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[MIS17-P23] Distributions of long chain diols in modern sediments from the Seto Inland Sea: Implications for paleoenvironments
Keywords:Long chain diols, Eustigmatophyte, algal biomarker, modern sediment, coastal area, Seto Inland Sea
Long chain diols are widely distributed in both marine and freshwater environments. Previous studies have been proposed the use of long chain diols as paleoenvironmental indicators. Various ratios of C28–C32 1,13-, 1,14- and 1,15-alkyl diols have been proposed as markers for freshwater influence or upwelling (Diol index; Versteegh et al. 1997; Rampen et al., 2008; 2014), as well as a proxy for the past sea surface temperature (Long chain diol index; Rampen et al., 2012). Several distinct organisms have been suggested as biological sources for long chain diols; i.e. marine and freshwater Eustigmatophyte algae (1,13- and 1,15-alkyl diols) and the marine diatom genus Proboscia (C28 and C30 1,14-alkyl diols).
In the present study, we investigate the long chain diol compositions in the surface and subsurface sediment cores from the Seto Inland Sea to examine the relations of diol compositions and environmental factors in the coastal region. The cores were taken from Osaka Bay and Harima-nada Bay (eastern part of Seto Inland Sea), in which lengths are 20 cm and 40 cm, respectively. These cores are divided and analyzed in every 5 cm (12 samples).
The long chain diols predominantly consist of C30 and C32 1,15-alkyl diols in both Osaka Bay and Harima-nada Bay. Low abundance of C28 and C30 1,14-diols implicates the occurrence of the diatom genus Proboscia in Seto Inland Sea, however its siliceous tests have not been identified. The rest of long chain diols are probably derived from Eustigmatophyte algae or the other unknown producers. A ratio between C30 and C32 1,15-alkyl diol is clearly different between Osaka Bay and Harima-nada Bay, while the general distributions of long chain diols are not significantly varied with depth within each location. The relative abundance of C32 1,15-alkyl diol is higher than most marine sediments reported in previous studies, which possibly attributed to the strong influence by riverine input due to the vicinity to the Yodo River estuary.
Rampen et al., 2008., Earth Planet. Sci. Let. 276, 207–213.
Rampen et al., 2014. Geochim. Cosmochim. Acta 144, 59–71.
Versteegh et al., 1997, Org. Geochem. 27, 1–13.
In the present study, we investigate the long chain diol compositions in the surface and subsurface sediment cores from the Seto Inland Sea to examine the relations of diol compositions and environmental factors in the coastal region. The cores were taken from Osaka Bay and Harima-nada Bay (eastern part of Seto Inland Sea), in which lengths are 20 cm and 40 cm, respectively. These cores are divided and analyzed in every 5 cm (12 samples).
The long chain diols predominantly consist of C30 and C32 1,15-alkyl diols in both Osaka Bay and Harima-nada Bay. Low abundance of C28 and C30 1,14-diols implicates the occurrence of the diatom genus Proboscia in Seto Inland Sea, however its siliceous tests have not been identified. The rest of long chain diols are probably derived from Eustigmatophyte algae or the other unknown producers. A ratio between C30 and C32 1,15-alkyl diol is clearly different between Osaka Bay and Harima-nada Bay, while the general distributions of long chain diols are not significantly varied with depth within each location. The relative abundance of C32 1,15-alkyl diol is higher than most marine sediments reported in previous studies, which possibly attributed to the strong influence by riverine input due to the vicinity to the Yodo River estuary.
Rampen et al., 2008., Earth Planet. Sci. Let. 276, 207–213.
Rampen et al., 2014. Geochim. Cosmochim. Acta 144, 59–71.
Versteegh et al., 1997, Org. Geochem. 27, 1–13.