Characteristics of Energy Distribution for N, P and C Sequestration by Microcystis Aeruginosa Under Blue and Orange Light

Abstract

Investigating the mechanisms of cyanobacterial bloom is a crucial topic in the field of bloom control. Previous studies showed that orange light can stimulate the growth of cyanobacteria, whereas blue light can enhance the production of phycobiliprotein. But the underlying mechanisms remain inadequately understood. In this study, Microcystis aeruginosa (FACHB-905) was cultured on different nitrogen and phosphorus concentrations under blue, orange, and white LED light. Growth rates, nutrient uptake rates, and key enzyme activities were detected to investigate the influence of light quality on nutrient uptake and to analyze energy distribution. The results show that the growth rate of M. aeruginosa was higher under orange light. Higher glutamine synthetase (GS) (1.39×10⁻⁷ U·cell⁻¹), H⁺-ATPase (3.31×10⁻⁷ μ·mol·h⁻¹·cell⁻¹) activity, and low carbon fixation efficiency (1.60 mg·L⁻¹·d⁻¹) were observed. Under blue light, the growth rate was the lowest, the activities of carbonic anhydrase (CA) (3.15×10⁻⁶ EU· cell⁻¹) and carbon fixation efficiency (2.31 mg·L⁻¹·d⁻¹) were highest. GS activity (1.19×10⁻⁷U·cell⁻¹) and nitrite reductase (NR) activity (0.06×10⁻⁴ nmol·h⁻¹·cell⁻¹) were the lowest. Under white light, the activities of NR (0.63×10⁻⁴ nmol·h⁻¹·cell⁻¹), GS (1.58×10⁻⁷ U·cell⁻¹), and H⁺-ATPase (4.12×10⁻⁷ μ·mol·h⁻¹·cell⁻¹) were highest, carbon fixation efficiency (1.41 mg·L⁻¹·d⁻¹) was lower. These results suggested that the energy absorbed by photosynthesis is primarily used for the NH₄⁺ absorption process under orange light, mainly for carbon sequestration under blue light, and mainly for NO₃⁻ uptake under white light. Our results indicated that orange light can promote the growth of M. aeruginosa by enhancing its nitrogen uptake, while blue light can increase its carbon sequestration.

Keywords: Light quality, Microcystis aeruginosa, Nutrient uptake, Energy distribution, Carbon sequestration