Importance of Bacterial Maintenance Respiration in a Subarctic Estuary : a Proof of Concept from the Field

• Published in: Microbial Ecology
• Main Authors: Vikström, Kevin, Wikner, Johan
• Format: Article in Journal/Newspaper
• Language: English
• Published: Umeå universitet, Institutionen för ekologi, miljö och geovetenskap 2019
• Subjects: Marine; Bacteria; Maintenance; Respiration; Stoichiometry; Model; Ecology; Ekologi; Subarctic
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-152580; https://doi.org/10.1007/s00248-018-1244-7

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.