Catchment properties and the photosynthetic trait composition of freshwater plant communities

Abstract

Unlike in land plants, photosynthesis in many aquatic plants relies on bicarbonate in addition to carbon dioxide (CO2) to compensate for the low diffusivity and potential depletion of CO2 in water. Concentrations of bicarbonate and CO2 vary greatly with catchment geology. In this study, we investigate whether there is a link between these concentrations and the frequency of freshwater plants possessing the bicarbonate use trait. We show, globally, that the frequency of plant species with this trait increases with bicarbonate concentration. Regionally, however, the frequency of bicarbonate use is reduced at sites where the CO2 concentration is substantially above the air equilibrium, consistent with this trait being an adaptation to carbon limitation. Future anthropogenic changes of bicarbonate and CO2 concentrations may alter the species compositions of freshwater plant communities.

Interactive Effects of Rising Temperature and Nutrient Enrichment on Aquatic Plant Growth, Stoichiometry, and Palatability

“…In our experiment, the pH varied from 7 to 10 ( Figure S2), indicating that the major C source for the plant was bicarbonate (HCO 3 − ) (Maberly and Gontero, 2017), and V. spiralis could utilize bicarbonate as its main C source in this condition (Iversen et al, 2019). The alkalinity (mainly represented by bicarbonate, Figure S2) was almost always above 1.0 meq L −1 which indicates that the growth of V. spiralis might not be limited by C availability during the experiment (Vestergaard and Sand-Jensen, 2000a;Vestergaard and Sand-Jensen, 2000b).…”

Latitudinal variation in global range‐size of aquatic macrophyte species shows evidence for a Rapoport effect

“…However, there is some congruence between certain areas of the world modelled as having moderate to high values of catchment bicarbonate, as shown in Figure S2 of Iversen et al. (2019), and the locations of regions with high occurrence of agricultural land use (e.g. Europe, China).…”

“…The recent study by Iversen et al. (2019), which relates macrophyte traits to modelled catchment bicarbonate concentrations, mapped for the British Isles and at world scale, provides useful new information in this context. It is not possible to make direct quantitative comparison of their findings with the world distribution of cropland (as mapped in Appendix S2), owing to differences in grain scale.…”

Changes in the functional features of macrophyte communities and driving factors across a 70-year period

“…The importance of pH is different from that of lake size. In acid and neutral waters, increasing pH might first enable the occurrence of different kinds of species causing increases in functional diversity, as high pH is related to increasing levels of bicarbonate and the availability of carbon for macrophytes (Vestergaard & Sand-Jensen, 2000;Iversen et al 2019). Nonetheless, there is no clear spatial pattern in changes of pH from the 1940s to 2017 (Fig.…”