Toxigenic Microcystis aeruginosa (Cyanobacteria) affects the population growth of twocommon green microalgae. Evidence of other allelopathic metabolites different to cyanotoxins

• Published in: Journal of phycology
• Main Authors: Hernández-Zamora, Miriam, Santiago-Martínez, Elisa, Martínez-Jerónimo, Fernando
• Format: Journal Article
• Language: English
• Published: United States 14.05.2021
• Subjects: Allelopathic interactions; Phytoplankton community; Harmful cyanobacterial blooms; Eutrophication; Microcystins
• ISSN: 1529-8817

Agriculture runoffs and discharge of wastewaters are the major causes of eutrophication. Although eutrophication could promote the thriving of any phytoplankter, frequently harmful algal blooms (HABs) are dominated by cyanobacteria. Currently, HABs dominated by the toxigenic cyanobacterium Microcystis aeruginosa in lakes and reservoirs are the main environmental concerns worldwide. This study was aimed to determine how M. aeruginosa (Ma) modifies the population growth of Pseudokirchneriella subcapitata (Ps) and Ankistrodesmus falcatus (Af). Growth kinetics were determined for each species and in the combinations: Ps-Ma, Af-Ma, Af-Ps, and Ps-Af-Ma. At the end of experiments, photosynthetic pigments, phycobiliproteins, and microcystins were quantified. The Logistic equation significantly described the growth trend for all the tested species, enabling the identification of negative effects since the first stages in the population growth in co-cultures with the cyanobacterium; in addition, the interaction effects in the growth rate and in the maximum attainable population density were determined. The biomass of A. falcatus, and P. subcapitata was significantly higher when cultured individually than in all the combinations with the cyanobacterium. The concentration of chlorophyll a and b, as well as carotenoids, was lower in combined cultures, but phycobiliproteins content in the cultures with M. aeruginosa was not significantly affected. M. aeruginosa negatively affected the growth of microalgae, but A. falcatus was significantly more inhibited than P. subcapitata; however, microcystins concentration was significantly reduced in the co-cultures with microalgae. Results could help to explain the displacements of microalgae when cyanobacteria are present, giving place to cyanobacterial blooms in eutrophic freshwaters.