Shifts in the carbon dynamics in a tropical lowland river system (Tana River, Kenya) during flooded and non-flooded conditions

Geeraert, Naomi; Omengo, Fred; Borges, Alberto; Govers, Gérard; Bouillon, Steven

doi:10.1007/s10533-017-0292-2

Cited by 26 publications

(36 citation statements)

References 64 publications

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“…No permanent tributaries are present over this distance, which makes it an ideal setting to compare incoming and outgoing fluxes of water, sediment and C (Geeraert et al, 2017). Some "lagas" (temporary rivers) are present, but they are only active for a few days per year.…”

Section: Study Areamentioning

confidence: 99%

“…Data on total suspended matter (TSM) concentrations were gathered during (1) (Geeraert et al, 2017). The dataset of Garissa was further expanded with data from monthly (Tamooh et al, 2014) and biweekly (unpublished data) monitoring over the period January 2009 -December 2013 (n POC =85, n DOC =68, n DIC =86).…”

Section: Fluxes Of Sediment and Carbonmentioning

confidence: 99%

“…The dataset of Garissa was further expanded with data from monthly (Tamooh et al, 2014) and biweekly (unpublished data) monitoring over the period January 2009 -December 2013 (n POC =85, n DOC =68, n DIC =86). The sampling protocols used to obtain concentrations of POC, DOC and DIC 20 have been presented in Geeraert et al (2017) for the wet season campaigns, and in Tamooh et al (2014) for the biweekly and monthly samples, where a different method for DIC concentration was used.…”

Section: Fluxes Of Sediment and Carbonmentioning

confidence: 99%

“…The long-term balance of the C species also suggests a net retention of C within the river stretch for POC, DOC and DIC, with an average annual amount of ~18 000 tC yr -1 , ~920 tC yr -1 and ~1200 tC yr -1 , respectively. Although these measurements give no indication to the fate of the retained C, part of the POC will likely be deposited in the floodplain while some will be respired, while the excess DIC is expected to have evaded to the atmosphere, 15 as has been quantified for distinct wet seasons in the Tana River (Geeraert et al, 2017).…”

Section: Differences In Longitudinal Fluxesmentioning

confidence: 99%

“…5 days, and the response of the C concentration during the wet seasons. Therefore, a newly collected dataset focused on the daily C dynamics during three wet seasons at Garissa and Garsen (Geeraert et al, 2017).…”

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confidence: 99%

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Seasonal and inter-annual variations in carbon fluxes in a tropical river system (Tana River, Kenya)

Geeraert

Omengo

Tamooh

et al. 2017

Preprint

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Abstract. Quantification of sediment and carbon (C) fluxes in rivers with strong seasonal and inter-annual variability 10 presents a challenge for global flux estimates as measurement periods are often too short to cover all hydrological conditions. We studied the dynamics of the Tana River (Kenya) from 2012 to 2014 through daily monitoring of sediment concentrations at three sites (Garissa, Tana River Primate Reserve and Garsen) and daily monitoring of C concentrations in Garissa and Garsen during three distinct seasons. In wet seasons, C fluxes were dominated by particulate organic C (POC) and decreased downstream. Dry season fluxes of dissolved inorganic C (DIC) and POC had a similar share in total C flux at 15 both locations while POC fluxes increased downstream. The dissolved organic C (DOC) flux did not show strong spatial nor temporal variations. The construction of constituent rating curves with a bootstrap method in combination with daily discharge data provided potential sediment and C flux ranges as a function of annual discharge. At low annual discharge, our estimates generally predict a net decrease of sediment and C storage between the upstream and downstream site. As the annual discharge increases, our simulations shift toward net retention. This analysis allowed us to infer how 20 variations in discharge regime, related to climate or human impacts, may affect riverine fluxes. Overall, we estimate that retention was dominant: integration over all simulations resulted in an average net retention of sediment (~2.9 Mt yr -1 ), POC (~18000 tC yr -1 ), DOC (~920 tC yr -1 ) and DIC (~1200 tC yr -1 ) over the 73 years of discharge measurements.

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Section: Study Areamentioning

confidence: 99%

Section: Fluxes Of Sediment and Carbonmentioning

confidence: 99%

Section: Fluxes Of Sediment and Carbonmentioning

confidence: 99%

Section: Differences In Longitudinal Fluxesmentioning

confidence: 99%

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confidence: 99%

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Seasonal and inter-annual variations in carbon fluxes in a tropical river system (Tana River, Kenya)

Geeraert

Omengo

Tamooh

et al. 2017

Preprint

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Riverine export of water, sediment and carbon during flood events in the arid to semi‐arid Wuding River on the Chinese Loess Plateau

Ran

Yang

Tian

et al. 2020

Earth Surf Processes Landf

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Floods have become increasingly important in fluvial export of water, sediment and carbon (C). Using high‐frequency sampling, the export of water, sediment and C was examined in the Wuding River catchment on the Chinese Loess Plateau. With groundwater as an important contributor to runoff all year round, floods were relatively less important in the export of water. However, large floods were disproportionately important in exporting sediment and inorganic C (DIC) and organic C (DOC and POC). The three largest floods in each year transported 53.6–97.3 and 41.4–77% of the annual sediment and C fluxes, respectively. An extreme flood in 2017 alone contributed 94.6 and 73.1% of the annual sediment and C fluxes, respectively, in just 7 days, which included 20.3, 92.1 and 35.7% of the annual DOC, POC and DIC fluxes, respectively. A stable carbon isotope (δ13C) analysis of POC indicated that modern soils and C3 plants were its primary source. Furthermore, floods greatly accelerated CO2 degassing due to elevated gas transfer velocity, although stream water CO2 partial pressure (pCO2) exhibited a decreasing trend with flow discharge. Although these results illustrated that increasing runoff diluted pCO2, the timing and magnitude of floods were found to be critical in determining the response of pCO2 to flow dynamics. Low‐magnitude floods in the early wet season increased pCO2 because of enhanced organic matter input, while subsequent large floods caused a lower pCO2 due to greatly reduced organic matter supply. Finally, continuous monitoring of a complete flood event showed that the CO2 efflux during the flood (2348 ± 664 mg C m–2 day–1) was three times that under low‐flow conditions (808 ± 98 mg C m–2 day–1). Our study suggests that infrequent, heavy storm events, which are predicted to increase under climate change, will greatly alter the transport regimes of sediment and C. © 2020 John Wiley & Sons, Ltd.

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Dynamics and fluxes of organic carbon and nitrogen in two Guiana Shield river basins impacted by deforestation and mining activities

Gallay¹,

Mora

Martinez

et al. 2017

Hydrological Processes

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Deforestation and mining activities have proven to be very damaging to rivers because these activities disturb the environmental characteristics of rivers. Thus, the concentrations of dissolved organic carbon (DOC), particulate organic carbon (POC), particulate nitrogen (PN), and Chlorophyll-a (Chl-a) were measured monthly during 2 hydrological years in the Maroni and Oyapock Rivers to assess the dynamics and fluxes of organic carbon and nitrogen in these 2 Guiana Shield basins, which have been strongly (Maroni) and weakly (Oyapock) impacted by deforestation and mining activities. The 2-year time series show that DOC, POC, PN, and Chl-a concentrations vary seasonally with discharge in both rivers, indicating a hydrologically dominated control. Temporal patterns of DOC, POC, and PN indicate that these variables show maximum concentrations in rising waters due to the yield of organic matter and nitrogen accumulated in soils, which are incorporated into the rivers during rainfall. However, the Chl-a concentrations were at a maximum during low-water stages. The C/N and C/Chl-a ratios also showed a seasonal trend, with lower values during the low water periods due to an increase in algal biomass. During high water, the POC in both rivers is the result of terrestrial organic matter, whereas during low-water autochthonous organic matter can reach up to 34% of the POC. The mean annual fluxes of TOC and PN were higher (4.56 × 10 5 tonC year −1 and 1.77 × 10 4 tonN year −1 , respectively) in the Maroni River than those (1.84 × 10 5 tonC year −1 and 0.54 × 10 4 tonN year −1 , respectively) in the Oyapock River. However, the specific fluxes of DOC, POC, and PN from both basins were nearly the same. Although gold mining activities are performed in both basins, there is no conclusive evidence regarding the impact of these activities on the dynamics of organic matter and particulate nitrogen in the Maroni and Oyapock Rivers.

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Shifts in the carbon dynamics in a tropical lowland river system (Tana River, Kenya) during flooded and non-flooded conditions

Cited by 26 publications

References 64 publications

Seasonal and inter-annual variations in carbon fluxes in a tropical river system (Tana River, Kenya)

Seasonal and inter-annual variations in carbon fluxes in a tropical river system (Tana River, Kenya)

Riverine export of water, sediment and carbon during flood events in the arid to semi‐arid Wuding River on the Chinese Loess Plateau

Dynamics and fluxes of organic carbon and nitrogen in two Guiana Shield river basins impacted by deforestation and mining activities

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