“…A data matrix, including algal cell density (ACD, cell/L), pH, dissolved oxygen (DO, mg/L), five-day biochemical oxygen demand (BOD 5 , mg/L), ammonia nitrogen (NH 3 -N, mg/L), total phosphorus (TP, mg/L), total nitrogen (TN, mg/L), fluoride (F − , mg/L), water temperature (WT, °C), sulphate (SO 4 2− , mg/L), faecal coliform bacteria (F. coli, colonies/L), mercury (Hg, μg/L), arsenic (As, μg/L), copper (Cu, μg/L), zinc (Zn, μg/L), selenium (Se, μg/L), flow velocity (V, m/s), and flow discharge (Q, m 3 /s), was used for the first step of analysis. Since the water quality of the main canal maintained an excellent status (Nong et al, 2020;Tang et al, 2022), and most of the heavy metal elements and physicochemical indicators had narrow vary ranges, the WT, Q, V, DO, NH 3 -N, TP, and TN were selected as the basic indicators that may affect ACD in the main canal based on the pre-review (Song et al, 2018;Zhang et al, 2018;Gao et al, 2022). The ACD was obtained by collecting 1,000 mL of water samples at 0.5 m below the river center's surface and adding 10-15 mL of Lugol's iodine solution.…”