Heavy metal contamination of water bodies has become a critical global environmental issue. Algae-based photosynthesis assays have emerged as an effective tool for rapid on-site detection of water toxicity. However, due to the varying photosynthetic responses of different algal species to toxic substances, the most suitable algal species for sensitive and rapid detection of the toxicity of heavy metal polluted water remains unclear. In order to realize emergency monitoring and early warning of heavy metal pollution in water, in this present study, the cyanobacterium Microcystis aeruginosa and the green alga Chlorella pyrenoidosa were used as test organisms, and chlorophyll fluorescence induction kinetics technology was used to systematically investigated the changes and response characteristics of chlorophyll fluorescence rise induction kinetics (OJIP) curves and photosynthetic fluorescence parameters (Fv/Fm and Fv/Fo) of the two freshwater algal species under typical heavy metal pollutants Hg, Cu, and Cr(III) exposure. Thus, suitable algal species for rapid and sensitive detection of the toxicity of heavy metal polluted water was identified. The results indicated that when the exposure time was 5 min, 0.5 mg L−1 Hg, Cu, and Cr(III) all caused significant changes in the OJIP curves of M. aeruginosa, and the degree of change in the OJIP curve gradually increased with the increase of heavy metal concentration. However, when the OJIP curve of C. pyrenoidosa showed significant changes, the concentrations of Hg, Cu, and Cr(III) needed to reach > 10, 5, and 20 mg L−1, respectively. In terms of photosynthetic fluorescence parameters Fv/Fm and Fv/Fo, for M. aeruginosa, the 5 min-LOEC of Hg, Cu, and Cr(III) were 5, 5, and 50 mg L−1, respectively, and the 120 min-LOEC of Hg, Cu, and Cr(III) were 0.1, 5 (Fv/Fm)/1 (Fv/Fo), and 10 mg L−1, respectively; while for C. pyrenoidosa, the 5 min-LOEC of the same three heavy metals were > 10, 10, and > 50 mg L−1, and the 120 min-LOEC were 5, 5, and > 50(Fv/Fm)/20 (Fv/Fo) mg L−1. During the exposure time of 5 min to 120 min, for M. aeruginosa, the LOEC values of these three heavy metals were all lower than or equal to those values for C. pyrenoidosa. Meanwhile, the 120 min-EC50 values of the three heavy metals for M. aeruginosa were also lower than those values for C. pyrenoidosa using Fv/Fm and Fv/Fo as toxicity response indexes. So, compared with C. pyrenoidosa, the photosynthesis of M. aeruginosa has a more rapid and more sensitive response to heavy metal pollutants. Therefore, the method by using M. aeruginosa photosynthesis for water toxicity detection can significantly shorten the detection time and improve the sensitivity of toxicity detection of heavy metal polluted water, and is a powerful tool for emergency monitoring and early warning of heavy metal contamination in water.

Selection of suitable algal species for rapid and sensitive detection of toxicity in heavy metal polluted water based on algal photosynthesis

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发表日期：

2025年8月26日

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Xiaoxuan Tan,
Tingting Gan,
Gaofang Yin,
Nanjing Zhao,
Peng Huang,
Ziqi Ye,
Lisha An,
Letong Li

摘要

Heavy metal contamination of water bodies has become a critical global environmental issue. Algae-based photosynthesis assays have emerged as an effective tool for rapid on-site detection of water toxicity. However, due to the varying photosynthetic responses of different algal species to toxic substances, the most suitable algal species for sensitive and rapid detection of the toxicity of heavy metal polluted water remains unclear. In order to realize emergency monitoring and early warning of heavy metal pollution in water, in this present study, the cyanobacterium Microcystis aeruginosa and the green alga Chlorella pyrenoidosa were used as test organisms, and chlorophyll fluorescence induction kinetics technology was used to systematically investigated the changes and response characteristics of chlorophyll fluorescence rise induction kinetics (OJIP) curves and photosynthetic fluorescence parameters (F_v/F_m and F_v/F_o) of the two freshwater algal species under typical heavy metal pollutants Hg, Cu, and Cr(III) exposure. Thus, suitable algal species for rapid and sensitive detection of the toxicity of heavy metal polluted water was identified. The results indicated that when the exposure time was 5 min, 0.5 mg L⁻¹ Hg, Cu, and Cr(III) all caused significant changes in the OJIP curves of M. aeruginosa, and the degree of change in the OJIP curve gradually increased with the increase of heavy metal concentration. However, when the OJIP curve of C. pyrenoidosa showed significant changes, the concentrations of Hg, Cu, and Cr(III) needed to reach > 10, 5, and 20 mg L⁻¹, respectively. In terms of photosynthetic fluorescence parameters F_v/F_m and F_v/F_o, for M. aeruginosa, the 5 min-LOEC of Hg, Cu, and Cr(III) were 5, 5, and 50 mg L⁻¹, respectively, and the 120 min-LOEC of Hg, Cu, and Cr(III) were 0.1, 5 (F_v/F_m)/1 (F_v/F_o), and 10 mg L⁻¹, respectively; while for C. pyrenoidosa, the 5 min-LOEC of the same three heavy metals were > 10, 10, and > 50 mg L⁻¹, and the 120 min-LOEC were 5, 5, and > 50(F_v/F_m)/20 (F_v/F_o) mg L⁻¹. During the exposure time of 5 min to 120 min, for M. aeruginosa, the LOEC values of these three heavy metals were all lower than or equal to those values for C. pyrenoidosa. Meanwhile, the 120 min-EC₅₀ values of the three heavy metals for M. aeruginosa were also lower than those values for C. pyrenoidosa using F_v/F_m and F_v/F_o as toxicity response indexes. So, compared with C. pyrenoidosa, the photosynthesis of M. aeruginosa has a more rapid and more sensitive response to heavy metal pollutants. Therefore, the method by using M. aeruginosa photosynthesis for water toxicity detection can significantly shorten the detection time and improve the sensitivity of toxicity detection of heavy metal polluted water, and is a powerful tool for emergency monitoring and early warning of heavy metal contamination in water.