Allelopathic Potential of the Cyanotoxins Microcystin-LR and Cylindrospermopsin on Green Algae

Abstract

Allelopathic interactions are widespread in all aquatic habitats, among all groups of aquatic primary biomass producers, including cyanobacteria. Cyanobacteria are producers of potent toxins called cyanotoxins, whose biological and ecological roles, including their allelopathic influence, are still incompletely understood. The allelopathic potential of the cyanotoxins microcystin-LR (MC-LR) and cylindrospermopsin (CYL) on green algae (Chlamydomonas asymmetrica, Dunaliella salina, and Scenedesmus obtusiusculus) was established. Time-dependent inhibitory effects on the growth and motility of the green algae exposed to cyanotoxins were detected. Changes in their morphology (cell shape, granulation of the cytoplasm, and loss of flagella) were also observed. The cyanotoxins MC-LR and CYL were found to affect photosynthesis to varying degrees in the green algae Chlamydomonas asymmetrica, Dunaliella salina, and Scenedesmus obtusiusculus, affecting chlorophyll fluorescence parameters such as the maximum photochemical activity (Fv/Fm) of photosystem II (PSII), the non-photochemical quenching of chlorophyll fluorescence (NPQ), and the quantum yield of the unregulated energy dissipation Y(NO) in PSII. In the context of ongoing climate change and the associated expectations of the increased frequency of cyanobacterial blooms and released cyanotoxins, our results demonstrated the possible allelopathic role of cyanotoxins on competing autotrophs in the phytoplankton communities.

Review of Allelopathy in Green Tides: The Case of Ulva prolifera in the South Yellow Sea

“…Fatty acids are important participants in the chemical communication network of the intricate undersea ecosystems. As Teneva et al (2023) have pointed out, important allelopathy between algae and phytoplankton [ 28 ]. To an expert on the subject, the significance of fatty acids like hexadecanoic acid and octadecenoic acid, which is from Ulva linza , can influence the growth of phytoplankton populations along the shore [ 39 ].…”

“…The green tide process is greatly aided by these compounds, which may be stimulating or inhibiting, therefore controlling competition and biodiversity in the environment. Citing Teneva et al (2023) and Chia et al (2021), cyanobacteria, for instance, release two toxins, microcystin-LR and cylindrospermopsin, which prevent green macroalgae from growing [28,29]. Not only can microalgae interact chemically, but macrophytes and microalgae do too.…”