Dissolved Organic Matter Processing in Pristine Antarctic Streams

Accelerated glacier melt and runoff may lead to inputs of labile dissolved organic matter (DOM) to downstream ecosystems and stimulate the associated biogeochemical processes. However, still little is known about glacial DOM composition and its downstream processing before entering the ocean, although the function of DOM in food webs and ecosystems largely depends on its composition. Here, we employ a set of molecular and optical techniques (UV–vis absorption and fluorescence spectroscopy, 1H NMR, and ultrahigh-resolution mass spectrometry) to elucidate the composition of DOM in Antarctic glacial streams and its downstream change. Glacial DOM consisted largely of a mixture of small microbial-derived biomolecules. 1H NMR analysis of bulk water revealed that these small molecules were processed downstream into more complex, structurally unrecognizable molecules. The extent of processing varied between streams. By applying multivariate statistical (compositional data) analysis of the DOM molecular data, we identified molecular compounds that were tightly associated and moved in parallel in the glacial streams. Lakes in the middle of the flow paths enhanced water residence time and allowed for both more DOM processing and production. In conclusion, downstream processing of glacial DOM is substantial in Antarctica and affects the amounts of biologically labile substrates that enter the ocean

Litter carbon dynamics analysis in forests in an arid ecosystem with a model incorporating the physical removal of litter

金沢大学理工研究域自然システム学系Arid land afforestation could be a countermeasure for global warming, and a project for developing and evaluating techniques for arid land afforestation and reforestation has been carried out in Sturt Meadows near Leonora, Western Australia. As a part of this project, the litter carbon dynamics were investigated at three Acacia aneura forest sites, using a litter carbon model incorporating the physical removal of litter by winds, floods, etc. Based on the field observation data of above ground plant biomass, annual litter fall, existing amount of the litter, and also litter decomposition rate constants separately obtained for leaf litter and woody litter, we investigated the carbon flows at these forest sites, especially the annual amount of litter physically removed from the sites by floods or winds. As a result, it is estimated that annual physical removal of litter amounted to 59-75% of the annual litter fall, and the litter removal rate constants were from 0.38 to 0.55 year-1. Roughly one third to a half of the existing litter is removed annually from the sites. There was also a tendency that as the canopy coverage decreases, the litter removal rate constant increases. For this type of ecosystem, which is susceptible to the run-off of water and strong winds, we consider the taking into account of the physical removal of the litter is essential for analyzing the carbon dynamics in the ecosystem. © 2008 Elsevier B.V. All rights reserved

Serum cystatin C levels to predict serum concentration of digoxin in Japanese patients

Cystatin C (Cys-C) has been recently paid great attention as a better endogenous marker of the glomerular filtration rate than creatinine (Cr). In this study, the usefulness of Cys-C was compared with Cr in terms of the estimation of the steady-state serum trough concentrations of digoxin in Japanese patients. Forty patients treated with digoxin and 56 healthy elderly subjects were participated in this study. The serum levels of Cys-C and Cr in the patients were higher than those in the healthy elderly subjects, but the increase of Cys-C was more predominant in the patients. Their levels were well-correlated for both of the healthy elderly subjects (r=0.691) and patients (r=0.774), but the serum concentrations of digoxin were better correlated with those of the reciprocal values of Cr (r=0.667) than those of Cys-C (r=0.383), presumably due to the fact that digoxin and Cr were excreted via both glomerular filtration and tubular secretion. Cys-C is useful for the substratification of the patients diagnosed to have normal renal function with Cr of &#60; 1.3 mg/dL into those with normal and pseudo-normal renal function, resulting in the corresponding serum concentrations of digoxin.</p