The dynamic changes of stable isotopic ratios of carbon and nitrogen in suspended and sedimented particulate organic matter during a phytoplankton bloom

The dynamic changes of carbon and nitrogen stable isotopic ratios in suspended and sedimented particulate matter were observed together with many other chemical and biological properties during a phytoplankton bloom induced by nutrient addition in a controlled ecosystem enclosure (CEE, about 70 m3) in Saanich Inlet, British Columbia, Canada. Both of the stable isotopic ratios of carbon (δ13C) and nitrogen (δ15N) in suspended particulate organic matter showed characteristic patterns of variations in surface water during the bloom. The δ13C of suspended particulate matter increased with the growth of phytoplankton population and decreased gradually after the depletion of NO3− and NO2−. The δ15N of suspended particulate matter was very low soon after the beginning of phytoplankton bloom, but the value increased rapidly with the decrease in NO3− and NO2−, and reached maximal value following nutrient depletion, after which the δ15N remained high until the end of the experiment. In order to understand such variations of δ13C and δ15N, we made the mass and isotopic balance models of carbon and nitrogen for the upper layer of the CEE, and simulated the temporal variations of δ13C and δ15N of particulate organic matter using them in connection with several hypotheses on the isotope fractionations associated with the uptake of inorganic substrates by phytoplankton. While neither change in the dissolved inorganic carbon (i.e., its isotope ratio and/or molecular CO2 concentration) nor the phytoplankton species compositions can well explain the variation of δ13C, this variation can be well simulated considering the effect of change in the specific production rate of particulate organic carbon. On the other hand, the variations of δ15N can be clearly understood by a first-order isotope fractionation model under the assumption of large isotopic fractionation during the assimilation of NO3− and NO2− by phytoplankton. The particulate organic matter produced in the nutrient controlled phytoplankton bloom can be classified into three phases from an isotopic viewpoint: (I) the early stage of the phytoplankton bloom when NO3− plus NO2− were still in excess in sea water (high δ13C but low δ15N), (II) the late stage of the bloom when NO3− plus NO2− had just been depicted (high δ13C and high δ15N) and (III) the steady state phase, a few days after the depletion of NO3− plus NO2− (low δ13C but high δ15N). The cooperative variation of δ13C and δ15N in the suspended and sedimented particulate organic matter was also demonstrated

Studies on Chemical Composition and Feeding Value of Forage Crops : (XVI) A Comparison of the Nutritive Value Among Bermudagrass, Bahiagrass, Orchardgrass and Tall Fescue

中国地域の中山間部の盆地にある岡山県酪農試験場において生産された暖地型牧草群としてのバーミューダグラス,バヒアグラス,寒地型牧草群としてのオーチャードグラス,トールフェスクの飼料価値を比較検討した. 得られた結果は次のとおりである. 1.寒地型草群は粗蛋白質,純蛋白質,粗脂肪,粗灰分,Ca,P,K,Mgの各成分含量において暖地型草種よりすぐれた. 2.寒地型草群は暖地型草群に比較して乾物,粗蛋白質,NFEおよび粗繊維の消化率が高く,DCPとTDN含量においてもまさった. 3.可消化乾物摂取量や窒素の体内蓄積は寒地型草群がはるかにすぐれた. 4.暖地型草群の給与に際しては,とくにエネルギーや蛋白質の補給に留意すべきである

Natural 15 N Abundance of Plants and Soil N in a Temperate Coniferous Forest

Measurement of nitrogen isotopic composition (δ 15 N) of plants and soil nitrogen might allow the characteristics of N transformation in an ecosystem to be detected. We tested the measurement of δ 15 N for its ability to provide a picture of N dynamics at the ecosystem level by doing a simple comparison of δ 15 N between soil N pools and plants, and by using an existing model. δ 15 N of plants and soil N was measured together with foliar nitrate reductase activity (NRA) and the foliar NO 3 – pool at two sites with different nitrification rates in a temperature forest in Japan. δ 15 N of plants was similar to that of soil NO 3 – in the high-nitrification site. Because of high foliar NRA and the large foliar NO 3 – pool at this site, we concluded that plant δ 15 N indicated a great reliance of plants on soil NO 3 – there. However, many δ 15 N of soil N overlapped each other at the other site, and δ 15 N could not provide definitive evidence of the N source. The existing model was verified by measured δ 15 N of soil inorganic N and it explained the variations of plant δ 15 N between the two sites in the context of relative importance of nitrification, but more information about isotopic fractionations during plant N uptake is required for quantitative discussions about the plant N source. The model applied here can provide a basis to compare δ 15 N signatures from different ecosystems and to understand N dynamics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41374/1/10021_2002_Article_132.pd

Effects of empagliflozin in patients with chronic kidney disease from Japan: exploratory analyses from EMPA–KIDNEY

Background: EMPA–KIDNEY assessed the effects of empagliflozin 10 mg once daily vs. placebo in 6609 patients with chronic kidney disease (CKD) at risk of progression, including 612 participants from Japan. Methods: Eligibility required an estimated glomerular filtration rate (eGFR) of ≥ 20  Results: Japanese participants had higher levels of albuminuria and eGFR than those from non-Japan regions. During a median of 2.0 year follow-up, a primary outcome occurred in 432 patients (13.1%) in the empagliflozin group and in 558 patients (16.9%) in the placebo group (hazard ratio [HR], 0.72, 95% confidence interval [95%CI] 0.64–0.82; P  Conclusions: Empagliflozin safely reduced the risk of “kidney disease progression or cardiovascular death” in patients with CKD, with consistent effects in participants from Japan