Browse
Submit Data
Databases
API
Help

Dataset Information

23 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Turbulence in a small boreal lake: Consequences for air-water gas exchange.

ABSTRACT: The hydrodynamics within small boreal lakes have rarely been studied, yet knowing whether turbulence at the air-water interface and in the water column scales with metrics developed elsewhere is essential for computing metabolism and fluxes of climate-forcing trace gases. We instrumented a humic, 4.7 ha, boreal lake with two meteorological stations, three thermistor arrays, an infrared (IR) camera to quantify surface divergence, obtained turbulence as dissipation rate of turbulent kinetic energy (ε) using an acoustic Doppler velocimeter and a temperature-gradient microstructure profiler, and conducted chamber measurements for short periods to obtain fluxes and gas transfer velocities (k). Near-surface ε varied from 10^-8 to 10^-6 m² s^-3 for the 0-4 m s^-1 winds and followed predictions from Monin-Obukhov similarity theory. The coefficient of eddy diffusivity in the mixed layer was up to 10^-3 m² s^-1 on the windiest afternoons, an order of magnitude less other afternoons, and near molecular at deeper depths. The upper thermocline upwelled when Lake numbers (L _N ) dropped below four facilitating vertical and horizontal exchange. k computed from a surface renewal model using ε agreed with values from chambers and surface divergence and increased linearly with wind speed. Diurnal thermoclines formed on sunny days when winds were < 3 m s^-1, a condition that can lead to elevated near-surface ε and k. Results extend scaling approaches developed in the laboratory and for larger water bodies, illustrate turbulence and k are greater than expected in small wind-sheltered lakes, and provide new equations to quantify fluxes.

SUBMITTER: MacIntyre S

PROVIDER: S-EPMC8048862 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Unraveling the Contribution of Turbulence and Bubbles to Air-Water Gas Exchange in Running Waters.

Project description:Quantifying air-water gas exchange is critical for estimating greenhouse gas fluxes and metabolism in aquatic ecosystems. In high-energy streams, the gas exchange rate k is poorly constrained, due to an incomplete understanding of turbulence and bubble contributions to k. We performed a flume experiment with air bubble additions to evaluate the combined effects of turbulence and bubbles on k for helium, argon, xenon, and methane. We created contrasting hydraulic conditions by varying channel slope, bed roughness, water discharge, and bubble flux. We found that k increased from 1-4 to 17-66 m d-1 with increases in turbulence and bubble flux metrics. Mechanistic models that explicitly account for these metrics, as well as gas diffusivity and solubility, agreed well with the data and indicated that bubble-mediated gas exchange accounted for 64-93% of k. Bubble contributions increased with bubble flux but were independent of gas type, as bubbles did not equilibrate with the water. This was evident through modeled bubble life and equilibration times inferred from bubble size distributions obtained from underwater sound spectra. Sound spectral properties correlated well with turbulence and bubble flux metrics. Our results demonstrate that (a) mechanistic models can be applied to separate free surface- and bubble-mediated gas exchange in running waters, (b) bubble life and equilibration times are critical for accurate scaling of k between different gases, and (c) ambient sound spectra can be used to approximate contributions of turbulence and bubbles.

| S-EPMC9285787 | biostudies-literature

A Comparison of Air Insufflation, Water Immersion and Water Exchange Colonoscopy in CRC Screening

Project description:Water-aided method for colonoscopy can be broadly subdivided into two major categories. Water Immersion (WI), characterized by suction removal of the infused water predominantly during the withdrawal phase of colonoscopy, and Water Exchange (WE), characterized by suction removal of infused water predominantly during the insertion phase of colonoscopy. Several studies showed that WE significantly reduces pain compared to WI and colonoscopy with traditional air insufflation (AI), increases the number of unsedated procedures and adenoma detection rate (ADR), in particular proximal ADR. This randomized controlled trial will be a direct comparison of Air Insufflation, Water Immersion and Water Exchange to test the hypothesis that WAC (particularly WE) would significantly decrease pain score during colonoscopy in average-risk screening patients. Several other secondary outcomes will also be analyzed.

| 2139246 | ecrin-mdr-crc

A Comparison of Air Insufflation, Water Immersion and Water Exchange Colonoscopy in Diagnostic Patients

Project description:Water-aided method for colonoscopy can be broadly subdivided into two major categories. Water Immersion (WI), characterized by suction removal of the infused water predominantly during the withdrawal phase of colonoscopy, and Water Exchange (WE), characterized by suction removal of infused water predominantly during the insertion phase of colonoscopy. Several studies showed that WE significantly reduces pain compared to WI and colonoscopy with traditional air insufflation (AI), increases the number of unsedated procedures and adenoma detection rate (ADR), in particular proximal ADR. This randomized controlled trial will be a direct comparison of Air Insufflation, Water Immersion and Water Exchange to test the hypothesis that WAC (particularly WE) would significantly decrease pain score during colonoscopy in diagnostic patients. Several other secondary outcomes will also be analyzed.

| 2139310 | ecrin-mdr-crc

Air-water PCB fluxes from southwestern Lake Michigan revisited.

Project description:From simultaneous air and water polychlorinated biphenyl (PCB) measurements collected in September 2010, we re-evaluated the direction and magnitude of net air-water exchange of PCBs in southwest Lake Michigan and compared them with estimations made using similar approaches 15 years prior. Air and water samples were collected during a research expedition on Lake Michigan at 5 km off the coast of Chicago, with prevailing winds from the southwest of our location. Gas-phase ΣPCB concentrations ranged from 190 to 1100 pg m-3 with a median of 770 pg m-3, which is similar to the concentrations measured in the City of Chicago at the same time and similar to concentrations measured in this part of the lake over the last 20 years. Water dissolved-phase ΣPCB concentrations ranged from 150 to 170 pg L-1 with a median of 160 pg L-1, which is one-tenth of that measured in the 1990s. ƩPCB net fluxes showed a slightly absorptive behavior, with a median of (-) 21 ng m-2 day-1 and an interquartile range of (-) 47 to (+) 5 ng m-2 day-1, where (-) and (+) fluxes indicate absorption and volatilization, respectively. Airborne PCB concentrations were higher when the winds were coming from Chicago and drive the deposition. Our fluxes are not significantly different from estimations from 1994 and 1995 and suggest that absorption of PCBs into the waters is slightly more prevalent than 15 years ago. It was confirmed that Chicago remains an important atmospheric source of PCBs to Lake Michigan.

| S-EPMC6834886 | biostudies-literature

Vertical stratification of bacteria and archaea in sediments of a small boreal humic lake.

Project description:Although sediments of small boreal humic lakes are important carbon stores and greenhouse gas sources, the composition and structuring mechanisms of their microbial communities have remained understudied. We analyzed the vertical profiles of microbial biomass indicators (PLFAs, DNA and RNA) and the bacterial and archaeal community composition (sequencing of 16S rRNA gene amplicons and qPCR of mcrA) in sediment cores collected from a typical small boreal lake. While microbial biomass decreased with sediment depth, viable microbes (RNA and PLFA) were present all through the profiles. The vertical stratification patterns of the bacterial and archaeal communities resembled those in marine sediments with well-characterized groups (e.g. Methanomicrobia, Proteobacteria, Cyanobacteria, Bacteroidetes) dominating in the surface sediment and being replaced by poorly-known groups (e.g. Bathyarchaeota, Aminicenantes and Caldiserica) in the deeper layers. The results also suggested that, similar to marine systems, the deep bacterial and archaeal communities were predominantly assembled by selective survival of taxa able to persist in the low energy conditions. Methanotrophs were rare, further corroborating the role of these methanogen-rich sediments as important methane emitters. Based on their taxonomy, the deep-dwelling groups were putatively organo-heterotrophic, organo-autotrophic and/or acetogenic and thus may contribute to changes in the lake sediment carbon storage.

| S-EPMC6476745 | biostudies-literature

Land Use Affects Carbon Sources to the Pelagic Food Web in a Small Boreal Lake.

Project description:Small humic forest lakes often have high contributions of methane-derived carbon in their food webs but little is known about the temporal stability of this carbon pathway and how it responds to environmental changes on longer time scales. We reconstructed past variations in the contribution of methanogenic carbon in the pelagic food web of a small boreal lake in Finland by analyzing the stable carbon isotopic composition (?13C values) of chitinous fossils of planktivorous invertebrates in sediments from the lake. The ?13C values of zooplankton remains show several marked shifts (approx. 10 ‰), consistent with changes in the proportional contribution of carbon from methane-oxidizing bacteria in zooplankton diets. The results indicate that the lake only recently (1950s) obtained its present state with a high contribution of methanogenic carbon to the pelagic food web. A comparison with historical and palaeobotanical evidence indicates that this most recent shift coincided with agricultural land-use changes and forestation of the lake catchment and implies that earlier shifts may also have been related to changes in forest and land use. Our study demonstrates the sensitivity of the carbon cycle in small forest lakes to external forcing and that the effects of past changes in local land use on lacustrine carbon cycling have to be taken into account when defining environmental and ecological reference conditions in boreal headwater lakes.

| S-EPMC4972442 | biostudies-literature

Invasive floating macrophytes reduce greenhouse gas emissions from a small tropical lake.

Project description:Floating macrophytes, including water hyacinth (Eichhornia crassipes), are dominant invasive organisms in tropical aquatic systems, and they may play an important role in modifying the gas exchange between water and the atmosphere. However, these systems are underrepresented in global datasets of greenhouse gas (GHG) emissions. This study investigated the carbon (C) turnover and GHG emissions from a small (0.6 km(2)) water-harvesting lake in South India and analysed the effect of floating macrophytes on these emissions. We measured carbon dioxide (CO2) and methane (CH4) emissions with gas chambers in the field as well as water C mineralization rates and physicochemical variables in both the open water and in water within stands of water hyacinths. The CO2 and CH4 emissions from areas covered by water hyacinths were reduced by 57% compared with that of open water. However, the C mineralization rates were not significantly different in the water between the two areas. We conclude that the increased invasion of water hyacinths and other floating macrophytes has the potential to change GHG emissions, a process that might be relevant in regional C budgets.

| S-EPMC4742780 | biostudies-other

The vortex gas scaling regime of baroclinic turbulence.

Project description:The mean state of the atmosphere and ocean is set through a balance between external forcing (radiation, winds, heat and freshwater fluxes) and the emergent turbulence, which transfers energy to dissipative structures. The forcing gives rise to jets in the atmosphere and currents in the ocean, which spontaneously develop turbulent eddies through the baroclinic instability. A critical step in the development of a theory of climate is to properly include the eddy-induced turbulent transport of properties like heat, moisture, and carbon. In the linear stages, baroclinic instability generates flow structures at the Rossby deformation radius, a length scale of order 1,000 km in the atmosphere and 100 km in the ocean, smaller than the planetary scale and the typical extent of ocean basins, respectively. There is, therefore, a separation of scales between the large-scale gradient of properties like temperature and the smaller eddies that advect it randomly, inducing effective diffusion. Numerical solutions show that such scale separation remains in the strongly nonlinear turbulent regime, provided there is sufficient drag at the bottom of the atmosphere and ocean. We compute the scaling laws governing the eddy-driven transport associated with baroclinic turbulence. First, we provide a theoretical underpinning for empirical scaling laws reported in previous studies, for different formulations of the bottom drag law. Second, these scaling laws are shown to provide an important first step toward an accurate local closure to predict the impact of baroclinic turbulence in setting the large-scale temperature profiles in the atmosphere and ocean.

| S-EPMC7060697 | biostudies-literature

Universal model for water costs of gas exchange by animals and plants.

Project description:For terrestrial animals and plants, a fundamental cost of living is water vapor lost to the atmosphere during exchange of metabolic gases. Here, by bringing together previously developed models for specific taxa, we integrate properties common to all terrestrial gas exchangers into a universal model of water loss. The model predicts that water loss scales to gas exchange with an exponent of 1 and that the amount of water lost per unit of gas exchanged depends on several factors: the surface temperature of the respiratory system near the outside of the organism, the gas consumed (oxygen or carbon dioxide), the steepness of the gradients for gas and vapor, and the transport mode (convective or diffusive). Model predictions were largely confirmed by data on 202 species in five taxa--insects, birds, bird eggs, mammals, and plants--spanning nine orders of magnitude in rate of gas exchange. Discrepancies between model predictions and data seemed to arise from biologically interesting violations of model assumptions, which emphasizes how poorly we understand gas exchange in some taxa. The universal model provides a unified conceptual framework for analyzing exchange-associated water losses across taxa with radically different metabolic and exchange systems.

| S-EPMC2889562 | biostudies-literature

Investigation of Cecal Intubation Rates and Pain Levels Between Water Exchange and Air Insufflation Flexible Sigmoidoscopy

Project description:This study evaluates how often patients without sedation that receive screening sigmoidoscopy are able to have their full colon examined without significant discomfort by comparing a new colonoscopy technique known as the water exchange technique to the traditional air insufflation technique. It compares the differences between complete colon exam rates for water exchange when compared to the traditional air technique. Patients will be randomised and blinded to the procedure type. Previous studies have shown that the water exchange method is associated with a significant reduction in discomfort and often allows patients to receive colonoscopy without sedation or with only minimal sedation. However, the potential for water exchange to be used in the screening setting has yet to be evaluated. As per standard practices in sigmoidoscopy screening, patients will not be sedated. However, unlike standard practices in sigmoidoscopy screening, while maintaining minimal levels of discomfort, the investigators will attempt to scope beyond the distal colon.

| 2248694 | ecrin-mdr-crc

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data