| 1. |
- Bento, Luiz, et al.
(författare)
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Regulation in the Metabolism and Community Structure of a Tropical Salt Flat after Rainfall
- 2017
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Ingår i: Journal of Coastal Research. - : COASTAL EDUCATION & RESEARCH FOUNDATION. - 0749-0208 .- 1551-5036. ; 33:2, s. 304-308
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Tidskriftsartikel (refereegranskat)abstract
- Tropical salt flats typically lack a water column for most of the year, which means that rainfall is probably one of the major factors that regulate benthic microalgae and metabolism in areas subjected to periodic drought. Therefore, the goal of this study was to evaluate the effects of rainfall on the ecological function and community structure of a tropical mangrove salt flat area. This study showed that the highest primary production and respiration fluxes were recorded on the last day of sampling when it rained (-7.6 and 4.7 mmol C-CO2 m(-2) h(-1), respectively). Net primary production increased significantly compared with the dry period that preceded the rain event. The results also suggested that community structure was regulated by rainfall. After the rain event, abundance increased by one order of magnitude, but the diversity and evenness indices decreased. These results demonstrate that rain does have strong regulatory effects on the ecological function and structure of tropical salt flats.
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| 2. |
- Machado-Silva, Fausto, et al.
(författare)
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Dark carbon fixation in stream carbon cycling
- 2023
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Ingår i: Limnology and Oceanography. - : WILEY. - 0024-3590 .- 1939-5590.
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Tidskriftsartikel (refereegranskat)abstract
- Headwater streams are often characterized by turbulence, organic matter inputs from terrestrial systems, net heterotrophy, and the microbial loop supplying carbon and energy for consumers. However, ecological models overlook dark carbon fixation (DCF), the light-independent inorganic carbon uptake, mainly based on chemosynthesis, using energy yields from redox reactions. The quantification of microbial biomass production, including DCF, heterotrophic production (HP), gross primary production (GPP), and ecosystem respiration (ER) in lotic aquatic systems, has long yet to be addressed. Here, we investigate HP and DCF in water, sediment, and litter in addition to GPP and ER from streams in pristine rainforests in three distinct sub-basins of the Amazon River, assessing the variety of turbid, black, and clear waters. We observed mean (min-max) values of microbial biomass production of about 0.1 (0.02-1.2), 3.2 (0.8-14.1), and 0.1 (0.02-0.5) mg C m-2 h-1 in water, sediment, and litter samples, in which DCF : HP showed mean (min-max) values of 0.5 (0.2-2), 0.02 (0.001-0.07), and 0.2 (0.001-0.5). Hence, measurements yielded DCF of similar magnitude as HP in water and litter but significantly lower in sediment, indicating that DCF supplied more carbon to planktonic and litter microbes than in top sediments of streams. Literature comparisons show similar DCF and GPP, both being lower than ER in streams. Finally, we found stream DCF higher than in lentic systems, suggesting that flow and turbulence may accelerate chemosynthesis.
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| 3. |
- Pangala, Sunitha R., et al.
(författare)
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Large emissions from floodplain trees close the Amazon methane budget
- 2017
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 552:7684, s. 230-
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Tidskriftsartikel (refereegranskat)abstract
- Wetlands are the largest global source of atmospheric methane (CH4)(1), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain(2,3), the largest natural geographic source of CH4 in the tropics, consistently underestimate the atmospheric burden of CH4 determined via remote sensing and inversion modelling(4,5), pointing to a major gap in our understanding of the contribution of these ecosystems to CH4 emissions. Here we report CH4 fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH4 emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests(6) and tropical peat swamp forests(7), representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (delta C-13) of -66.2 +/- 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 +/- 1.8 to 21.2 +/- 2.5 teragrams of CH4 a year, in addition to the 20.5 +/- 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a topdown regional estimate of CH4 emissions of 42.7 +/- 5.6 teragrams of CH4 a year for the Amazon basin, based on regular vertical lower-troposphere CH4 profiles covering the period 2010-2013. We find close agreement between our top-down and combined bottom-up estimates, indicating that large CH4 emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH4 budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH4 emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH4 source when trees are combined with other emission sources.
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