| 1. |
- 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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| 2. |
- 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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| 3. |
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| 4. |
- Hirata, Rafael Y. S., et al.
(författare)
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Platinum nanoparticle-based microreactors protect against the behavioral and neurobiological consequences of chronic stress exposure
- 2022
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Ingår i: Brain Research Bulletin. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0361-9230 .- 1873-2747. ; 190
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Tidskriftsartikel (refereegranskat)abstract
- Excitotoxicity is described as the exacerbated activation of glutamate AMPA and NMDA receptors that leads to neuronal damage, and ultimately to cell death. Astrocytes are responsible for the clearance of 80-90% of syn-aptically released glutamate, preventing excitotoxicity. Chronic stress renders neurons vulnerable to excitotox-icity and has been associated to neuropsychiatric disorders, i.e., anxiety. Microreactors containing platinum nanoparticles (Pt-NP) and glutamate dehydrogenase have shown in vitro activity against excitotoxicity. The purpose of the present study was to investigate the in vivo effects of these microreactors on the behavioral and neurobiological effects of chronic stress exposure. Rats were either unstressed or exposed for 2 weeks to an unpredictable chronic mild stress paradigm (UCMS), administered intra-ventral hippocampus with the micro -reactors (with or without the blockage of astrocyte functioning), and seven days later tested in the elevated T -maze (ETM; Experiment 1). The ETM allows the measurement of two defensive responses, avoidance and escape, in terms of psychopathology respectively related to generalized anxiety and panic disorder. Locomotor activity in an open field was also measured. Since previous evidence shows that stress inhibits adult neurogenesis, we evaluated the effects of the different treatments on the number of cells expressing the marker of migrating neuroblasts doublecortin (DCX) in the dorsal and ventral hippocampus (Experiment 2). Results showed that UCMS induces anxiogenic effects, increases locomotion, and decreases the number of DCX cells in the dorsal and ventral hippocampus, effects that were counteracted by microreactor administration. This is the first study to demonstrate the in vivo efficacy of Pt-NP against the behavioral and neurobiological effects of chronic stress exposure.
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| 5. |
- Cássia-Silva, C., et al.
(författare)
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Higher evolutionary rates in life-history traits in insular than in mainland palms
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Isolated islands, due to the reduced interspecific competition compared to mainland habitats, present ecological opportunities for colonizing lineages. As a consequence, island lineages may be expected to experience higher rates of trait evolution than mainland lineages. However, island effects on key life-history traits of vascular plants remain underexplored at broad spatiotemporal scales, even for emblematic island clades such as palms. Here, we used phylogenetic comparative methods to evaluate potential differences in size and macroevolutionary patterns of height and fruit diameter among mainland, continental, and volcanic island palms. Further, phylogenetic beta-diversity was used to determine if lineage turnover supported an adaptive radiation scenario on volcanic islands. Volcanic island palms were taller than their continental island and mainland counterparts, whereas continental island palms exhibited smaller fruit size. Height and fruit size of palms evolved under evolutionary constraints towards an optimal value. However, scenarios of adaptive radiation and niche conservatism were not supported for the height and fruit size of volcanic and mainland palm clades, respectively, as expected. Instead, continental island palms exhibited higher evolutionary rates for height and fruit size. Insular palm assemblages (continental and volcanic) are composed of unique lineages. Beyond representing evolutionary sources of new palm lineages, our results demonstrate that insular habitats are important in shaping palm trait diversity. Also, the higher phenotypic evolutionary rates of continental island palms suggest disparate selection pressures on this habitat type, which can be an important driver of trait diversification over time. Taken together, these results stress the importance of insular habitats for conservation of functional, phylogenetic, and taxonomic diversity of palms. © 2020, The Author(s).
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