Response Of Attached Algae On Submerged Plants To Different Nutrient Concentrations

The attached algae owns a unique ecological niche and plays an important role in the aquatic ecosystem. The attached algae communities can produce high primary productivity as nutrition sources for a variety of aquatic animals, and affect the nutrient salt content in water many ways. The attached algae on the surface of large submerged plants can influence their distribution, which causes regime shift.In this article, through field investigation and microcosm experiments,responses of the attached algae to eutrfication level were studied, the results were followed obtained:1. Five sampling sites were set along northwest to southeast in Baiyangdian lake, and water samples and whole plants of Certophyllum demersum were collected. The results showed that water quality in all sampling sites were in eutrophication level, which were heavy eutrofication level in Dongguan port and Yuanyang island, were middle eutrophication level. Eutrophication level decreased in sampling order.Major attached algae flora that affect Ceratophyllum demersum were identified to belong to 65 species, 7 Phylums, which Bacillariophyta, Chlorophyta and Cyanophyta were dominant. Among them, the dominant species of attached algae included Eunotia lunaris, Cladophora sp. and Ankistrodesmus angustus. Density of attached algae decreased in sampling order, and inhibition rate of attached algae on photosynthesis rate of Ceratophyllum demersum decreased too, which indicated that high nutritive concentration would lead to increase of attached algae on submerged plants that affect their survival and distribution. That may be an importantreason that macrophytic lake shifit to algae lake.2. Aquatic microcosms were established based on Myriophyllum spicatum and the density of attached algae and water quality were investigated under adding different nutrient addition regularly. The experiment of 2012 and 2013 showed that in condition of continuous low and medium levels of nutritive salt addition, attached algae and phytoplankton maintained at a relatively low level at the initial stage, and reached a high level after 30 d. In group E of big nutrition pulses in 2012 and Group F with the maximum nutritive salt additon in 2013, there existed an outbreak attached algae and phytoplankton. After a period of cultivation, with the Myriophyllum spicatum’s absorption to nitrogen and phosphorus in water bodies, the number of attached algae and phytoplankton did not rise any longer and remained stable. When Myriophyllum spicatum decayed, attached algae and phytoplankton under different treatments increased significantly and maintained at a higher density.