2.2.2. Process Analysis of Microbial Degradation of Algal Organic Matter Using the Fractionation Procedure

The above-described long-term microbial degradation systems were repeated under the same controlled conditions in which 0.5 L of the extracted filtrates and concentrated solids, which were resuspended in an equal volume of sterile water, were added to the filtered lake water that served as the algal-derived filtrate and algal residual exudative organic matter groups. These two treatments were also conducted in triplicate in the dark for 80 d. As for the bulk algal-derived DOM and control groups, subsamples from the algalderived filtrate and algal residual exudative organic matter groups were also collected on days 0, 1, 2, 4, 8, 12, 20, 31, 40, 52, 61, and 80 for analyses of planktonic bacterial abundance and determination of DOC and nutrient concentrations and compositions. Intriguingly, we observed that the water color of the algal-derived filtrate group changed dramatically (from brilliant blue to emerald green); therefore, an additional sample was collected on day 3.

#### *2.3. Sample Analysis*
