Allelopathic effects of gramineous plant extracts on Spirogyra communis growth: insights from Zizania latifolia, Phragmites australis, and Digitaria sanguinalis.

The overgrowth of algae, such as Spirogyra communis (S. communis), has emerged as a significant ecological issue, exacerbated by the increasing problem of eutrophication in aquatic ecosystems. S. communis overgrowth can result in the deterioration of water quality and a decline in biodiversity. To mitigate the proliferation of S. communis under conditions of water eutrophication, the inhibitory effects of ethanol extracts from gramineous plants, Zizania latifolia (Z. latifolia), Phragmites australis (P. australis), and Digitaria sanguinalis (D. sanguinalis) on the growth of S. communis were investigated. The results demonstrated that the ethanol extract of D. sanguinalis at a concentration of 10 g/L exhibited the best inhibitory effect. The D. sanguinalis ethanol extracts significantly reduced the chlorophyll a (Chl-a) content and soluble protein levels in the algal cells, leading to severe oxidative damage and triggering antioxidant responses. The structure of algal cells was compromised, resulting in their inhibited growth or even death. Gas chromatography-mass spectrometry (GC-MS) analysis identified fatty acids and terpenoids as the primary allelopathic compounds responsible for algal inhibition in the D. sanguinalis ethanol extracts. In addition, the results of the ecotoxicity test indicated that at a concentration of 10 g/L, which was used to inhibit the growth of S. communis, the ethanol extract of D. sanguinalis posed less ecological risk to aquatic organisms, including zebrafish and Vallisneria natans (V. natans). Based on these findings, the ethanol extract of D. sanguinalis shows promising potential as an algal inhibitor.