** Progress in Earth and Planetary Science is the official journal of the Japan Geoscience Union, published in collaboration with its 51 society members.
** Progress in Earth and Planetary Science is partly financially supported by a Grant-in-Aid for Publication of Scientific Research Results to enhance dissemination of information of scientific research.
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Review
Biogeosciences
201502201502
Biochemical and physiological bases for the use of carbon and nitrogen isotopes in environmental and ecological studies
Ohkouchi N, Ogawa N O, Chikaraishi Y, Tanaka H, Wada E
Carbon isotopic composition, Nitrogen isotopic composition, Ecosystem, Food web, Chlorophyll, Trophic position, Amino acid, Animal organ
Trophic positions of organisms from Lake Baikal based on the nitrogen isotopic composition of amino acids (glutamic acid and phenylalanine). "TP" denotes trophic position.
We review the biochemical and physiological bases of the use of carbon and nitrogen isotopic compositions as an approach for environmental and ecological studies. Biochemical processes commonly observed in the biosphere, including the decarboxylation and deamination of amino acids, are the key factors in this isotopic approach. The principles drawn from the isotopic distributions disentangle the complex dynamics of the biosphere and allow the interactions between the geosphere and biosphere to be analyzed in detail. We also summarize two recently examined topics with new datasets: the isotopic compositions of individual biosynthetic products (chlorophylls and amino acids) and those of animal organs for further pursuing the basis of the methodology. As a tool for investigating complex systems, compound-specific isotopic analysis compensates the intrinsic disadvantages of bulk isotopic signatures. Chlorophylls provide information about the particular processes of various photoautotrophs, whereas amino acids provide a precise measure of the trophic positions of heterotrophs. The isotopic distributions of carbon and nitrogen in a single organism as well as in the whole biosphere are strongly regulated, so that their major components such as amino acids are coordinated appropriately rather than controlled separately.
