Maternal effects on offspring population dynamics in Brachionus calyciflorus differ between exposure to non-toxic...

Maternal effects can shape offspring phenotypes related to fitness and thus play an important role in regulating population dynamics. The inhibitory effect of bloom algae Microcystis aeruginosa (particularly toxin-producing strains) on rotifers has been extensively studied. However, it remains unclear whether the transgenerational consequences of cyanobacterial blooms are driven primarily by intact algal cells or by dissolved microcystin. Here, we used a two-generation cross-exposure design to compare how maternal exposure to non-toxic M. aeruginosa cells or purified microcystin-LR (MC-LR) affected the population dynamics, life-history traits, and morphology of offspring in the rotifer Brachionus calyciflorus. When offspring exposed to the same non-toxic M. aeruginosa environment as their mothers, maternal exposure aggravated decrease in survival, population growth rate, and body size. By contrast, when offspring exposed to the same MC-LR environment as their mothers, maternal exposure enhanced population growth and reproductive performance. These contrasting responses indicate that non-toxic M. aeruginosa cells and dissolved MC-LR generate distinct maternal effects on rotifer demography. The responses to non-toxic M. aeruginosa are consistent with non-adaptive maternal effects under stronger maternal stress, whereas the responses to MC-LR are consistent with anticipatory maternal effects in a matching toxin environment. Distinguishing algal-cell effects from toxin-mediated effects may improve ecological risk assessment and prediction of zooplankton dynamics during cyanobacterial blooms.