Does Photomineralization of Dissolved Organics Matter in Temperate Rivers?

Maavara, Taylor; Logozzo, L. A.; Stubbins, Aron; Aho, Kelly S.; Brinkerhoff, Craig; Hosen, Jacob D.; Raymond, Peter A.

doi:10.1029/2021jg006402

Cited by 15 publications

(22 citation statements)

References 75 publications

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“…DOC

{t}_{s}

measured from 20 combined photooxidation/bioassays were comparatively much lower (median: 314 hr) (Figure 8), indicating quicker mineralization when considering in situ photo‐ and biotic oxidations together. Particularly, photodegradation is a widely recognized process that promotes microbial breakdown (Allesson et al., 2016; Lu et al., 2013) though either photo‐ or microbial oxidation alone is insignificant for DOC removal in river networks (del Giorgio & Pace, 2008; Maavara et al., 2021). DOC

{v}_{f}

chosen for Da scaling in this analysis (0.038 m d −1 , corresponding of a

{t}_{s}

of 720 hr or WRT of a 6–7 order river network) (Wollheim et al., 2015) falls between DOC uptake determined from the solute addition and dark bioassay methods (Figure 8).…”

Section: Discussionmentioning

confidence: 99%

“…DOC cycling in river networks involves multiple processes that contribute simultaneously to its gains/losses within rivers (Battin et al., 2008; Bernhardt et al., 2018; Kaplan & Cory, 2016). In situ photooxidation (Maavara et al., 2021) and biotic mineralization (del Giorgio & Pace, 2008; Raymond & Bauer, 2000) are the two main processes contributing to permanent DOC removal and CO 2 emission from river systems. The magnitude of DOC removal rate in river networks is however difficult to quantify due to the complex interplays among multiple biotic/abiotic processes that contribute to DOC concentration variations in spatially distributed river networks (Lv et al., 2019; Wollheim et al., 2015).…”

Section: Discussionmentioning

confidence: 99%

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Global Controls on DOC Reaction Versus Export in Watersheds: A Damköhler Number Analysis

Liu

Maavara

Brinkerhoff

et al. 2022

Global Biogeochemical Cycles

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The relative capacity for watersheds to eliminate or export reactive constituents has important implications on aquatic ecosystem ecology and biogeochemistry. Removal efficiency depends on factors that affect either the reactivity or advection of a constituent within river networks. Here, we characterized Damköhler number (Da) for dissolved organic carbon (DOC) uptake in global river networks. Da equals the advection to reaction timescale ratio and thus provides a unitless indicator for DOC reaction intensity during transport within river networks. We aim to demonstrate the spatial and temporal patterns and interplays among factors that determine DOC uptake across global river networks. We show that watershed size imposes a primary control on river network DOC uptake due to a three orders of magnitude difference in water residence time (WRT) between the smallest and largest river networks. DOC uptake capacity in tropical river networks is 2–6 times that in temperate and the Arctic river networks, coinciding with larger DOC removals in warm than in cold watersheds. River damming has a profound impact on DOC uptake due to significantly extended WRTs, particularly in temperate watersheds where most constructed dams are situated. Global warming is projected to increase river network DOC uptake by ca. 19% until year 2100 under the RCP4.5 scenario.

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“…DOC

{t}_{s}

{v}_{f}

chosen for Da scaling in this analysis (0.038 m d −1 , corresponding of a

{t}_{s}

of 720 hr or WRT of a 6–7 order river network) (Wollheim et al., 2015) falls between DOC uptake determined from the solute addition and dark bioassay methods (Figure 8).…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Global Controls on DOC Reaction Versus Export in Watersheds: A Damköhler Number Analysis

Liu

Maavara

Brinkerhoff

et al. 2022

Global Biogeochemical Cycles

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“…Despite having shown that photomineralization can be important in river networks relative to biomineralization, its importance is close to negligible relative to the magnitude of DOC fluxes in both lakes and rivers. Maavara et al (2021) considered the importance of photomineralization in the Connecticut River watershed's river reaches in terms of its ability to eliminate DOC from the water column and found that per‐reach removal ( R i , Eq. 13) was 0.026–0.18% of the DOC flux at median flows.…”

Section: Model Output and Discussionmentioning

confidence: 99%

“…Complete photooxidation of DOC to dissolved inorganic carbon (DIC) (i.e., photomineralization, ψ), in each river reach and lake segment is based on the formulation (Koehler et al 2012;Cory and Kling 2018;Maavara et al 2021):…”

Section: Photomineralizationmentioning

confidence: 99%

“…We develop a spatially explicit mass balance model of DOC sources, sinks, and transport through the Connecticut River watershed in the northeastern United States and southern Canada. An existing body of literature dedicated to quantifying Connecticut River watershed metabolism, carbon dynamics, and hydrology make the Connecticut an ideal watershed for such an exercise, as ample information is available to parameterize a model (Hosen et al 2019; Brinkerhoff et al 2021; Hosen et al 2021; Maavara et al 2021; Yoon et al 2021; Aho et al 2021 a , b ). We track terrestrial DOC loading, production via GPP, consumption by microbial uptake (biomineralization) and photomineralization and the cascading downstream transport through 98,254 stream reaches and lake segments at an average length resolution of 511 m, from first order through 8 th ‐order streams, rivers, ponds, lakes, and reservoirs.…”

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Watershed DOC uptake occurs mostly in lakes in the summer and in rivers in the winter

Maavara

Brinkerhoff

Hosen

et al. 2023

Limnology & Oceanography

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River networks transport dissolved organic carbon (DOC) from terrestrial uplands to the coastal ocean. The extent to which a reach or lake within a river network uptakes DOC depends on the stream order, the seasonal conditions, and the flow. At the watershed scale, it remains unclear whether DOC uptake is dominated by biological processes such as respiration, or abiotic processes like photomineralization. The partitioning of DOC uptake in lakes vs. rivers is also unclear. In this study, we present a new model that unifies year-round controls on DOC cycling for an entire river network, including river-lake connectivity, to elucidate the importance of biotic vs. abiotic controls on DOC uptake. We present the Catchment UPtake and Sinks by Season, Order, and Flow for DOC (CUPS-OF-DOC) model, which quantifies terrestrial DOC loading, gross primary productivity, and uptake via microbes and photomineralization. The model is applied to the Connecticut River Watershed, and accounts for cascading reach-and lake-scale DOC cycling across 98 scenarios spanning combinations of flows, seasons, and stream orders. We show that riverine DOC uptake is nearly constant with stream order, but the proportion of DOC uptake from photomineralization varies. Photomineralization dominates in rivers in most flow conditions and stream orders, especially in winter, accounting for at least half of whole-watershed DOC uptake in February across all flows. Whole-watershed summer DOC uptake occurs mostly via biomineralization in lakes, accounting for 80% of DOC uptake during the growing season, despite accounting for less than 6% of watershed open water surface area.

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Dissolved organic matter transformations in a freshwater rivermouth

et al. 2023

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River-to-lake transitional areas are biogeochemically active ecosystems that can alter the amount and composition of dissolved organic matter (DOM) as it moves through the aquatic continuum. However, few studies have directly measured carbon processing and assessed the carbon budget of freshwater rivermouths. We compiled measurements of dissolved organic carbon (DOC) and DOM in several water column (light and dark) and sediment incubation experiments conducted in the mouth of the Fox river (Fox rivermouth) upstream from Green Bay, Lake Michigan. Despite variation in the direction of DOC fluxes from sediments, we found that the Fox rivermouth was a net sink of DOC where water column DOC mineralization outweighed the release of DOC from sediments at the rivermouth scale. Although we found DOM composition also changed during our experiments, alterations in DOM optical properties were largely independent of the direction of sediment DOC fluxes. We found a consistent decrease in humic-like and fulvic-like terrestrial DOM and a consistent increase in the overall microbial composition of rivermouth DOM during our incubations. Moreover, greater ambient total dissolved phosphorus concentrations were positively associated with the consumption of terrestrial humic-like, microbial protein-like, and more recently derived DOM but had no effect on bulk DOC in the water column. Unexplained variation indicates that other environmental controls and water column processes affect the processing of DOM in this rivermouth. Nonetheless, the Fox rivermouth appears capable of substantial DOM transformation with implications for the composition of DOM entering Lake Michigan.

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Does Photomineralization of Dissolved Organics Matter in Temperate Rivers?

Cited by 15 publications

References 75 publications

Global Controls on DOC Reaction Versus Export in Watersheds: A Damköhler Number Analysis

Global Controls on DOC Reaction Versus Export in Watersheds: A Damköhler Number Analysis

Watershed DOC uptake occurs mostly in lakes in the summer and in rivers in the winter

Dissolved organic matter transformations in a freshwater rivermouth

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