Review of studies on biomass‐density relationships (including self‐thinning lines) in seaweeds: Main contributions and persisting misconceptions

SUMMARY Ecological models relating biomass and density are relatively simple to calculate and offer information on, for example, the interactions among organisms and size constraints. Biomass‐density relationships have mostly been studied for terrestrial plants, but recently they have also been increasingly investigated for seaweeds. Unfortunately, a number of misconceptions have limited the overall contribution of algal studies to biomass‐density theory in general. Aiming to improve this situation, the present paper first summarizes the current knowledge on biomass‐density theory, particularly focusing on the main concepts that, with varying degrees of validity, exist in the published literature: the self‐thinning rule (in its boundary and dynamic interpretations), the interspecific biomass‐density relationship, and the ultimate biomass‐density line. Afterwards, the present paper provides a critical review of past biomass‐density studies on seaweeds. The main contributions of studies on clonal and unitary species are discussed, while the misconceptions that persist to these days are identified in order to help future studies to be based on solid grounds.