Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River basin

Zuijdgeest, Alissa; Zurbrügg, Roland; Blank, Nanina; Fulcri, R.; Senn, David B.; Wehrli, Bernhard

doi:10.5194/bg-12-7535-2015

Cited by 16 publications

(28 citation statements)

References 60 publications

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“…Strong increases in pCO 2 downstream of the Barotse Plains and other flooded systems in the Zambezi catchment have also been observed during the rainy season (Teodoru et al 2015). The Barotse Plains showed high DOC and low SPM concentrations during peak flow in 2013 (Zuijdgeest et al 2015). Retention of particulate organic matter and net export of dissolved organic matter indicated degradation processes dominated over primary production in April 2013 (Zuijdgeest et al 2015).…”

Section: Phase 1: Expansionmentioning

confidence: 93%

“…Emissions of greenhouse gases have been linked to natural barriers (waterfalls), and hydropower reservoirs (DelSontro et al 2011), and the presence of floodplain areas, with highest concentrations of CO 2 and methane found just downstream of extensive floodplain areas (Teodoru et al 2015). Temporal variations of concentrations and trends in dissolved and particulate organic carbon (DOC and POC, respectively) and greenhouse gases in the river system have been observed between periods of high and low flows (Teodoru et al 2015;Zuijdgeest et al 2015;Zurbrügg et al 2013). …”

Section: Study Sitementioning

confidence: 99%

“…The probe in Senanga was deployed from a floating jetty, roughly 5 m from an outer bend of the river. The Zambezi was horizontally well-mixed (Zuijdgeest et al 2015). Though there typically is some flooding upstream of the first sensor location, the bulk of the seasonal flooding occurs between these two locations.…”

Section: Probe Deploymentmentioning

confidence: 99%

“…This was probably due to calculation artifacts relating to the boundaries of the time series and small variations in the two records. The travel time at the end of the dry season was therefore manually adjusted to a smooth increase from 3 to 8 days, where the minimum of 3 days is determined based on acoustic Doppler current profiler flow measurements at several locations along the Barotse Plains from April 2013 (Zuijdgeest et al 2015). At the end of the year, travel times were again set manually to 3 days to match the observations and correct for boundary-related calculation artifacts (Online Resource 3).…”

Section: Inundation Dynamicsmentioning

confidence: 99%

“…The Barotse Plains showed high DOC and low SPM concentrations during peak flow in 2013 (Zuijdgeest et al 2015). Retention of particulate organic matter and net export of dissolved organic matter indicated degradation processes dominated over primary production in April 2013 (Zuijdgeest et al 2015). DOC concentrations in the Okavango delta peaked two to four weeks before peak flood (Mladenov et al 2005).…”

Section: Phase 1: Expansionmentioning

confidence: 99%

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Hysteresis effects in organic matter turnover in a tropical floodplain during a flood cycle

2016

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Tropical inland waters are increasingly recognized for their role in the global carbon cycle, but uncertainty about the effects of such systems on the transported organic matter remains. The seasonal interactions between river, floodplain, and vegetation result in highly dynamic systems, which can exhibit markedly different biogeochemical patterns throughout a flood cycle. In this study, we determined rates and governing processes of organic matter turnover. Multi-probes in the Barotse Plains, a pristine floodplain in the Upper Zambezi River (Zambia), provided a high-resolution data set over the course of a hydrological cycle. The concentrations of oxygen, carbon dioxide, dissolved organic carbon, and suspended particulate matter in the main channel showed clear hysteresis trends with expanding and receding water on the floodplain. Lower oxygen and suspended matter concentrations prevailed at longer travel times of water in the floodplain, while carbon dioxide and dissolved organic carbon concentrations were higher when the water spent more time on the floodplain. Maxima of particulate loads occurred before highest water levels, whereas the maximum in dissolved organic carbon load occurred during the transition of flooding and flood recession. Degradation of terrestrial organic matter occurred mainly on the floodplain at increased floodplain residence times. Our data suggest that floodplains become more intense hotspots at prolonged travel time of the flood pulse over the floodplain.

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Section: Phase 1: Expansionmentioning

confidence: 93%

Section: Study Sitementioning

confidence: 99%

Section: Probe Deploymentmentioning

confidence: 99%

Section: Inundation Dynamicsmentioning

confidence: 99%

Section: Phase 1: Expansionmentioning

confidence: 99%

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Hysteresis effects in organic matter turnover in a tropical floodplain during a flood cycle

2016

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A synthesis of floodplain aquatic ecosystem metabolism and carbon flux using causal criteria analysis

McInerney

Giling

Wolfenden

et al. 2022

Limnology & Oceanography

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The transformation of solar energy into organic matter by autotrophs (gross primary production [GPP]) and the use of that energy by autotrophs and heterotrophs (ecosystem respiration [ER]) describe the total energy available to support food webs. Rates of GPP and ER vary with temperature, light, hydrology, nutrients, and organic matter supply and quality yet despite their obvious importance, spatiotemporal variation of metabolic patterns among floodplain habitats, and their relationship to inundation dynamics remain unclear. We set out to review the peerreviewed literature surrounding the influence of the magnitude, frequency, and duration of floodplain inundation on aquatic ecosystem metabolism and carbon flux by rigorously testing a suite of cause-effect hypotheses using a causal criteria analysis. Causal criteria analysis is a literature synthesis approach developed to address a lack of experimental data and subsequent weak inference of causal relationships. We found support for 3 of the 14 hypotheses we tested relating to putative causal relationships: (1) large floods transfer more carbon from floodplains to the river channel than small floods via the increase in inundation area leading to more overall leaching of floodplain litter, (2) in high turbidity floodplain habitats rates of GPP are reduced by restrictions to photic depth, and (3) a positive correlation between nutrients and GPP-generally GPP in floodplain wetlands increases with nutrient levels. We obtained inconsistent evidence for a causal relationship between macrophytes and aquatic GPP, with studies reporting both a negative influence from decreased light caused by macrophyte shading and a positive influence from structural support provided by macrophytes for periphyton growth. For the remaining 10 hypotheses, there was insufficient evidence to support causal relationships, including for any hypotheses relating to frequency or duration of floodplain inundation. Our results emphasize that despite an apparent wealth of metabolic studies in riverine ecosystems, floodplain metabolic dynamics remain poorly studied, likely due to less investment and increased difficulty compared to lotic waters. The review also highlighted aspects of floodplain aquatic ecosystem metabolism for which there are significant knowledge gaps in the literature, in particular metabolic responses to inundation frequency and duration. Our results call attention to the importance of site specificity and temporal changes when predicting putative cause-effect relationships between floodplain inundation and metabolic patterns.

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Nutrients in tropical and temperate rivers and floodplains – comparison of the Rivers Songkhram (Thailand) and Narew (Poland)

et al. 2023

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Ecological processes in floodplains may function differently across climate regions. We compared the river discharge, water chemistry, and nutrient budget and balance of floodplain vegetation in a temperate climate (River Narew, Poland) with those in a tropical climate (River Songkhram, Thailand). Both rivers show a discharge regime with a flood pulse, following snowmelt (Narew) or monsoon rainfall (Songkhram), with peak discharges roughly 25 times higher in the River Songkhram. Electrical Conductivity (EC) values of both rivers are generally comparable, while nutrient concentrations are somewhat higher in the temperate River Narew (with total phosphorus (TP) approximately 1.5 and total inorganic nitrogen (TIN) approximately 2.2 times higher than in Songkhram). A comparison of the nutrient budget of floodplain vegetation suggests that soil is the most important source of nutrients for most vegetation types, i.e., Narew sedge (N), Narew forest floor (N and P), Songkhram bamboo (N and P), and Songkhram grass (P). Additionally, floodwater is the main input source of P for the Narew sedge and a secondary input source for Songkhram grass. Vegetation close to the river tends to have higher productivity, emphasizing the nutrient-filtering function of floodplain vegetation. For both rivers, nutrient input into the floodplains by floodwater is higher than nutrient export from the floodplains, indicating that both floodplains have a nutrient sink function. These findings demonstrate that the floodwater pulse is a source of nutrient input for floodplain vegetation in both temperate and tropical climates, with the soil playing a vital role in the nutrient budgets and balance.

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Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River basin

Cited by 16 publications

References 60 publications

Hysteresis effects in organic matter turnover in a tropical floodplain during a flood cycle

Hysteresis effects in organic matter turnover in a tropical floodplain during a flood cycle

A synthesis of floodplain aquatic ecosystem metabolism and carbon flux using causal criteria analysis

Nutrients in tropical and temperate rivers and floodplains – comparison of the Rivers Songkhram (Thailand) and Narew (Poland)

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