Using in-situ optical sensors to study dissolved organic carbon dynamics of streams and watersheds: A review

Ruhala, Sydney S.; Zarnetske, Jay P.

doi:10.1016/j.scitotenv.2016.09.113

Cited by 87 publications

(73 citation statements)

References 47 publications

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“…; Isaak et al . ; Ruhala & Zarnetske ). Such studies identify mechanisms ultimately responsible for the temporal and spatial variability revealed by periodic synoptic sampling.…”

Section: Discussionmentioning

confidence: 99%

“…; Kirchner et al . ; Ruhala & Zarnetske ), but they are too expensive to equip headwater catchments, which are thousands of times more abundant than the larger rivers where most monitoring currently occurs. This headwater conundrum is particularly problematic for developing nations where the largest increases in nutrient pollution are occurring (Seitzinger et al .…”

Section: Introductionmentioning

confidence: 97%

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Unexpected spatial stability of water chemistry in headwater stream networks

et al. 2017

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Understanding how water and solutes enter and propagate through freshwater landscapes in the Anthropocene is critical to protecting and restoring aquatic ecosystems and ensuring human water security. However, high hydrochemical variability in headwater streams, where most carbon and nutrients enter river networks, has hindered effective modelling and management. We developed an analytical framework informed by landscape ecology and catchment hydrology to quantify spatiotemporal variability across scales, which we tested in 56 headwater catchments, sampled periodically over 12 years in western France. Unexpectedly, temporal variability in dissolved carbon, nutrients and major ions was preserved moving downstream and spatial patterns of water chemistry were stable on annual to decadal timescales, partly because of synchronous variation in solute concentrations. These findings suggest that while concentration and flux cannot be extrapolated among subcatchments, periodic sampling of headwaters provides valuable information about solute sources and subcatchment resilience to disturbance.

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“…; Isaak et al . ; Ruhala & Zarnetske ). Such studies identify mechanisms ultimately responsible for the temporal and spatial variability revealed by periodic synoptic sampling.…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Unexpected spatial stability of water chemistry in headwater stream networks

et al. 2017

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“…Metabolism of organic matter (OM) in freshwater ecosystems plays a large role in global biogeochemical cycles 1–3 , as freshwater ecosystems emit more than 2 Pg C yr −1 into the atmosphere 4,5 . These emissions are largely dominated by contributions from river corridors 1,5,6 , and within the river corridor, areas of groundwater-surface water mixing (hyporheic zones) have a disproportionate impact on aerobic respiration 7–9 . Recent field observations have suggested that OM chemistry, and in particular OM thermodynamics, are key to predicting aerobic respiration in hyporheic zones 10–12 .…”

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confidence: 99%

Carbon limitation leads to thermodynamic regulation of aerobic metabolism

Garayburu‐Caruso

Stegen

Song

et al. 2020

Preprint

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13Organic matter (OM) metabolism in freshwater ecosystems is a critical source of uncertainty in 14 global biogeochemical cycles, yet aquatic OM cycling remains poorly understood. Here, we 15 present the first work to explicitly test OM thermodynamics as a key regulator of aerobic 16 respiration, challenging long-held beliefs that organic carbon and oxygen concentrations are the 17 primary determinants of respiration rates. We pair controlled microcosm experiments with 18 ultrahigh-resolution OM characterization to demonstrate a clear relationship between OM 19 thermodynamic favorability and aerobic respiration under carbon limitation. We also 20 demonstrate a shift in the regulation of aerobic respiration from OM thermodynamics to nitrogen 21 content when carbon is in excess, highlighting a central role for OM thermodynamics in aquatic 22 biogeochemical cycling particularly in carbon-limited ecosystems. Our work therefore 23 illuminates a structural gap in aquatic biogeochemical models and presents a new paradigm in 24 which OM thermodynamics and nitrogen content interactively govern aerobic respiration. 25 26 27 3 Metabolism of organic matter (OM) in freshwater ecosystems plays a large role in global 28 biogeochemical cycles 1-3 , as freshwater ecosystems emit more than 2 Pg C yr -1 into the 29 atmosphere 4,5 . These emissions are largely dominated by contributions from river corridors 1,5,6 , 30 and within the river corridor, areas of groundwater-surface water mixing (hyporheic zones) have 31 a disproportionate impact on aerobic respiration 7-9 . Recent field observations have suggested that 32 OM chemistry, and in particular OM thermodynamics, are key to predicting aerobic respiration 33 in hyporheic zones 10-12 . If supported, these observations challenge a widespread paradigm that 34 organic carbon and oxygen concentrations are the primary determinants of aerobic respiration 35 rates and highlight a key source of model uncertainty. Yet, no work has provided direct evidence 36 for OM thermodynamics as a regulator of aerobic respiration in a controlled laboratory 37 environment. Demonstrating this behavior would identify mechanisms that drive field-based 38 phenomena and would enable key properties of OM to be represented in predictive models, 39 thereby contributing to reducing the uncertainty in modeling river corridor biogeochemical 40 cycling 13,14 . 41We use highly controlled aerobic microcosms, non-invasive dissolved oxygen consumption 42 rates, and ultrahigh-resolution OM characterization to investigate the role of OM chemistry in 43 determining aerobic respiration in hyporheic zone sediments. Based on field observations 10-12 , 44 we hypothesized that OM chemistry, including thermodynamic favorability and nitrogen (N) 45 content, would regulate aerobic respiration. Historically, investigations of thermodynamic 46 constraints on microbial metabolism have primarily focused on oxidation-reduction reactions 47 premise that using oxygen as the terminal electron acceptor provides sufficient energy ...

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“…These sensors use algorithms to calculate solute concentrations based on absorbance at a specific wavelength or multiple wavelengths. Although the use of in situ UV-Vis sensors presents several challenges, such as biofouling [23], local calibration [24,25], and power supply [24,26], numerous studies have used such sensors in the field [20,21,[27][28][29][30]. In most of these studies, grab samples analyzed in the laboratory were used to validate data recorded by the sensor [24,31].…”

Section: Introductionmentioning

confidence: 99%

Diurnal Patterns in Solute Concentrations Measured with In Situ UV-Vis Sensors: Natural Fluctuations or Artefacts?

Jacobs

Weeser

Rufino

2020

Sensors

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In situ spectrophotometers measuring in the UV-visible spectrum are increasingly used to collect high-resolution data on stream water quality. This provides the opportunity to investigate short-term solute dynamics, including diurnal cycling. This study reports unusual changes in diurnal patterns observed when such sensors were deployed in four tropical headwater streams in Kenya. The analysis of a 5-year dataset revealed sensor-specific diurnal patterns in nitrate and dissolved organic carbon concentrations and different patterns measured by different sensors when installed at the same site. To verify these patterns, a second mobile sensor was installed at three sites for more than 3 weeks. Agreement between the measurements performed by these sensors was higher for dissolved organic carbon (r > 0.98) than for nitrate (r = 0.43–0.81) at all sites. Higher concentrations and larger amplitudes generally led to higher agreement between patterns measured by the two sensors. However, changing the position or level of shading of the mobile sensor resulted in inconsistent changes in the patterns. The results of this study show that diurnal patterns measured with UV-Vis spectrophotometers should be interpreted with caution. Further work is required to understand how these measurements are influenced by environmental conditions and sensor-specific properties.

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Using in-situ optical sensors to study dissolved organic carbon dynamics of streams and watersheds: A review

Cited by 87 publications

References 47 publications

Unexpected spatial stability of water chemistry in headwater stream networks

Unexpected spatial stability of water chemistry in headwater stream networks

Carbon limitation leads to thermodynamic regulation of aerobic metabolism

Diurnal Patterns in Solute Concentrations Measured with In Situ UV-Vis Sensors: Natural Fluctuations or Artefacts?

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