Biochemical and physiological bases for the use of carbon and nitrogen isotopes in environmental and ecological studies

Abstract

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.

Use of compound‐specific nitrogen isotope analysis of amino acids in trophic ecology: assumptions, applications, and implications

“…The b value of animals in these systems should be corrected using animal-specific mixing proportions of vascular and non-vascular plants before calculating their TP. Without calculating mixing proportions, the TP values of sea turtles, polychaeta, and some stream macroinvertebrates are significantly underestimated (Arthur et al 2014;Ishikawa et al 2014;Choi et al 2017 (Chikaraishi et al 2007;Ohkouchi and Takano 2014;Ohkouchi et al 2015). The use of the d…”

“…Detailed comments on the analytical procedures and biochemical basis for both methods is beyond the scope of this paper, and is holistically overviewed in elsewhere (e.g., Wada et al 2013;Ohkouchi et al 2015Ohkouchi et al , 2017McMahon and McCarthy 2016). In this paper, only the three most critical features of both the methods in the context of food web science were highlighted, as follows.…”

Stable Isotopes from Museum Specimens May Provide Evidence of Long-Term Change in the Trophic Ecology of a Migratory Aerial Insectivore

“…Interpretation of stable isotope ratios remains challenging because it relies on knowing the isotopic signatures of the relevant producers in an ecosystem (Ohkouchi et al, 2015). In marine systems, sampling of the phytoplankton or primary consumers, like forage fish, have been used to estimate baseline isotope values for particular food chains (Blight et al, 2015).…”

A review by the chief editors of some of the most popular papers published by PEPS in 2014–2015

“…Ohkouchi et al (2015) reviewed the latest results from this research field together with the underlying theoretical background, and discussed how biochemical processes commonly observed in the biosphere, including the decarboxylation and deamination of amino acids, are the key factors in this isotopic approach. Energy flow in ecosystems is essential for understanding the surface environment of this planet, and compound-specific isotopic analysis is effective for this kind of the study.…”