Diatom distribution in the surficial sediments of Lake Fuxian, Yunnan Plateau, China
Examination of surficial sediments at 14 sites shows minor, but consistent differences in the numbers and kinds of diatom assemblages in different regions of Lake Fuxian. Diatom assemblages in the surficial sediments at all sites were dominated by Cyclotella ocellata, Cyclotella rhomboideo-elliptica, Stephanodiscus hantzschii, Fragilaria crotonensis Cyclostephanos dubius and Stephanodiscus minutulus Aulacoseira granulata Achnanthes minutissima. A detrended correspondence analysis (DCA) defined two groups of sites generally corresponding to the two main parts of the Lake Fuxian basin. They reflected the two geomorphological regions of the lake basin, which basin in the northern were wider and deeper than that in the southern basin and the corresponding differences in hydrochemistry. It was characterized by lower diatom abundance in the southern part of the lake where there was main inflow water with high nutrient concentrations flows from the eutrophic Lake Xingyun. The total diatom abundance was 4.8 × 107 valves g-1 and 3.6 × 107 valves g-1 in northern and southern part of the lake, respectively. It was characterized by higher abundance of S. minutulus in the northern part of the lake (18.2%); there were some phosphorus post-mines which led to higher total phosphorus concentration than that in southern part. The most outstanding characteristic of diatom assemblages from Lake Fuxian lost the extreme degree of endemism with increasing trophic levels. Endemic diatoms species are not the most abundant component of assemblages at all sites. Small abundances of benthic diatoms were found in all samples. Although low abundances were present in sediments, the benthic diatom flora was very diverse. Species diversity was increased in Lake Fuxian, which may be related to natural influences of nutrient loads and local anthropogenic effects.
Key words: Lake Fuxian, diatom, distribution, surficial sediments, China.