Competitive dominance of Microcystis aeruginosa against Raphidiopsis raciborskii is strain- and temperature-dependent

Abstract

Microcystis aeruginosa and Raphidiopsis raciborskii (previously Cylindrospermopsis raciborskii) are both common bloom-forming cyanobacteria which can coexist but alternatively dominate in freshwater ecosystems. To predict their blooming dynamics, we need to understand the potential environmental factors determining their succession. In the present study, we examined the pairwise competition of the three M. aeruginosa strains (FACHB905, 469 and 915) with one R. raciborskii strain (N8) at three temperature levels (16 °C, 24 °C, and 32 °C). We found that the competitive ability of three Microcystis strains were highly variable. M. aeruginosa FACHB905 was the strongest competitor among them which can finally exclude R. raciborskii N8 regardless of initial biovolume ratios and temperature levels. The competitive exclusion of N8 by 915 also was observed at 24 °C, but they coexisted at 16 °C and 32 °C. We observed that M. aeruginosa FACHB469 and R. raciborskii N8 were able to coexist under all the temperature levels, and M. aeruginosa FACHB469 was the weakest competitor among the three M. aeruginosa strains. Rates of competitive exclusion (RCE) showed that temperature affects the competition between three M. aeruginosa strains and R. raciborskii N8. M. aeruginosa strains always grew quickly at 24 °C and significantly enlarged its dominance in the co-culture system, while R. raciborskii N8 was able to maintain its initial advantages at both 16 and 32 °C. The competitive advantage of M. aeruginosa FACHB905 may be explained by allelopathic interactions through its allelochemicals and other secondary metabolites other than microcystin. We concluded that both strain difference and temperature can affect the competition between M. aeruginosa and R. raciborskii. Our results highlighted the complexity of cyanobacterial dynamics in waterbodies where there exist multiple strains.

Competitive interactions as a mechanism for chemical diversity maintenance in Nodularia spumigena

“…More specifically, Lei et al . 98 showed that the allelopathic effect of Microcystis aeruginosa towards Raphidiopsis raciborskii was strain-dependent. Therefore, using single-strain N. spumigena cultures in studies on allelopathy will not help understand the in-situ effects of N. spumigena population composed of coexistent strains.…”

Recent Advances in the Ecology of Bloom-Forming Raphidiopsis (Cylindrospermopsis) raciborskii: Expansion in China, Intraspecific Heterogeneity and Critical Factors for Invasion

“…Likewise, the model prediction of species competition outcomes is strongly affected by the growth variability of strains [78]. These findings demonstrate the intraspecific heterogeneity for R. raciborskii and M. aeruginosa [44].…”

“…Recent investigations have revealed high genetic and phenotypic diversity within the population of R. raciborskii [40][41][42]. The adaptation mechanisms of different strains were divergent and the competitive advantage of R. raciborskii against Microcystis aeruginosa was strain dependent [43][44][45][46]. These findings indicated apparent intraspecific heterogeneity in R. raciborskii.…”

Early detection and the importance of environmental drivers for the invasive cyanobacterium Raphidiopsis raciborskii

“…and P. agardhii were the less dominant taxa in all treatments and, in particular, P. agardhii was negatively affected by the low temperature. Temperature, in general, is one of the most important factors influencing phytoplankton growth, nutrient uptake, spatial-temporal distribution in freshwater systems and competition is one of the major factor shaping phytoplankton structure and succession in freshwaters (Lei et al, 2020). In this experiment, temperature was the most significant factor affecting the growth and structure of the phytoplankton assemblage.…”