Many inland waters exhibit complete or partial desiccation, or have vanished due to global change, exposing sediments to the atmosphere. Yet, data on carbon dioxide (CO 2) emissions from these sediments are too scarce to upscale emissions for global estimates or to understand their fundamental drivers. Here, we present the results of a global survey covering 196 dry inland waters across diverse ecosystem types and climate zones. We show that their CO 2 emissions share fundamental drivers and constitute a substantial fraction of the carbon cycled by inland waters. CO 2 emissions were consistent across ecosystem types and climate zones, with local characteristics explaining much of the variability. Accounting for such emissions increases global estimates of carbon emissions from inland waters by 6% (~0.12 Pg C y −1). Our results indicate that emissions from dry inland waters represent a significant and likely increasing component of the inland waters carbon cycle.
Alternating tangential flow (ATF) filtration has been used with success in the Biopharmaceutical industry as a lower shear technology for cell retention with perfusion cultures. The ATF system is different than tangential flow filtration; however, in that reverse flow is used once per cycle as a means to minimize fouling. Few studies have been reported in the literature that evaluates ATF and how key system variables affect the rate at which ATF filters foul. In this study, an experimental setup was devised that allowed for determination of the time it took for fouling to occur for given mammalian (PER.C6) cell culture cell densities and viabilities as permeate flow rate and antifoam concentration was varied. The experimental results indicate, in accordance with D'Arcy's law, that the average resistance to permeate flow (across a cycle of operation) increases as biological material deposits on the membrane. Scanning electron microscope images of the post-run filtration surface indicated that both cells and antifoam micelles deposit on the membrane. A unique mathematical model, based on the assumption that fouling was due to pore blockage from the cells and micelles in combination, was devised that allowed for estimation of sticking factors for the cells and the micelles on the membrane. This model was then used to accurately predict the increase in transmembane pressure during constant flux operation for an ATF cartridge used for perfusion cell culture.
The Mekong Delta is the most important rice‐ and shrimp‐producing region for food and economic security in Vietnam. Rice‐shrimp farming is practised where salinity fluctuates substantially between wet and dry seasons. Research points to several potential risk factors for rotational systems, but how these link directly to both rice and shrimp production remains poorly quantified for systems that stock and harvest animals year‐round. We examined water and soil quality of 18 rice‐shrimp‐crab ponds, in which shrimp and crab are grown in both wet and dry seasons, in the Cà Mau Province of Vietnam. Multiple lines of evidence indicated that environmental conditions experienced by both rice and shrimp were suboptimal and contributed to low yields and survival. Year‐round cropping of shrimp and crab was associated with sustained suboptimal salinity, intensified by drought, for the wet‐season cultivation of rice. Although rice seedlings were sown in all 18 ponds, only three had a harvestable crop. Low shrimp production and survival was associated with sustained suboptimal water temperatures (too high), salinity (too high in the dry season and too low in the wet season) and dissolved oxygen concentrations (too low). Food availability and quality may also have affected shrimp production. Improving productivity of rice‐shrimp‐crab ponds in the study region may require (1) separation of rice and shrimp crops and improving efficiency of soil washing practices such that salinity conditions are more suitable for each when grown, and (2) management intervention to increase oxygenation of water, and the availability and quality of food for shrimp.
Concentrations of CO 2 are commonly suboptimal for plant production in greenhouses. Here, a new strategy using crop-residues and animal-manure composting (CRAM) was developed to increase CO 2 concentration throughout the day. During the whole cultivation period, CRAM-treated greenhouses had CO 2 concentrations that were more than twice that of the control greenhouses. This resulted in yields of celery (Apium graveolens L.), leaf lettuce (Lactuca virosa L.), stem lettuce (Lactuca saiva L.), oily sowthistle (Sonchus oleraceus L.), and Chinese cabbage (Brassica chinensis L.) that were 270%, 257%, 87%, 140%, and 227% higher than those in control greenhouses, respectively. The effect of CRAM on vegetable-quality parameters was also examined. Nitrate concentrations deceased in celery, leaf lettuce, oily sowthistle, and Chinese cabbage by 8%, 36%, 30%, and 20%, respectively. The concentrations of soluble sugars in oily sowthistle and Chinese cabbage were significantly increased by the composting procedure. In addition, the ascorbic acid concentrations increased in all five species, with average increases of 13%, 39%, 25%, 72%, and 37% for celery, leaf lettuce, stem lettuce, oily sowthistle, and Chinese cabbage, respectively. It is concluded that CO 2 fertilization using CRAM in greenhouses increases yields and improves quality of common vegetables.
Grazing management is a known influence of carbon accumulation in agricultural soil, but there is conflicting evidence on the extent. This study compared organic carbon and nitrogen stocks at the conclusion of a 5‐year grazing trial on a fertilised native pasture in south‐eastern Australia. The study included three grazing treatments: ungrazed, tactically grazed (set stocking with biannual rest periods) and cell grazed (intense stocking with frequent long rest periods). There was no influence of grazing treatment detected on pasture sward composition when averaged over seasons or on total nitrogen or bulk density. The cell grazing treatment had total carbon stock of 32·9 Mg C ha−1 (SE = 1·8) in the 0–0·30 m soil layer, which was a significant increase (p < 0·05) relative to the ungrazed treatment at 25·6 Mg C ha−1 but not statistically greater than the tactical treatment at 29·5 Mg C ha−1. There was no difference detected in labile carbon stocks to 0·30 m, which indicates that differences in soil carbon due to grazing was accumulated over the 5‐year trial rather than reflecting short‐term seasonal impacts. We propose that a combination of factors contributed to a greater stock of soil carbon under grazed pastures including differences in plant shoot/root allocation, root growth and root turnover with defoliation under grazing as well as lower plant productivity where grazing is excluded because of shading and nutrient tie‐up. This study demonstrates removing grazing pressure may lead to lower soil carbon stocks in native pastures over time and provides evidence of the potential for grazing management to increase soil carbon in the short‐term. Copyright © 2016 John Wiley & Sons, Ltd.
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