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To estimate polychlorinated biphenyls (PCBs) pollution by the 2011 earthquake and tsunami off the Pacific coast of Tohoku, we report monitoring results of their concentration in deep-sea fish, benthic invertebrates, and sediments collected off Tohoku in 2012–014. Total concentration of PCBs in the deep-sea organisms ranges from 0.12 to 51 ng g−1 dry weight (8.7–374 ng g−1 lipid), whereas that of sediments ranges from 0.086 to 4.0 ng g−1 dry sediment. These ranges are well below the regulatory standards determined by the Ministry of the Environment in Japan (pelagic fish: 500 ng g−1 dry weight, pelagic sediment: 10 μg g−1 dry sediment). With the reported data before the 2011 tsunami event, we did not find any significant increase in PCBs concentration off Tohoku during 2012–2014. For the biological samples, we also measured the nitrogen isotopic composition of individual amino acids for determining the precise trophic position to examine possible biomagnification through the food web. We did not find any significant correlation between the trophic position and PCB concentration.

Chloropigments and their derivative pheopigments preserved in sediments can directly be linked to photosynthesis. Their carbon and nitrogen stable isotopic compositions have been shown to be a good recorder of recent and past surface ocean environmental conditions tracing the carbon and nitrogen sources and dominant assimilation processes of the phytoplanktonic community. In this study we report results from combined compound-specific radiocarbon and stable carbon and nitrogen isotope analysis to examine the time-scales of synthesis and fate of chlorophyll-a and its degradation products pheophytin-a, pyropheophytin-a, and 132,173-cyclopheophorbide-a-enol until burial in Black Sea core-top sediments. The pigments are mainly of marine phytoplanktonic origin as implied by their stable isotopic compositions. Pigment δ15N values indicate nitrate as the major uptake substrate but 15N-depletion towards the open marine setting indicates either contribution from N2-fixation or direct uptake of ammonium from deeper waters. Radiocarbon concentrations translate into minimum and maximum pigment ages of approximately 40 to 1200 years. This implies that protective mechanisms against decomposition such as association with minerals, storage in deltaic anoxic environments, or eutrophication-induced hypoxia and light limitation are much more efficient than previously thought. Moreover, seasonal variations of nutrient source, growth period, and habitat and their associated isotopic variability are likely at least as strong as long-term trends. Combined triple isotope analysis of sedimentary chlorophyll and its primary derivatives is a powerful tool to delineate biogeochemical and diagenetic processes in the surface water and sediments, and to assess their precise time-scales.

Periphytic algae attached to a streambed substrate (periphyton) are an important primary producer in stream ecosystems. We determined the isotopic composition of chlorophyll a in periphyton collected from a stream flowing on limestone bedrock in the Seri River, central Japan. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) and natural radiocarbon abundances (Δ14C) were measured in chlorophyll a (δ13Cchl, δ15Nchl and Δ14Cchl) and bulk (δ13Cbulk, δ15Nbulk and Δ14Cbulk) for periphyton, a pure aquatic primary producer (Cladophora sp.) and a terrestrial primary producer (Quercus glauca). Periphyton δ13Cbulk and δ13Cchl values did not necessarily correspond to δ13Cbulk for an algal-grazing specialist (Epeorus latifolium). Periphyton Δ14Cchl values (−258 ‰ in April and −190 ‰ in October) were slightly lower than Δ14Cbulk values (−228 ‰ in April and −179 ‰ in October) but were close to the Δ14C value for dissolved inorganic carbon (DIC; −217 ± 31 ‰), which is a mixture of weathered carbonates (Δ14C = −1000 ‰), CO2 derived from aquatic and terrestrial organic matters (variable Δ14C) and dissolved atmospheric CO2 (Δ14C approximately +30 ‰ in 2013). Δ14Cchl values were also close to Δ14Cbulk for E. latifolium (−215 ‰ in April and −199 ‰ in October) and Cladophora sp. (−210 ‰), whereas the Δ14Cbulk value for Q. glauca (+27 ‰) was closer to Δ14C for atmospheric CO2. Although the bulk isotopic composition of periphyton is recognised as a surrogate for the photosynthetic algal community, natural periphyton is a mixture of aquatic and terrestrial organic materials. Our results indicate that the bulk periphyton matrix at the study site consists of 89 to 95 % algal carbon (derived from 14C-depleted DIC) and 5 to 11 % terrestrial organic carbon (derived from 14C-enriched atmospheric CO2).

The unidentified infrared (UIR) bands have been ubiquitously observed in various astrophysical environments and consist of a series of emission features arising from aromatic and/or aliphatic C-C and C-H bonds [1]. Therefore, their carriers are thought to be related to interstellar organics. However, our knowledge on the true carriers of the UIR bands is still limited. Recently [4] has proposed Mixed Aromatic Aliphatic Organic Nanoparticles, which contains hetero atoms in addition to conventional hydrocarbon models, as a more realistic interpretation of the band carriers. The challenges toward identifying the carriers of the UIR bands are still ongoing. Past studies have shown that the UIR bands observed around classical novae, which characterized by the presence of broad feature around 8μm[2], are somewhat different from those observed in other astrophysical environment. Here we report the success of experimentally synthesizing the organics called Nitrogen-included Carbonaceous Compounds (NCC; [7]) whose infrared properties can reproduce the UIR bands observed in classical novae.

Joint carbon and nitrogen isotope measurements were made from chlorins (chlorophyll a, phaeophytin a and pyrophaeophytin a) extracted from the last glacial-interglacial transition sediments of Lake Suigetsu, central Japan. These data highlight both the potential and difficulty of using chlorin-specific isotopes to track aquatic change from lake sediments. δ13C and δ15N of the three chlorins show coherent patterns with time, supporting the theory that phaeophytin a and pyrophaeophytin a are early diagenetic products of chlorophyll a and that despite this transition, their isotopic signatures remain intact. However, our data suggest that the isotopic composition of phaeophytin a and pyrophaeophytin a can be imprecise proxies for the isotope composition of chlorophyll a, possibly owing to the complex array of factors which affect the synthesis, transformation and sedimentation of these phaeopigments in nature. The total accumulation of organic matter in Lake Suigetsu appears to be controlled by the balance of allocthonous and authocthonous material as reflected by the C/N ratio. However, both bulk organic and chlorin-specific δ13C show similar changes, suggesting that the first order variability in bulk organic δ13C reflects aquatic change. By contrast, there is no similarity between chlorin and bulk δ15N, suggesting that interpretation of bulk δ15N in this setting is compromised by diagenetic alteration. The isotopic composition of chlorins are interpreted to reflect the response of aquatic primary productivity to post-glacial environmental change. However, further research into the synthesis and transformation of chlorins in the modern environment is required in order to facilitate a more rigorous approach to interpreting isotope ratios in chlorins extracted from sediments.

Chloropigments and their derivative pheopigments preserved in sediments can directly be linked to photosynthesis. Their carbon and nitrogen stable isotopic compositions have been shown to be a good recorder of recent and past surface ocean environmental conditions tracing the carbon and nitrogen sources and dominant assimilation processes of the phytoplanktonic community. In this study we report results from combined compound-specific radiocarbon and stable carbon and nitrogen isotopic analysis to examine the timescales of synthesis and fate of chlorophyll-a and its degradation products pheophytin-a, pyropheophytin-a, and 132,173-cyclopheophorbide-a-enol until burial in Black Sea surface sediments. The pigments are mainly of marine phytoplanktonic origin as implied by their stable isotopic compositions. Pigment δ15N values indicate nitrate as the major uptake substrate but 15N-depletion towards the open marine setting indicates contribution from N2-fixation. Radiocarbon concentrations translate into minimum and maximum pigment ages of approximately 40 to 1200 years. This implies that protective mechanisms against decomposition such as association with minerals or eutrophication-induced hypoxia and light limitation are much more efficient than previously thought. However, seasonal variations of nutrient source, growth period, and habitat and their associated isotopic variability are likely at least as strong as long-term trends. Combined triple isotopic analysis of sedimentary chlorophyll and its primary derivatives is a powerful tool to delineate biogeochemical and diagenetic processes in the surface water and assess their precise timescales.

We determined the mean crustal uplifting rate during the late Holocene along the Soya Coast, Lützow-Holm Bay, East Antarctica, by dating a marine-lacustrine transition recorded in lake sediments. We focused on temporal variations in the chemical composition of sediments recovered from Lake Skallen Oike at Skallen and Lake Oyako at Skarvsnes. Both sets of lake sediments record environmental changes associated with a transition from marine to lacustrine (fresh water) settings, as indicated by analyses of sedimentary facies for carbon and nitrogen contents, nitrogen isotopic compositions (15N/14N), and major element concentrations. Changes in the dominant primary producers during the marine-lacustrine transition were also clearly revealed by biogenic Opal-A, diatom assemblages, and gradient gel electrophoresis (DGGE) with 16S rRNA gene analysis. Geochronology based on radiocarbon dating of acid-insoluble organic carbon suggested that the environmental transition from saline to fresh water occurred at 2940±100 cal yr BP at L. Skallen and 1060±90 cal yr BP at L. Oyako. Based on these data and a linear approximation model, we estimated a mean crustal uplifting rate of 3.6 mm yr−1 for the period since the marine-lacustrine transition via brackish condition; this uplift is attributed to glacial-isostatic rebound along the Soya Coast. The geological setting was the primary factor in controlling the emergence event and the occurrence of simultaneous changes in sedimentary and biological facies along the zone of crustal uplift.

We determined both the nitrogen and carbon isotopic compositions of various vanadyl alkylporphyrins isolated from siliceous marine sediments of the Onnagawa Formation (middle Miocene, northeastern Japan) to investigate the biogeochemistry and ecology of photoautotrophs living in the paleo-ocean. The distinctive isotopic signals support the interpretations of previous works that the origin of 17-nor-deoxophylloerythroetioporphyrin (DPEP) is chlorophylls-c1-3, whereas 8-nor-DPEP may have originated from chlorophylls-a2 or b2 or bacteriochlorophyll-a. Although DPEP and cycloheptanoDPEP are presumably derived from common precursory pigments, their isotopic compositions differed in the present study, suggesting that the latter represents a specific population within the photoautotrophic community. The average δ15N value for the entire photoautotrophic community is estimated to be –2 to +1‰ from the δ15N values of DPEP (–6.9 to –3.6‰; n=7), considering that the empirical isotopic relationships that the tetrapyrrole nuclei of chloropigments are depleted in 15N by ~4.8‰ and enriched in 13C by ~1.8‰ relative to the whole cells. This finding suggests that nitrogen utilized in the primary production was supplied mainly through N2-fixation by diazotrophic cyanobacteria. Based on the δ13C values of DPEP (–17.9 to –15.6‰; n=7), we estimated isotopic fractionation associated with photosynthetic carbon fixation to be 8–14‰. This range suggests the importance of β-carboxylation and/or active transport of the carbon substrate, indicating in turn the substantial contribution of diazotrophic cyanobacteria to primary production. Based on the δ15N values of 17-nor-DPEP (–7.4 to –2.4‰ n=7), the δ15N range of chlorophylls-c-producing algae was estimated to be –3 to +3‰. This relative depletion in sup>15N suggests that these algae mainly utilized nitrogen regenerated from diazotrophic cyanobacteria. Given that diatoms are likely to have constituted the chlorophylls-c-producing algae within the biogenic-silica-rich Onnagawa Formation, cyanobacteria-hosting diatoms may have been important contributors to primary production.

Publisher Summary This chapter presents a study, which determines the carbon and nitrogen isotope ratios of various pelagic organisms and fish scale specimens to elucidate the food web structure in Lake Baikal and to reconstruct fluctuations in global and lacustrine environments in the recent past. It seeks to emphasize that our fish scale specimens can serve as a valuable medium for recording changes in paleo-lacustrine environments. Carbon and nitrogen isotope ratios are measured in pelagic organisms collected in Lake Baikal and in scale specimens of omul fish collected. The nitrogen isotope ratio of the pelagic organisms showed a clear trend toward step-wise enrichment with trophic level. The carbon isotope data suggests that pelagic phytoplankton are the primary carbon source of the pelagic food web, because the carbon isotope values of the consumers are close to those of pelagic phytoplankton. The carbon isotope values recorded in omul scales showed a trend to gradually decrease. The trend reflected the decreasing carbon isotope values in atmospheric carbon dioxide, which is caused by the release of fossil–fuel carbon into the atmosphere. Periodic variations are observed in the carbon isotope value records of omul scales, which may be related to variations in ecological or physiological factors.

Compound-specific H, C and N isotope analyses by gas chromatography–isotope ratio mass spectrometry (GC/IRMS) have widely been used for various studies, because it allows a rapid and precise isotope analysis of specific molecules of a small amount (nanomolar amount of the element) in complex mixture. However, its application for tetrapyrrole pigments (i.e. chlorophylls) is limited due to their high molecular weight and conjugated structures. In this study, we developed a method to determine nitrogen isotopic composition (dN) of chlorophylls, by the use of chemical degradation treatment prior to the isotope analysis. Chlorophylls were isolated by high-performance liquid chromatography. The isolated chlorophylls were transformed to pyropheophorbide derivatives by HCl treatment, and subsequently degraded to pyrrole units (maleimides) by chromic acid oxidation (Fig. 1). These chemical degradations have no substantial isotopic fractionation for chlorophyll nitrogen, and thus dN values of the pyrrole units can be determined precisely by GC/IRMS. Analytical error (1r, standard deviation) of the isotope measurement was always better than ±0.5&, with the minimum sample amount of 15 ngN.