High-resolution Sedimentary Records In The Qingshitan Reservoir And Their Response To Human Activities

Along with the rapid economic development and population growth within the Qingshitan Reservoir catchment, a variety of cage fishing culture industries and tourism industry have been rising, recently. As a result, the eutrophication process and the water quality degradation in Q ingshitan reservoir have been accelerated. In order to detect the historical ecological evolution and compare the different evolutional procession in different trophic conditions of a resevior, multi-proxy records(i.e., biological and geochemical proxies) were obtained from two sediment cores drilled from the west lake area(QST-S1-A) and east lake area(QST-S4-A) of the Qingshitan Reservoir. The results of this study are expected to provide constructive suggestions for eutrophication control in Qingshitan Reservoir.Diatoms assemblage composition was examined from 24 sediment samples sectioned at 1-cm interval in Core QST-S1-A and 29 sediment samples sectioned at 1-cm interval in Core QST-S4-A. Based on the chronological framework established through 210 Pb and 137 Cs dating, the diatoms assemblages were used to reconstruct the eutrophication process in Q ingshitan reservoir. The major results of the study are as follows:1. The mean sedimentation rate was 0.40 cm/a and 0.47 cm/a in Core QST-S1-A and QST-S4-A of the Qingshitan Reservoir, respectively.2. A total of 293 species(including species variants) belonging to 57 genera from 10 families of 6 orders were identified. The dominant species include Discostella stelligera, Achnanthidium rivulare, Cyclotella hubeiana, A. minutissimum, A. catenatum, Aulacoseira distans, A. ambigua f. japonica and A. ambigua.3. The two sediment cores were divided into four consecutive diatom zones based on a sequential cluster analysis(CONISS). From the bottom upward, the diatom assemblage zones and the change trend of nutrient concentrations(TN、TP) revealed eutrophication processes of different pace in the reservoir. The eutrophication process of west lake area was faster than in east lake area.4. The changes in diatom community succession and nutrient concentrations revealed that the west lake area in Q ingshitan reservoir has much higher levels and increasing faster than east lake area. This contrast suggests that cage fishing culture industry and developing tourism industry accelerated the eutrophication processes.