Harmful Algal Blooms of Noctiluca scintillans Resulted from Wastewater of Aquaculture in the Waters Around the Naozhou Island, Zhanjiang, China

An investigation of harmful algal blooms of Noctiluca scintillans was conducted in the waters around the Naozhou Island, Zhanjiang, China. The investigation showed that the harmful algal blooms appeared in the waters around the Island when the sea temperature was 19 ℃, the salinity 27-32, the pH 6.87-8.33, the dissolved oxygen 2.81-8.11 mg·L-1, the chemical oxygen demand 0.97-492.28 mg·L-1, the ammonia nitrogen 0.002-0.258 mg·L-1, the nitrate 0.04-0.262 mg·L-1, the nitrite 0.005-0.175 mg·L-1, the inorganic nitrogen 0.047-0.529 mg·L-1, and the reactive phosphate 0.048-1.682 mg·L-. This was due to the fact that large amounts of eutrophic waste water were discharged into the sea waters directly from the local prawn ponds due to pond cleaning. This mass of eutrophic waste water was the major factor that caused the harmful algal blooms of N. scintillans covering the waters 2 km long and 50 m wide, or a sea area of 10 hectares in the waters around the Island.