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Improved accuracy of optode‐based oxygen consumption measurements by removal of system drift and nonlinear derivation
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
(EcoChange; UMFpub)
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). (EcoChange; UMFpub)
2019 (engelsk)Inngår i: Limnology and Oceanography: Methods, E-ISSN 1541-5856, Vol. 17, nr 3, s. 179-189Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This method evaluation aimed to improve the accuracy and precision of the previously published method to measure oxygen consumption using optodes with integrated temperature and salinity correction in dark incubations. Significant short‐term system drift currently requires a correction to remove the drift, thus reducing the precision of the oxygen consumption rates. Frequent nonlinear declines in oxygen concentration with time also call for improved data analysis and identification of its origin. Optodes in titanium casings (Aanderaa™ model 4330) with low oxygen binding properties showed no significant system drift in autoclaved seawater. Nonlinear oxygen dynamics fitting a quadratic polynomial occurred in 28% of 230 field samples, independent of season and water depth. Polynomial curve fit resulted in 64% higher respiration rates when derived within 1 h of the quality assured incubation, than obtained when using linear fit. Carbon substrate limitation explained the nonlinearity of oxygen decline during dark incubations. Pretreatment of the optode attached to stoppers with 0.3 mol dm−3 hydrochloric acid resulted in the most stable performance of the sensor and simultaneously provided proper cleaning of the equipment. A conservative detection limit of 0.97 μmol O2 dm−3 d−1 was calculated for the titanium optodes, matching other methods for oxygen consumption reported in the literature. Thus, we recommend the use of model 4330 optode pretreated with HCl and the derivation of initial respiration rates by a quadratic polynomial function for best accuracy and precision of oxygen consumption in oxygenated surface waters.

sted, utgiver, år, opplag, sider
John Wiley & Sons, 2019. Vol. 17, nr 3, s. 179-189
HSV kategori
Identifikatorer
URN: urn:nbn:se:umu:diva-152581DOI: 10.1002/lom3.10297ISI: 000461209600001Scopus ID: 2-s2.0-85058957567OAI: oai:DiVA.org:umu-152581DiVA, id: diva2:1255803
Forskningsfinansiär
Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGEThe Kempe Foundations, JCK‐1716
Merknad

Originally included in thesis in manuscript form with title "Improved accuracy of optode-based oxygen consumption measurements by removal of system drift and non-linear derivation".

Tilgjengelig fra: 2018-10-15 Laget: 2018-10-15 Sist oppdatert: 2023-02-03bibliografisk kontrollert
Inngår i avhandling
1. Importance of bacterial maintenance respiration and baseline respiration for development of coastal hypoxia
Åpne denne publikasjonen i ny fane eller vindu >>Importance of bacterial maintenance respiration and baseline respiration for development of coastal hypoxia
2018 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Reduced oxygen concentrations and increasing hypoxic zones havebecome more common in the sea due to climate change andeutrophication. The main cause of oxygen loss in oxygenatedenvironments is respiration. Respiration rates can be estimated usingoptode methodologies which utilize dynamic luminescence quenching toestimate the oxygen concentration declines in dark incubations. Apublished optode methodology was improved by using optodes withtitanium housing instead of plastic housing plausibly trapping oxygen.Drift was highly reduced by the titanium casings leading to a higherprecision and lower detection limit of 0.97 mmol O2 m-3 d-1. 28% ofmeasurements were shown to have non-linear oxygen concentrationdeclines. The rate of oxygen change was derived with a 2nd degreepolynomial at 1 hour from the incubation start. The majority of non-lineardeclines were concave and due to carbon substrate limitation. Analyzingnon-linear trends linearly, a common practice, leads to anunderestimation of respiration by up to 64%.

Bacterial maintenance respiration (Rm) was studied using anecophysiological model unverified in natural environments. The modelwas applicable at high productivities but a quadratic model wasdemonstrated to give a better fit. Rm was found to represent a significantpart in the sub-arctic estuary contributing to 58% of the annual specificbacterial respiration. Therefore, Rm may be more important in nature thanpreviously recognized. The ecophysiological model is driven solely by thebacterial specific growth rate (μ) where the relative influence of Rm iselevated as μ decreases. As a consequence, I hypothesize that a reductionin nutrients may not decrease the oxygen consumption but rather shiftbacterial growth based respiration to Rm as μ approaches zero.Baseline respiration (Rbl), defined as ecosystem respiration disconnectedfrom contemporary primary produced carbon, was also studied. Rbl wasshown to be largely supplied by allochthonous carbon in a coastalecosystem and had a contribution of 50% to the annual planktoncommunity respiration in the sub-arctic estuary studied. I claim that Rbland Rm are crucial to include for understanding and managingdevelopment of aquatic hypoxia in an effective and economic manner.

sted, utgiver, år, opplag, sider
Umeå: Umeå Universitet, 2018. s. 40
Emneord
Ecology, Respiration, Estuarine, Allochthonous, Maintenance, primary production, bacterial production
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-152587 (URN)978-91-7601-927-6 (ISBN)
Disputas
2018-11-09, N440, Naturvetarhuset, Umeå, 09:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2018-10-19 Laget: 2018-10-15 Sist oppdatert: 2019-03-19bibliografisk kontrollert

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