[Element contents of biofilm and suspended particulate in natural aquatic ecosystem]

The element contents of biofilms and suspended particulates in the natural aquatic ecosystem were studied, and the samples were collected in Kunming Lake of the Summer Palace in July and October 1999. The biofilm samples were observed through microscope and scanning electron microscope. Various inhabitants such as sessile bacteria, algae, and protozoa existed in the biofilms. The dry weights of biofilms increased with the longer growth period. The dry weight of biofilm at 1 m depth of water reached to 5.19 mg.cm-2 after the growth time of 78 days. The element contents in biofilm, suspended particulate, and lake water were analyzed by ICP-AES, and the results indicated that the element contents in biofilms were higher than those in the particulates. There was not an evident trend in the element contents of biofilms at the different water depth in the same site and growth time. At three sampling sites, the contents of Ca, Mg, K, Na, Al, Fe, and S in the biofilm samples were similar between 1 m and 1.5 m depth of water, but the contents of Mn, Sr, Ti, P, La, Co, Cu, Pb, Li, Ni, B, Ce, V, Be, and Cr were different in the biofilm samples of 1 m and 1.5 m depth of water. The element contents of biofilms increased with the longer growth time.