Desiccation time and rainfall control gaseous carbon fluxes in an intermittent stream

Abstract

Droughts are recognized to impact global biogeochemical cycles. However, the implication of desiccation on in-stream carbon (C) cycling is not well understood yet. We subjected sediments from a lowland, organic rich intermittent stream to experimental desiccation over a 9-week-period to investigate temporal changes in microbial functional traits in relation to their redox requirements, carbon dioxide (CO2) and methane (CH4) fluxes and water-soluble organic carbon (WSOC). Concurrently, the implications of rewetting by simulated short rainfalls (4 and 21 mm) on gaseous C fluxes were tested. Early desiccation triggered dynamic fluxes of CO2 and CH4 with peak values of 383 and 30 mg C m−2 h−1 (mean ± SD), respectively, likely in response to enhanced aerobic mineralization and accelerated evasion. At longer desiccation, CH4 dropped abruptly, likely because of reduced abundance of anaerobic microbial traits. The CO2 fluxes ceased later, suggesting aerobic activity was constrained only by extended desiccation over time. We found that rainfall boosted fluxes of CO2, which were modulated by rainfall size and the preceding desiccation time. Desiccation also reduced the amount of WSOC and the proportion of labile compounds leaching from sediment. It remains questionable to which extent changes of the sediment C pool are influenced by respiration processes, microbial C uptake and cell lysis due to drying-rewetting cycles. We highlight that the severity of the dry period, which is controlled by its duration and the presence of precipitation events, needs detailed consideration to estimate the impact of intermittent flow on global riverine C fluxes.

Carbon Biogeochemistry and Export Governed by Flow in a Non‐Perennial Stream

“…In contrast to low DO conditions during surface water disconnection, CO 2 concentrations would build up when the stream was at low flow. High concentrations of CO 2 and solutes may be typical of pools (Gómez-Gener et al, 2016;Looman et al, 2017) and sediments (Arce et al, 2021;Martinsen et al, 2019;von Schiller et al, 2019) in intermittent streams, and our measurements of concentration and emissions at low flow are within ranges of CO 2 reported for both perennial and intermittent small streams. Soils and dry sediments of non-perennial streams often have an uptick in respiration with rewetting (Arce et al, 2019;Schimel et al, 2011;Yu et al, 2014), consistent with the Birch effect (Birch, 1958).…”

“…Linking high‐frequency surface water coverage estimates with frequent discrete estimates of dry sediment emissions, to capture subtle and shorter‐term flow phase changes, would enable creation of a more robust non‐perennial stream CO 2 budget. It is also likely that precipitation falling on dry sediments during highly fragmented periods (when a small to moderate storm would not be enough to reconnect isolated surface water reaches) would stimulate a non‐trivial respiration pulse in the sediments and/or hyporheic zone (Arce et al., 2021). CO 2 and DOM generated by brief rewetting of dry reaches, and not exported or emitted, may add to carbon pools temporarily stored in the stream; the next wet‐up even may be large enough to degas dissolved CO 2 or be a storm more capable of scouring stored material.…”

Significant Emissions From Forest Drainage Ditches—An Unaccounted Term in Anthropogenic Greenhouse Gas Inventories?

“…These changes may have the effect of mitigating growing season ditch CH 4 emissions if watercourses dry out on a regular basis, but higher temperatures may also enhance ditch CO 2 emissions. Furthermore, changes to the timing of precipitation events could increase the occurrence of drought‐rewetting cycles which can be hot moments for fluvial GHG emission (Arce et al., 2021; Wallin et al., 2020). Regardless of future changes, it is clear that ditches have the potential to offset, at least to some extent, the NCS of GHG uptake provided by drained forested landscapes.…”

Microfluidic investigation of the impacts of flow fluctuations on the development of Pseudomonas putida biofilms

“…Additionally, the uctuation periods used in this study (5.6 minutes to 6 hours) resemble the durations of rainfall events (15 minutes to few hours) 52 , intermittent time period of water supply system (6 hours) 32 , and hydraulic retention time in the operation process of moving bed bio lm reactors (MBBR) (10 hours) 53 . Therefore, our results have potential implications for predicting and controlling bio lm development in natural and engineered systems, such as the drinking water distribution systems and medical devices, where bio lms are consistently exposed to uctuating ows 22,25,27 . The critical frequency (f cr = 2.4×10 − 4 Hz) identi ed in our study can be applied to control bio lm growth in these environments.…”

“…Hydrodynamic conditions, e.g., ow velocity and shear stress, are known to impact the development, or time evolution of bio lm properties [17][18][19][20][21] . However, the majority of current studies have focused on steady ow, i.e., time-invariant constant ow, despite the fact that uctuating ows are common in a wide variety of natural and industrial environments, such as in rivers due to rainfalls and droughts [22][23] , in pipes due to intermittent water usage [24][25] , and in circulatory systems due to pulsating heartbeat [26][27] . Fluctuating ow can impact bio lm development because the oscillatory components of uctuating ows alter the real-time distribution of pressure, velocity, and shear stress, as well as mixing and nutrient transport rates [28][29] .…”