The role of time and mixing in the degradation of terrestrial derived dissolved organic carbon in lakes of varying trophic status

Magyan, Sarah; Dempsey, Christopher M.

doi:10.1016/j.jpap.2021.100065

Cited by 5 publications

(3 citation statements)

References 26 publications

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“…For most parameters, especially S275-295, SR, and SUVA254, we observed clear changes with consistent direction (i.e. increasing or decreasing) as a function of tDOC loss for both the peatland-draining river samples and the coastal water samples, and these changes are consistent with those reported previously for tDOM photobleaching experiments (Du et al, 2016;Helms et al, 2013;Lee et al, 2018;Magyan & Dempsey, 2021). Notably, we observed that the coastal water samples mostly showed larger changes in optical properties for a given %tDOC loss than the river samples.…”

Section: Qualitative Proxies Of Tdoc Biogeochemical Processessupporting

confidence: 90%

The Validity of Optical Properties as Tracers of Terrigenous Dissolved Organic Carbon during Extensive Remineralization in Coastal Waters

Chen

Martin

Zhou

2023

Preprint

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Terrestrial dissolved organic carbon (tDOC) is significant for coastal carbon cycling, and absorbance and fluorescence spectroscopy of chromophoric and fluorescent dissolved organic matter (CDOM, FDOM) are widely used to study tDOC cycling. However, CDOM and FDOM are often amongst the more labile components of tDOC. Because few studies have compared CDOM and FDOM to measurements of both bulk tDOC concentration and tDOC remineralization, it remains unclear how accurately CDOM and FDOM actually trace tDOC in coastal waters when tDOC undergoes extensive remineralization. We collected a 4-year coastal timeseries in Southeast Asia, where tropical peatlands supply large tDOC inputs. A carbon stable isotope mass balance shows that on average 56% of tDOC was remineralized upstream of our site, while 77% of CDOM was bleached. Despite this extensive tDOC remineralization and preferential CDOM loss, optical properties could reliably quantify tDOC. CDOM spectral slope properties, such as S275–295, are exponentially related to tDOC; these are highly sensitive tDOC tracers at low, but not at high, tDOC concentrations. Other properties are linearly related to tDOC, and both specific ultraviolet absorbance (SUVA254) and DOC-normalized fluorescence intensity may be suitable to quantify tDOC over a wider range of concentrations. However, the optical properties did not show consistent changes with the extent of tDOC remineralization. Our data support the validity of CDOM and FDOM spectroscopy to trace tDOC across coastal gradients even after the majority of tDOC has been remineralized, but they also show that these measurements may not provide much information about tDOC biogeochemical processing.

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Section: Qualitative Proxies Of Tdoc Biogeochemical Processessupporting

confidence: 90%

The Validity of Optical Properties as Tracers of Terrigenous Dissolved Organic Carbon during Extensive Remineralization in Coastal Waters

Chen

Martin

Zhou

2023

Preprint

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“…The literature studies on the reaction rate of TOC in warmer or tropical climate are less. However, it was observed that the reaction rate varies anywhere between − 0.02 to 0.09 day −1 in colder temperature ranging between − 6 to 27 °C (Magyan and Dempsey 2021). The reaction rate observed in the current study for TOC varied between 0.02 to 0.05 day −1 (at an average water temperature of 26 ± 4 °C).…”

Section: Validation Of Conceptual Lake2k Modelcontrasting

confidence: 50%

Determination of degradation/reaction rate for surface water quality of recycled water using Lake2K model for large-scale water recycling

Verma,

Thattaramppilly,

Manisha

et al. 2023

Environ Sci Pollut Res

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The depletion of groundwater resources in the water-stressed regions has led to the overuse of surface water reservoirs. Recharging groundwater by rejuvenating dried surface reservoirs using recycled water is a new sustainable solution. To ensure the prevention of groundwater contamination and associated health risks (as recycled water is used), it is crucial to assess the surface reservoir water quality. The study for the first time suggests the Lake2K model, a one-dimensional mechanistic mass-balance model, to simulate the changes in water quality in a series of man-made surface water reservoirs where recycled water flows under an indirect groundwater recharge scheme (soil aquifer treatment system). The model was developed, calibrated, and validated using field observations to estimate degradation/reaction rate constants for various water quality parameters. The observed average degradation/reaction rate constants for parameters including ammonia-N, nitrate-N, total nitrogen, total organic carbon, and organic phosphorous were 0.043 day −1 , 0.04 day −1 , 0.043 day −1 , 0.055 day −1 , and 0.056 day −1 , respectively, which were found to be relatively high compared to existing literature, indicating a greater degradation of these parameters in warmer climates. The results showed that the water quality improved significantly as the water progressed through the reservoirs, aligning with field observations. Additionally, the simulated seasonal variations revealed that the maximum growth rate of phytoplankton occurred during July, August, and September for each reservoir, while the nutrient pool (nitrate-N and orthophosphates) experienced the greatest depletion during this growth period. These findings shed light on the dynamics of surface water quality in regions facing water scarcity and contribute to the development of sustainable groundwater management strategies.

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“…Filtration is essential for measuring microbial decomposition of DOC with studies recommending a 0.45 or 0.2 μm pore size to remove microbiota from samples (Bertilsson & Tranvik, 2000; Magyan & Dempsey, 2021). Many 0.45 and 0.2 μm filters, however, are composed of organic material such as cellulose acetate, which can induce contamination problems, leading some researchers to recommend 0.7 μm GF/F filters (Denis et al., 2017; Khan & Subramania‐Pillai, 2007).…”

Section: Methodsmentioning

confidence: 99%

Life after a fiery death: Fire and plant biomass loading affect dissolved organic matter in experimental ponds

Spiegel,

Mladenov,

Wall

et al. 2023

Global Change Biology

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Drier and hotter conditions linked with anthropogenic climate change can increase wildfire frequency and severity, influencing terrestrial and aquatic carbon cycles at broad spatial and temporal scales. The impacts of wildfire are complex and dependent on several factors that may increase terrestrial deposition and the influx of dissolved organic matter (DOM) from plants into nearby aquatic systems, resulting in the darkening of water color. We tested the effects of plant biomass quantity and its interaction with fire (burned vs. unburned plant biomass) on dissolved organic carbon (DOC) concentration and degradation (biological vs. photochemical) and DOM composition in 400 L freshwater ponds using a gradient experimental design. DOC concentration increased nonlinearly with plant biomass loading in both treatments, with overall higher concentrations (>56 mg/L) in the unburned treatment shortly after plant addition. We also observed nonlinear trends in fluorescence and UV‐visible absorbance spectroscopic indices as a function of fire treatment and plant biomass, such as greater humification and specific UV absorbance at 254 nm (a proxy for aromatic DOM) over time. DOM humification occurred gradually over time with less humification in the burned treatment compared to the unburned treatment. Both burned and unburned biomass released noncolored, low molecular weight carbon compounds that were rapidly consumed by microbes. DOC decomposition exhibited a unimodal relationship with plant biomass, with microbes contributing more to DOC loss than photodegradation at intermediate biomass levels (100–300 g). Our findings demonstrate that the quantity of plant biomass leads to nonlinear responses in the dynamics and composition of DOM in experimental ponds that are altered by fire, indicating how disturbances interactively affect DOM processing and its role in aquatic environments.

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The role of time and mixing in the degradation of terrestrial derived dissolved organic carbon in lakes of varying trophic status

Cited by 5 publications

References 26 publications

The Validity of Optical Properties as Tracers of Terrigenous Dissolved Organic Carbon during Extensive Remineralization in Coastal Waters

The Validity of Optical Properties as Tracers of Terrigenous Dissolved Organic Carbon during Extensive Remineralization in Coastal Waters

Determination of degradation/reaction rate for surface water quality of recycled water using Lake2K model for large-scale water recycling

Life after a fiery death: Fire and plant biomass loading affect dissolved organic matter in experimental ponds

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