Dissolved organic carbon lability increases with water residence time in the alluvial aquifer of a river floodplain ecosystem

Helton, Ashley M.; Wright, Meredith S.; Bernhardt, Emily S.; Poole, Geoffrey C.; Cory, Rose M.; Stanford, Jack A.

doi:10.1002/2014jg002832

Cited by 30 publications

(31 citation statements)

References 66 publications

(86 reference statements)

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“…Our measurements of the relative bioavailability of DOC are well within the range measured in other aquatic systems (Sondergaard and Middelboe, 1995;Stets and Cotner, 2008;Catalán et al, 2015;Helton et al, 2015;Frey et al, 2016). All but one of the systems we measured had BDOC values less than 50% of the total DOC pool, further supporting the idea that the bulk portion of DOC in freshwater is recalcitrant.…”

Section: Bioavailability Of Doc and Dopsupporting

confidence: 82%

Bioavailability of Dissolved Organic Phosphorus in Temperate Lakes

Thompson

Cotner

2018

Front. Environ. Sci.

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Freshwater aquatic systems are biogeochemical hotspots, with heterotrophic bacteria rapidly cycling the compounds that pass through them. P is a key nutrient that controls primary production in many freshwater ecosystems and is important for understanding eutrophication in lakes. Previous work has often focused on the dynamics of inorganic phosphorus and its impact on primary production, however, the role of nutrients bound in more complex organic forms (such as dissolved organic phosphorus, DOP) in supporting primary production and harmful algal blooms has been neglected. Here, we quantify the bioavailability of dissolved organic carbon (DOC) and DOP in 27 aquatic systems across the Upper Midwest United States. Using exponential decay models, long-term nutrient degradation assays revealed that decay constants for DOP ranged from −0.001 per day to −0.12 per day with a median value of −0.01 per day. These rates were geographically variable and were as high or higher than DOC decay constants, which ranged from −0.003 per day to −0.024 per day with a median value of −0.01 per day. Additionally, total bioavailability of DOP ranged from 0 to 100% with a median value of 78% of the DOP pool, demonstrating that DOP bioavailability was highly variable across systems. In contrast, bioavailable DOC was more tightly constrained with values ranging from 4.37 to 53.81% of the total DOC pool with a median value of 24.95%. DOP bioavailability was negatively correlated with the DOC:DOP of the organic matter pool, suggesting that bioavailable DOP is drawn down in systems that are more likely to be P limited. Finally, we show that including estimates of DOC and DOP bioavailability reduces estimates of elemental imbalance experienced by aquatic bacteria.

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Section: Bioavailability Of Doc and Dopsupporting

confidence: 82%

Bioavailability of Dissolved Organic Phosphorus in Temperate Lakes

Thompson

Cotner

2018

Front. Environ. Sci.

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“…The nature of the covalent bonds and the structure of organic compounds that hold N and P also differentially influence the bioavailability and turnover of associated nutrients (Vitousek et al, 2002). Such complexity makes it difficult to predict the potential for bacterial usage of these resources in an ecologically meaningful way (Bronk et al, 2007;Berggren et al, 2015;Helton et al, 2015). It is generally thought that the major fraction of DOC originating from terrestrial soils is recalcitrant, yet bioavailability estimates from different lakes suggest that a variable proportion of DOC can be used by bacteria (e.g.…”

Section: Introductionmentioning

confidence: 99%

New insights on resource stoichiometry: assessing availability of carbon, nitrogen, and phosphorus to bacterioplankton

et al. 2017

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Abstract. Boreal lake and river ecosystems receive large quantities of organic nutrients and carbon (C) from their catchments. How bacterioplankton respond to these inputs is not well understood, in part because we base our understanding and predictions on "total pools", yet we know little about the stoichiometry of bioavailable elements within organic matter. We designed bioassays with the purpose of exhausting the pools of readily bioavailable dissolved organic carbon (BDOC), bioavailable dissolved nitrogen (BDN), and bioavailable dissolved phosphorus (BDP) as fast as possible. Applying the method in four boreal lakes at base-flow conditions yielded concentrations of bioavailable resources in the range 105-693 µg C L −1 for BDOC (2 % of initial total DOC), 24-288 µg N L −1 for BDN (31 % of initial total dissolved nitrogen), and 0.2-17 µg P L −1 for BDP (49 % of initial total dissolved phosphorus). Thus, relative bioavailability increased from carbon (C) to nitrogen (N) to phosphorus (P). We show that the main fraction of bioavailable nutrients is organic, representing 80 % of BDN and 61 % of BDP. In addition, we demonstrate that total C : N and C : P ratios are as much as 13-fold higher than C : N and C : P ratios for bioavailable resource fractions. Further, by applying additional bioavailability measurements to seven widely distributed rivers, we provide support for a general pattern of relatively high bioavailability of P and N in relation to C. Altogether, our findings underscore the poor availability of C for support of bacterial metabolism in boreal C-rich freshwaters, and suggest that these ecosystems are very sensitive to increased input of bioavailable DOC.

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“…The aquatic DOM pool is a complex mixture that reflects both source material and processing along the watershed terrestrial-aquatic continuum, and as a result it can show significant spatial and temporal variation (Hudson et al, 2007;Graeber et al, 2012;Wallin et al, 2015). Both DOC concentration and DOM composition can serve as indicators of watershed characteristics (Koehler et al, 2009), hydrologic flow paths (Johnson et al, 2011;Helton et al, 2015), and watershed biogeochemical processes (Emili and Price, 2013). DOM composition can also influence its role in downstream processing and ecological function, such as susceptibility to biological (Judd et al, 2006) and physiochemical interactions (Yamashita and Jaffé, 2008).…”

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confidence: 99%

A global hotspot for dissolved organic carbon in hypermaritime watersheds of coastal British Columbia

et al. 2017

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Abstract. The perhumid region of the coastal temperate rainforest (CTR) of Pacific North America is one of the wettest places on Earth and contains numerous small catchments that discharge freshwater and high concentrations of dissolved organic carbon (DOC) directly to the coastal ocean. However, empirical data on the flux and composition of DOC exported from these watersheds are scarce. We established monitoring stations at the outlets of seven catchments on Calvert and Hecate islands, British Columbia, which represent the rain-dominated hypermaritime region of the perhumid CTR. Over several years, we measured stream discharge, stream water DOC concentration, and stream water dissolved organic-matter (DOM) composition. Discharge and DOC concentrations were used to calculate DOC fluxes and yields, and DOM composition was characterized using absorbance and fluorescence spectroscopy with parallel factor analysis (PARAFAC). The areal estimate of annual DOC yield in water year 2015 was 33.3 Mg C km −2 yr −1 , with individual watersheds ranging from an average of 24.1 to 37.7 Mg C km −2 yr −1 . This represents some of the highest DOC yields to be measured at the coastal margin. We observed seasonality in the quantity and composition of exports, with the majority of DOC export occurring during the extended wet period (September-April). Stream flow from catchments reacted quickly to rain inputs, resulting in rapid export of relatively fresh, highly terrestrial-like DOM. DOC concentration and measures of DOM composition were related to stream discharge and stream temperature and correlated with watershed attributes, including the extent of lakes and wetlands, and the thickness of organic and mineral soil horizons. Our discovery of high DOC yields from these small catchments in the CTR is especially compelling as they deliver relatively fresh, highly terrestrial organic matter directly to the coastal ocean. Hypermaritime landscapes are common on the British Columbia coast, suggesting that this coastal margin may play an important role in the regional processing of carbon and in linking terrestrial carbon to marine ecosystems.

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Dissolved organic carbon lability increases with water residence time in the alluvial aquifer of a river floodplain ecosystem

Cited by 30 publications

References 66 publications

Bioavailability of Dissolved Organic Phosphorus in Temperate Lakes

Bioavailability of Dissolved Organic Phosphorus in Temperate Lakes

New insights on resource stoichiometry: assessing availability of carbon, nitrogen, and phosphorus to bacterioplankton

A global hotspot for dissolved organic carbon in hypermaritime watersheds of coastal British Columbia

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