143 Coalescense During Early Recruitment of Mazzaella Laminarioides

Coalescence in seaweeds is known to occur in the laboratory among young and older sporelings and in the field between neighboring conspecific clumps. However, because spores and germlings are difficult to study in the field, it is as yet unknown at which stage of population development coalescence is most important. Since many seaweeds disperse aggregated propagules, often with a sticky mucilagous envelope around the spores, aggregated recruitment and coalescence might be more important at early stages of population establishment than among fully grown, well established clumps. Using recruitment plates maintained during several experimental times in the field, we are evaluating the above idea with mid‐intertidal populations of Mazzaella laminarioides. During high fertility seasons, close to 45% of the spores settling within or at close (<1 m) distances of the bed exhibited aggregated recruitment, forming groups of 2 to 150+spores. The probability of aggregated recruitments is a function of dispersal distance and spore density. The number of sporelings produced is a function of spore density and coalescence. Highest after‐recruitment mortality (first 15 days) occurs among solitary recruits, followed by sporelings conformed by small number of spores (2–4). Approximately 50% of the spores recruited, isolated or in group, coalesce within these 15 days, gradually forming massive sporelings with increasingly larger basal areas. Thus, after recruitment, sporelings may disappear (die), survive or coalesce. These three alternatives are integrated in a new demographic model for coalescing seaweeds (supported by grant FONDECYT 1020855).