Catchment properties and the photosynthetic trait composition of freshwater plant communities

English. Funding: L.L.I. was funded by the Carlsberg Foundation (CF17-0155 and CF18-0062). L.B.-S. was funded by the Aage V. JensenFoundation. D.G. was funded by the Polish National Agency forAcademic Exchange (PPN/BEK/2018/1/00401), J.A. was fundedby The Academy of Finland (332652), and K.S.-J. was funded bythe Carlsberg Foundation (grant CF14-0136).

English. Funding: L.L.I. was funded by the Carlsberg Foundation (CF17- 0155 and CF18-0062). L.B.-S. was funded by the Aage V. Jensen Foundation. D.G. was funded by the Polish National Agency for Academic Exchange (PPN/BEK/2018/1/00401), J.A. was funded by The Academy of Finland (332652), and K.S.-J. was funded by the Carlsberg Foundation (grant CF14-0136).

English. Freshwater plants can be broadly divided into two major categories according to their photosynthetic traits: Some use carbon dioxide as their carbon source, whereas others use bicarbonate. Iversen et al. found that the relative concentrations of these two inorganic carbon forms in water determine the functional composition of plant communities across freshwater ecosystems (see the Perspective by Marcé and Obrador). They created global maps revealing that community composition is structured by catchment geology and not climate (in contrast to the terrestrial realm, where the trait composition is structured by temperature and rainfall). Anthropogenic influences from land-use change are causing large-scale increases in bicarbonate concentrations in freshwater catchments and are thus leading to wholesale changes in the composition of their aquatic plant communities.