To date, empirical relationships have been observed for the distributions and variations of stable nitrogen and carbon isotope ratios (delta N-15 and delta C-13, respectively) in ecosystems as well as in living organisms. Here, we investigated delta N-15 values of internal organs of various animal species, including insects, fish, amphibians, reptiles, birds, and mammals. The delta N-15 differences of these organs from the corresponding muscles vary within a range of +/- 4 parts per thousand. In general, the delta N-15 values of the brain and heart are higher than those of the corresponding muscles, except in birds. This may indicate that excreted ammonia is recycled in their cecum. We propose a kinetic descriptive schemas for a nitrogen isotope model of deamination that maintains a TDF of 8.0 parts per thousand for glutamate in muscle mitochondria. Differences in the delta N-15 in skeletal muscle, heart, and brain are evident across species because the cells that make up the organ differ greatly in shape and organization, and the amount and shape of mitochondria distributed in these organs change dynamically. These facts may be the first step to clarify the significance of organ delta N-15 variation for animal growth physiology and possibly for animal biochemical evolution. These evidences of delta N-15 variations at intact and organ level in biota may provide a new broad avenue to investigate paleoecology and its environmental conditions.

生物の安定同位体比は、捕食者自身の代謝系の駆動様式や行動変化に起因するものと、食物網が存在する地域性に起 因するものの2つの要因によって決定される。そこで本研究では栄養塩や水温などの海洋環境の違いによって、低次生 態系における食物網にどのような違いがあるのかを見るために、西部北太平洋亜寒帯海域及び亜熱帯海域において、動 物プランクトン及び海水試料を季節及び鉛直層別に採集を行い比較検証した。本研究では、特にメソ動物プランクトン 群集を中心に群集構造と栄養動態について時空間的にどのように変動をするのか同位体比から検証を行った。 2010年 2月から 2011年 7月まで、海洋研究開発機構(JAMSTEC)の観測点K2(47oN, 160oE)及びS1(30oN, 145oE)に おいて動物プランクトン試料の採集及び採水を行った。試料は多段開閉式ネット IONESSを用いて 0-50, 50-100, 100-150,

We studied the distribution of dissolved O2, CO2, CH4, and N2O in a coastal swamp system in Thailand with the goal to characterize the dynamics of these gases within the system. The gas concentrations varied spatially and seasonally in both surface and ground waters. The entire system was a strong sourcefor CO2 and CH4, and a possible sink for atmospheric N2O. Seasonal variation in precipitation primarily regulated the redox conditions in the system. However, distributions of CO2, CH4, and N2O in the river that received swamp waters were not always in agreement with redox conditions indicated by dissolvedO2 concentrations. Sulfate production through pyriteoxidation occurred in the swamp with thin peat layerunder aerobic conditions and was reflected by elevatedSO 4 2− /Cl− in the river water. When SO 4 2− /Cl− was high, CO2 and CH4 concentrations decreased, whereas the N2O concentration increased. The excess SO 4 2− in the river water was thus identified as a potential indicator for gas dynamics in this coastal swamp system.

The natural abundance of 13 C and 15 N was measured in basidiocarps of at least 115 species in 88 genera of ectomycorrhizal, wood‐decomposing and litter‐decomposing fungi from Japan and Malaysia. The natural abundance of 13 C and 15 N was also measured in leaves, litter, soil and wood from three different sites. 15 N and 13 C were enriched in ectomycorrhizal and wood‐decomposing fungi, respectively, relative to their substrates. Ectomycorrhizal and wood‐decomposing fungi could be distinguished on the basis of their δ 13 C and δ 15 N signatures. Although there was high variability in the isotopic composition of fungi, the following isotope‐ enrichment factors (ε, mean±SD) of the fungi relative to substrates were observed: ε ectomycorrhizal fungi/litter = 6.1±0.4‰ 15 N ε ectomycorrhizal fungi/wood = 1.4±0.8‰ 13 C ε wood‐decomposing fungi/wood = −0.6±0.7‰ 15 N ε wood‐decomposing fungi/wood = 3.5±0.9‰ 13 C The basis of isotope fractionation in C metabolism from wood to wood‐decomposing fungus is discussed.

Carbon and nitrogen stable isotope compositions of organic matter, TOC/TN ratio, and manganese concentration in a sediment core that was collected in northern parr of Lake Baikal (VER92ST10-GC2, water depth at 922 m, about 3 m long) were investigated to elucidate the origin of the sedimentary organic matter and its associated environmental factors.The sediment core was composed of mainly two parts: turbidite sections and other sections. Constant delta(13)C and delta(15)N values of the rurbidite sections were observed (-26.8 +/- 0.2 parts per thousand, for delta(13)C and 3.2 +/- 0.1 parts per thousand for delta(15)N) throughout the core. The higher delta(13)C in turbidite sections (about -27 parts per thousand) than that of the other sections (-31 to -29 parts per thousand) was clearly observed, and delta(15)N was different between turbidite sections (about 3 parts per thousand) and other sections (3 to 5 parts per thousand). delta(13)C of Other sections was close to that of pelagic phytoplankton, indicating that sediment other than turbidite sections is composed of autochthonous components. The variation of stable isotopes in other sections may be possibly caused by the changes in either phytoplankton growth rate or contribution ratios of terrestrial to aquatic plants for delta(13)C. Either denitrification or fluctuation of delta(15)N in pelagic phytoplankton can be the cause of variable delta(15)N in other sections.

Nitrogen and carbon isotope ratios of surface sediments and benthic animals, and nitrogen isotope ratio of nitrate were measured to establish the isotopic biogeochemical structure in the Yodo River watershed. The δ15N of sediments in Lake Biwa, located in the middle reach of the Yodo River watershed, were the highest values in the watershed. The δ15N values of nitrate were also significantly higher in comparison with those of lakes in other watersheds. This fact suggested that denitrification was occurring on a large scale in Lake Biwa. Based on the isotope mass-balance, ca. 50% of nitrogen introduced into the North Basin of Lake Biwa seemed to be released as nitrogen gas through the denitrification process. δ13C values of benthic animals (aquatic insects) in the upper reach of the Yodo River watershed were 6 to 13‰ higher than those of sediments. This fact suggested that the aquatic insects in the upper reach foraged organic matter produced in the river ecosystem. The higher δ13C values of sediments and benthic animals in the South Basin of Lake Biwa and the Yodo River indicated that the middle to lower reaches in the Yodo River watershed were progressively influenced/transformed by human activities.

A simple, precise method for determining the carbon stable isotope ratio of total dissolved inorganic C (Sigma CO2) in freshwater samples is described. Water samples are packed in airtight glass bottles of known inner volume (similar to 70 ml) with no air bubbles. Subsequently, a headspace of 5.0 ml is created inside each bottle with pure helium gas, and each sample is acidified by adding 0.5 ml of a CO2-free, 6.0 N HCl solution. After the original dissolved CO2 has equilibrated with the headspace gas, a portion of this headspace gas is subsampled and injected into the GC/C/IRMS (gas chromatograph/combustion furnace/isotoperatio mass spectrometer) system to determine the carbon isotope ratio of the CO2. The isotope ratio of CO2 remaining in the liquid phase is calculated by temperature-dependent isotope discrimination between gas and aqueous phases. The isotope ratio of Sigma CO2 of the original sample is then derived assuming isotope mass balance. The analytical precision of this method is +/-0.1 parts per thousand. The method enables a single operator to determine the isotopic ratio in at least 60 lake-water samples within 3 d of sampling.

Isotopic, biogeochemical and ecological structure can provide a new dimension for understanding material flows, and the simultaneous function and structure of an ecosystem. Distributions ofδ13C andδ15N for biogenic substances in the Nanakita river estuary involving Gamo lagoon in Japan were investigated to construct isotope biogeochemical and ecological structure for assessing fate and transfer of organic matter, and food web structure. The isotopic framework of the ecosystem was successfully described in aδ15N–δ13C map. In this estuary the variations of isotope ratios of biogenic substances were clearly explained by the mixing of land-derived organic matter, and marine-derived organic matter.

Primary production by phytoplankton in the eutrophic Mikawa Bay, Japan, was studied by simultaneous measurements of natural carbon isotope ratio (δ13C) and short-term carbon uptake rates (13C tracer study) of size-fractionated nannoplankton (<10 μm) and net plankton (>10 μm) samples. Short-term photosynthetic rates, which represent the physiological state of algae, were variable regardless of standing stock sizes. Theδ13C values of particulate organic carbon (POC) in June and July displayed horizontal variations for both the net plankton fraction (−19.8 to −12.7‰) and the nannoplankton fraction (−22.0 to −12.8‰). For both fractions, low concentrations of POC had more negativeδ13C values (−22 to −18‰). Highδ13C values for the net plankton were found when POC concentrations were much higher, due to red tide. This suggests that the increase in algal standing crop for the net plankton fraction resulted from accelerated photosynthetic activity. However the nannoplankton fractions with higher POC values have relatively lowδ13C values.

Vertical distribution, chlorophylla (chla) and phaeopigment concentrations in the gut, and natural nitrogen isotope ratio (δ15N) were investigated for pelagic amphipodsThemisto japonica (Bovallius) collected from the Sea of Japan in July 1987. Differences in diel vertical migration behavior were clearly observed between small and largeT. japonica. Many small (<5 mm body length) amphipods appeared in the phytoplankton-rich shallow layers. Their gut pigment concentrations were higher (mean 0.52 ± 0.15µg chla g−1 amphipod) than those of large amphipods (mean 0.33±0.14µg g−1); this implies that the amphipods fed on a large amount of phytoplankton during the early stage of life. Theδ15N values of small amphipods were lower (5.7 to 6.3‰) than those of large amphipods (6.8 to 11.7‰), reflecting the lower trophic level of small amphipods compared to large ones. Theδ15N values for small amphipods were similar to those of herbivorous zooplankton. The amphipods' feeding behavior thus changes from herbivorous to carnivorous as they grow.

A combined gas chromatography/combustion/isotope ratio mass spectrometer (GC/C/IRMS) system was employed to develop a rapid and simple method for measuring δ13C of bubble methane collected from wetlands. In spite of incomplete combustion of methane to CO2, calibration using standard methane can provide reproducible data with accuracy of ±0.5‰. Duplicate analyses of two gaseous samples were successfully measured within 20 min.

The relationship between carbon isotope discrimination and the specific growth rate of a green alga Chlamydomonas reinhardtii Dangeard (IAM C-238) was studied in the continuous culture system under constant CO2 pressure. In both the nitrate-limited and the light-limited conditions, carbon isotope discrimination (Δδ13C) between alga and CO2 was dependent upon the specific growth rate of alga. The algal VC value increased with the specific growth rate (μ). In natural environments, the variations in carbon isotope ratio of phytoplankton or particulate organic carbon may be mainly attributed to change in the specific growth rate of phytoplankton, at least for the case in which the δ13C values for CO2 (aq) and HCO3- in water are kept constant.

In today’s societies, scavengers play an important role as providers of nature’s contribution to people (NCP), such as disease control and carcass removal. Yet very little is known about the non-material NCP (i.e. nature’s effects on subjective and psychological aspects of people’s well-being) that scavengers provide societies with. The first aim of this study is to determine which species of obligate and facultative scavengers provide different non-material NCP in Spain, including recreational and aesthetic experiences, learning and inspiration, and supporting identities. The second aim is to identify which ecological variables determine their capacity to provide the aforementioned non-material NCP. To assess non-material NCP nationwide, data were collected from different sources, including the Internet (websites of nature photography and wildlife watching tours, Global Biodiversity Information Facility, and Google Trends), outreach magazines and scientific articles. A top predator, Canis lupus, followed by an obligate scavenger, Gyps fulvus, were among the most prominent species to provide multiple non-material NCP. Aesthetic experiences were provided mainly by common species, such as Genetta genetta, Milvus migrans and corvids. The NCP of recreation and learning by civil society were provided by threatened and charismatic species, such as C. lupus, Ursus arctos and Aquila adalberti. Knowledge acquired by scientists was provided mainly by meso-carnivores. Finally, the NCP of supporting identities was related with species capable of providing beneficial and detrimental contributions, such as C. lupus and Sus scrofa. Integrating data mined from different sources has allowed it to reveal the interweaving among non-material categories. Recognising that all species of scavengers are essential for providing non-material NCP can raise society’s awareness about their important cultural role and may, hence, contribute to their conservation.

The stable isotope ratios of nitrogen were measured in the mysid,Neomysis intermedia, together with various biogenic materials in a eutrophic lake, Lake Kasumigaura, in Japan throughout a year of 1984/85. The mysid, particulate organic matter (POM, mostly phytoplankton), and zooplankton showed a clear seasonal change in δ15N with high values in spring and fall, but the surface bottom mud did not. A year to year variation as well as seasonal change in δ15N was found in the mysid. The annual averages of δ15N of each material collected in 1984/85 are as follows: surface bottom mud, 6.3‰ (range: 5.7–6.9‰); POM, 7.9‰ (5.8–11.8‰); large sized mysid, 11.6‰ (7.7–14.3‰); zooplankton, 12.5‰ (10.0–16.4‰); prawn, 13.2‰ (9.9–15.4‰); goby, 15.1‰ (13.8–16.7‰). The degree of15N enrichment by the mysid was determined as 3.2‰ by the laboratory rearing experiments. The apparent parallel relationship between the POM and the mysid in the temporal patterns of δ15N with about 3‰ difference suggests the POM (mostly phytoplankton) as a possible food source ofN. intermedia in this lake through the year.

Distributions of δ15N and δ13C for biogenic substances in the Antarctic Ocean and in the Otsuchi River estuary in Japan were investigated to construct isotope biogeochemical framework for assessing marine ecosystems. The isotopic compositions of phytoplankton were particularly low in the Antarctic Ocean. High nitrate concentration and high PCO2 in the surface sea waters, and the low light intensity seem to enhance the kinetic isotope fractionations that preferred the depletion of 15N and 13C in the algal body A clear-cut linear relationship between animal δ15N and its trophic level was obtained in the Antarctic system. In the estuary, the variation of isotope ratios were principally governed by the mixing of land-derived organic matter, marine phytoplankton, and seagrasses. A food-chain effect of 15N enrichment was also confirmed. An isotopically ordered structure was presented for a marine estuarine ecosystem. The isotopic abundances in a food web vary mainly because of the variation in 15N and 13C contents of primary producers grown under different circumstantial conditions and because of the enrichment of 15N along food chains.