12:00 PM - 12:15 PM
[MIS23-06] Variation factors of the coastal lagoon environment and ecosystem since the modern period in Hokkaido, Japan
Keywords:lagoon, Paleoenvironment, Diatom, Anthropogenic effect
Mokoto-ko is seasonally ice-covered small lagoon, however, has a large 167 times catchment area. At present, Mokoto-ko is an eutrophic lagoon, and anoxic bottom water mass was observed. In January 2009, 1.8 m long sediment cores (09Mk-1C) was obtained from the northern part of basin using a push-in piston corer. There is the clear lamina layer throughout this core. Based on the sediment core analysis, eutrophication of lagoon Mokoto-ko started in late 1950s by phosphorus input, which is probably related with the development of dairy farming in the catchment area. On the other hand, lagoon environment and ecosystem showed drastic fluctuation. A sudden eutrophication and fresh water input of this lagoon has a strong relationship with heavy precipitation in its catchment. In this area, frequency of the heavy precipitation has good correlation with the phase of the Arctic Oscillation, meaning that Arctic Oscillation partially controlled the lagoon environment and ecosystem. In this presentation, impact of climate change on the lagoon ecosystem is discussed based on this periodical environmental change in addition to the impact of human activity.