Author(s): Kouki Sugihara; Makoto Nakatsugawa
Linked Author(s): Makoto Nakatsugawa
Keywords: No Keywords
Abstract: This study clarifies the water quality characteristics of stagnant, eutrophic water bodies that freeze over in winter, based on our surveys and simulations, and examines how climate change may influence those characteristics. The surveys found that climate-change-related increases in water temperature were suppressed by ice covering the water area, which also blocked oxygen supply. It was also clarified that the bottom sediment consumed oxygen and turned the water layers anaerobic beginning from the bottom layer, and that nutrient salts eluted from the bottom sediment. These eluted nutrient salts were stored in the water body until the ice melted. Climate change was surveyed as having caused decreases in nutrient salts concentration because of the shortened ice-cover period; however, Biological Oxygen Demand (BOD) showed a tendency to increase in spring with the proliferation of phytoplankton that was promoted by the climatechange-related increase in water temperature. To forecast water quality by using these findings, particularly the influence of climate change, we constructed a water quality simulation model that incorporates the freezing-over of water bodies. The constructed model shows good temporal and spatial reproducibility and enables water quality to be forecast throughout the year, including the ice-cover period. The forecasts using the model agree well with the survey results of shortened ice period and climate-change-related increase in BOD in spring.
Year: 2012