Hot spots for carbon emissions from Mediterranean fluvial networks during summer drought

Gómez‐Gener, Lluís; Obrador, Biel; Schiller, Daniel von; Marcé, Rafael; Casas-Ruiz, Joan Pere; Proia, Lorenzo; Acuña, Vicenç; Catalán, Núria; Muñoz, Isabel; Koschorreck, Matthias

doi:10.1007/s10533-015-0139-7

Cited by 67 publications

(91 citation statements)

References 87 publications

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“…Hence, in both our study and that of Obrador et al (), water metabolic proxies (as N, P, or conductivity) emerge as key drivers of C cyclization. This reinforces the expected positive trophic dependence of CO 2 fluxes on the availability of organic C in water and sediments, with emission peaks associated to dystrophic habitats (Gómez‐Gener et al, ).…”

Section: Discussionsupporting

confidence: 79%

“…Results from the present study highlight the relevant role of topography and river water variations on the metabolic activities of aquatic habitats and their emerging bottoms along a lowland riverscape, exemplified by widely different CO 2 and CH 4 concentrations and exchange rates (see Gómez‐Gener et al, ; Obrador et al, ; Raymond et al, ). Specifically, a progressive clear reduction in the water CO 2 release was observed moving from river waters to the marginal aquatic habitats.…”

Section: Discussionmentioning

confidence: 60%

“…CO 2 and CH 4 fluxes were measured with an indirect method to avoid the habitat perturbation due to benthic chamber deployment in water (see Guérin et al, ; Vachon, Praire, & Cole, ). This method can potentially underestimate the CH 4 fluxes as it does not take into account CH 4 ebullition, although in running waters, isolated pools and dry river beds CH 4 fluxes depend almost exclusively on diffusive processes (Gómez‐Gener et al, ). Likely, in the investigated habitats, the CH 4 ebullition flux is negligible, because the sediment is mainly sandy, with organic matter <4.00%.…”

Section: Methodsmentioning

confidence: 99%

“…Studies on these issues are available for boreal and tropical areas, especially for lentic water bodies or waterlogged soils (Abril et al, ; Campeau & Del Giorgio, ; Guérin, Abril, Tremblay, & Delmas, ; Repo et al, ; Sturtevant & Oechel, ), and for few altered lotic systems within agricultural watersheds (Halbedel & Koschorreck, ; Hope, Palmer, Billet, & Dawson, ). Among the expected scenarios, intermittent rivers are of growing concern, because they display CO 2 emission rates comparable with those measured in the surrounding terrestrial areas and much greater than the CO 2 efflux from neighbouring stagnant waters (Gómez‐Gener et al, ; von Schiller et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Connectivity and habitat typology drive CO₂ and CH₄ fluxes across land–water interfaces in lowland rivers

et al. 2018

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Lowland rivers are assumed to be a net source of carbon dioxide (CO2) and methane (CH4). However, little is known about the contribution of marginal permanent and temporary riverine aquatic systems to river carbon metabolism. Elevation, in relation to flooding, hydro‐morphological, and ecological features of such habitats, can affect the gas fluxes across the water–atmosphere interfaces and the periodically air‐exposed riverbeds. This hypothesis was investigated in the lowland sector of the Po River (Northern Italy) from May to September 2008. Five different aquatic habitats were considered: the main river course; a backwater habitat; and three lateral lentic waterbodies—an oxbow and two quarry lakes of different age. The water mass was always CO2 and CH4 supersaturated, and gas fluxes were from the water to the atmosphere. In the highly dynamic river course and backwaters, CO2 emission rates were nearly one order of magnitude greater than in the lentic and hypoxic oxbow and quarry lakes. By contrast, CH4 fluxes peaked in the lentic, deeper, and permanent water bodies. At sediment–atmosphere interfaces, the CO2 emissions increased along an organic matter, a water saturation, and a chlorophyll a gradient, attaining the maximum rates in the periodically air‐exposed riverbed and marginal sandy sediments. These differences in gas fluxes resulted from either the submersion persistence or the alternation of submersion and emersion phases, which were ultimately due to the gap between elevation and river water variations. All this stresses the critical role of marginal aquatic habitats for river C budget.

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Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 60%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Connectivity and habitat typology drive CO₂ and CH₄ fluxes across land–water interfaces in lowland rivers

et al. 2018

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“…entering dormancy, maintaining osmotic equilibrium, reducing their growth and respiration rates, or finding refuge in deeper sediment; Orchard & Cook, 1983;Moyano, Manzoni, & Chenu, 2013;Sabater, Timoner, Borrego, & Acuña, 2016), bacteria are generally less tolerant than aquatic fungi, which can move more easily across the dry habitat. Nonetheless, although long-term drought may significantly compromise key stream biogeochemical processes at the landscape scale, previous studies observed that streambed microorganisms are able to maintain ecosystem energy flow, extracellular enzyme activities and carbon processing to some extent when the river dries up (Gómez-Gener et al, 2015;Marxsen, Zoppini, & Wilczek, 2010). Nonetheless, although long-term drought may significantly compromise key stream biogeochemical processes at the landscape scale, previous studies observed that streambed microorganisms are able to maintain ecosystem energy flow, extracellular enzyme activities and carbon processing to some extent when the river dries up (Gómez-Gener et al, 2015;Marxsen, Zoppini, & Wilczek, 2010).…”

Section: Introductionmentioning

confidence: 99%

Key role of streambed moisture and flash storms for microbial resistance and resilience to long‐term drought

et al. 2018

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Spatial and temporal widening of drought periods together with occurrence of flash storm events are consequences of global change affecting temporary stream ecosystems. Streambed heterotrophic microbes and the key biogeochemical processes they carry on could be endangered by the strengthening of drought episodes. Here, we performed a 165‐day experiment through 12 streambed sediment columns to study heterotrophic microbial functional and structural responses to long‐term drought. Two sediment depths (surface and hyporheic) and leaf litter were monitored under three treatments: control (maintained in wet, pool‐like conditions), dry (5 months of drought), and dry–storm (5 months of drought including two flash storms). All treatments were then followed by rewetting. Surface sediment followed by leaf litter was the most affected by the long‐term drought as shown by the reduction of polysaccharidic enzyme activities and litter decomposition rate, although lignin decomposition was not affected. This resulted in a greater use of recalcitrant compounds which might be due to reduced labile organic matter sources and the greater resistance of fungi than bacteria to drought. Moreover, in surface sediment, bacterial viability and algal biomass were reduced while the production of extracellular polymeric substances was intensified with dryness, suggesting its potential role as survival strategy. Hyporheic sediments appeared more resistant to long‐term drought, and this might be linked to its slightly higher water content (2.5%) than the surface (0.5%) during drying together with a greater content of fine material that allowed fungi and bacteria to survive and extracellular enzyme activities to be maintained. Microbial resilience to long‐term drought in sediment and leaf litter was promoted by the flash storms as shown by the fast recovery of enzyme activities, bacterial viability and leaf litter decomposition rate in the dry–storm treatment, once rewetted. Storms might liberate previously occluded carbon sources that fuel the fast microbial reactivation as well as providing sediment moisture for microbial survival. Our results highlight that long‐term drought may compromise stream biogeochemical processes linked to organic matter decomposition and that microbes are highly sensitive to minimal water content changes. Thus, long‐term drought consequences could be mitigated by occasional precipitations or by natural streambed moisture.

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Low contribution of internal metabolism to carbon dioxide emissions along lotic and lentic environments of a Mediterranean fluvial network

et al. 2016

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Inland waters are significant sources of carbon dioxide (CO2) to the atmosphere. CO2 supersaturation and subsequent CO2 emissions from inland waters can be driven by internal metabolism, external inputs of dissolved inorganic carbon (DIC) derived from the catchment, and other processes (e.g., internal geochemical reactions of calcite precipitation or photochemical mineralization of organic solutes). However, the sensitivity of the magnitude and sources of CO2 emissions to fluvial network hydromorphological alterations is still poorly understood. Here we investigated both the magnitude and sources of CO2 emissions from lotic (i.e., running waters) and lentic (i.e., stagnant waters associated to small dams) waterbodies of a Mediterranean fluvial network by computing segment‐scale mass balances of CO2. Our results showed that sources other than internal metabolism sustained most (82%) of the CO2 emissions from the studied fluvial network. The magnitude and sources of CO2 emissions in lotic waterbodies were highly dependent on hydrology, with higher emissions dominated by DIC inputs derived from the catchment during high flows and lower emissions partially fueled by CO2 produced biologically within the river during low flows. In contrast, CO2 emissions in lentic waterbodies were low, relatively stable over the time and the space, and dominated by DIC inputs from the catchment regardless of the different hydrological situations. Overall, our results stress the sensitivity of fluvial networks to human activities and climate change and particularly highlight the role of hydromorphological conditions on modulating the magnitude and sources of CO2 emissions from fluvial networks.

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Hot spots for carbon emissions from Mediterranean fluvial networks during summer drought

Cited by 67 publications

References 87 publications

Connectivity and habitat typology drive CO₂ and CH₄ fluxes across land–water interfaces in lowland rivers

Connectivity and habitat typology drive CO₂ and CH₄ fluxes across land–water interfaces in lowland rivers

Key role of streambed moisture and flash storms for microbial resistance and resilience to long‐term drought

Low contribution of internal metabolism to carbon dioxide emissions along lotic and lentic environments of a Mediterranean fluvial network

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Hot spots for carbon emissions from Mediterranean fluvial networks during summer drought

Cited by 67 publications

References 87 publications

Connectivity and habitat typology drive CO2 and CH4 fluxes across land–water interfaces in lowland rivers

Connectivity and habitat typology drive CO2 and CH4 fluxes across land–water interfaces in lowland rivers

Key role of streambed moisture and flash storms for microbial resistance and resilience to long‐term drought

Low contribution of internal metabolism to carbon dioxide emissions along lotic and lentic environments of a Mediterranean fluvial network

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Connectivity and habitat typology drive CO₂ and CH₄ fluxes across land–water interfaces in lowland rivers

Connectivity and habitat typology drive CO₂ and CH₄ fluxes across land–water interfaces in lowland rivers