Algae extermination by a novel algicide (DMPAI) with low-dose and field experiment

Abstract

Using a low dose of a novel algicide (didecyl methyl propyl ammonium iodide or DMPAI), the field-based inhibition test of the cyanobacterium Microcystis aeruginosa bloom was investigated. The results showed that the cell growth of M. aeruginosa could be markedly inhibited and removed by DMPAI and the inhibition and removal rates increased with the DMPAI concentration inflation. Within 24 h, the cell density of M. aeruginosa was 8.84 × 107, 9.58 × 106, and 2.0 × 105 cell/L at 0.1, 0.5, and 1.0 mg/L of DMPAI, respectively, and, compared with control group, the cell inhibition and cell removal rates were 91.95 % and 56.45 %, and 99.83 % and 99.10 %, at 0.5 and 1.0 mg/L of DMPAI, respectively. The Fv/Fm value decreased from 0.47 to 0, and the Y (II) value declined from 0.33 to 0. Y (II), exhibiting a decreasing trend earlier than Fv/Fm. A 24-h acute toxicity test result of DMPAI on two nontargeted organisms, Daphnia magna and Carassius auratus, displayed that the safe concentration range for the application of DMPAI in field experiments was <5.0 mg/L. The field inhibition test of M. aeruginosa bloom in the enclosed area of 400 m2 in Taihu Lake revealed that, after using 1.0 mg/L of DMPAI, the density of M. aeruginosa decreased to 1.48–2.34 × 104 cells/mL for 1 d, 1.71–3.90 × 104 cells/mL for 2 d, and 1.53–9.48 × 104 cells/mL for 3 d, respectively. Compared with the control group, the average removal rate for M. aeruginosa reached up to 99.39–99.90 %. This study demonstrated that this new type of algicide in low concentration had strong removal and flocculation effects on cyanobacteria blooms and could be utilized for preventing cyanobacteria blooms for emergency management in the future.