scholarly journals Understanding Stream Metabolism with Reactive Tracers

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Aaron Sidder
Keyword(s):  
Ecosystem Respiration ◽  
Blue Dye ◽  
Stream Metabolism ◽  
Reactive Tracers

When the blue dye resazurin encounters living microorganisms, it transforms into fluorescent pink resorufin and helps scientists understand ecosystem respiration, but it has its limitations.

scholarly journals Large spatiotemporal variability in metabolic regimes for an urban stream draining four wastewater treatment plants with implications for dissolved oxygen monitoring

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0256292
Author(s):  
Sarah H. Ledford ◽  
Jacob S. Diamond ◽  
Laura Toran
Keyword(s):  
Wastewater Treatment ◽  
Dissolved Oxygen ◽  
Ecosystem Function ◽  
Ecosystem Respiration ◽  
Incident Light ◽  
Treatment Plant ◽  
Spatiotemporal Variability ◽  
Urban Stream ◽  
Water Quality Criteria ◽  
Stream Metabolism

Urbanization and subsequent expansion of wastewater treatment plant (WWTP) capacity has the potential to alter stream metabolic regimes, but the magnitude of this change remains unknown. Indeed, our understanding of downstream WWTP effects on stream metabolism is spatially and temporally limited, and monitoring designs with upstream-downstream comparison sites are rare. Despite this, and despite observed spatiotemporal variability in stream metabolic regimes, regulators typically use snapshot monitoring to assess ecosystem function in receiving streams, potentially leading to biased conclusions about stream health. To address these important practical issues, we assessed the spatiotemporal variability in stream metabolism at nine sites upstream and downstream of four WWTPs in a suburban stream. We used one year (2017–2018) of high-frequency dissolved oxygen (DO) data to model daily gross primary productivity (GPP) and ecosystem respiration (ER). We found that GPP was 1.7–4.0 times higher and ER was 1.2–7.2 times higher downstream of the WWTPs, especially in spring when light was not limited by canopy shading. Critically, we observed that these effects were spatially limited to the kilometer or so just downstream of the plant. These effects were also temporally limited, and metabolic rates upstream of WWTPs were not different from sites downstream of the plant after leaf-out at some sites. Across sites, regardless of their relation to WWTPs, GPP was positively correlated with potential incident light suggesting that light is the dominant control on GPP in this system. Temporal windowing of DO to proposed regulatory monitoring lengths revealed that the violation frequency of water quality criteria depended on both the monitoring interval and start date. We conclude that spatiotemporal variability in metabolism and DO are crucial considerations when developing monitoring programs to assess ecosystem function, and that evidence of WWTP effects may only arise during high light conditions and at limited scales.

scholarly journals Resistance and resilience of stream metabolism to high flow disturbances

2020 ◽  
Author(s):  
Brynn O'Donnell ◽  
Erin R. Hotchkiss
Keyword(s):  
Dynamic Equilibrium ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Ecosystem Processes ◽  
High Flow ◽  
Running Waters ◽  
Stream Metabolism ◽  
Metabolic Resistance ◽  
Disturbance Intensity ◽  
Flow Disturbances

Abstract. Streams are ecosystems organized by disturbance. One of the most frequent and variable disturbances in running waters is elevated flow. Yet, we still have few estimates of how ecosystem processes, such as stream metabolism (gross primary production and ecosystem respiration; GPP and ER), respond to high flow events. Furthermore, we lack a predictive frame- work for understanding controls on within-site metabolic responses to flow disturbances. Using five years of high-frequency dissolved oxygen data from an urban- and agriculturally-influenced stream, we estimated daily GPP and ER and analyzed metabolic changes across 15 isolated high flow events. Metabolism was variable from day to day, even during lower flows. Thus, we calculated metabolic resistance as the magnitude of departure from the dynamic equilibrium during antecedent lower flows and quantified resilience from the days until GPP and ER returned to the range of antecedent dynamic equilibrium. We evaluated correlations between metabolic resistance and resilience with characteristics of each high flow event, antecedent conditions, and time since last flow disturbance. ER was more resistant and resilient than GPP. GPP was typically suppressed following flow disturbances, regardless of disturbance intensity. In contrast, the ER magnitude of departure increased with disturbance intensity. Additionally, GPP was less resilient and took longer to recover (0 to > 9 days, mean = 2.2) than ER (0 to 2 days, mean = 0.6). Given the flashy nature of streams draining human-altered landscapes and the variable consequences of flow for GPP and ER, testing how ecosystem processes respond to flow disturbances is essential to an integrative understanding of ecosystem function.

scholarly journals Moderate increases in channel discharge are positively related to ecosystem respiration in forested Ozark streams

2021 ◽  
Author(s):  
Allyn K. Dodd ◽  
Daniel D. Magoulick ◽  
Michelle A. Evans-White
Keyword(s):  
Primary Production ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Carbon Sources ◽  
Flow Regimes ◽  
Water Source ◽  
Stream Metabolism ◽  
Global Trends ◽  
Ecosystem Level ◽  
And Function

ABSTRACTThe natural flow regime is considered the “master variable” in lotic systems, controlling structure and function at organismal, population, community, and ecosystem levels. We sought to estimate forested headwater stream metabolism across two dominant flow regimes (Runoff and Groundwater) in northern Arkansas and evaluate potential differences in, and drivers of, gross primary production, ecosystem respiration, and net ecosystem metabolism. Flow regimes differed in intermittency, substrate heterogeneity, hyporheic connectivity, and dominant water source (subsurface runoff vs. groundwater), which we expected to result in differences in primary production and respiration. Average daily gross primary production (GPP) and ecosystem respiration (ER) estimated from field data collected from May 2015-June 2016 tended to be greater in Groundwater streams. Respiration was positively related to discharge (R2= 0.98 p< 0.0001) and net metabolism became more heterotrophic with increasing average annual discharge across sites (R2= 0.94, p= 0.0008). Characterizing ecosystem-level responses to differences in flow can reveal mechanisms governing stream metabolism and, in turn, provide information regarding trophic state and energy inputs as efforts continue to determine global trends in aquatic carbon sources and fates.

scholarly journals Variation of stream metabolism along a tropical environmental gradient

2018 ◽  
Author(s):  
Wesley A. Saltarelli ◽  
Walter K. Dodds ◽  
Flavia Tromboni ◽  
Maria do Carmo Calijuri ◽  
Vinicius Neres-Lima ◽  
...  
Keyword(s):  
Land Use ◽  
Total Phosphorus ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Canopy Cover ◽  
Tropical Streams ◽  
Nutrient Concentrations ◽  
Stream Metabolism ◽  
Mixed Effect ◽  
Single Station

Stream metabolism is affected by both natural and human-induced processes. While metabolism has multiple implications for ecological processes, relatively little is known about how metabolic rates are influenced by land use in tropical streams. In this study, we assessed the metabolic characteristics and related environmental factors of six streams located in a transition area from Cerrado to Atlantic Forest (São Carlos/Brazil). Three streams were relatively preserved, while three were flowing through more agriculturally and/or urban impacted watersheds. Surface water samples were analyzed for biological and physico-chemical parameters as well as discharge and percentage of canopy cover. Metabolism was determined through the single-station method to estimate gross primary production (GPP), ecosystem respiration (ER) and net ecosystem production (NEP) with BAyesian Single-station Estimation (BASE). Nutrient concentrations tended to be higher in impacted versus preserved streams (e.g., average total phosphorus between 0.028-0.042 mg L-1 and 0.009-0.038 mg L-1, respectively). Average canopy cover varied between 58 and 77%, with no significant spatial or seasonal variation. All streams were net heterotrophic (ER exceeded GPP) in all sampling periods. GPP rates were always lower than 0.7 gO2 m-2 d-1 in all streams and ER varied from 0.6 to 42.1 gO2 m-2 d-1.  Linear Mixed-Effect models showed that depth, discharge, velocity and total phosphorus are the most important predictors for GPP. For ER, depth, velocity and canopy cover are significant potential predictors. Canopy cover was the main light limiting factor and influenced stream metabolism. Our findings reinforced the concepts that shifts in the shading effect provided by vegetation (e.g., through deforestation) or changes in discharge (e.g., through land use conversion or water abstractions) can impact freshwater metabolism. Our study suggests that human activities in low latitude areas can alter tropical streams’ water quality, ecosystem function, and the degree of riparian influence. Our data showed that tropical streams can be especially responsive to increases of organic matter inputs leading to high respiration rates and net heterotrophy, and this should be considered to support management and restoration efforts.

scholarly journals The Metabolic Regimes at the Scale of an Entire Stream Network Unveiled Through Sensor Data and Machine Learning

Ecosystems ◽  
2021 ◽  
Author(s):  
Pier Luigi Segatto ◽  
Tom J. Battin ◽  
Enrico Bertuzzo
Keyword(s):  
Machine Learning ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Light Availability ◽  
Sensor Data ◽  
Stream Metabolism ◽  
River Continuum ◽  
Stream Network ◽  
Network Scale ◽  
Clear Peak

AbstractStreams and rivers form dense networks that drain the terrestrial landscape and are relevant for biodiversity dynamics, ecosystem functioning, and transport and transformation of carbon. Yet, resolving in both space and time gross primary production (GPP), ecosystem respiration (ER) and net ecosystem production (NEP) at the scale of entire stream networks has been elusive so far. Here, combining Random Forest (RF) with time series of sensor data in 12 reach sites, we predicted annual regimes of GPP, ER, and NEP in 292 individual stream reaches and disclosed properties emerging from the network they form. We further predicted available light and thermal regimes for the entire network and expanded the library of stream metabolism predictors. We found that the annual network-scale metabolism was heterotrophic yet with a clear peak of autotrophy in spring. In agreement with the River Continuum Concept, small headwaters and larger downstream reaches contributed 16% and 60%, respectively, to the annual network-scale GPP. Our results suggest that ER rather than GPP drives the metabolic stability at the network scale, which is likely attributable to the buffering function of the streambed for ER, while GPP is more susceptible to flow-induced disturbance and fluctuations in light availability. Furthermore, we found large terrestrial subsidies fueling ER, pointing to an unexpectedly high network-scale level of heterotrophy, otherwise masked by simply considering reach-scale NEP estimations. Our machine learning approach sheds new light on the spatiotemporal dynamics of ecosystem metabolism at the network scale, which is a prerequisite to integrate aquatic and terrestrial carbon cycling at relevant scales.

First experiences with a new radiopharmaceutical for sentinel lymph node detection in malignant melanoma

2004 ◽  
Vol 43 (01) ◽  
pp. 10-15 ◽  
Author(s):  
R. A. Schmid ◽  
C. Kunte ◽  
B. Konz ◽  
K. Hahn ◽  
M. Weiss
Keyword(s):  
Lymph Node ◽  
Sentinel Lymph Node ◽  
Malignant Melanoma ◽  
Sentinel Node ◽  
Gamma Probe ◽  
Blue Dye ◽  
Sentinel Nodes ◽  
Technetium 99M ◽  
Positive Rate ◽  
Metastatic Involvement

Summary Aim of this study was to localize the sentinel lymph node by lymphoscintigraphy using technetium-99m colloidal rhenium sulphide (Nanocis®), a new commercially available radiopharmaceutical. Due to the manufacturers’ instructions it is licensed for lymphoscintigraphy. Patients, methods: 35 consecutive patients with histologically proved malignant melanoma, but without clinical evidence of metastases, were preoperatively examined by injecting 20-40 MBq Nanocis® with (mean particle size: 100 nm; range: 50-200 nm) intradermally around the lesion. Additionally blue dye was injected intaoperatively. A hand-held gamma probe guided sentinel node biopsy. Results: During surgery, the preoperatively scintigraphically detected sentinel lymph nodes were identified in 34/35 (97%) patients. The number of sentinel nodes per patient ranged from one to four (mean: n = 1.8). Histologically, metastatic involvement of the sentinel lymph node was found in 12/35 (34%) patients; the sentinel lymph node positive-rate (14/63 SLN) was 22%. Thus, it is comparable to the findings of SLN-mapping using other technetium-99m-labeled nanocolloides. Conclusion: 99mTc-bound colloidal rhenium sulphide is also suitable for sentinel node mapping.

Using of modified-bentonite as low-cost sorbent for removal of methylene blue dye from aqueous solution

2020 ◽  
Vol 27 (2) ◽  
pp. 45-54
Author(s):  
Saraa Muwafaq Ibrahim ◽  
Ziad T. Abd Ali
Keyword(s):  
Aqueous Solution ◽  
Methylene Blue ◽  
Silanol Group ◽  
Infrared Spectrometry ◽  
Blue Dye ◽  
Ammonium Bromide ◽  
Vibration Band ◽  
Order Kinetic ◽  
Methylene Blue Dye ◽  
Modified Bentonite

Batch experiments have been studied to remove methylene blue dye (MB) from aqueous solution using modified bentonite. The modified bentonite was synthesized by replacing exchangeable calcium cations in natural bentonite with cationic surfactant cetyl trimethyl ammonium bromide (CTAB). The characteristics of modified bentonite were studied using different analysis such as Scanning electronic microscopy (SEM), Fourier transform infrared spectrometry (FTIR) and surface area. Where SEM shows the natural bentonite has a porous structure, a rough and uneven appearance with scattered and different block structure sizes, while the modified bentonite surface morphology was smooth and supplemented by a limited number of holes. On other hand, (FTIR) analysis that proved NH group aliphatic and aromatic group of MB and silanol group are responsible for the sorption of contaminate. The organic matter peaks at 2848 and 2930 cm-1 in the spectra of modified bentonite which are sharper than those of the natural bentonite were assigned to the CH2 scissor vibration band and the symmetrical CH3 stretching absorption band, respectively, also the 2930 cm-1 peak is assigned to CH stretching band. The batch study was provided the maximum removal efficiency (99.99 % MB) with a sorption capacity of 129.87 mg/g at specified conditions (100 mg/L, 25℃, pH 11 and 250rpm). The sorption isotherm data fitted well with the Freundlich isotherm model. The kinetic studies were revealed that the sorption follows a pseudo-second-order kinetic model which indicates chemisorption between sorbent and sorbate molecules.

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