Alex Enrich-Prast

Bio: Alex Enrich-Prast is an academic researcher from Linköping University. The author has contributed to research in topics: Dissolved organic carbon & Organic matter. The author has an hindex of 30, co-authored 98 publications receiving 3462 citations. Previous affiliations of Alex Enrich-Prast include Aarhus University & Federal Fluminense University.

Freshwater Methane Emissions Offset the Continental Carbon Sink

Abstract: Inland waters (lakes, reservoirs, streams, and rivers) are often substantial methane (CH4) sources in the terrestrial landscape. They are, however, not yet well integrated in global greenhouse gas (GHG) budgets. Data from 474 freshwater ecosystems and the most recent global water area estimates indicate that freshwaters emit at least 103 teragrams of CH4 year−1, corresponding to 0.65 petagrams of C as carbon dioxide (CO2) equivalents year−1, offsetting 25% of the estimated land carbon sink. Thus, the continental GHG sink may be considerably overestimated, and freshwaters need to be recognized as important in the global carbon cycle.

Anaerobic ammonium oxidation in an estuarine sediment

Abstract: The occurrence and significance of the anammox (anaerobic ammonium oxidation) process relative to denitrification was studied in photosynthetically active sediment from 2 shallow-water estuaries: Randers Fjord and Norsminde Fjord, Denmark. Anammox accounted for 5 to 24% of N2 pro- duction in Randers Fjord sediment, whereas no indication was seen of the process in sediment from Nors- minde Fjord. It is suggested that the presence of anammox in Randers Fjord and its absence from Nors- minde Fjord is associated with differences in the availability of NO3 - + NO2 - (NOx - ) in the suboxic zone of the sediment. In Randers Fjord, NOx - is present in the water column throughout the year and NOx - porewater profiles showed that NOx - penetrates into the suboxic zone of the sediment. In Norsminde Fjord, NOx - is absent from the water column during the summer months and, via assimilation, benthic mi- croalgae may prevent penetration of NOx - into the suboxic zone of the sediment. Volume-specific anam- mox rates in Randers Fjord were comparable with rates measured previously in Skagerrak sediment by other investigators, but denitrification rates were 10 to 15 times higher. Thus, anammox contributes less to N2 production in Randers Fjord than in Skagerrak sediment. We propose that the lower contribution of anammox in Randers Fjord is linked to the higher availability of easily accessible carbon, which sup- ports a higher population of denitrifying bacteria. Amplification of DNA extracted from the sediment sam- ples from Randers Fjord using planctomycete-specific primers yielded 16S rRNA gene sequences closely related to candidatus Scalindua sorokinii found in the Black Sea by other investigators. The present study thus confirms the link between the presence of bacteria affiliated with candidatus S. sorokinii and the anammox reaction in marine environments. Anammox rates in sediment with intact chemical gradients were estimated using both 15 N and microsensor techniques. Anammox rates estimated with microsensors were less than 22% of the rates measured with isotopes. It is suggested that this discrepancy was due to the presence of fauna, because the applied 15 N technique captures total N2 production while the micro- sensor technique only captures diffusion-controlled N2 production at the sediment surface. This hypo- thesis was verified by consistent agreement between the methods when applied to defaunated sediments.

Methane Emissions from Pantanal, South America, during the Low Water Season : Toward More Comprehensive Sampling

Abstract: Freshwater environments contribute 75% of the natural global methane (CH4) emissions. While there are indications that tropical lakes and reservoirs emit 58-400% more CH4 per unit area than similar ...

Large emissions from floodplain trees close the Amazon methane budget

Abstract: Wetlands are the largest global source of atmospheric methane (CH4), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain, the largest natural geographic source of CH4 in the tropics, consistently underestimate the atmospheric burden of CH4 determined via remote sensing and inversion modelling, 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 and tropical peat swamp forests, representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (δ13C) 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 'top-down' 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.

Greenhouse gas production in low-latitude lake sediments responds strongly to warming

Abstract: Inland water sediments receive large quantities of terrestrial organic matter and are globally important sites for organic carbon preservation. Sediment organic matter mineralization is positively ...

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Climate Change 2007: The Physical Science Basis.

Abstract: Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

Reducing food’s environmental impacts through producers and consumers

Abstract: Food’s environmental impacts are created by millions of diverse producers. To identify solutions that are effective under this heterogeneity, we consolidated data covering five environmental indicators; 38,700 farms; and 1600 processors, packaging types, and retailers. Impact can vary 50-fold among producers of the same product, creating substantial mitigation opportunities. However, mitigation is complicated by trade-offs, multiple ways for producers to achieve low impacts, and interactions throughout the supply chain. Producers have limits on how far they can reduce impacts. Most strikingly, impacts of the lowest-impact animal products typically exceed those of vegetable substitutes, providing new evidence for the importance of dietary change. Cumulatively, our findings support an approach where producers monitor their own impacts, flexibly meet environmental targets by choosing from multiple practices, and communicate their impacts to consumers.