56 research outputs found

    Optofluidic lab-on-a-chip for rapid algae population screening

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    Abstract: The rapid identification of algae species is not only of practical importance when monitoring unwanted adverse effects such as eutrophication, but also when assessing the water quality of watersheds. Here, we demonstrate a lab-on-a-chip that functions as a compact robust tool for the fast screening, real-time monitoring, and initial classification of algae. The water-algae sample, flowing in a microfluidic channel, is sideilluminated by an integrated subsurface waveguide. The waveguide is curved to improve the device sensitivity. The changes in the transmitted optical signal are monitored using a quadrant-cell photo-detector. The signal-wavelets from the different quadrants are used to qualitatively distinguish different families of algae. The channel and waveguide are fabricated out of a monolithic fused-silica substrate using a femtosecond laser-writing process combined with chemical etching. This proof-ofconcept device paves the way for more elaborate femtosecond laser-based optofluidic micro-instruments incorporating waveguide networks designed for the real-time field analysis of cells and microorganisms

    The Cyanobacterial Hepatotoxin Microcystin Binds to Proteins and Increases the Fitness of Microcystis under Oxidative Stress Conditions

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    Microcystins are cyanobacterial toxins that represent a serious threat to drinking water and recreational lakes worldwide. Here, we show that microcystin fulfils an important function within cells of its natural producer Microcystis. The microcystin deficient mutant ΔmcyB showed significant changes in the accumulation of proteins, including several enzymes of the Calvin cycle, phycobiliproteins and two NADPH-dependent reductases. We have discovered that microcystin binds to a number of these proteins in vivo and that the binding is strongly enhanced under high light and oxidative stress conditions. The nature of this binding was studied using extracts of a microcystin-deficient mutant in vitro. The data obtained provided clear evidence for a covalent interaction of the toxin with cysteine residues of proteins. A detailed investigation of one of the binding partners, the large subunit of RubisCO showed a lower susceptibility to proteases in the presence of microcystin in the wild type. Finally, the mutant defective in microcystin production exhibited a clearly increased sensitivity under high light conditions and after hydrogen peroxide treatment. Taken together, our data suggest a protein-modulating role for microcystin within the producing cell, which represents a new addition to the catalogue of functions that have been discussed for microbial secondary metabolites

    The Interactive Effects of Ammonia and Microcystin on Life-History Traits of the Cladoceran Daphnia magna: Synergistic or Antagonistic?

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    The occurrence of Microcystis blooms is a worldwide concern that has caused numerous adverse effects on water quality and lake ecology. Elevated ammonia and microcystin concentrations co-occur during the degradation of Microcystis blooms and are toxic to aquatic organisms; we studied the relative and combined effects of these on the life history of the model organism Daphnia magna. Ammonia and microcystin-LR treatments were: 0, 0.366, 0.581 mg L−1 and 0, 10, 30, 100 µg L−1, respectively. Experiments followed a fully factorial design. Incubations were 14 d and recorded the following life-history traits: number of moults, time to first batch of eggs, time to first clutch, size at first batch of eggs, size at first clutch, number of clutches per female, number of offspring per clutch, and total offspring per female. Both ammonia and microcystin were detrimental to most life-history traits. Interactive effects of the toxins occurred for five traits: the time to first batch of eggs appearing in the brood pouch, time to first clutch, size at first clutch, number of clutches, and total offspring per female. The interactive effects of ammonia and microcystin appeared to be synergistic on some parameters (e.g., time to first eggs) and antagonistic on others (e.g., total offspring per female). In conclusion, the released toxins during the degradation of Microcystis blooms would result, according to our data, in substantially negative effect on D. magna

    Overvåking av Lyseren 2007

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    Årsliste 2007Spydeberg kommune, Hobøl vannvark BA og Lyseren/Hov vannver

    Tiltaksvurdering i Kolbotnvannet

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    I ”Tiltaksplan for VA 2006-2009” har Oppegård kommune planlagt et omfattende arbeid med å redusere tilførslene fra avløpsnettet, bl.a. med sikte på en bedring av vannkvaliteten i Kolbotnvannet. Et miljømål for Kolbotnvannet er en konsentrasjon av total-fosfor i overflatevannet på 15 mg/L. For at kommunen skulle få et best mulig grunnlag for å velge optimale løsninger for sine tiltak, ble NIVA spurt om å utføre modellberegninger for ulike typer tiltak og forventet effekt av disse. Modellen som er brukt, CE-QUAL-W2, er en 2-dimensjonal (lengde-dyp) modell som er godt egnet til eutrofieringsstudier. Den er kalibrert for Kolbotnvannet ut fra eksisterende overvåkingsdata, og kalibreringen gav et godt bilde av både tilstand og de dominerende prosessene i innsjøen. Etter kalibreringen produserte vi scenarier for effekten på innsjøen av 4 utvalgte eksterne og interne tiltak. For optimal effekt, både i forhold til fosforkonsentrasjon og økologisk tilstand, viser modelleringen at en kombinasjon av reduksjon i eksterne tilførsler og tilsetning av oksygen til bunnvannet å være den løsningen som samsvarer best med det uttalte miljømålet til Kolbotnvannet. Tiltakene forutsetter en nøye oppfølging, for å optimalisere og justere drift av evt. anlegg ut fra obserberte effekter