Compilation of a) carbon and b) nitrogen isotopic compositions of inorganic substrates and autotrophs from natural environments. All the samples shown here were collected from Japan or the northwest Pacific Ocean, except the atmospheric CO2 and N2. Note that most terrestrial plants were collected from cultivated areas, so their nitrogen isotopic compositions are more or less affected by chemical fertilizers. Sources: 1Cunz (2011), 2Kroopnick (1985), GEOSECS Station 224, 3Chikaraishi and Naraoka (2003), 4Wada et al. (1993), 5Mariotti (1983), 6Miyake and Wada (1967), 7Minagawa et al. (2001), 8Wada et al. (1975), 9Wada et al. (1986), 10Chikaraishi et al. (2005), 11Chikaraishi et al. (2010), 12Chikaraishi et al. (2009), 13Minagawa and Wada (1986), 14Wada et al. (2012).