Algicidal Activity of Cyperus rotundus Aqueous Extracts Reflected by Photosynthetic Efficiency and Cell Integrity of Harmful Algae Phaeocystis globosa

Abstract

Phaeocystis globosa is regarded as a notoriously harmful algal bloom species. Suppressing harmful algae using algicidal substances extracted from plants is considered an effective method. The physiological and biochemical processes of P. globosa were explored by exposure to different concentrations of aqueous extracts of Cyperus rotundus. All treatments indicated various inhibitory effects on the algal growth compared to the control samples without adding extracts. At 48 h, the 4, 8, and 16 mg/mL treatment groups showed a significant inhibitory effect, consistent with a decrease in the chlorophyll-a content and photosynthetic efficiency. The images of the transmission electron microscope (TEM) further confirmed that a subset of the cells in the treatment groups exhibited morphological anomalies. The algicidal active substances were mainly identified as phenolic acids containing maximal content of quinic acid in aqueous extracts according to the results of ultra-high-performance liquid chromatography-tandem time-of-flight mass spectrometer (UPLC-HRMS). The 50% anti-algal effect concentration of quinic acid was 22 mg/L at 96 h (EC50–96h). Thus, the phenolic acids might be considered as major inhibitors of the growth of P. globosa. These results demonstrated that the aqueous extracts of C. rotundus could potentially control the growth of P. globosa.

Effects of Two Potential Allelochemicals on the Photosystem II of Nitzschia closterium and Monostroma nitidum

“…For example, phenolic acids 2-phenylphenol, p-hydroxybenzoic acid, protocatechuic acid, ellagic acid, gallic acid, p-coumaric acid and vanillic acid have effective allelopathic effects on the growth of harmful algae [48][49][50][51][52][53]. Additionally, some organic acids such as quinic acid, hexanedioic acid, linoleic acid, αlinoleic acid, palmitic acid and azelaic acid also exhibit strong allelopathic potential on controlling harmful algae [54][55][56][57][58]. However, Nakai et al found that quinic acid had no algal suppression effect [19].…”