2.3. Benthic algae culture
Benthic algae used in the SRP release experiment were cultured in a laboratory and grown in the twelve sediment core samples. Two-hundred milliliters of lake water were carefully poured into each sediment core tube. Four sediment cores were kept in the dark, where no benthic algae would grow. Eight sediment cores were kept in a light–dark cycle of 12 L:12 D, with an average light intensity of 15.8 ± 9.4 μmol/(m2·s) in daytime and darkness at night, which would lead to abundant benthic algae in two weeks. After the culture of the eight sediment cores, four of these cores with benthic algae were used to measure the Chl a concentration and determine the dominant taxa. The Chl a concentration was measured after the Chl a was extracted by ethanol from the sediment cores at room temperature according to a spectrophotometrical analysis technique from Jespersen and Christoffersen (1987), and the average Chl a concentration was 86 ± 4 mg/m2. The dominant taxa were found, using a microscope (Hu and Wei, 2006), to be Oscillatoria tenuis Ag. and Navicula spp. (class Diatom). The other four sediment cores with benthic algae were combined with the four sediment cores without benthic algae to examine the effect of benthic algae on the SRP release rate from sediments.