range of tensiometers are feasible and applicable. The pF-meter performed satisfactorily and is a promising candidate for irrigation control. Suitable crop models for being part of this approach were found and their properties formulated. Factors that define the behavior of DI systems regarding WP and water consumption were investigated and assessed. This research allowed for drawing the first conclusions about the potential range of operations of sensor-based DI systems for achieving high WP with high reliability through its systematical investigation of such systems. However, this study needs validation and is therefore limited with regard to exact values of derived thresholds.

Matter retention in streams and rivers is an ecosystem service of outstanding ecological as well as economic importance. Studying and monitoring instream nitrate dynamics is essential to reduce the tremendous consequences of eutrophication of freshwater systems and coastal zones. Moreover, the cycling of nitrate in lotic systems is a paradigm for the instream transport and transformation behavior of any other reactive substance subjected to human perturbation of its natural cycle. Identifying instream processes and drivers that dictate nitrate transport in rivers and quantifying the capacity of rivers to retain nitrate is therefore of scientific as well as political interest and was the motivation for this thesis. Even though understanding and monitoring of instream nitrate dynamics is advanced compared to most other emerging substances of concern (e.g. pharmaceuticals, synthetic and natural hormones), methodologies to directly assess nitrate dynamics are still limited, leaving a high degree of uncertainty to descriptive and predictive models. One major problem of common data acquisition is that the temporal and spatial variability of nitrate processing rates arising from the complex interactions of hydrological and biogeochemical drivers cannot be captured with traditional methods. For technical reasons, most studies have been conducted in small (and rather pristine) streams. Thus, particularly the functional behavior of larger rivers and anthropogenically modified systems is widely uncharacterized. In this work, two methodologies were developed which allow quantitatively assessing nitrate dynamics on two relevant scales: The reach scale (1), which is of particular interest for monitoring strategies and local hyporheic nutrient fluxes (2), with the hyporheic zone being a key compartment in instream solute cycling. In order to assess the seasonal fluctuation in nitrate dynamics (3), a primary demand on the methods was that they operate continuous or over longer time spans. On the reach scale, a combined two-station time-series and longitudinal profiling approach based on measurements from automated sensors, provided novel insights into seasonal variations of nitrogen processing and allowed quantitative comparison of the dynamics in a natural versus a heavily modified reach. Uptake was lower and the influence of season on uptake rates more marked in the modified reach. Continuous implementation of the proposed approach, fully covering the annual variations, can essentially improve existing monitoring practices by quantifying the effect of altered morphology and water chemistry on retention rates. Hyporheic passive flux meters are an efficient tool to quantify time integrative hyporheic nutrient fluxes. In combination with other measurements, the results from a field application unraveled an unexpected hyporheic source-sink behavior for nitrate at the study reach. Different to common observations, not the upper most layer of the hyporheic zone but the layer between 15 and 30 cm was most efficient in removing nitrate, assumedly because substrate limitation is irrelevant in agricultural (nutrient and DOC enriched) streams. Further, higher discharge did not increase hyporheic exchange, because the monotonous morphology and absence of bedforms reduced the usually dominating effect of increased drag resistance with higher flow. The studies presented here deliver empirical evidence that, on both investigated scales, anthropogenic modifications substantially impact instream nitrate dynamics. Alterations to channel morphology, riparian vegetation, hydrology and water quality change principal ecosystem functions relevant for solute retention in streams and rivers. The presented results show that anthropogenically modified systems may therefore behave unexpectedly if predictions are built on the driver-response correlations observed in natural systems. Worldwide a large proportion of rivers and streams are modified by humans. However, altered systems are not adequately represented in studies focusing on solute dynamics. Efficient management of such systems, including evaluation of measures to reduce the nitrogen burden on receiving water bodies, requires quantitative knowledge on instream processes and governing drivers. Continuous or time integrative observations are more representative for the solute cycling characteristics of a system than “snapshot”-like assessments. The new methodologies thereby also facilitate extrapolation of local measurements and linking the resulting data with catchment scale models. Overall synthesis of the presented results suggests that such measurements of nitrate dynamics in streams may be used as an indicator for the ecosystem integrity. / Der Rückhalt von Stoffen in Flüssen und Bächen ist eine Ökosystem-Dienstleistung von grösster ökologischer wie auch wirtschaftlicher Bedeutung. Um die negativen Auswirkungen durch Eutrophierung von Süsswasserkörpern und Küstengebieten zu reduzieren, ist es erforderlich, die Stickstoffdynamik in Fliessgewässern zu untersuchen und zu überwachen. Darüber hinaus, kann der Umsatz von Nitrat in lotischen Systemen als Paradigma für den Transport und die Transformation anderer reaktiver Substanzen von anthropogenem Ursprung gesehen werden. Die Prozesse zu identifizieren, die den Nitrattransport in Fliessgewässern und deren Kapazität Nitrat zurückzuhalten beeinflussen, ist somit von wissenschaftlichem wie auch von politischem Interesse und war die Motivation für diese Arbeit. Obwohl unser Wissen über das Verhalten von Nitrat in Fliessgewässern, im Vergleich zu vielen erst neuerdings an Bedeutung gewinnender Substanzen (z.B. Arzneimittelrückstände, synthetische und natürliche Hormone) fortgeschritten ist, fehlen Methoden um die Nitratdynamik im Fliessgewässer zu erfassen. Dadurch ist die Überwachung wie auch der Vorhersage des Nitratexports durch Fliessgewässer mit grossen Unsicherheiten behaftet. Ein Hauptproblem bei der Datenerfassung ist, dass die Umsatzraten von Nitrat aufgrund der komplexen Zusammenspiele von biogeochemischen wie auch hydrologischen Einflussfaktoren, sowohl räumlich wie auch zeitlich stark schwanken. Ausserdem wurden aus technischen Gründen die meisten Studien bislang in kleinen (und eher unberührten) Flüssen durchgeführt. Deshalb bestehen insbesondere über das Exportverhalten grosser und anthropogen veränderter Systeme grosse Unsicherheiten. In dieser Arbeit wurden zwei Methoden entwickelt, die es erlauben, die Nitratdynamiken auf zwei relevanten Grössenskalen zu erfassen: Einmal über eine Flussstrecke von einigen Kilometern und zum anderen lokal in der Hyporheischen Zone. Die erste Skala (Flusstrecke) ist insbesondere für die Entwicklung von Monitoring-Strategien wichtig. Die Hyporheische Zone ist als Schlüsselkompartiment für den Stoffumsatz in Fliessgewässern von Bedeutung. Da zeitliche (z.B. saisonale) Schwankungen im Nitratumsatz erfasst werden sollten, war eine primäre Herausforderung an die Methoden, dass sie für die kontinuierliche Aufzeichnung über länger Zeitspannen geeignet sind. Für die Fliessgewässerstrecke wurde eine Bilanzierung von Zeitreihen zwischen zwei Stationen mit Messungen über das Längsprofil kombiniert. Die Zeitreihen wurden mit automatisierten Sensoren aufgenommen. Der hier entwickelte Ansatz von Messung und Auswertung lieferte neue Erkenntnisse über die saisonale Variation des Stickstoffumsatzes und ermöglichte einen quantitativen Vergleich zwischen einem natürlichen und einem anthropogen überprägten Gewässerabschnitt. Der Nitratrückhalt im veränderten Abschnitt war niedriger und der Einfluss der Jahreszeit auf die Umsatzraten war stärker ausgeprägt. Eine dauerhafte Installierung des Messaufbaus, der die gesamten Jahresschwankungen abdeckt, könnte die existierenden Überwachungsverfahren erheblich verbessern, weil so der Effekt der Fliessgewässermorphologie und der Wasserchemie auf die Umsatzraten berücksichtigt werden können. Hyporheische Passive Flux Meter sind ein Instrument für die zeitlich gemittelte Quantifizierung von Nitratflüsse durch die Hyporheische Zone. In Kombination mit weiteren Messungen brachten die Ergebnisse einer Freilandmessung unerwartete Ergebnisse über die Entstehung und den Abbau von Nitrat in der Hyporheischen Zone des untersuchten Flusses zum Vorschau. Anders als üblicher Weise beobachtet, war der Abbau von Nitrat nicht in der obersten Schicht der Hyporheischen Zone, sondern in einer Tiefe von 15 bis 30 cm am effizientesten. Wahrscheinlich verhalten sich landwirtschaftlich beeinflusste Gewässer (die mit Nitrat und organischen Stoffen angereichert sind) diesbezüglich nicht laut Lehrbuchmeinung, weil es nicht zur Stofflimitierung in tieferen Schichten kommt. Ebenso unerwartet führten höhere Abflüsse nicht zu vermehrtem hyporheischen Austausch. Es zeigte sich, dass durch die Begradigung des Fliessgewässers, der normalerweise auftretende Austausch an Gewässerbettformen, der mit zunehmenden Abfluss steigt, nicht relevant ist. Die hier vorgestellten Studien liefern empirische Beweise, dass auf beiden untersuchten Skalen anthropogene Veränderungen die Nitratdynamik im Fliessgewässer erheblich beeinflussen. Eingriffe in die Morphologie, Ufervegetation, Hydrologie und Wasserqualität verändern wesentliche Ökosystem-Funktionen, die relevant für den Stoffrückhalt in Flüssen und Bächen sind. Die präsentierten Ergebnisse zeigen dass sich anthropogen veränderte Systeme überraschend verhalten, wenn Vorhersagen auf Aktio-Reaktio-Korrelationen getroffen werden, die aus Beobachtungen in natürlichen Systemen abgeleitet wurden. Weltweit ist ein grosser Anteil der Flüsse und Bäche durch Menschen verändert. Solche beeinträchtigten Fliessgewässer sind jedoch nicht angemessen in Studien über Stoffdynamiken vertreten untersuchen. Effizientes Management solcher Fliessgewässer, ebenso wie die Beurteilung von Massnahmen um die Nitratlast auf die empfangenden Fliessgewässer zu reduzieren, benötigen quantitative Aussagen über Prozesse und vorherrschende Auslöser. Kontinuierliche wie auch zeitlich integrierende Beobachtungen sind repräsentativer als Schnappschuss-Aufnahmen. Die neuen Methoden erleichtern damit auch die Übertragung lokaler Messungen und die Einbindung der gewonnenen Daten in Einzugsgebiet Modelle. Die hier vorgestellten Ergebnisse zeigen des Weiteren, dass die Nitratdynamik in einem Fliessgewässer als Indikator für die Intaktheit des Ökosystems verwendet werden kann.

No description available.

Anaerobic digestion technologies have been utilized in Vietnam for more than 30 years with thousands of domestic small scale plants, mostly for agricultural and livestock wastes. For municipal solid waste (MSW) the development of biogas plants is far below the current high waste generation rates. The aim of this paper is to present the results of a feasibility assessment of implementing AD to treat the organic fraction of municipal solid waste (OFMSW) in Vietnam. For this purpose, an environmental analysis was performed comparing three treatment scenarios: two hypothetical AD technologies (a wet and a dry fermentation system) and the existing industrial composting facility at Nam Binh Duong Waste Treatment Complex in South Vietnam. This study sought for the technology to recover the most possible resources and energy from the OFMSW, and reduce greenhouse gas (GHG) emissions. The results were then combined with a policy review to support a holistic approach on the feasibility of these technologies in Vietnam. The outcome indicates that by implementing the dry AD system, up to 16.7 GWh of power and 14.4 GWh of heat energy can be generated annually and it can potentially save up to 5,400 Mg of CO2 equivalent per year, presenting the highest resource/energy benefits. The performance of the wet system and composting facility present some advantages particularly if there is a previous segregation of the organic material from the rest of the household wastes. Moreover, current reforms in Vietnam demonstrate the government’s interest in AD technologies, translated into the development of fiscal and financial revenues which incentivize participation from the public and private sector. Finally, these technologies are constantly under development and have the potential to be further improved, which gives hopes that waste treatment systems can be optimized to meet the waste and energy challenges of the future generations. / Phương pháp lên men kị khí đã được áp dụng tại Việt Nam từ hơn 30 năm nay với hàng nghìn các công trình nhỏ chủ yếu xử lý chất thải nông nghiệp và chăn nuôi. Sự phát triển hiện nay của các nhà máy sinh khí biogas còn quá ít cho xử lý lượng phát thải cao rác thải đô thị. Bài báo này trình bày các kết quả việc đánh giá tính khả thi khi áp dụng công nghệ lên men kị khí xử lý phần hữu cơ của chất thải rắn đô thị tại Việt Nam. Với mục đích này, phân tích môi trường được thực hiện để so sánh ba kịch bản xử lý: hai công nghệ lên men kị khí giả định (một cho công nghệ lên men ướt và một cho công nghệ lên men khô) và nhà máy hiện hữu lên men hiếu khí làm phân bón compost tại khu liên hợp xử lý chất thải Nam Bình Dương ở miền Nam Việt Nam. Nghiên cứu này tìm kiếm giải pháp công nghệ để thu hồi nhiều nhất có thể các tài nguyên và năng lượng từ rác thải đô thị và và giảm phát thải khí nhà kính. Các kết quả sau đó được kết hợp với đánh giá chính sách để hỗ trợ cách tiếp cận toàn diện về tính khả thi của các công nghệ này vào Việt Nam. Kết quả cho thấy áp dụng công nghệ lên men kị khí khô có thể tạo ra đến 16,7 GWh điện năng và 14,4 GWh nhiệt năng hàng năm và có khả năng làm giảm đến 8,000 Mg CO2 tương đương mỗi năm, thể hiện lợi ích cao nhất giữa tài nguyên và năng lượng. Hiệu suất của hệ thống lên men kị khí ướt và lên men hiếu khí thể hiện một số lợi thế đặc biệt khi nguyên liệu hữu cơ cho quá trình lên men được tiền phân loại ra khỏi hỗn hợp rác sinh hoạt. Hơn nữa, các đổi mới hiện nay ở Việt Nam thể hiện sự quan tâm của Chính phủ đến các công nghệ lên men kị khí, thể hiện qua sự tăng trưởng tài chính và doanh thu để khuyến khích sự tham gia của khu vực công và tư nhân. Chắc chắn rằng các công nghệ sẽ liên tục được phát triển và có khả năng được cải tiến tốt hơn, mang đến cho chúng ta những hy vọng rằng các hệ thống xử lý chất thải được tối ưu hóa để đáp ứng được các thách thức về chất thải và năng lượng của các thế hệ tương lai.

No description available.

No description available.

In order to improve the production of acarbose, the fermentation medium of acarbose-producing strain Actinoplanes sp. KCTC 9161 – L14 mutant was optimized in this internship. Fractional factorial design was employ to investigate the influences of glucose, maltose and corn power on acarbose production (by a-glucosidase inhibitory ability). Two significant factors: glucose and maltose have significant and positive effects on acarbose amount. In addition, a model was obtained from the regression results of fractional factorial experiment. Other success, we demonstrated that chromatography by active charcoal column can used to purify acarbose from fermentation broth. Acarbose amount in purification solution was 191.5 g/L and an acarbose - purification process was inducted. / Nhằm mục đích nâng cao khả năng sinh tổng hợp hoạt chất acarbose từ chủng đột biến Actinoplanes sp. KCTC 9161-L14, môi trường lên men của chủng dùng để sản xuất acarbose đã được tối ưu hóa. Một phần mềm thiết kế đã được thiết lập để khảo sát ảnh hưởng của glucose, maltose và bột ngô đến khả năng sản xuất acarbose (thông qua hoạt tính ức chế a-glucosidase). Kết quả đã cho thấy, hai yếu tố glucose và maltose có ý nghĩa quan trọng và ảnh hưởng trực tiếp đến khả năng sinh tổng hợp acarbose. Một phương trình đã được hình thành từ kết quả tối ưu. Bên cạnh đó, chúng tôi đã chứng minh được cột sắc ký sử dụng than hoạt tính có thể tinh sạch acarbose từ dịch lên men. Hàm lượng acarbose trong dung dịch tinh sạch đạt 191,5 g/l và một quy trình tinh sạch acarbose được đề xuất.

Research and application of microbial control of brown spot disease on the dragon fruit caused by fungi Neoscytalidium dimetiatum have important implications towards the safe and sustainable dragon fruit production. In this article, the research team has identified two strains of microorganisms capable of inhibiting fungi Neoscytalidium dimitiatum denoted A3, B7. Classification results determined that A3 belongs to Actinomyces group 3 with similarities of 100% (1500/1500 bp) with 16S rDNA segment of Streptomyces fradiae; B7 with similarities of 100% (1414/1414 bp) with 16S rDNA segment of bacteria Bacillus polyfermenticus and ensure biosafety when released into the environment. / Nghiên cứu ứng dụng vi sinh vật kiểm soát bệnh đốm nâu trên cây thanh long do nấm Neoscytalidium dimetiatum gây ra có ý nghĩa quan trọng hướng tới ngành sản xuất thanh long an toàn và bền vững. Trong bài viết này nhóm nghiên cứu đã xác định được hai chủng vi sinh vật có khả năng ức chế nấm Neoscytalidium dimitiatum cao kí hiệu là A3, B7. Kết quả phân loại xác định chủng A3 thuộc nhóm xạ khuẩn 3 tương đồng 100% (1500/1500 bp) với đoạn 16S rDNA của Streptomyces fradiae; chủng B7 tương đồng 100% (1414/1414 bp) với đoạn 16S của vi khuẩn Bacillus polyfermenticus và đảm bảo an toàn sinh học khi phóng thích ra môi trường.

In this study, we tested the long-term and negative effects of microcystin-producing cyanobacterium Microcystis aeruginosa from Vietnam on Daphnia magna under the laboratory conditions. The test organisms were fed with mixtures of green alga Scenedesmus armatus. and toxic M. aeruginosa at different ratios (10% Microcystis + 90% Scenedesmus, 50% Microcystis + 50% Scenedesmus, 100% Microcystis, and 100% Scenedesmus) for over a period of 21 days. The life history traits of the organisms such as, survival, maturation, fecundity were daily recorded. Besides, the intrinsic population rate of D. magna in each treatment was also calculated based on the survivorship, the reproductive age and the clutch size of the animals. The results showed that survival, maturation and reproduction of the D. magna fed with 10, 50 and 100% M. aeruginosa was impaired. Additionally, the intrinsic population rate of the exposed D. magna was lower than that of the control. This study evidenced the adverse effects of toxic M. aeruginosa on both the individual and intrinsic population levels of D. magna. To our knowledge, this is the first report on the chronically detrimental impacts of toxic M. aeruginosa isolated from Vietnam on D. magna and contributed the scientific information on the severe influences of toxic cyanobacteria world wide. / Trong bài viết này, chúng tôi nghiên cứu ảnh hưởng xấu mãn tính của loài vi khuẩn lam Microcystis aeruginosa có khả năng sản sinh độc tố microcysin từ Việt Nam lên Daphnia magna trong điều kiện phòng thí nghiệm. Sinh vật thí nghiệm được cho ăn với hỗn hợp tảo lục Scenedesmus armatus và M. aeruginosa có độc ở các tỷ lệ khác nhau (10% Microcystis + 90% Scenedesmus, 50% Microcystis + 50% Scenedesmus, 100% Microcystis, và 100% Scenedesmus) trong thời gian 21 ngày. Các đặc điểm vòng đời của sinh vật bao gồm sức sống, sự thành thục, sức sinh sản được theo dõi hàng ngày. Bên cạnh đó, tỷ lệ phát triển quần thể của D. magna trong từng lô thí nghiệm cũng được tính toán dựa vào sức sống, tuổi sinh sản và kích cỡ sinh sản của sinh vật. Kết quả cho thấy, sức sống, tuổi thành thục và sự sinh sản của D. magna cho ăn với 10, 50 và 100% M. aeruginosa bị ảnh hưởng xấu. Bên cạnh đó, tỷ lệ phát triển quần thể của D. magna trong lô phơi nhiễm thấp hơn so với đối chứng. Nghiên cứu này chứng minh ảnh hưởng xấu của M. aeruginosa có độc lên cả hai mức độ cá thể và quần thể của D. magna. Theo hiểu biết của chúng tôi, đây là báo cáo đầu tiên về ảnh hưởng xấu mãn tính của M. aeruginosa có độc phân lập từ Việt Nam lên D. magna and đóng góp thêm thông tin khoa học cho những ảnh hưởng nghiêm trọng của vi khuẩn lam có độc trên khắp thế giới.