THE CHANGE OF OSTRACODS AND BIOSILICON FROM LAKE LUGU SEDIMENT RECORD AND THE CAUSE ANALYSIS IN LAST HUNDRED YEARS.

Numerous palaeoclimatic and modem instrumental data indicated that the climate of Yunnan-Guizhou Plateau has undergone a significant warming during the past century. In this research. biological silicon, ostracods, physicochemical proxies of Lake Lugu sediment core were analyzed to illuminate the change on the lake ecosystem and their cause analysis in the past century. The correlations between those proxies and the temperature and precipitation data of the Lijiang region during 1951-2010 AD were analyzed. The results showed that: biosilicon, ostracods and physicochemical proxies changed greatly with the depth of the sediment, especially 14.5 cm which represent for the past 70 years. The results of ostracods combination showed that since 1990, the relative abundance of cold water species reduced, such as Cyclocypris and Candona. while the relative abundance of the warm water species increased, like Eucypris and Cypris. Limnocythere was the dorminant species in the core. The absolute abundance of ostracoda increased sharply from the end of last century and reduced rapidly in recent years. The content of biological silicon maintained at a relative higher level since 1990. which indicated that the primary productivity was relatively high in Lake Lugu during this period and phytoplankton containing silicon (e.g. Diatoms) increased. Therefore climate change in this region led to the increase of primary productivity in lake Lugu over the last 20 years. [ABSTRACT FROM AUTHOR]