European native Myriophyllum spicatum showed a higher ${\text{HCO}}_{3}^{ - }$ use capacity than alien invasive Myriophyllum heterophyllum

Abstract

Light, temperature, and the availability of carbon are three major drivers of submerged plant growth, photosynthesis, and competitive strength. A laboratory study using a three factorial experimental design (light × temperature × CO₂) was carried out to evaluate growth responses (RGR (relative growth rate), LDMC (leaf dry matter content), and root:shoot ratio) and physiological changes (pigment characteristics and net photosynthesis under CO₂ depletion) in the European native Myriophyllum spicatum and the non-native invasive M. heterophyllum to changes in the three variables. Both species showed temperature optima of 21°C and highest growth rates under high-light and high CO₂ conditions. Additionally, the capacity of both to use ${\text{HCO}}_{3}^{ - }$ was significantly higher in plants acclimated to CO₂ depletion than for plants growing in CO₂-rich water. Summarizing, both species showed their ability to grow under variable conditions, but M. spicatum is the better ${\text{HCO}}_{3}^{ - }$ user and showed better acclimation in growth and physiological parameters to CO₂ depletion. Overall, native M. spicatum reached higher growth rates and showed a better acclimation to low CO₂ conditions than the non-native M. heterophyllum. Thus, the ${\text{HCO}}_{3}^{ - }$ use capacity alone cannot explain the success of evergreen M. heterophyllum in formerly M. spicatum-dominated waters.