Summer depth distribution profiles of dissolved CO2 and O2 in shallow temperate lakes reveal trophic state and lake type specific differences

Laas, Alo; Cremona, Fabien; Meinson, Pille; Rõõm, Eva-Ingrid; Nõges, Tiina; Nõges, Peeter

doi:10.1016/j.scitotenv.2016.05.038

Cited by 17 publications

(15 citation statements)

References 39 publications

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“…Polymictic lakes undergo mixing more than twice a year [26] and take a position between the daily recurring stratified-mixing lakes and the dimictic lakes. In polymictic lakes, stratification may last for hours [30], days [28,31], weeks [32] or months [32]. Polymictic lakes may therefore share some of the features described here, though being less prominent.…”

Section: Discussionmentioning

confidence: 68%

Extreme diel dissolved oxygen and carbon cycles in shallow vegetated lakes

2017

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A common perception in limnology is that shallow lakes are homogeneously mixed owing to their small water volume. However, this perception is largely gained by downscaling knowledge from large lakes to their smaller counterparts. Here we show that shallow vegetated lakes (less than 0.6 m), in fact, undergo recurring daytime stratification and nocturnal mixing accompanied by extreme chemical variations during summer. Dense submerged vegetation effectively attenuates light and turbulence generating separation between warm surface waters and much colder bottom waters. Photosynthesis in surface waters produces oxygen accumulation and CO depletion, whereas respiration in dark bottom waters causes anoxia and CO accumulation. High daytime pH in surface waters promotes precipitation of CaCO which is re-dissolved in bottom waters. Nocturnal convective mixing re-introduces oxygen into bottom waters for aerobic respiration and regenerated inorganic carbon into surface waters, which supports intense photosynthesis. Our results reconfigure the basic understanding of local environmental gradients in shallow lakes, one of the most abundant freshwater habitats globally.

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Section: Discussionmentioning

confidence: 68%

Extreme diel dissolved oxygen and carbon cycles in shallow vegetated lakes

2017

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“…For instance, one study of 52 lakes in Quebec, Canada identified mean bacterioplankton RQ values of 0.81 in net autotrophic (P:R > 1) lakes vs. 1.35 in net heterotrophic (P:R < 1) lakes (Berggren et al 2012). Errors are propagated by estimating carbon dynamics using dissolved O 2 measurements, especially in lakes where the saturation of O 2 and CO 2 may be poorly coupled (Laas et al 2016; Peeters et al 2016). For instance, in highly alkaline lakes (i.e., >1 meq L −1 ) calcite precipitation can surpass aquatic metabolism as a dominant driver of lake carbon dynamics (Laas et al 2016; Khan et al 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Errors are propagated by estimating carbon dynamics using dissolved O 2 measurements, especially in lakes where the saturation of O 2 and CO 2 may be poorly coupled (Laas et al 2016; Peeters et al 2016). For instance, in highly alkaline lakes (i.e., >1 meq L −1 ) calcite precipitation can surpass aquatic metabolism as a dominant driver of lake carbon dynamics (Laas et al 2016; Khan et al 2020). This problem is resolved by simultaneously measuring O 2 and CO 2 in lakes (Laas et al 2016; Vachon et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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Shoring up the foundations of production to respiration ratios in lakes

Vadeboncoeur

2021

Limnology & Oceanography

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The ratio of primary production to ecosystem respiration rates (P:R ratio) is an ostensibly simple calculation that is used to characterize lake function, including trophic status, the incorporation of terrestrial organic carbon into lacustrian food webs, and the direction of carbon dioxide (CO 2 ) flux between a lake and the atmosphere. However, many predictive links between P:R ratios and lake ecosystem function stem from a historically plankton-centric perspective and the common use of the diel oxygen curve approach. We review the evolution of the use of P:R ratios and examine common assumptions underlying their application to (1) eutrophication, (2) carbon flux through lake food webs, and (3) the role of lakes in the global carbon budget. Foundational P:R studies have been complicated principally by the following: most P:R ratios were calculated from mid-lake measurements and failed to incorporate nonplanktonic dynamics; there has been confusion regarding the food web implications when P:R ≠ 1; and CO 2 fluxes between lakes and the atmosphere are influenced by nonmetabolic processes. We argue for a re-assessment, or shoring up, of several fundamental assumptions that continue to guide metabolism research in lakes by accounting for mixing, benthic-littoral processes, groundwater fluxes, and abiotic controls on gas dynamics to better understand lake food webs and accurately integrate lake ecosystems into landscape-scale carbon cycling models.

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“…Bevelhimer et al [20] quantified GHG emissions from six hydropower reservoirs in the southwestern United States via selected emission mechanisms, namely diffusive emissions, ebullition, and tailwater degassing, and found diffusive emissions to be dominant. Under increased rainfall, flooding may transport large amounts of organic matter into the artificial reservoir from the upper watershed; this organic matter is accumulated in the lake and decomposed to emit final products such as gaseous CO 2 and CH 4 , which maintain the CO 2 supersaturation in the hypolimnion [21,22].…”

Section: Introductionmentioning

confidence: 99%

pCO2 Dynamics of Stratified Reservoir in Temperate Zone and CO2 Pulse Emissions During Turnover Events

Park

Chung

2018

Water

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This study explores the dynamic changes in the partial pressure of CO2 (pCO2) with depth, and the temporal variations of CO2 net atmospheric flux (NAF) in a stratified reservoir. A total of 16 field campaigns were conducted from the summer stratification to fall turnover period in 2017. A random forest (RF) model was developed to estimate the pCO2 using concurrently measured water quality variables. The results showed that the vertical distribution of pCO2 and associated temporal variations of the NAF are closely related to the stratification strength of the reservoir. The reservoir surface pCO2 was supersaturated (1542 µatm) in summer (July 11), but this decreased to undersaturation as algae grew. Meanwhile, dissolved CO2 continuously accumulated below the reservoir mixed-layer due to the thermal stratification barrier and organic-rich floodwater intrusion. Vertical mixing began instantly as the stratification strength began to weaken in mid-October, and the surface pCO2 increased sharply up to 1934 µatm. Consequently, the NAF drastically increased to 3235 mg−CO2 m−2·day−1, which implies that the NAF changes seasonally and large CO2 pulsing occurs during the turnover events. The results provide valuable information about pCO2 variability and physical mixing processes, as well as carbon budget estimation in stratified reservoirs, and offer an improved understanding of these phenomena.

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Summer depth distribution profiles of dissolved CO2 and O2 in shallow temperate lakes reveal trophic state and lake type specific differences

Cited by 17 publications

References 39 publications

Extreme diel dissolved oxygen and carbon cycles in shallow vegetated lakes

Extreme diel dissolved oxygen and carbon cycles in shallow vegetated lakes

Shoring up the foundations of production to respiration ratios in lakes

pCO2 Dynamics of Stratified Reservoir in Temperate Zone and CO2 Pulse Emissions During Turnover Events

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