Growth and production of new recruits and adult individuals of Ascophyllum nodosum at a non-harvested population at its southern limit, NW Spain.

English. Populations near the geographic distributionlimits of the species are considered to live under suboptimalconditions, and hence, slight environmental changescan be critical for their survival. The potential sensitivityto disturbances of the long-living macroalga Ascophyllumnodosum was analyzed by the determination of growth,recruitment, mortality, and production of biomass of apopulation near its southern distribution limit. Recruitment,survival and growth rates of <2 years old individualswere determined in a new population growing inexperimentally denudated squares. Demographic data for>2 years old individuals were obtained from individuals inthe original population after estimating their age from thenumber of gas bladders in the thallus. Growth and survivalwere described as continuous nonlinear functions of ageapplied to the population and were further used to makedemography-based production estimates. Recruitment ofA. nodosum in denudated substrates seemed to require aprevious cover of other macroalgae (as Fucus vesiculosus)as the only cohort detected during the 26-monthperiod of the study was observed after F. vesiculosus individualsstarted to increase. The low production estimates(2,033 g m−2 for a 10 year period) and poor recruitmentmay indicate a slow recuperation of this population todenudation. However, the large variability observed in the estimated growth curves of different populations alongthis southern distribution area suggests a large influence oflocal conditions that may help to overcome environmentalchanges at regional scales.

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