Chlorophytes prolong mixotrophic Ochromonas eliminating Microcystis: Temperature-dependent effect

Area of Science:

• Aquatic Ecology
• Microbiology
• Environmental Science

Background:

• Harmful cyanobacterial blooms (e.g., Microcystis) threaten aquatic ecosystems due to eutrophication and warming.
• Protozoan grazing offers a potential biological control method for toxic cyanobacteria and microcystin degradation.
• Interactions with other algae species can influence the efficacy of protozoan grazing on Microcystis.

Purpose of the Study:

• To investigate the impact of chlorophytes (beneficial algae) on the ability of Ochromonas (a flagellate) to control Microcystis populations and degrade microcystins.
• To assess the influence of temperature on these interactions.

Main Methods:

• Laboratory experiments were conducted using Ochromonas, Microcystis, and chlorophytes at varying temperatures.
• Microcystis population dynamics, microcystin concentrations, and algal community composition were monitored over time.

Main Results:

• Ochromonas successfully reduced Microcystis populations and degraded microcystins in the presence of chlorophytes.
• The presence of chlorophytes prolonged the elimination time of Microcystis, with temperature influencing the rate.
• Chlorophytes increased in abundance as Microcystis declined under Ochromonas grazing, while Microcystis dominated in cultures without Ochromonas.

Conclusions:

• Chlorophytes can extend the duration of Microcystis elimination by Ochromonas but do not prevent it.
• Protozoan grazing on Microcystis facilitates the dominance of beneficial chlorophytes, contributing to improved water quality and reduced ecological risk.