European native Myriophyllum spicatum showed a higher $${\text{HCO}}_{3}^{ - }$$ 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 9 temperature 9 CO 2 ) 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 CO 2 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 highlight and high CO 2 conditions. Additionally, the capacity of both to use HCO À 3 was significantly higher in plants acclimated to CO 2 depletion than for plants growing in CO 2 -rich water. Summarizing, both species showed their ability to grow under variable conditions, but M. spicatum is the better HCO À 3 user and showed better acclimation in growth and physiological parameters to CO 2 depletion. Overall, native M. spicatum reached higher growth rates and showed a better acclimation to low CO 2 conditions than the nonnative M. heterophyllum. Thus, the HCO À 3 use capacity alone cannot explain the success of evergreen M. heterophyllum in formerly M. spicatum-dominated waters.

European invasion in progress: Myriophyllum heterophyllum Michx. (Haloragaceae) in Croatia

“…Similarly, Thum & Lennon (2010) reported M. heterophyllum from ʺhigher orderʺ lakes characterized as large, low elevation systems with relatively high pH, alkalinity and conductivity. The optimum temperature for M. heterophyllum is about 20°C (Hussner & Jahns, 2015). According to Starmühler (2009), the taxon was found in a 3-10 m deep lake on the island of Krk, northern Adriatic.…”

Acclimation of photosynthesis to supersaturated CO2 in aquatic plant bicarbonate users

“…The affinity ratio for HCO 3 − relative to CO 2 during photosynthesis was highly variable among the 10 tested species (0.11–0.61), and it was suppressed for all species (to 0–0.28) by acclimation to elevated CO 2 . This phenomenon has been shown before for a few freshwater plants and marine macroalgae (Sand‐Jensen & Gordon, , ; Hussner & Jahns, ), but it is confirmed here for the first time as a general phenomenon for many species acclimated to specific air‐saturated and supersaturated CO 2 concentrations. It can be regarded as a suitable cost–benefit response because investment in costly HCO 3 − use mechanisms is futile, when free CO 2 is readily available.…”

“…CO 2 addition was adjusted for each pot with the needle regulator. The pH in the LC treatment was held constant at 8.2 ± 0.2, while pH in the HC treatment was fixed at 6.7 ± 0.2, resulting in CO 2 concentrations of 0.012 m m in the LC and 0.263 m m in the HC treatment (Hussner & Jahns, ). Due to the continuous addition of CO 2 in the HC treatment, DIC reached 0.8–0.95 m m , close to the 0.85 m m of the ambient air bubbled LC treatments.…”

“…Photosynthesis and growth rate of these freshwater plants, despite their ability to use HCO 3 − , can be severely constrained by inorganic carbon supply in water at air saturation, and therefore, they will be stimulated by CO 2 supersaturation. While in the short term, submerged aquatic plants show a strong stimulation of photosynthesis under elevated CO 2 availabilities, and this stimulation is more pronounced in plants acclimated to CO 2 limitation and HCO 3 − use (Sand‐Jensen & Gordon, ; Madsen, Maberly & Bowes, ; Hussner & Jahns, ), the long‐term effects may be less as found in terrestrial plants. Terrestrial plants exhibit a relatively modest (<20%) stimulation of growth rates by elevated CO 2 (Long et al ., ; Leakey et al ., ).…”

Aquatic invasive species: general trends in the literature and introduction to the special issue

“…They showed that this species is very resistant to submergence and that this feature may be one of the reasons for its success in habitats heavily disturbed by floods. Another experiment, carried out by Hussner & Jahns (2015) in Germany, evaluated the effects of light, temperature, and carbon availability on the invasive species Myriophyllum heterophyllum, and compared it with the European native M. spicatum. They showed that the native species attains better use of bicarbonate and has higher growth rates than the invasive species under low CO 2 availability.…”