Pulsed terrestrial organic carbon persists in an estuarine environment after major storm events

2020 ◽  
Author(s):  
Eero Asmala ◽  
Christopher Osburn ◽  
Ryan Paerl ◽  
Hans Paerl
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
River Estuary ◽  
River Mouth ◽  
Neuse River Estuary ◽  
Storm Events ◽  
Dynamic Component ◽  
Neuse River ◽  
Doc Concentration ◽  
A Minor

<p>The transport of dissolved organic carbon from land to ocean is a large and dynamic component of the global carbon cycle. Export of dissolved organic carbon from watersheds is largely controlled by hydrology, and is exacerbated by increasing major rainfall and storm events, causing pulses of terrestrial dissolved organic carbon (DOC) to be shunted through rivers downstream to estuaries. Despite this increasing trend, the fate of the pulsed terrestrial DOC in estuaries remains uncertain. Here we present DOC data from 1999 to 2017 in Neuse River Estuary (NC, USA) and analyze the effect of six tropical cyclones (TC) during that period on the quantity and fate of DOC in the estuary. We find that that TCs promote a considerable increase in DOC concentration near the river mouth at the entrance to the estuary, on average an increase of 200 µmol l<sup>-1</sup> due to storms was observed. TC-induced increases in DOC are apparent throughout the estuary, and the duration of these elevated DOC concentrations ranges from one month at the river mouth to over six months in lower estuary. Our results suggest that despite the fast mineralization rates, the terrestrial DOC is processed only to a minor extent relative to the pulsed amount entering the estuary. We conclude that the vast quantity of organic carbon delivered to estuaries by TCs transform estuaries from active biogeochemical processing “reactors” of organic carbon to appear more like passive shunts due to the sheer amount of pulsed material rapidly flushed through the estuary.</p>

Extreme weather events modulate processing and export of dissolved organic carbon in the Neuse River Estuary, NC

2019 ◽  
Vol 219 ◽  
pp. 189-200 ◽  
Author(s):  
Alexandria G. Hounshell ◽  
Jacob C. Rudolph ◽  
Bryce R. Van Dam ◽  
Nathan S. Hall ◽  
Christopher L. Osburn ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
River Estuary ◽  
Extreme Weather ◽  
Neuse River Estuary ◽  
Extreme Weather Events ◽  
Neuse River ◽  
Weather Events

Seasonal changes in pathways of dissolved organic carbon through a hillslope soil (Xeralf) with contrasting texture

Soil Research ◽  
1992 ◽  
Vol 30 (4) ◽  
pp. 465 ◽  
Author(s):  
DJ Chittleborough ◽  
KRJ Smettem ◽  
E Cotsaris ◽  
FW Leaney
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Overland Flow ◽  
Podzolic Soil ◽  
Marked Decrease ◽  
Soil Surface ◽  
Storm Events ◽  
Dry Period ◽  
Doc Concentration ◽  
Texture Contrast

The pathways of dissolved organic carbon (DOC) through a podzolic soil (Xeralf) with strong texture contrast are described. During winter, most of the DOC passes through macropores in the profile and flows laterally through the B horizons. During summer the presence of dry, hydrophobic organic matter on the soil surface and the A1 horizon causes DOC to flow overland. DOC concentrations vary seasonally. Highest concentrations are measured during summer overland flow. For all horizons, the longer the dry period the greater the DOC concentration in the subsequent flow. During storm events there is a marked flushing effect in the B horizons but in the A horizon and the surface, DOC concentrations tend to rise. There was a marked decrease in DOC concentration in flow from the B3 compared to the upper horizons. This may be due to adsorption by fine clays lining the macropores.

scholarly journals The relative importance of photodegradation and biodegradation of terrestrially derived dissolved organic carbon across four lakes of differing trophic status

2020 ◽  
Vol 17 (24) ◽  
pp. 6327-6340
Author(s):  
Christopher M. Dempsey ◽  
Jennifer A. Brentrup ◽  
Sarah Magyan ◽  
Lesley B. Knoll ◽  
Hilary M. Swain ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Trophic Status ◽  
Dissolved Inorganic Carbon ◽  
Freshwater Ecosystems ◽  
Total Carbon ◽  
Relative Importance ◽  
Storm Events ◽  
Lake Ecosystems ◽  
Doc Concentration

Abstract. Outgassing of carbon dioxide (CO2) from freshwater ecosystems comprises 12 %–25 % of the total carbon flux from soils and bedrock. This CO2 is largely derived from both biodegradation and photodegradation of terrestrial dissolved organic carbon (DOC) entering lakes from wetlands and soils in the watersheds of lakes. In spite of the significance of these two processes in regulating rates of CO2 outgassing, their relative importance remains poorly understood in lake ecosystems. In this study, we used groundwater from the watersheds of one subtropical and three temperate lakes of differing trophic status to simulate the effects of increases in terrestrial DOC from storm events. We assessed the relative importance of biodegradation and photodegradation in oxidizing DOC to CO2. We measured changes in DOC concentration, colored dissolved organic carbon (specific ultraviolet absorbance – SUVA320; spectral slope ratio – Sr), dissolved oxygen, and dissolved inorganic carbon (DIC) in short-term experiments from May–August 2016. In all lakes, photodegradation led to larger changes in DOC and DIC concentrations and optical characteristics than biodegradation. A descriptive discriminant analysis showed that, in brown-water lakes, photodegradation led to the largest declines in DOC concentration. In these brown-water systems, ∼ 30 % of the DOC was processed by sunlight, and a minimum of 1 % was photomineralized. In addition to documenting the importance of photodegradation in lakes, these results also highlight how lakes in the future may respond to changes in DOC inputs.

scholarly journals Nitrogen and dissolved organic carbon (DOC) losses from an artificially drained grassland on organic soils

2014 ◽  
Vol 11 (15) ◽  
pp. 4123-4137 ◽  
Author(s):  
B. Tiemeyer ◽  
P. Kahle
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Arable Land ◽  
Organic Soils ◽  
N Losses ◽  
Total N ◽  
Dynamic Component ◽  
Small Catchment ◽  
Doc Concentration

Abstract. Nitrate–nitrogen (NO3–N) as well as dissolved organic carbon (DOC) and nitrogen (DON) concentrations and losses were studied for three and two years, respectively, in a small catchment dominated by a degraded peatland used as intensive grassland. Concentrations in the shallow groundwater were spatially and temporally very variable, with NO3–N being the most dynamic component (7.3 ± 12.5 mg L−1) and ranging from 0 to 79.4 mg L−1. Average NO3–N concentrations of 10.3 ± 5.4 mg L−1 (0 to 25.5 mg L−1) in the ditch draining the catchment and annual NO3–N losses of 19, 35 and 26 kg ha−1 confirmed drained peatlands as an important source of diffuse N pollution. The highest NO3–N losses occurred during the wettest year. Resulting from concentration of 2.4 ± 0.8 mg L−1 (0.7 to 6.2 mg L−1), DON added a further 4.5 to 6.4 kg ha−1 to the N losses and thus formed a relevant (15%) component of the total N losses. Ditch DOC concentrations of 24.9 ± 5.9 mg L−1 (13.1 to 47.7 mg L−1) resulted in DOC losses of 66 kg ha−1 in the wet year of 2006/2007 and 39 kg ha−1 in the dry year of 2007/2008. Ditch DOC concentration were lower than the groundwater DOC concentration of 50.6 ± 15.2 mg L−1 (14.9 to 88.5 mg L−1). Both DOC and N concentrations were governed by hydrological conditions, but NO3–N reacted much faster and clearer on rising discharge rates than DOC, which tended to be higher under drier conditions. In the third year of the study, the superposition of a very wet summer and land use changes from grassland to arable land in a part of the catchment suggests that, under re-wetting conditions with a high groundwater table in summer, NO3–N would diminish quickly, while DOC would remain on a similar level. Further intensification of the land use, on the other hand, would increase N losses to receiving water bodies.

scholarly journals The relative importance of photodegradation and biodegradation of terrestrially derived dissolved organic carbon across four lakes of differing trophic status

2020 ◽  
Author(s):  
Christopher M. Dempsey ◽  
Jennifer A. Brentrup ◽  
Sarah Magyan ◽  
Lesley B. Knoll ◽  
Hilary M. Swain ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Trophic Status ◽  
Dissolved Inorganic Carbon ◽  
Freshwater Ecosystems ◽  
Total Carbon ◽  
Optical Characteristics ◽  
Relative Importance ◽  
Storm Events ◽  
Doc Concentration

Abstract. Outgassing of carbon dioxide (CO2) from freshwater ecosystems comprises 12–25 % of the total carbon flux from soils and bedrock. This CO2 is largely derived from both biodegradation and photodegradation of terrestrial dissolved organic carbon (DOC) entering lakes from wetlands and soils in the watersheds of lakes. In spite of the significance of these two processes in regulating rates of CO2 outgassing, their relative importance remains poorly understood in lake ecosystems. In this study, we used groundwater from the watersheds of one subtropical and three temperate lakes of differing trophic status to simulate the effects of increases in terrestrial DOC from storm events. We assessed the relative importance of biodegradation and photodegradation in oxidizing DOC to CO2. We measured changes in DOC concentration, the optical characteristics of the DOC (SUVA320 and Sr), dissolved oxygen, and dissolved inorganic carbon (DIC) in short-term experiments from May–August, 2016. In all lakes, photodegradation led to larger changes in DOC and DIC concentrations and optical characteristics than biodegradation. A descriptive discriminant analysis showed that in brown-water lakes, photodegradation led to the largest declines in DOC concentration. In these brown-water systems, ~ 30 % of the DOC was processed by sunlight and ~ 2 % was photo mineralized. In addition to documenting the importance of photodegradation in lakes, these results also highlight how lakes in the future may respond to changes in DOC inputs.

Continuous resistivity profiling data from the upper Neuse River Estuary, North Carolina, 2004-2005

2006 ◽  
Author(s):  
VeeAnn A. Cross ◽  
John F. Bratton ◽  
Emile M. Bergeron ◽  
Jeff K. Meunier ◽  
John Crusius ◽  
...  
Keyword(s):  
North Carolina ◽  
River Estuary ◽  
Neuse River Estuary ◽  
Neuse River ◽  
Resistivity Profiling

scholarly journals Three representative UK moorland soils show differences in decadal release of dissolved organic carbon in response to environmental change

2011 ◽  
Vol 8 (12) ◽  
pp. 3661-3675 ◽  
Author(s):  
M. I. Stutter ◽  
D. G. Lumsdon ◽  
A. P. Rowland
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Environmental Change ◽  
Soil Properties ◽  
Process Models ◽  
Environmental Drivers ◽  
Specific Response ◽  
Soil C ◽  
Doc Concentration ◽  
Mineral Soils

Abstract. Moorland carbon reserves in organo-mineral soils may be crucial to predicting landscape-scale variability in soil carbon losses, an important component of which is dissolved organic carbon (DOC). Surface water DOC trends are subject to a range of scaling, transport and biotic processes that disconnect them from signals in the catchment's soils. Long-term soil datasets are vital to identify changes in DOC release at source and soil C depletion. Here we show, that moorland soil solution DOC concentrations at three key UK Environmental Change Network sites increased between 1993–2007 in both surface- and sub- soil of a freely-draining Podzol (48 % and 215 % increases in O and Bs horizons, respectively), declined in a gleyed Podzol and showed no change in a Peat. Our principal findings were that: (1) considerable heterogeneity in DOC response appears to exist between different soils that is not apparent from the more consistent observed trends for streamwaters, and (2) freely-draining organo-mineral Podzol showed increasing DOC concentrations, countering the current scientific focus on soil C destabilization in peats. We discuss how the key solubility controls on DOC associated with coupled physico-chemical factors of ionic strength, acid deposition recovery, soil hydrology and temperature cannot readily be separated. Yet, despite evidence that all sites are recovering from acidification the soil-specific responses to environmental change have caused divergence in soil DOC concentration trends. The study shows that the properties of soils govern their specific response to an approximately common set of broad environmental drivers. Key soil properties are indicated to be drainage, sulphate and DOC sorption capacity. Soil properties need representation in process-models to understand and predict the role of soils in catchment to global C budgets. Catchment hydrological (i.e. transport) controls may, at present, be governing the more ubiquitous rises in river DOC concentration trends, but soil (i.e. source) controls provide the key to prediction of future C loss to waters and the atmosphere.

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