College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China; Beijing Key Laboratory of Biodiversity and Organic Farming, China Agricultural University, Beijing, 100193, China.
College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China; Beijing Key Laboratory of Biodiversity and Organic Farming, China Agricultural University, Beijing, 100193, China.
J Environ Manage. 2022 Jun 15;312:114904. doi: 10.1016/j.jenvman.2022.114904. Epub 2022 Mar 25.
Allelochemicals are widely accepted as promising algaecide to mitigate Microcystis-dominated cyanobacterial blooms (MCBs). Allelopathic algicidal effect of single luteolin or kaempferol against Microcystis had been confirmed, but their joint effect against Microcystis was unclear. This study comprehensively explored time-dependent joint effect and mechanisms of luteolin and kaempferol on Microcystis growth during 14 day-test. The 50%-inhibitory threshold of their mixture (IC) was verified as 4.872 and 5.211 mg/L at equitoxic ratio, and 5.167 and 4.487 mg/L at equivalent ratio, respectively, on day 8 and 14. Using toxicity unit, isobologram and predictive models, results revealed that luteolin and kaempferol at equivalent ratio interacted additively at lower, median and higher dosages, while at equitoxic ratio interacted additively at lower dosage but synergistically at median and higher dosages in Microcystis on day 8 and 14, implying that their equitoxic mixture posed better algicidal effect against Microcystis. Various dosages of equitoxic mixture concurrently decreased aqueous and total microcystins (MCs) contents along test. Thus, luteolin and kaempferol could be jointly applied as high-efficacy and eco-safe algaecide with declined MCs pollution risks. As mixture dosage elevated, more strongly weakened cellular MCs retention and inhibited cellular photosynthetic pigments content during late stage, as well as decreased aqueous MCs content long test, jointly explained increasing growth inhibition ratio with rising mixture dosage. Yet, cell damage was gradually repaired due to early stimulated antioxidant defense at each mixture dosage, thus cell damage might not be a major reason for inhibited growth under mixture stress. This study provided novel insights and guidance to coupled application of luteolin and kamepferol for mitigating MCBs and decreasing MCs pollution risks.
化感物质被广泛认为是一种有前途的杀藻剂，可以减轻微囊藻为主的蓝藻水华（MCBs）。已经证实，单独的木犀草素或山奈酚对微囊藻具有化感杀藻作用，但它们对微囊藻的联合作用尚不清楚。本研究在 14 天试验中全面探讨了木犀草素和山奈酚对微囊藻生长的时间依赖性联合作用及其机制。在等毒性比下，混合物的 50%抑制阈值（IC）在第 8 天和第 14 天分别为 4.872 和 5.211mg/L，在等效比下分别为 5.167 和 4.487mg/L。使用毒性单位、等对数图和预测模型，结果表明，在较低、中等和较高剂量下，木犀草素和山奈酚在等效比下呈相加作用，而在等毒性比下，在第 8 天和第 14 天，在较低剂量下呈相加作用，在中等和较高剂量下呈协同作用，这表明它们的等毒性混合物对微囊藻具有更好的杀藻作用。不同剂量的等毒性混合物同时降低了水中和总微囊藻毒素（MCs）的含量。因此，木犀草素和山奈酚可以作为高效、生态安全的杀藻剂联合应用，降低 MCs 污染风险。随着混合物剂量的增加，在后期更强烈地削弱细胞 MCs 保留能力，抑制细胞光合色素含量，并在整个试验过程中降低水中 MCs 含量，这共同解释了随着混合物剂量的增加，生长抑制率的增加。然而，由于每个混合物剂量下早期刺激抗氧化防御，细胞损伤逐渐得到修复，因此，细胞损伤可能不是混合物胁迫下生长受到抑制的主要原因。本研究为木犀草素和山奈酚联合应用减轻 MCBs 和降低 MCs 污染风险提供了新的见解和指导。
