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

Abstract

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 high-productivity 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 O day cell 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). 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.

Prokaryotic maintenance respiration and growth efficiency field patterns reproduced by temperature and nutrient control at mesocosm scale

“…The influence of ρ m in the control is probably underestimated. The pattern of ρ versus μ indicates a higher share of ρ m during winter conditions (Figure 3B), matching observed field value in April (1.8 fmol O 2 cell À1 d À1 , ±0.45 95% CI) (Vikström & Wikner, 2019).…”

“…The prokaryotic respiration rate estimates (PR) were determined by measuring oxygen in prefiltered samples (1.2 μm) with optodes during incubations as described earlier (Vikström & Wikner, 2019;Wikner et al, 2013) using an incubator box based on the Peltier element technique (±0.1 C). Four slots of the incubator box were set at 1 C, while the remaining four were set at 10 C. Briefly, 1 dm 3 sample bottles filled with <1.2 μm filtered seawater samples with a magnetic stirrer and optode stopper were inserted in the slot of the incubator box.…”

“…The addition of nutrients was used to simulate increased nutrient supply from protozoan and zooplankton excretion and sloppy feeding during late summer. We hypothesized that the winter conditions should lead to low μ and thus high ρ m , while late summer conditions would provide low ρ m at high μ. ρ m was assumed to be described by the established relationship between ρ and μ (Vikström & Wikner, 2019). The overarching aim of this study was thus to experimentally reproduce, at the mesocosm scale, patterns of ρ observed in the field, enabling controlled investigation of ρ m and its influence on PGE.…”

Response of Coastal Shewanella and Duganella Bacteria to Planktonic and Terrestrial Food Substrates

“…Earlier studies have shown that the BGE correlates positively with the bacterial growth rates and the net primary productivity in the ecosystem ( del Giorgio and Cole, 1998 ; Alonso-Sáez et al, 2008 ). When the bacterial production decreases, a larger proportion of the consumed carbon is allocated for maintenance energy and the growth efficiency decreases ( del Giorgio and Cole, 1998 ; Eiler et al, 2003 ; Vikström and Wikner, 2019 ). Thus, a larger fraction of the consumed carbon would be respired, and a smaller fraction used for building new biomass.…”

Regulation of Bacterial Metabolic Activities and Community Composition by Temperature in a Fringing Coral Reef

“…Fluctuations in BP or BR might cause a large variation in BGE. The maintenance respiration of bacterial cells makes up more than half of the bulk BR (Vikström & Wikner, 2019) and varies in a wide range with environmental variability (Carlson et al., 2007). Consequently, seasonal variability in BGE was more complicated than expected.…”