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Importance of Bacterial Maintenance Respiration in a Subarctic Estuary: a Proof of Concept from the Field
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, Department of Ecology and Environmental Sciences. (UMFpub; EcoChange)
2019 (English)In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 77, no 3, p. 574-586Article in journal (Refereed) Published
Abstract [en]

Bacterial respiration contributes to atmospheric carbon dioxide accumulation and development of hypoxia and is a critical, often overlooked, component of ecosystem function. This study investigates the concept that maintenance respiration is a significant proportion of bacterial respiration at natural nutrient levels in the field, advancing our understanding of bacterial living conditions and energy strategies. Two river-sea transects of respiration and specific growth rates were analyzed representing low- and highproductivity conditions (by in situ bacterial biomass production) in a subarctic estuary, using an established ecophysiological linear model (the Pirt model) estimating maintenance respiration. The Pirt model was applicable to field conditions during high, but not low, bacterial biomass production. However, a quadratic model provided a better fit to observed data, accounting for the maintained respiration at low μ. A first estimate of maintenance respiration was 0.58 fmol O2 day−1 cell−1 by the quadratic model. Twenty percent to nearly all of the bacterial respiration was due to maintenance respiration over the observed range of μ (0.21– 0.002 day−1 ). In the less productive condition, bacterial specific respiration was high and without dependence on μ, suggesting enhanced bacterial energy expenditure during starvation. Annual maintenance respiration accounted for 58% of the total bacterioplankton respiration based on μ from monitoring data. Phosphorus availability occasionally, but inconsistently, explained some of the remaining variation in bacterial specific respiration. Bacterial maintenance respiration can constitute a large share of pelagic respiration and merit further study to understand bacterial energetics and oxygen dynamics in the aquatic environment.

Place, publisher, year, edition, pages
Springer, 2019. Vol. 77, no 3, p. 574-586
Keywords [en]
Marine, Bacteria, Maintenance, Respiration, Stoichiometry, Model
National Category
Ecology
Identifiers
URN: urn:nbn:se:umu:diva-152580DOI: 10.1007/s00248-018-1244-7ISI: 000464747100002Scopus ID: 2-s2.0-850526177522-s2.0-85052617752OAI: oai:DiVA.org:umu-152580DiVA, id: diva2:1255801
Available from: 2018-10-15 Created: 2018-10-15 Last updated: 2019-06-13Bibliographically approved
In thesis
1. Importance of bacterial maintenance respiration and baseline respiration for development of coastal hypoxia
Open this publication in new window or tab >>Importance of bacterial maintenance respiration and baseline respiration for development of coastal hypoxia
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2018. p. 40
Keywords
Ecology, Respiration, Estuarine, Allochthonous, Maintenance, primary production, bacterial production
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-152587 (URN)978-91-7601-927-6 (ISBN)
Public defence
2018-11-09, N440, Naturvetarhuset, Umeå, 09:00 (English)
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Supervisors
Available from: 2018-10-19 Created: 2018-10-15 Last updated: 2019-03-19Bibliographically approved

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Vikström, KevinWikner, Johan

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