Figure 9: Experimental results suggest that the dominant process through which hypoxia affects sediment organic carbon differs between weekly and multiannual timescales. Left: in microcosm incubations, short-term (weeks) periods of hypoxia led to increased DOC and aqueous Fe, while decreasing sediment OC. On a whole-ecosystem scale, hypolimnetic Fe was closely correlated with oxygen concentrations, and short periods of hypoxia decreased both Fe-OC and OC in sediment. Consequently, Fe-OC protection appears to be a more dominant control on sediment OC sequestration than respiration on short timescales. Right: two years of summer hypoxia in FCR led to increased OC in sediment on a whole-ecosystem scale, suggesting that respiration may be a more dominant control on OC sequestration than protection by Fe on this timescale.
4.1 Short-term periods of hypoxia lead to release of Fe-protected OC and decrease total sediment OC
Both whole-ecosystem and microcosm experiments suggest that short-term periods (i.e., weeks) of hypoxia can dramatically alter OC and Fe cycling. Whole-ecosystem experiments revealed changes in hypolimnetic DOC and Fe, sediment OC, and sediment Fe-OC associated with water-column oxygenation (Figures 4, 5, 9), while microcosm incubations showed clear differences in aqueous Fe, and DOC and sediment OC among treatments (Figures 7, 8). The magnitude of these effects was substantial: on a whole-ecosystem scale, two weeks of hypoxic conditions decreased both sediment Fe-OC and total sediment OC by a mean of 30%. Declining Fe-OC and total OC in sediment, as well as concomitant increases in Fe and OC in overlying water, are consistent with the expectation that hypoxia causes reductive dissolution of Fe(III) in Fe-OC complexes, releasing soluble Fe and DOC on day to week scales (e.g., Carey et al., 2018; Pan et al., 2016; Patzner et al., 2020; Peter et al., 2016; Skoog & Arias-Esquivel, 2009; Figures 1, 9).
Our results contribute to an accumulating body of evidence that short-term fluctuations in oxygen concentrations have important effects on OC storage in soils and sediment. Previous research has shown that recently-formed Fe-OC associations may be particularly prone to hypoxic release, and reduction of Fe(III) in Fe-OC compounds can increase OC respiration rates during hypoxic conditions (Chen et al., 2020). As a result of these and other processes, periodic fluctuations in oxygen conditions may sustain or stimulate respiration rates relative to both constant oxic and constant hypoxic conditions (Bastviken et al., 2004; Huang et al., 2021). Furthermore, while OC released from Fe is likely to be aromatic and therefore potentially resistant to respiration (e.g., Riedel et al., 2013), this OC is susceptible to photo-oxidation upon release as DOC to the water column. Here, we found substantial decreases in sediment OC and Fe-OC following two weeks of hypoxia, with restored OC and Fe-OC after two weeks of oxic conditions (Figure 4, S3), suggesting that at least a fraction of the sediment Fe-OC pool is sensitive to short-term changes in oxygen concentrations in overlying water on a whole-ecosystem scale.
While sediment Fe-OC responded to oxygenation on a whole-ecosystem scale, Fe-OC did not vary significantly among oxygen treatments in experimental incubations, and observed changes in aqueous Fe and DOC in microcosms were asynchronous. These observations suggest that Fe may not be driving the observed oxygen-dependent changes in OC in microcosm sediments. We expect that this difference between microcosm and whole-ecosystem results may derive at least in part from the sediments we analyzed: whole-ecosystem samples were composed of the top 1 cm of sediment from sediment cores, while sediment for the experimental incubations was sampled using an Ekman grab sampler, and therefore included deeper layers of sediment. In soil, deeper horizons are thought to have more stable Fe-OC aggregates (Rumpel & Kögel-Knabner, 2011). Our results suggest that the same pattern may be true in sediments, resulting in burial of stable Fe-OC compounds in deeper sediments over time.
Formation and dissociation of Fe-OC complexes are two of many ways in which Fe and OC are impacted by hypoxia; both Fe and OC can also respond independently to changes in DO concentrations. Fe is oxidized from Fe(II) (soluble) to Fe(III) minerals (insoluble) both biotically and abiotically under oxic conditions (Kappler et al., 2021). Increased microbial biomass may be partially responsible for the increase in sediment OC under oxic conditions in experimental microcosms, as we observed the formation of orange (likely Fe-oxidizing) biofilms on top of the sediment layer in oxic microcosms (Figure S2). Fe reduction is also often associated with an increase in pH, which may increase the solubility of OC (Tavakkoli et al., 2015). However, pH did not differ consistently between microcosm treatments in this study and remained circumneutral on a whole-ecosystem scale (Figure S7 and S8). Likewise, other metals (e.g., aluminum, calcium, manganese) may release OC from sediment under hypoxic conditions, though the influence of these alternative metals on OC release is likely less quantitatively important than Fe (e.g., Wang et al. 2021). While these alternative mechanisms likely play a role in Fe and OC release, the decrease in Fe-OC and total OC following inactivation of the oxygenation system in FCR suggests that, at least for some surficial sediments, short (~2 week) periods of hypoxia can cause Fe-OC complexes to dissociate and decrease sediment OC burial on a whole-ecosystem scale.
4.2 Over multiannual timescales, OC respiration rates play a greater role than Fe-OC in determining the net effect of hypoxia on sediment OC content
Over multiannual timescales (2019–2021), exposure to seasonal hypoxia increased the amount of OC in sediments from FCR by 57% without changing the amount of Fe-OC (Figure 6). This clearly contrasts with short-term experimental results, which showed decreased OC content following short periods of hypoxia (section 4.3). While many factors could affect OC and Fe-OC over multiannual timescales, the fact that no comparable effects were seen in the unoxygenated reference reservoir (BVR) suggests that these changes may be attributed to changes in DO concentrations in overlying water. Over two years of summer hypoxia, OC levels in sediment from FCR increased to the extent that they were no longer significantly different from the hypoxic reference reservoir (Figure 6), suggesting that legacy effects of oxygen conditions on total sediment OC may diminish after a two-year interval.
Increases in sediment OC content with increased hypoxic duration are consistent with a reduction in sediment OC respiration rates under hypoxic conditions (Carey et al., 2018; Hargrave, 1969; Walker & Snodgrass, 1986). OC respiration rates decrease under hypoxic conditions because OC must be broken down using alternative electron acceptors, which produce a lower energy yield (Bastviken et al., 2003, 2004). Previous work conducted in BVR found that CO2 was the dominant terminal electron acceptor in the hypolimnion during hypoxic summer conditions (producing CH4), and CO2 has one of the lowest energy yields of alternate electron acceptors (McClure et al., 2021). As less OC is respired in hypoxic hypolimnetic water and sediments, OC can consequently accumulate more quickly in surficial sediments. Our results suggest that over multiannual timescales, this process (decreased respiration under hypoxic conditions) outweighs the counteracting decrease in Fe protection of OC that we observed during short periods of hypoxia.
Sediment Fe-OC content (per g sediment mass) did not significantly change after two years of hypoxic conditions in FCR (Figure 6), indicating that at least a fraction of these compounds are able to withstand fluctuations in environmental redox conditions. Long-term stability of Fe-OC complexes can be promoted by the formation of strong chemical bonds between OC and mineral surfaces, and these bonds continue to form over time through the rearrangement of organic molecules (Kaiser et al., 2007). Likewise, associations between Fe and OC can help to maintain a pool of small (high surface area) Fe particles that are particularly likely to associate with OC, as associations with OC can inhibit the conversion of these particles into larger, more crystalline Fe forms (called Ostwald ripening; e.g., Hiemstra et al. 2019; Zhao et al. 2022). Decreased accessibility to microbial decomposition (e.g., through burial) may further increase the ability of Fe-OC compounds to persist over time (Kaiser & Guggenberger, 2003; Kleber et al., 2015). In FCR, the history of oxic conditions (2013–2019) may have contributed to the formation of particularly stable Fe-OC complexes in sediment, which were then able to withstand two summers of hypoxia.
Importantly, much of the OC that accumulated under hypoxic conditions did not end up being bound to Fe. This result may be due to Fe oxidation state, as sorptive associations between DOC and Fe in sediment are much less likely to form if Fe is in a reduced state (Fe(II); Nierop et al., 2002). Changes in oxygen conditions are also likely to affect the composition of organic matter in sediments and in the water column (e.g., Riedel et al., 2013), potentially altering the capacity to associate with Fe. Because total OC increased following hypoxia and Fe-OC did not change, Fe-OC as a percentage of sediment OC was significantly lower after two years of hypoxia than before this hypoxic period. Declines in the percentage of OC that is bound to Fe may have important implications for ecosystem-scale carbon cycling, as OC that is associated with Fe is comparatively more protected from respiration (e.g., Chen et al., 2018, 2020; Hemingway et al., 2019; Kleber et al., 2005). Increased stocks of OC that are not associated with Fe may increase rates of methane production and OC release from the sediment to the water column (e.g., Hounshell et al., 2021), and could increase aerobic respiration rates under subsequent oxic periods (e.g., Chen et al., 2020; Huang et al., 2021).
4.3 Substantial OC and Fe cycling occurs at the sediment-water interface
Notably, the OC content of the top 1 cm of sediment was significantly lower than that of settling particulate material in both FCR and BVR, and nearly three times as much of this OC was bound to Fe in sediments compared to settling material (Figure 3). These results imply a substantial level of OC and Fe processing at the sediment-water interface, and they reinforce previous research in suggesting that the sediment-water interface is a hotspot for biogeochemical cycling freshwater lakes and reservoirs (e.g., Dadi et al., 2017; Hanson et al., 2015; Krueger et al., 2020).
From a mass-balance perspective, the difference in Fe-OC between settling material and surficial sediments suggests that Fe-OC complexes are either formed or preferentially preserved (compared to OC that is not associated with Fe) in sediments. Preferential preservation of Fe-OC is well-supported, as complexation with Fe has been shown to decrease OC turnover rates across multiple ecosystems (Eusterhues et al., 2014; Kaiser & Guggenberger, 2003; Kalbitz et al., 2005; Kleber et al., 2005; Lalonde et al., 2012; Mikutta & Kaiser, 2011). However, the difference in Fe-OC between settling material and surficial sediments likely also results in large part from Fe-OC associations formed in sediment (e.g., through adsorption of organic matter onto existing Fe minerals and Fe-OC complexes), as Fe(III) levels are much higher in sediments (e.g., Davison et al., 1991) and the composition of OC in sediments may be more preferable for complexation with Fe. While we did not measure OC quality in this study, we anticipate that settling material may have higher autochthonous OC levels and be more rapidly respired, while sediment OC may be enriched in allochthonous aromatic OC, which preferentially associates with Fe (Kramer et al., 2012; Riedel et al., 2013; Shields et al., 2016 ; Luo et al. 2022). Documenting changes in Fe-OC throughout the process of sediment diagenesis enhances our understanding of OC sequestration, as few if any previous studies have quantified the difference between Fe-OC inputs and stocks in aquatic sediments.
4.4 High Fe-OC levels reflect site-specific characteristics
On average, nearly one-third of surficial sediment OC was bound to Fe (dithionite-extractable) across two years in FCR and BVR (Figure 6). This percentage is far greater than that documented by Peter et al. (2018), where Fe-OC comprised ≤11% of total sediment OC across five boreal lakes. Furthermore, the levels of Fe-OC recorded here are higher than the mean of ​​21.5±8.6% reported for a broad range of marine sediments (Lalonde et al. 2012). With few other studies analyzing Fe-OC in freshwater lakes and reservoirs to date, our analysis provides new evidence that Fe-OC may play an important role in carbon sequestration in some freshwaters.
Despite having higher Fe-OC levels (as a percentage of total sediment OC) than most aquatic sediments studied to date, other sediment characteristics in FCR and BVR are within the range of those measured in other locations. FCR and BVR have much lower sediment OC content than the boreal lakes analyzed by Peter and Sobek (2018; 14–38% of sediment mass), but higher sediment OC than the primarily marine sediments analyzed by Lalonde et al. (2012; 0–7% of sediment mass). Fe concentrations are high in sediment from FCR and BVR, with a mean of 53,466 mg/kg dry weight (Krueger et al., 2020). However, Peter and Sobek (2018) observed low Fe-OC as a percentage of sediment OC (µ=6.7%) in one extremely high-Fe lake (Övre Skärsjön; 226,172 mg/kg reducible Fe in sediment). Likewise, pH in FCR and BVR is circumneutral (Figure S8), well within the range of 5.4–7.6 reported by Peter and Sobek (2018), and both Peter and Sobek (2018) and Lalonde et al. (2012) included a range of oxic and hypoxic sediments in their analyses.
Differences in the percentage of organic matter that is bound to Fe may result from numerous site-specific factors. For example, increasing ratios of Fe:OC and increasing absolute concentrations of Fe and OC can all increase the amount of Fe-OC coprecipitation (Chen et al., 2016; Kleber et al., 2015 and references therein). Likewise, differing Fe forms, Fe-weathering rates, OC quality, and pH may also impact the formation and stability of Fe-OC complexes (Curti et al., 2021; Kaiser et al., 2007; Kaiser & Guggenberger, 2003; Kleber et al., 2015; Luo et al. 2022); these differences may derive from contrasting geology, catchment vegetation, and trophic status, among many other factors. Disentangling the multiple interacting factors that can influence Fe-OC dynamics across sites will require Fe-OC characterization at a greater number and diversity of lakes and reservoirs. Such research will be essential to understanding how freshwater OC sequestration may be affected by global changes in Fe concentrations (Weyhenmeyer et al., 2014), water temperatures (Dokulil et al., 2021; O’Reilly et al., 2015), and pH (Garmo et al., 2014; Gavin et al., 2018; Stoddard et al., 1999), among other factors.
5. Conclusions
Results from this study help reconcile previous Fe-OC research and shed light on how declining oxygen concentrations may impact the role of lakes and reservoirs in the global carbon cycle. Research across terrestrial soils and marine sediments has provided contradictory evidence that Fe-OC complexes are (1) readily dissociated under hypoxic conditions and (2) capable of promoting sediment OC burial into deeper (hypoxic) layers over the course of decades to millennia. Here, we find that the timescale of analysis plays a critical role in understanding the net effect of hypoxia on sediment OC and Fe-OC. Specifically, a portion of the Fe-OC pool in surficial sediment is highly responsive to hypoxia in overlying water on a weekly timescale, resulting in decreased sediment OC. However, over longer timescales, the decrease in OC that results from dissociation of Fe-OC complexes is outweighed by the increase in sediment OC that results from slower respiration rates under hypoxia, and Fe-OC complexes buried in deeper sediment layers may be particularly resistant to hypoxic release. At both timescales, our results reinforce that Fe may serve as one of several important controls over OC cycling and sediment preservation of OC in freshwater ecosystems. As the duration of hypoxia increases in lakes and reservoirs, our results suggest that OC dynamics will respond non-linearly. While short periods of hypoxia may decrease OC burial, increasing prevalence and duration of hypoxia over multiannual timescales has the potential to increase OC burial in freshwater sediment, intensifying the role of freshwaters as sinks in the global carbon cycle.  
Acknowledgements
We are grateful for ongoing partnerships with the Western Virginia Water Authority that facilitated this research. Additionally, we thank the Virginia Tech Reservoir Group for helping to collect these data, particularly Adrienne Breef-Pilz for organizing the 2021 field season and helping to collect sediment cores in 2021, James Maze and Dexter Howard for helping to collect sediment cores in 2019, Ryan McClure for leading CTD data collection before 2019, and Alex Hounshell for organizing the 2019 field season. We thank Whitney Woelmer for making the map of study sites (Figure 2), Chip Frazier and Jeb Barrett for providing access to laboratory equipment, and Jeff Parks in the VT ICP-MS lab for analyzing Fe samples. This work is supported by the Institute for Critical Science and Applied Technology at Virginia Tech and the U.S. National Science Foundation (NSF) foundation grants DGE-1651272, DEB-1753639, SCC-1737424, DBI-1933016, and DBI-1933102.
Author Contributions
ASL conceptualized this study with CCC and MES. ASL performed chemical Fe-OC extractions, analyzed data, developed figures, and wrote this manuscript with MES, MEL, and CCC. BRN led analytical chemistry methods development and performed DOC analyses. NWH and MES oversaw whole-ecosystem Fe sampling, analysis, and data collation. MES performed speciation-solubility calculations. AD helped to design and run the microcosm experiment and process sediment samples. HLW collated and processed whole-ecosystem DOC and YSI data and reviewed code for this manuscript. CCC oversaw whole-ecosystem experiments. All authors edited and approved the final manuscript.
Open Research
All data used in this study are available in the Environmental Data Initiative (Carey et al., 2021; Carey, Lewis, Howard, et al., 2022; Carey, Lewis, McClure, et al., 2022; Carey, Wander, McClure, et al., 2022; Lewis et al., 2022; Lewis, Schreiber, et al., 2022; Schreiber et al., 2022). Code to reproduce results in this manuscript is available in a Zenodo repository (Lewis, 2022).

 

References
Adhikari, D., & Yang, Y. (2015). Selective stabilization of aliphatic organic carbon by iron oxide. Scientific Reports, 5(1), 11214. https://doi.org/10.1038/srep11214
Akima, H., Gebhardt, A., Petzold, T., Maechler, M., & code), bilinear. (2022). akima: Interpolation of Irregularly and Regularly Spaced Data (Version 0.6-3.4). Retrieved from https://CRAN.R-project.org/package=akima
American Public Health Association. (2018a). 3125 metals by inductively coupled plasma-mass spectrometry. In Standard Methods For the Examination of Water and Wastewater. American Public Health Association. https://doi.org/10.2105/smww.2882.048
American Public Health Association. (2018b). 5310 total organic carbon (toc). In Standard Methods For the Examination of Water and Wastewater. American Public Health Association. https://doi.org/10.2105/SMWW.2882.104
Arndt, S., Jørgensen, B. B., LaRowe, D. E., Middelburg, J. J., Pancost, R. D., & Regnier, P. (2013). Quantifying the degradation of organic matter in marine sediments: A review and synthesis. Earth-Science Reviews, 123, 53–86. https://doi.org/10.1016/j.earscirev.2013.02.008
Auguie, B. (2019). egg: Extensions for “ggplot2”: Custom Geom, Custom Themes, Plot Alignment, Labelled Panels, Symmetric Scales, and Fixed Panel Size (Version 0.4.5). Retrieved from https://CRAN.R-project.org/package=egg
Bai, J., Luo, M., Yang, Y., Xiao, S., Zhai, Z., & Huang, J. (2021). Iron-bound carbon increases along a freshwater−oligohaline gradient in a subtropical tidal wetland. Soil Biology and Biochemistry, 154, 108128. https://doi.org/10.1016/j.soilbio.2020.108128
Ball, J. W., & Nordstrom, D. K. (1991). User’s manual for WATEQ4F, with revised thermodynamic data base and text cases for calculating speciation of major, trace, and redox elements in natural waters (USGS Numbered Series No. 91–183). User’s manual for WATEQ4F, with revised thermodynamic data base and text cases for calculating speciation of major, trace, and redox elements in natural waters (Vol. 91–183). U.S. Geological Survey. https://doi.org/10.3133/ofr91183
Barber, A., Brandes, J., Leri, A., Lalonde, K., Balind, K., Wirick, S., et al. (2017). Preservation of organic matter in marine sediments by inner-sphere interactions with reactive iron. Scientific Reports, 7(1), 366. https://doi.org/10.1038/s41598-017-00494-0
Bartosiewicz, M., Przytulska, A., Lapierre, J.-F., Laurion, I., Lehmann, M. F., & Maranger, R. (2019). Hot tops, cold bottoms: Synergistic climate warming and shielding effects increase carbon burial in lakes. Limnology and Oceanography Letters, 4(5), 132–144. https://doi.org/10.1002/lol2.10117
Bastviken, D., Olsson, M., & Tranvik, L. (2003). Simultaneous measurements of organic carbon mineralization and bacterial production in oxic and anoxic lake sediments. Microbial Ecology, 46(1), 73–82. https://doi.org/10.1007/s00248-002-1061-9
Bastviken, D., Persson, L., Odham, G., & Tranvik, L. (2004). Degradation of dissolved organic matter in oxic and anoxic lake water. Limnology and Oceanography, 49(1), 109–116. https://doi.org/10.4319/lo.2004.49.1.0109
Bastviken, D., Tranvik, L. J., Downing, J. A., Crill, P. M., & Enrich-Prast, A. (2011). Freshwater methane emissions offset the continental carbon sink. Science, 331(6013), 50–50. https://doi.org/10.1126/science.1196808
Battin, T. J., Luyssaert, S., Kaplan, L. A., Aufdenkampe, A. K., Richter, A., & Tranvik, L. J. (2009). The boundless carbon cycle. Nature Geoscience, 2(9), 598–600. https://doi.org/10.1038/ngeo618
Beauvois, A., Vantelon, D., Jestin, J., Bouhnik-Le Coz, M., Catrouillet, C., Briois, V., et al. (2021). How crucial is the impact of calcium on the reactivity of iron-organic matter aggregates? Insights from arsenic. Journal of Hazardous Materials, 404, 124127. https://doi.org/10.1016/j.jhazmat.2020.124127
Björnerås, C., Weyhenmeyer, G. A., Evans, C. D., Gessner, M. O., Grossart, H.-P., Kangur, K., et al. (2017). Widespread increases in iron concentration in European and North American freshwaters. Global Biogeochemical Cycles, 31(10), 1488–1500. https://doi.org/10.1002/2017GB005749
Brothers, S., Köhler, J., Attermeyer, K., Grossart, H. P., Mehner, T., Meyer, N., et al. (2014). A feedback loop links brownification and anoxia in a temperate, shallow lake. Limnology and Oceanography, 59(4), 1388–1398. https://doi.org/10.4319/lo.2014.59.4.1388
Carey, C. C., Doubek, J. P., McClure, R. P., & Hanson, P. C. (2018). Oxygen dynamics control the burial of organic carbon in a eutrophic reservoir. Limnology and Oceanography Letters, 3(3), 293–301. https://doi.org/10.1002/lol2.10057
Carey, C. C., Wander, H. L., Woelmer, W. M., Lofton, M. E., Breef-Pilz, A., Doubek, J. P., et al. (2021). Water chemistry time series for Beaverdam Reservoir, Carvins Cove Reservoir, Falling Creek Reservoir, Gatewood Reservoir, and Spring Hollow Reservoir in southwestern Virginia, USA 2013-2020 [Data set]. Environmental Data Initiative. https://doi.org/10.6073/PASTA/6343E979A970E8A2590B4A450E851DD2
Carey, C. C., Hanson, P. C., Thomas, R. Q., Gerling, A. B., Hounshell, A. G., Lewis, A. S. L., et al. (2022). Anoxia decreases the magnitude of the carbon, nitrogen, and phosphorus sink in freshwaters. Global Change Biology, 28(16), 4861–4881. https://doi.org/10.1111/gcb.16228
Carey, C.C., A.S. Lewis, D.W. Howard, W.M. Woelmer, P.A. Gantzer, K.A. Bierlein, J.C. Little, and WVWA. 2022. Bathymetry and watershed area for Falling Creek Reservoir, Beaverdam Reservoir, and Carvins Cove Reservoir ver 1. Environmental Data Initiative. https://doi.org/10.6073/pasta/352735344150f7e77d2bc18b69a22412 (Accessed 2022-11-21).
Carey, C. C., Thomas, R. Q., & Hanson, P. C. (2022). General Lake Model-Aquatic EcoDynamics model parameter set for Falling Creek Reservoir, Vinton, Virginia, USA 2013-2019 [Data set]. Environmental Data Initiative. https://doi.org/10.6073/PASTA/9F7D037D9A133076A0A0D123941C6396
Carey, C. C., Wander, H. L., McClure, R. P., Lofton, M. E., Hamre, K. D., Doubek, J. P., et al. (2022). Secchi depth data and discrete depth profiles of photosynthetically active radiation, temperature, dissolved oxygen, and pH for Beaverdam Reservoir, Carvins Cove Reservoir, Falling Creek Reservoir, Gatewood Reservoir, and Spring Hollow Reservoir in southwestern Virginia, USA 2013-2021 [Data set]. Environmental Data Initiative. https://doi.org/10.6073/PASTA/887D8AB8C57FB8FDF3582507F3223CD6
Carey, C. C., Lewis, A. S. L., McClure, R. P., Gerling, A. B., Breef-Pilz, A., & Das, A. (2022). Time series of high-frequency profiles of depth, temperature, dissolved oxygen, conductivity, specific conductance, chlorophyll a, turbidity, pH, oxidation-reduction potential, photosynthetic active radiation, and descent rate for Beaverdam Reservoir, Carvins Cove Reservoir, Falling Creek Reservoir, Gatewood Reservoir, and Spring Hollow Reservoir in Southwestern Virginia, USA 2013-2021 [Data set]. Environmental Data Initiative. https://doi.org/10.6073/PASTA/C4C45B5B10B4CB4CD4B5E613C3EFFBD0
Carey, C. C., Wander, H. L., Howard, D. W., Niederlehner, B. R., Woelmer, W. M., Lofton, M. E., et al. (2022). Water chemistry time series for Beaverdam Reservoir, Carvins Cove Reservoir, Falling Creek Reservoir, Gatewood Reservoir, and Spring Hollow Reservoir in southwestern Virginia, USA 2013-2021 [Data set]. Environmental Data Initiative. https://doi.org/10.6073/PASTA/7BD797155CDBB5F1ACDF0547C6BA9023
Carpenter, S. R. (1996). Microcosm experiments have limited relevance for community and ecosystem ecology. Ecology, 77(3), 677–680. https://doi.org/10.2307/2265490
Chapman, M. J., Cravotta III, C. A., Szabo, Z., & Lindsey, B. D. (2013). Naturally occurring contaminants in the Piedmont and Blue Ridge crystalline-rock aquifers and Piedmont Early Mesozoic basin siliciclastic-rock aquifers, eastern United States, 1994–2008. Retrieved June 25, 2022, from https://pubs.er.usgs.gov/publication/sir20135072
Chen, C., Meile, C., Wilmoth, J., Barcellos, D., & Thompson, A. (2018). Influence of pO2 on Iron Redox Cycling and Anaerobic Organic Carbon Mineralization in a Humid Tropical Forest Soil. Environmental Science & Technology, 52(14), 7709–7719. https://doi.org/10.1021/acs.est.8b01368
Chen, C., Hall, S. J., Coward, E., & Thompson, A. (2020). Iron-mediated organic matter decomposition in humid soils can counteract protection. Nature Communications, 11(1), 2255. https://doi.org/10.1038/s41467-020-16071-5
Chen, K.-Y., Chen, T.-Y., Chan, Y.-T., Cheng, C.-Y., Tzou, Y.-M., Liu, Y.-T., & Teah, H.-Y. (2016). Stabilization of Natural Organic Matter by Short-Range-Order Iron Hydroxides. Environmental Science & Technology, 50(23), 12612–12620. https://doi.org/10.1021/acs.est.6b02793
Curti, L., Moore, O. W., Babakhani, P., Xiao, K.-Q., Woulds, C., Bray, A. W., et al. (2021). Carboxyl-richness controls organic carbon preservation during coprecipitation with iron (oxyhydr)oxides in the natural environment. Communications Earth & Environment, 2(1), 1–13. https://doi.org/10.1038/s43247-021-00301-9
Dadi, T., Wendt-Potthoff, K., & Koschorreck, M. (2017). Sediment resuspension effects on dissolved organic carbon fluxes and microbial metabolic potentials in reservoirs. Aquatic Sciences, 79(3), 749–764. https://doi.org/10.1007/s00027-017-0533-4
Davison, W., Grime, G. W., Morgan, J. a. W., & Clarke, K. (1991). Distribution of dissolved iron in sediment pore waters at submillimetre resolution. Nature, 352(6333), 323–325. https://doi.org/10.1038/352323a0
Dean, W. E., & Gorham, E. (1998). Magnitude and significance of carbon burial in lakes, reservoirs, and peatlands, 4.
Deemer, B. R., Harrison, J. A., Li, S., Beaulieu, J. J., DelSontro, T., Barros, N., et al. (2016). Greenhouse gas emissions from reservoir water surfaces: A new global synthesis. BioScience, 66(11), 949–964. https://doi.org/10.1093/biosci/biw117
DelSontro, T., Beaulieu, J. J., & Downing, J. A. (2018). Greenhouse gas emissions from lakes and impoundments: Upscaling in the face of global change. Limnology and Oceanography Letters, 3(3), 64–75. https://doi.org/10.1002/lol2.10073
Dokulil, M. T., de Eyto, E., Maberly, S. C., May, L., Weyhenmeyer, G. A., & Woolway, R. I. (2021). Increasing maximum lake surface temperature under climate change. Climatic Change, 165(3), 56. https://doi.org/10.1007/s10584-021-03085-1
Dzialowski, A. R., Rzepecki, M., Kostrzewska-Szlakowska, I., Kalinowska, K., Palash, A., & Lennon, J. T. (2014). Are the abiotic and biotic characteristics of aquatic mesocosms representative of in situ conditions? Journal of Limnology, 73(3). https://doi.org/10.4081/jlimnol.2014.721
Einola, E., Rantakari, M., Kankaala, P., Kortelainen, P., Ojala, A., Pajunen, H., et al. (2011). Carbon pools and fluxes in a chain of five boreal lakes: A dry and wet year comparison. Journal of Geophysical Research: Biogeosciences, 116(G3). https://doi.org/10.1029/2010JG001636
Eusterhues, K., Neidhardt, J., Hädrich, A., Küsel, K., & Totsche, K. U. (2014). Biodegradation of ferrihydrite-associated organic matter. Biogeochemistry, 119(1–3), 45–50. https://doi.org/10.1007/s10533-013-9943-0
Fisher, B. J., Moore, O. W., Faust, J. C., Peacock, C. L., & März, C. (2020). Experimental evaluation of the extractability of iron bound organic carbon in sediments as a function of carboxyl content. Chemical Geology, 556, 119853. https://doi.org/10.1016/j.chemgeo.2020.119853
Fisher, B. J., Faust, J. C., Moore, O. W., Peacock, C. L., & März, C. (2021). Technical Note: Uncovering the influence of methodological variations on the extractability of iron bound organic carbon, 20.
Garmo, Ø. A., Skjelkvåle, B. L., de Wit, H. A., Colombo, L., Curtis, C., Fölster, J., et al. (2014). Trends in surface water chemistry in acidified areas in Europe and North America from 1990 to 2008. Water, Air, & Soil Pollution, 225(3), 1880. https://doi.org/10.1007/s11270-014-1880-6
Gavin, A. L., Nelson, S. J., Klemmer, A. J., Fernandez, I. J., Strock, K. E., & McDowell, W. H. (2018). Acidification and climate linkages to increased dissolved organic carbon in high-elevation lakes. Water Resources Research, 54(8), 5376–5393. https://doi.org/10.1029/2017WR020963
Gerling, A. B., Browne, R. G., Gantzer, P. A., Mobley, M. H., Little, J. C., & Carey, C. C. (2014). First report of the successful operation of a side stream supersaturation hypolimnetic oxygenation system in a eutrophic, shallow reservoir. Water Research, 67, 129–143. https://doi.org/10.1016/j.watres.2014.09.002
Gerling, A. B., Munger, Z. W., Doubek, J. P., Hamre, K. D., Gantzer, P. A., Little, J. C., & Carey, C. C. (2016). Whole-catchment manipulations of internal and external loading reveal the sensitivity of a century-old reservoir to hypoxia. Ecosystems, 19(3), 555–571. https://doi.org/10.1007/s10021-015-9951-0
Gibbs, M. M. (1979). A simple method for the rapid determination of iron in natural waters. Water Research, 13(3), 295–297. https://doi.org/10.1016/0043-1354(79)90209-4
Grolemund, G., & Wickham, H. (2011). Dates and Times Made Easy with lubridate. Journal of Statistical Software, 40, 1–25. https://doi.org/10.18637/jss.v040.i03
Hamre, K. D., Lofton, M. E., McClure, R. P., Munger, Z. W., Doubek, J. P., Gerling, A. B., et al. (2018). In situ fluorometry reveals a persistent, perennial hypolimnetic cyanobacterial bloom in a seasonally anoxic reservoir. Freshwater Science, 37(3), 483–495. https://doi.org/10.1086/699327
Hanson, P. C., Pace, M. L., Carpenter, S. R., Cole, J. J., & Stanley, E. H. (2015). Integrating landscape carbon cycling: research needs for resolving organic carbon budgets of lakes. Ecosystems, 18(3), 363–375. https://doi.org/10.1007/s10021-014-9826-9
Hargrave, B. T. (1969). Similarity of oxygen uptake by benthic communities. Limnology and Oceanography, 14(5), 801–805. https://doi.org/10.4319/lo.1969.14.5.0801
Harris, D., Horwáth, W. R., & Kessel, C. van. (2001). Acid fumigation of soils to remove carbonates prior to total organic carbon or CARBON-13 isotopic analysis. Soil Science Society of America Journal, 65(6), 1853–1856. https://doi.org/10.2136/sssaj2001.1853
Heerah, K. M., & Reader, H. E. (2022). Towards the identification of humic ligands associated with iron transport through a salinity gradient. Scientific Reports, 12(1), 15545. https://doi.org/10.1038/s41598-022-19618-2
Hemingway, J. D., Rothman, D. H., Grant, K. E., Rosengard, S. Z., Eglinton, T. I., Derry, L. A., & Galy, V. V. (2019). Mineral protection regulates long-term global preservation of natural organic carbon. Nature, 570(7760), 228–231. https://doi.org/10.1038/s41586-019-1280-6
Herzog, S. D., Gentile, L., Olsson, U., Persson, P., & Kritzberg, E. S. (2020). Characterization of Iron and Organic Carbon Colloids in Boreal Rivers and Their Fate at High Salinity. Journal of Geophysical Research: Biogeosciences, 125(4), e2019JG005517. https://doi.org/10.1029/2019JG005517
Hiemstra, T., Mendez, J. C., & Li, J. (2019). Evolution of the reactive surface area of ferrihydrite: time, pH, and temperature dependency of growth by Ostwald ripening. Environmental Science: Nano, 6(3), 820–833. https://doi.org/10.1039/C8EN01198B
Hounshell, A. G., McClure, R. P., Lofton, M. E., & Carey, C. C. (2021). Whole-ecosystem oxygenation experiments reveal substantially greater hypolimnetic methane concentrations in reservoirs during anoxia. Limnology and Oceanography Letters, 6(1), 33–42.
Huang, W., Wang, K., Ye, C., Hockaday, W. C., Wang, G., & Hall, S. J. (2021). High carbon losses from oxygen-limited soils challenge biogeochemical theory and model assumptions. Global Change Biology, 27(23), 6166–6180. https://doi.org/10.1111/gcb.15867
Jane, S., Hansen, G., Kraemer, B., Leavitt, P., Mincer, J., North, R., et al. (2021). Widespread deoxygenation of temperate lakes. Nature, 594. https://doi.org/10.1038/s41586-021-03550-y
Jenny, J.-P., Francus, P., Normandeau, A., Lapointe, F., Perga, M.-E., Ojala, A., et al. (2016). Global spread of hypoxia in freshwater ecosystems during the last three centuries is caused by rising local human pressure. Global Change Biology, 22(4), 1481–1489. https://doi.org/10.1111/gcb.13193
Kaiser, K., & Guggenberger, G. (2003). Mineral surfaces and soil organic matter. European Journal of Soil Science, 54(2), 219–236. https://doi.org/10.1046/j.1365-2389.2003.00544.x
Kaiser, K., Mikutta, R., & Guggenberger, G. (2007). Increased stability of organic matter sorbed to ferrihydrite and goethite on aging. Soil Science Society of America Journal, 71(3), 711–719. https://doi.org/10.2136/sssaj2006.0189
Kalbitz, K., Schwesig, D., Rethemeyer, J., & Matzner, E. (2005). Stabilization of dissolved organic matter by sorption to the mineral soil. Soil Biology and Biochemistry, 37(7), 1319–1331. https://doi.org/10.1016/j.soilbio.2004.11.028
Kappler, A., Bryce, C., Mansor, M., Lueder, U., Byrne, J. M., & Swanner, E. D. (2021). An evolving view on biogeochemical cycling of iron. Nature Reviews Microbiology, 1–15. https://doi.org/10.1038/s41579-020-00502-7
Kassambara, A. (2020). ggpubr: “ggplot2” Based Publication Ready Plots (Version 0.4.0). Retrieved from https://CRAN.R-project.org/package=ggpubr
Kassambara, A. (2021). rstatix: Pipe-Friendly Framework for Basic Statistical Tests (Version 0.7.0). Retrieved from https://CRAN.R-project.org/package=rstatix
Keitt, T. (2022). colorRamps: Builds Color Tables (Version 2.3.1). Retrieved from https://CRAN.R-project.org/package=colorRamps
Kim, J., & Kim, T.-H. (2020). Distribution of Humic Fluorescent Dissolved Organic Matter in Lake Shihwa: the Role of the Redox Condition. Estuaries and Coasts, 43(3), 578–588. https://doi.org/10.1007/s12237-018-00491-0
Kirk, G. (2004). Reduction and Oxidation. In G. Kirk (Ed.), The Biogeochemistry of Submerged Soils (pp. 93–134). John Wiley & Sons, Ltd. https://doi.org/10.1002/047086303X.ch4
Kleber, M., Mikutta, R., Torn, M. S., & Jahn, R. (2005). Poorly crystalline mineral phases protect organic matter in acid subsoil horizons. European Journal of Soil Science, 56(6), 717–725. https://doi.org/10.1111/j.1365-2389.2005.00706.x
Kleber, M., Eusterhues, K., Keiluweit, M., Mikutta, C., Mikutta, R., & Nico, P. S. (2015). Chapter One - Mineral–Organic Associations: Formation, Properties, and Relevance in Soil Environments. In D. L. Sparks (Ed.), Advances in Agronomy (Vol. 130, pp. 1–140). Academic Press. https://doi.org/10.1016/bs.agron.2014.10.005
Knoll, L. B., Vanni, M. J., Renwick, W. H., Dittman, E. K., & Gephart, J. A. (2013). Temperate reservoirs are large carbon sinks and small CO2 sources: Results from high-resolution carbon budgets. Global Biogeochemical Cycles, 27(1), 52–64. https://doi.org/10.1002/gbc.20020
Kottek, M., Grieser, J., Beck, C., Rudolf, B., & Rubel, F. (2006). World Map of the Köppen-Geiger climate classification updated. Meteorologische Zeitschrift, 259–263. https://doi.org/10.1127/0941-2948/2006/0130
Kramer, M. G., & Chadwick, O. A. (2018). Climate-driven thresholds in reactive mineral retention of soil carbon at the global scale. Nature Climate Change, 8(12), 1104–1108. https://doi.org/10.1038/s41558-018-0341-4
Kramer, M. G., Sanderman, J., Chadwick, O. A., Chorover, J., & Vitousek, P. M. (2012). Long-term carbon storage through retention of dissolved aromatic acids by reactive particles in soil. Global Change Biology, 18(8), 2594–2605. https://doi.org/10.1111/j.1365-2486.2012.02681.x
Krueger, K. M., Vavrus, C. E., Lofton, M. E., McClure, R. P., Gantzer, P., Carey, C. C., & Schreiber, M. E. (2020). Iron and manganese fluxes across the sediment-water interface in a drinking water reservoir. Water Research, 182, 116003. https://doi.org/10.1016/j.watres.2020.116003
Lalonde, K., Mucci, A., Ouellet, A., & Gélinas, Y. (2012). Preservation of organic matter in sediments promoted by iron. Nature, 483(7388), 198–200. https://doi.org/10.1038/nature10855
LaRowe, D. E., & Van Cappellen, P. (2011). Degradation of natural organic matter: A thermodynamic analysis. Geochimica et Cosmochimica Acta, 75(8), 2030–2042. https://doi.org/10.1016/j.gca.2011.01.020
Lau, M. P., & del Giorgio, P. (2020). Reactivity, fate and functional roles of dissolved organic matter in anoxic inland waters. Biology Letters, 16(2), 20190694. https://doi.org/10.1098/rsbl.2019.0694
Lewis, A. S. L. (2022). Effects of hypoxia on coupled carbon and iron cycling in two freshwater reservoirs v1.1.0. Zenodo. https://doi.org/10.5281/zenodo.7527419
Lewis, A. S. L., Niederlehner, B. R., Das, A., Wander, H. L., Schreiber, M. E., & Carey, C. C. (2022). Experimental microcosm incubations assessing the effect of hypoxia on aqueous iron and organic carbon, pH, sediment organic carbon, and sediment iron-bound organic carbon. Environmental Data Initiative. https://doi.org/10.6073/pasta/60a7784acef3038d3c8a16776a5b5746
Lewis, A. S. L., Schreiber, M. E., Niederlehner, B. R., Das, A., & Carey, C. C. (2022). Total organic carbon, total nitrogen, and iron-bound organic carbon in surficial sediment and settling particulate material from Falling Creek and Beaverdam Reservoirs in 2019 and 2021. Environmental Data Initiative. https://doi.org/10.6073/pasta/a1d49c266b57465daa863cde4b1d4b4e
Luo, C., Wen, S., Lu, Y., Dai, J., & Du, Y. (2022). Coprecipitation of humic acid and phosphate with Fe(III) enhances the sequestration of carbon and phosphorus in sediments. Chemical Geology, 588, 120645. https://doi.org/10.1016/j.chemgeo.2021.120645
Marking, L. L., & Dawson, V. K. (1973). Toxicity of quinaldine sulfate to fish (Report No. 48) (pp. 0–8). La Crosse, WI. Retrieved from http://pubs.er.usgs.gov/publication/2001015
McClure, R. P., Schreiber, M. E., Lofton, M. E., Chen, S., Krueger, K. M., & Carey, C. C. (2021). Ecosystem-Scale Oxygen Manipulations Alter Terminal Electron Acceptor Pathways in a Eutrophic Reservoir. Ecosystems, 24(6), 1281–1298. https://doi.org/10.1007/s10021-020-00582-9
Mendonça, R., Müller, R. A., Clow, D., Verpoorter, C., Raymond, P., Tranvik, L. J., & Sobek, S. (2017). Organic carbon burial in global lakes and reservoirs. Nature Communications, 8(1), 1694. https://doi.org/10.1038/s41467-017-01789-6
Mikutta, R., & Kaiser, K. (2011). Organic matter bound to mineral surfaces: Resistance to chemical and biological oxidation. Soil Biology and Biochemistry, 43(8), 1738–1741. https://doi.org/10.1016/j.soilbio.2011.04.012
Munger, Z. W., Carey, C. C., Gerling, A. B., Doubek, J. P., Hamre, K. D., McClure, R. P., & Schreiber, M. E. (2019). Oxygenation and hydrologic controls on iron and manganese mass budgets in a drinking-water reservoir. Lake and Reservoir Management, 35(3), 277–291. https://doi.org/10.1080/10402381.2018.1545811
Nierop, K. G. J., Jansen, B., & Verstraten, J. M. (2002). Dissolved organic matter, aluminium and iron interactions: precipitation induced by metal/carbon ratio, pH and competition. The Science of the Total Environment, 300(1–3), 201–211. https://doi.org/10.1016/s0048-9697(02)00254-1
O’Reilly, C. M., Sharma, S., Gray, D. K., Hampton, S. E., Read, J. S., Rowley, R. J., et al. (2015). Rapid and highly variable warming of lake surface waters around the globe. Geophysical Research Letters, 42(24), 10,773-10,781. https://doi.org/10.1002/2015GL066235
Oyewumi, O., & Schreiber, M. E. (2017). Using column experiments to examine transport of As and other trace elements released from poultry litter: Implications for trace element mobility in agricultural watersheds. Environmental Pollution, 227, 223–233. https://doi.org/10.1016/j.envpol.2017.04.063
Pacheco, F. S., Roland, F., & Downing, J. A. (2014). Eutrophication reverses whole-lake carbon budgets. Inland Waters, 4(1), 41–48. https://doi.org/10.5268/IW-4.1.614
Pan, W., Kan, J., Inamdar, S., Chen, C., & Sparks, D. (2016). Dissimilatory microbial iron reduction release DOC (dissolved organic carbon) from carbon-ferrihydrite association. Soil Biology and Biochemistry, 103, 232–240. https://doi.org/10.1016/j.soilbio.2016.08.026
Patzner, M. S., Mueller, C. W., Malusova, M., Baur, M., Nikeleit, V., Scholten, T., et al. (2020). Iron mineral dissolution releases iron and associated organic carbon during permafrost thaw. Nature Communications, 11(1), 6329. https://doi.org/10.1038/s41467-020-20102-6
Peter, S., & Sobek, S. (2018). High variability in iron-bound organic carbon among five boreal lake sediments. Biogeochemistry, 139(1), 19–29. https://doi.org/10.1007/s10533-018-0456-8
Peter, S., Isidorova, A., & Sobek, S. (2016). Enhanced carbon loss from anoxic lake sediment through diffusion of dissolved organic carbon. Journal of Geophysical Research: Biogeosciences, 121(7), 1959–1977. https://doi.org/10.1002/2016JG003425
Peter, S., Agstam, O., & Sobek, S. (2017). Widespread release of dissolved organic carbon from anoxic boreal lake sediments. Inland Waters, 7(2), 151–163. https://doi.org/10.1080/20442041.2017.1300226
Raymond, P. A., Hartmann, J., Lauerwald, R., Sobek, S., McDonald, C., Hoover, M., et al. (2013). Global carbon dioxide emissions from inland waters. Nature, 503(7476), 355–359. https://doi.org/10.1038/nature12760
Riedel, T., Zak, D., Biester, H., & Dittmar, T. (2013). Iron traps terrestrially derived dissolved organic matter at redox interfaces. Proceedings of the National Academy of Sciences, 110(25), 10101–10105. https://doi.org/10.1073/pnas.1221487110
Rumpel, C., & Kögel-Knabner, I. (2011). Deep soil organic matter—a key but poorly understood component of terrestrial C cycle. Plant and Soil, 338(1), 143–158. https://doi.org/10.1007/s11104-010-0391-5
Schindler, D. W. (1998). Whole-ecosystem experiments: replication versus realism: the need for ecosystem-scale experiments. Ecosystems, 1(4), 323–334. https://doi.org/10.1007/s100219900026
Schreiber, M. E., Hammond, N. W., Krueger, K. M., Munger, Z. W., Ming, C. L., Breef-Pilz, A., & Carey, C. C. (2022). Time series of total and soluble iron and manganese concentrations from Falling Creek Reservoir and Beaverdam Reservoir in southwestern Virginia, USA from 2014 through 2021 [Data set]. Environmental Data Initiative. https://doi.org/10.6073/PASTA/7CDF3D7A234963B265F09B7D6D08F357
Shields, M. R., Bianchi, T. S., Gélinas, Y., Allison, M. A., & Twilley, R. R. (2016). Enhanced terrestrial carbon preservation promoted by reactive iron in deltaic sediments. Geophysical Research Letters, 43(3), 1149–1157. https://doi.org/10.1002/2015GL067388
Skoog, A. C., & Arias-Esquivel, V. A. (2009). The effect of induced anoxia and reoxygenation on benthic fluxes of organic carbon, phosphate, iron, and manganese. Science of The Total Environment, 407(23), 6085–6092. https://doi.org/10.1016/j.scitotenv.2009.08.030
Sobek, S., Durisch-Kaiser, E., Zurbrügg, R., Wongfun, N., Wessels, M., Pasche, N., & Wehrli, B. (2009). Organic carbon burial efficiency in lake sediments controlled by oxygen exposure time and sediment source. Limnology and Oceanography, 54(6), 2243–2254. https://doi.org/10.4319/lo.2009.54.6.2243
Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Soil Series Classification Database. Available online. Accessed [11/21/2022].
Sondheim, M. W., & Standish, J. T. (1983). Numerical analysis of a chronosequence including an assessment of variability. Canadian Journal of Soil Science, 63(3), 501–517. https://doi.org/10.4141/cjss83-052
Stoddard, J. L., Jeffries, D. S., Lükewille, A., Clair, T. A., Dillon, P. J., Driscoll, C. T., et al. (1999). Regional trends in aquatic recovery from acidification in North America and Europe. Nature, 401(6753), 575–578. https://doi.org/10.1038/44114
Tavakkoli, E., Rengasamy, P., Smith, E., & McDonald, G. K. (2015). The effect of cation–anion interactions on soil pH and solubility of organic carbon. European Journal of Soil Science, 66(6), 1054–1062. https://doi.org/10.1111/ejss.12294
Thompson, A., Chadwick, O. A., Rancourt, D. G., & Chorover, J. (2006). Iron-oxide crystallinity increases during soil redox oscillations. Geochimica et Cosmochimica Acta, 70(7), 1710–1727. https://doi.org/10.1016/j.gca.2005.12.005
Thompson, J., Poulton, S. W., Guilbaud, R., Doyle, K. A., Reid, S., & Krom, M. D. (2019). Development of a modified SEDEX phosphorus speciation method for ancient rocks and modern iron-rich sediments. Chemical Geology, 524, 383–393. https://doi.org/10.1016/j.chemgeo.2019.07.003
Tranvik, L. J., Cole, J. J., & Prairie, Y. T. (2018). The study of carbon in inland waters—from isolated ecosystems to players in the global carbon cycle. Limnology and Oceanography Letters, 3(3), 41–48. https://doi.org/10.1002/lol2.10068
Trapletti, A., Hornik, K., & code), B. L. (BDS test. (2022). tseries: Time Series Analysis and Computational Finance (Version 0.10-51). Retrieved from https://CRAN.R-project.org/package=tseries
USGCRP, 2018: Second State of the Carbon Cycle Report (SOCCR2): A Sustained Assessment Report. [Cavallaro, N., G. Shrestha, R. Birdsey, M. A. Mayes, R. G. Najjar, S. C. Reed, P. Romero-Lankao, and Z. Zhu (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 878 pp., doi: 10.7930/SOCCR2.2018
Virginia Division of Mineral Resources. (2003). Digital representation of the 1993 geologic map of Virginia.
von Wachenfeldt, E., Sobek, S., Bastviken, D., & Tranvik, L. J. (2008). Linking allochthonous dissolved organic matter and boreal lake sediment carbon sequestration: The role of light-mediated flocculation. Limnology and Oceanography, 53(6), 2416–2426. https://doi.org/10.4319/lo.2008.53.6.2416
Walker, R. R., & Snodgrass, W. J. (1986). Model for sediment oxygen demand in lakes. Journal of Environmental Engineering, 112(1), 25–43. https://doi.org/10.1061/(ASCE)0733-9372(1986)112:1(25)
Wang, S., Jia, Y., Liu, T., Wang, Y., Liu, Z., & Feng, X. (2021). Delineating the Role of Calcium in the Large-Scale Distribution of Metal-Bound Organic Carbon in Soils. Geophysical Research Letters, 48(10), e2021GL092391. https://doi.org/10.1029/2021GL092391
Weyhenmeyer, G. A., Prairie, Y. T., & Tranvik, L. J. (2014). Browning of boreal freshwaters coupled to carbon-iron interactions along the aquatic continuum. PloS One, 9(2), e88104. https://doi.org/10.1371/journal.pone.0088104
Wickham, H., Averick, M., Bryan, J., Chang, W., McGowan, L. D., François, R., et al. (2019). Welcome to the Tidyverse. Journal of Open Source Software, 4(43), 1686. https://doi.org/10.21105/joss.01686
Williamson, C. E., Overholt, E. P., Pilla, R. M., Leach, T. H., Brentrup, J. A., Knoll, L. B., et al. (2015). Ecological consequences of long-term browning in lakes. Scientific Reports, 5(1), 1–10. https://doi.org/10.1038/srep18666
Winslow, L., Read, J., Woolway, R., Brentrup, J., Leach, T., Zwart, J., et al. (2019). rLakeAnalyzer: Lake Physics Tools (Version 1.11.4.1). Retrieved from https://CRAN.R-project.org/package=rLakeAnalyzer
Woelmer, W., Hounshell, A. G., Lofton, M. E., Wander, H. L., Lewis, A. S. L., Scott, D., & Carey, C. C. (2022, June 25). The importance of time and space in biogeochemical heterogeneity and processing along the reservoir ecosystem continuum. Earth and Space Science Open Archive. https://doi.org/10.1002/essoar.10511710.1
Woodward, H. P. (1932). Geology and Mineral Resources of the Roanoke Area, Virginia.
Yang, L., Choi, J. H., & Hur, J. (2014). Benthic flux of dissolved organic matter from lake sediment at different redox conditions and the possible effects of biogeochemical processes. Water Research, 61, 97–107. https://doi.org/10.1016/j.watres.2014.05.009