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Precise continuous measurements of pelagic respiration in coastal waters with Oxygen Optodes
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). (Johan Wikner ; EcoChange)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (UMFpub)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
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2013 (English)In: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, Vol. 11, 1-15 p.Article in journal (Refereed) Published
Abstract [en]

An analytical setup for respiration rate measurements was developed and evaluated in pelagic water samples using a commercially available optical oxygen sensor (Optode (TM)). This setup required the development of a gas tight stopper to connect the sensors to a 1 dm(3) glass sample bottle, precise temperature control (+/- 0.05 degrees C), and proper stirring of samples. The detection limit and precision of the method was 0.3 mmol O-2 m(-3) d(-1). This was similar to the detection limit for the high-precision Winkler titration method reported in field studies. When compared with the Winkler method, the Optode sensor enabled operator-independent, high temporal resolution measurement of respiration, better coverage of plankton groups and detection of non-linear oxygen decline, without the need for wet chemistry. Respiration rates measured by the Optodes showed good accuracy when compared with measurements made with the Winkler titration method (3% deviation), followed the expected temperature response (Q(10) = 3.0), were correlated with chlorophyll a and were congruent with earlier reported values in the literature. The main source of uncertainty was a necessary correction for system drift during the incubation period, due to oxygen release from the plastic components. Additionally, less stringent temperature control on board research vessels during rough seas reduced the precision. We conclude that the developed Optode system can be used to measure respiration in productive coastal waters. Samples from cold or deep waters were, however, often below the detection limit.

Place, publisher, year, edition, pages
Association for the Sciences of Limnology and Oceanography , 2013. Vol. 11, 1-15 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:umu:diva-62731DOI: 10.4319/lom.2013.11.1ISI: 000317920600001OAI: oai:DiVA.org:umu-62731DiVA: diva2:577723
Available from: 2012-12-16 Created: 2012-12-16 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Coastal microbial respiration in a climate change perspective
Open this publication in new window or tab >>Coastal microbial respiration in a climate change perspective
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In a climate change perspective increased precipitation and temperature are expected which should influence the coastal microbial food web. Precipitation will have a strong impact on river flow and thereby increase the carbon input to the coastal zone as well as lowering the marine salinity by dilution with freshwater. Simultaneously temperature may increase by 2-5 °C, potentially influencing e.g. metabolic processes. Consequences of this have been evaluated in this thesis with focus on microbial respiration in paper II and IV. A temperature increase of 3 °C will have a marked effect on microbial respiration rates in the coastal zone. The effect of temperature on microbial respiration showed a median Q10 value of 25 with markedly higher values during winter conditions (around 0°C). These Q10 values are several-fold higher than found in oceanic environments. The conclusion was in accordance with a consistent temperature limitation of microbial respiration during an annual field study, however, shifting to DOC limitation at the elevated temperature. Neither bacterial production nor phytoplankton production showed a consistent temperature effect, suggesting that the biomass production at the base of the food web is less sensitive to a temperature increase. Results from both a field study and a fully factorial microcosm experiment supported the conclusion. Our results suggested that areas dealing with hypoxia today will most likely expand in the future, due to increased respiration caused by higher temperatures and larger riverine output of dissolved organic carbon. 

Pelagic respiration measurements in the sea are relatively scarce in the literature, mainly due to the lack of sufficiently good and user friendly techniques. New methods such as the dynamic luminescence quenching technique for oxygen concentration have been developed. This makes it possible to obtain continuous measurements of oxygen in an enclosed vial. Two different commercially available systems based on the dynamic luminescence quenching technique were evaluated from the aspect of precision, accuracy and detection limit when applied to respiration measurements in natural pelagic samples. The Optode setup in paper III showed a practical detection limit of 0.30 mmol m-3 d-1, which can be applied to measure respiration in productive coastal waters (used in paper IV). This included development of a stopper where the sensor was attached, stringent temperature control, proper stirring and compensation for an observed system drift. For controlled laboratory experiments with organisms smaller than 1 µm the Sensor Dish Reader (paper I) has sufficient detection limit of (4.8 mmol m-3 d-1). This required a stringent temperature control and manual temperature correction. The Sensor Dish Reader gives the opportunity to perform multiple treatments at low cost (used in paper II), but the precision is too low for field studies due to the between ampule variation.

Abstract [sv]

Östersjön är ett brackvatten hav som sträcker sig från Bottenviken i norr till de danska sunden i söder och omsluts av en landmassa som representeras av nio länder. Denna miljö är på många sett unik genom stor sötvattenpåverkan och litet utbyte med världshaven (30 års omsättningstid). Östersjön utsätts framförallt för tillförsel av ämnen från såväl naturliga som antropogena aktiviteter. Något som ofta uppmärksammas är problem med syrefria områden och döda havsbottnar. Detta anses påverkas av både klimatförändringar och övergödning. En av de biologiska prosesser som påverkar syresituationen i haven är respiration, syreförbrukning, som utförs av de flesta levande organismerna i Östersjön. Den här avhandlingen presenterar resultat på hur bakteriers syreförbrukning påverkas av de förändringar vi förväntar oss i vårt klimat i framtiden. Det är framförallt ökad temperatur och ökat vattenflöde i våra floder som i sin tur leder till snabbare omsättning och tillförsel av näring åt bakteriesamhället. Resultaten från artiklarna II och IV visar att den potentiella temperaturökningen som väntas skulle öka syreförbrukningen i kustnära områden. Den blir extra stor i kustområden, troligen på grund av stor tillgång på organiskt material från älvarna. Även den högre tillförseln av näringsämnen kan ökan syreförbrukningen enligt artikel II. De områden som idag är syrefattiga kommer på grund av detta att expandera, framförallt längs kusterna där nya områden kan uppstå. Eventuellt kan det vara en förklaring till den ökande ytan av syrefria bottnar i i Östersjön och världshaven.

För att kunna utföra mätningar av syreförbrukning krävs väldigt precisa och gärna användarvänliga metoder som lätt kan tillämpas i fält. I avhandlingen presenteras hur två olika mätmetoder optimeras för att göra tillförlitliga förbrukningsmätningar av syre. Ny teknik gör att syrehalten kan mätas med en ljusbaserad metod som skiljer sig från dagens kemiska bl.a. genom att resultaten kan följas löpande på en dator. De båda metoderna kräver en väldigt precis temperaturkontroll. Optod uppsättningen presenterad i artikel III innefattaer en volym på 1 liter och organismer upp till en storlek på 50 μm omfattas i den uppmäta syreföbrukningen. Denna metod rekommenderas fö fätmäningar, och anvädes föfätmäningar i Artikel IV. I utvecklingen ingick utformning av en kork fö att montera optod-sensorn i. I artikel I presenteras en utrustning som baseras påen mindre volym (5 ml) vilket innebä att endast mäningar påbakterier och organismer mindre ä 1 μm kan anses tillfölitliga. Detta i kombination med viss variation mellan mäflaskor gö att den framföallt rekomenderas fö anvädning i laboratoriemiljö Det systemet anvädes fö mäningarna av syreföbrukning i laboratorieexperimentet som presenteras i artikel II.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2012. 18 p.
National Category
Ecology
Research subject
biology
Identifiers
urn:nbn:se:umu:diva-62734 (URN)978-91-7459-517-8 (ISBN)
Public defence
2013-01-24, KBC-huset, KB3A9, Umeå Universitet, Umeå, 13:00 (English)
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Available from: 2012-12-20 Created: 2012-12-16 Last updated: 2017-09-01Bibliographically approved

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Wikner, JohanPanigrahi, SatyaNydahl, AnnaLundberg, ErikBåmstedt, Ulf
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