Environmental changes in Syowa Station area of Antarctica during the last 2300 years inferred from organic components in lake sediment cores

rganic components in sediment cores from Namazu Ike(lake)(length 40cm) and O-ike(lake)(length 32cm) from Syowa Station area, Antarctica were studied to clarify their features in relation to paleoenvironmental changes, together with carbon-14 dating by Tandetron accelerator mass spectrometry. Namazu Ike sediment core was mainly composed of algal(mainly cyanobacteria) and aquatic moss debris, whereas O-ike sediment core was comprised of coarse and fine sands with the influence of algal(mainly cyanobacteria) debris. The ages of core bottoms of Namazu Ike and O-ike were estimated to be 1550 and 2330 years before present(yBP), respectively. The sedimentation rates of Namazu Ike and O-ike were calculated to be 30 and 59 years/cm, respectively. Very high total organic carbon(TOC) contents(average 24.5%) of Namazu Ike revealed that the sediment core was mainly composed of organic matter. Dramatic increase of TOC/total nitrogen ratios at a depth of 25cm in Namazu Ike strongly suggests that aquatic moss increased from 1100yBP to the core top. Changes in n-alkanes, n-alkanoic and n-alkenoic acids, and sterol compositions in the O-ike sediment core, suggest that microbial composition changed considerably, but their source organisms are not clear and further studies are required