I wonder if there is a clear consensus on the definition of “macrophyte”, as I found rather distinct definitions in the literature:

• Some sources (Bornette & Puijalon, 2009; Font-Quer, 1975; Schaumburg et al., 2004) claim it refers only to aquatic plants. For example, in Schaumburg et al. (2004) freshwater macroalgae are all encompassed under the name “Remaining phytobenthos”. The main problem I have with this definition is that there are several synonyms to refer to aquatic plants (aquatic plants, hydrophytes…) whereas there would not be a clear term for referring to all macroscopic aquatic vegetation, in spite of this term being of interest for referring to their shared ecosystem services or the fact they are all mostly studied by the same botanists.
• Others claim it refers to both aquatic plants and green macroalgae (Lacoul & Freedman, 2006; Padial et al. 2008). This is generally, under the justification that they belong to the same lineage. The main problem I have with this definition is that it is also done by emphasising their similar ecological roles, which are not exclusive of those organisms, and which are also aplicable to other macroalgae (red and brown).
• Others encompass freshwater plants and macroalgae (Chambers et al., 2008). The main problem I have with this definition is that it constrains the definition to freshwater or brackish ecosystems, whereas there is no clear reason to ignore the marine ecosystems, as there are organisms there with analogous ecosystem functions.
• Finally, other authors refer to all aquatic macroscopic vegetation, including macroalgae and plants as macrophytes(Hernandez et al., 2010; Lesiv et al. 2020; Ortega et al. 2020, Trevathan-Tackett et al. 2015). Lesiv et al. (2020) acknowledges that whilst plants and green algae are almost always considered as macrophytes, other macroalgae groups are considered as such too. I believe this is the most useful, as there are several names (both morphological and functional) to refer to aquatic plants (hydrophytes, marine/freshwater phanerogams … ) but there is no other word to refer to all these autotrophic macroscopic organisms that can be found in aquatic ecosystems (both freshwater and marine), which share several ecological traits.

There seems to be a tendency in authors that work on the marine environment to group all marine plants and macroalgae under the term “macrophyte”, whilst authors that work on freshwater environment tend to use a more restrictive definition, possibly as a result of the higher plant diversity and almost negligible xanthophyte and rhodophyte diversities. I’m more drawn to the all-inclusive definition, as it allows to refer to all macroscopic producers of all aquatic ecosystems in a simple and effective way, but I do wonder if there is a consensus on the use of this word or if other people have any comments on this regard.

Note: Please note that I considered the term “plant” as a way to refer only to members of the Plantae kingdom, disregarding the tendency of some authors to use the term to any kind of vegetation, as it can be misleading.

Bibiography

• Chambers, P. A., Lacoul, P., Murphy, K. J., & Thomaz, S. M. (2007). Global diversity of aquatic macrophytes in freshwater. Hydrobiologia, 595(1), 9–26. https://doi.org/10.1007/s10750-007-9154-6
• Bornette, G. & Puijalon, S. 2009. Macrophytes: Ecology of Aquatic Plants. In Encyclopedia of Life Sciences; John Wiley & Sons, Ltd.: Chich‐ester, UK.
• Hernandez, L., Bermejo, R., García-Marín, P., Brun, F.G., Vergara, J.J., 2010. MarineMacrophytes and the Water Framework Directive: Preliminary Studies in SouthernSpain. Ambientalia SPL.
• LACOUL, P. and FREEDMAN, B., 2006. Environmental influences on aquatic plants in freshwater ecosystems. Environ.rev., vol. 14, no. 2, p. 89-136
• Lesiv, M. S., Polishchuk, A. I., & Antonyak, H. L. (2020). Aquatic macrophytes: ecological features and functions. Studia Biologica, 14(2), 79–94. https://doi.org/10.30970/sbi.1402.619
• Ortega, A., Geraldi, N. R., & Duarte, C. M. (2020). Environmental DNA identifies marine macrophyte contributions to Blue Carbon sediments. Limnology and Oceanography, 65(12), 3139–3149. https://doi.org/10.1002/lno.11579
• Padial, A., Bini, L., & Thomaz, S. (2008). The study of aquatic macrophytes in Neotropics: a scientometrical view of the main trends and gaps. Brazilian Journal of Biology, 68(4 suppl), 1051–1059. https://doi.org/10.1590/s1519-69842008000500012
• Schaumburg, J., Schranz, C., Foerster, J., Gutowski, A., Hofmann, G., Meilinger, P., Schneider, S., & Schmedtje, U. (2004). Ecological classification of macrophytes and phytobenthos for rivers in Germany according to the water framework directive. Limnologica, 34(4), 283–301. https://doi.org/10.1016/s0075-9511(04)80002-1
• Trevathan-Tackett, S. M., Kelleway, J., Macreadie, P. I., Beardall, J., Ralph, P., & Bellgrove, A. (2015). Comparison of marine macrophytes for their contributions to blue carbon sequestration. Ecology, 96(11), 3043–3057. https://doi.org/10.1890/15-0149.1