High temperature and pH favor Microcystis aeruginosa to outcompete Scenedesmus obliquus

Abstract

Competition between cyanobacteria and green algae affects phytoplankton succession and the well-known cyanobacteria blooms. Climate warming and water acidification are two concerned environmental issues changing the freshwater ecosystems. To investigate the competitive responses of phytoplankton to warming and acidification, we co-cultured Microcystis aeruginosa and Scenedesmus obliquus at a temperature range of 15-35 °C and a pH range of 5-9. Results showed that S. obliquus was superior competitor at 15 °C. At 20-30 °C, the populations of both Scenedesmus and Microcystis were inhibited by the presence of each other. S. obliquus was in competitive domination at the initial phase of cultivation, but was finally replaced by M. aeruginosa. Microcystis kept competition advantage at 35 °C, whereas Scenedesmus outcompeted Microcystis at acidic conditions (pH ≤ 6). Neutral and weakly alkaline conditions (pH 7-9) supported the replacement of competition domination from Scenedesmus to Microcystis. The present study revealed that climate warming may accelerate the phytoplankton succession from green algae to cyanobacteria, with the predicted promoted cyanobacteria blooms. Nonetheless, water acidification causes Microcystis to be a weak competitor with green algae, suggesting that the advantageous effect of Microcystis toward green algae at high temperatures was controlled by other variables like the water pH.

Isolation and screening of microalgal species, native to Zimbabwe, with potential use in biodiesel production

“…possesses a superior growth rate advantage over Scenedesmus sp. when cultured at 20-35°C temperatures (Yang et al 2018). Microcystis' growth rate also fell within the range observed by Harke and Gobler (2013) when this microbe was cultured under low phosphorus conditions.…”

Distribution of the Harmful Bloom-Forming Cyanobacterium, <i>Microcystis aeruginosa</i>, in 88 Freshwater Environments across Japan

“…Therefore, a neutral to alkaline pH environment appears to be a significant factor for the maintenance of Microcystis populations. More specifically, Yang et al (2018) showed that a pH in the range of 7-8 was optimum for M. aeruginosa strain 7806, which belongs to MG1 in our genotype grouping, and conditions under pH 6 and over pH 9 were hostile to growth. The present results also showed that pH 7-8 was optimum for Microcystis populations because the majority of MG1dominated populations (65.9%, 27/41), which were designated as S-group-1, were derived from sites with a pH in this range.…”

Desmodesmus subspicatus co-cultured with microcystin producing (PCC 7806) and the non-producing (PCC 7005) strains of Microcystis aeruginosa

“…through the decrease of the integrity of the cell membrane. The study by Yang et al (2018) showed M. aeruginosa and Scenedesmus obliquus at the similar algal initial abundance of 1 × 10 5 cells mL −1 have negatively affected one another’s growth at 20–30 °C, depending on their physiological status. As temperature increased from 20 to 30 °C, the competitive advantages of the green alga was decreased where the green alga was superior for a shorter time at the initial phase of co-cultivation while towards the end of the co-cultivation period Microcystis resumed dominance in the mixed culture.…”