Organic geochemistry and inorganic geochemistry have developed independently without much interaction. In this paper, I introduce the organic-metal element interactions using rare earth elements (REE), which have been the subject of many previous studies in the field of inorganic geochemistry. Non-destructive X-ray speciation, which is expected to be increasingly used in organic geochemistry, is also introduced. Organic geochemistry and inorganic geochemistry have developed independently without much interaction. In this paper, I introduce the organic-metal element interactions using rare earth elements (REE), which have been the subject of many previous studies in the field of inorganic geochemistry. Non-destructive X-ray speciation, which is expected to be increasingly used in organic geochemistry, is also introduced.

Compound-specific stable isotope analysis of amino acids (CSIA-AAs) has increasingly been used in biogeochemical studies as a powerful tool for providing unprecedented accuracy in the understanding of ecological and environmental dynamics in ecosystems. In the present study, we applied this CSIA-AAs for illustrating the trophic identity of Ezo salamander that has ‘cannibalism’ as a life strategy for adapting to the aquatic-terrestrial boundary ecosystems. Ezo salamander has two types of cannibalism: to hasten the timing of metamorphosis, larvae can develop large bodies and broad heads that allow them to gulp down conspecifics (Type I); and, to delay the timing of metamorphosis, larvae feed on the extremities (i.e., limbs and tails) of conspecifics (Type II, not showing morphological development as in Type I). The results of CSIA-AAs for the salamanders in controlled feeding experiments reveal that the trophic elevation of salamanders without the presence of cannibalism is normal (i.e., one level higher than diets) whereas the elevation of salamanders with the presence of cannibalism is higher than one level for both types. Because salamanders (and also other amphibians) play a critical role both as consumers and prey in aquatic-terrestrial boundary ecosystems, a new insight about ‘the extent to which they can alter their trophic identity in response to cannibalism’ in the present study will be useful for better understanding the unique nutrient and energy cycle in transitional environments between aquatic and terrestrial ecosystems.

Long-chain (C₂₈, C₃₀, and C₃₂) alkyl diols (LCD) in marine sediments are considered to originate from marine diatom genus Proboscia and Eustigmatophytes. LCD has been proposed as a proxy for upwelling, riverine input and sea surface temperature, but has not yet been applied much to palaeoceanographic studies. Long-chain (C₂₇ and C₂₉) hydroxy alkenoates such as 12-hydroxy methyl alkanoate (MA) were found in marine sediments and also derived from diatom Proboscia. In this study, we analyzed LCD and 12-OH MA in surface sediment from the Northwest Pacific off the coast of Sanriku and Proboscia alata culture sample. We identified monosaturated and saturated 1,13-, 1,14-, and 1,15-diols, as well as saturated 12-OH MA.