| 1. |
- Costello, David M., et al.
(författare)
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Global patterns and controls of nutrient immobilization on decomposing cellulose in riverine ecosystems
- 2022
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Ingår i: Global Biogeochemical Cycles. - : John Wiley & Sons. - 0886-6236 .- 1944-9224. ; 36:3
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Tidskriftsartikel (refereegranskat)abstract
- Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter.
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| 2. |
- Thanh Son Dao, N., et al.
(författare)
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Toxic cyanobacteria from Tri An Reservoir, Vietnam
- 2010
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Ingår i: Nova Hedwigia: Zeitschrift für Kryptogamenkunde. - : Schweizerbart. - 0029-5035. ; 90:3-4, s. 433-448
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Tidskriftsartikel (refereegranskat)abstract
- Seven strains of cyanobacteria from Tri An Reservoir, a drinking water reservoir for millions of people in Southern Vietnam, were isolated, cultivated, identified and described. They originated from the species Microcystis aeruginosa, M. botrys, M. wesenbergii, Anabaena A. smithii, Aphanizomenon aphanizomenoides and Cylindrospermopsis raciborskii. Microcystin (MC) content in the cultures and two scum samples from Tri An Reservoir were determined by high performance liquid chromatography. Four variants of MC, MC-LR, MC-RR, MC-LA, MC-LY and one un-determined variant were detected in the scum samples but none were found in the cultures. The two variants MC-LA and MC-LY were recorded for the first time for Vietnam. Total MC concentrations in the two scum samples were 0.45 and 0.64 mg g(-1) dried weight, respectively. The genus Microcystis in Tri An Reservoir was assumed to be a MC producer as the other possible MC producing species A. circinalis was usually detected in lower quantities.
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| 3. |
- Tiegs, Scott D., et al.
(författare)
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Global patterns and drivers of ecosystem functioning in rivers and riparian zones
- 2019
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Ingår i: Science Advances. - Washington : American Association of Advancement in Science. - 2375-2548. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth's biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented "next-generation biomonitoring" by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.
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