Chapter 19 - Unveiling Secrets Locked in Great Ghost Lake in Taiwan

Abstract

A survey conducted to study the effect of acid rain on lakes of Taiwan revealed that the Great Ghost Lake is the deepest lake in Taiwan and is the only one where the subsurface waters are anoxic almost all year-round. With the lack of oxygen, the organic matter in the mud that accumulated on the bottom of the lake is also well preserved. And without any fish or other large organisms living in the lake, the mud remains undisturbed. Moreover as the lake is deep with steep slopes, the wind and waves could not disturb the mud either. In other words, there is always older mud lying beneath the younger mud. The mud with a well-preserved sequence had become an archive of past climatic events. Distinctive white laminations appear in the generally black sediments of the anoxic Great Ghost Lake in Taiwan. These white laminations have lower porosity, organic matter content, and magnetic susceptibility and contain organic matter most probably derived from phytoplankton. This suggests that they have been deposited in cooler and drier periods. The organic matter of the black sediments is mainly from land plants, suggesting deposition under warmer and wetter climates. These high-resolution data seem to reflect large-scale climatic changes.