[BPT04-P03] Comparison between assemblages of diatom fossil and biomarkers in surface sediments from Seto Inland Sea
Keywords:diatom assemblage, diatom biomarkers, HBIs, surface sediment, Seto Inland Seas
Diatom species such as small Thalassiosiraspp., skeletonema costatum, resting spore of Chaetoceros spp. and Neodelphyneis pelagica, which were reported by previous study (Hirose et al., 2008), are observed as the dominant taxa in all samples. Rhizosolenia spp. and Pleurosigma spp., known HBI producers, were occurred in low proportions. As specific diatom biomarkers, we identified C25 di- and tri-unsaturated highly branched isoprenoids (HBIs), along with relatively minor amount of C25 and C35 cyclic HBIs. Total abundances of diatom valves and HBIs were generally correlated, probably reflecting variations of diatom production. Meanwhile, Aki-bay and some samples of Harima-nada Bay were characterized with relatively low abundance of HBIs relative to valves. In these area, focused analysis on the minor diatom taxa would be needed to provide quantitative dataset to discuss further relation of HBIs and produces and their spatial distribution.