Effect of algal growth phase on Aureococcus anophagefferens susceptibility to hydrogen peroxide.

A cell's growth phase could affect its susceptibility to a biocide in microbial control. This study examines the growth phase dependent susceptibility of a brown tide bloom alga Aureococcus anophagefferens to microbial biocide hydrogen peroxide (H2O2). Test cultures of A. anophagefferens cells in exponential and stationary growth phase and similar initial cell density (1.6×10(6) cells mL(-1)) were exposed to 0.4-1.6 mg L(-1) H2O2. Changes in algal growth (in vivo fluorescence, total chlorophyll a, and cell density), cell physiology (maximum quantum yield of photosystem II, and total intracellular non-protein thiols), and H2O2 decomposition were quantified. Results show that the stationary phase cells are more susceptible to H2O2 than the exponential phase cells, and this is attributed to the weaker ROS (reactive oxygen species) scavenging system and consequently greater cell damage in stationary phase cells. The stationary phase cells potentially require 30-40% less H2O2 to reach 90% removal within 12 h of treatment as compared to the exponential phase cells. The results have practical implications in brown tide bloom control with respect to the timing and the dosage of H2O2 application.