**3. Results**

#### *3.1. Appearance and General Characteristics of Colored Blooms*

The colored blooms in the coastal mudflats and tide pools studied were pink, red, brown, or yellow-green (Figure S1) and had the odor of sulfide. The sulfide concentration and ORP (Eh) in these coastal environments varied between 6.2 and 12 mg-S2<sup>−</sup> <sup>L</sup>−1, and −170 and −320 mV, respectively (Table 1), suggesting that the studied sites were under strongly anaerobic anoxic conditions. On the other hand, the colored blooms and mats in the wastewater ditches were red and pink-brown and had much lower concentrations of sulfide (≤0.6 mg-S2<sup>−</sup> <sup>L</sup>−1) and higher Eh (−93 to 23 mV). These data evidenced marked physicochemical di fferences between the blooms/mats in the coastal environments and wastewater ditches.
