Predicting cyanobacterial decomposition response to multiple environmental factors through Central Composite Design method

Abstract

Abstract The phenomenon of cyanobacterial blooms has always attracted attention worldwide, most of which focuses on the occurrence mechanism and treatment methods of cyanobacterial blooms. Research on the relationship between the decomposing process of cyanobacterial blooms and environmental factors is relatively rare. Notably, the interaction between multiple environmental factors has not been reported yet. Therefore, we studied the cyanobacterial decomposition response to various environmental factors through response surface method and central composite design method. In this study, the concentrations of microcystins were determined by high performance liquid chromatography; the algal cell density of M. aeruginosa was assessed using a Sedgewick–Rafter counting chamber under a microscopic magnification of × 200–400; chlorophyll a was analyzed spectrophotometry at wavelengths of 665 and 750 nm using phaeopigment correction; and the correlation coefficients of polynomial model were analysis using Design Expert 8.0.6 (Stat-Ease, Inc., Minneapolis, MN, USA) The environmental factors included temperature, pH, dissolved oxygen, light intensity, and cyanobacteria cell density. Verification tests showed that the final optimized phytochemical conditions of cyanobacteria decomposition were: temperature 35 °C, pH 6.5, dissolved oxygen 5.5 mg/L, light intensity 3000 lx, and cyanobacterial cell density 8.5 × 109 cells/L. The intensity of the influence of various environmental factors on R Chla and C MC−LR followed: pH > DO > Lux > T > cell density, and cell density > Lux > DO > T > pH, respectively. This study contributes to the theoretical knowledge of the prediction and analysis of the cyanobacterial decomposition status in different external environments.