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

Populations near the geographic distribution limits of the species are considered to live under suboptimal conditions, and hence slight environmental changes can be critical for their survival. The potential sensitivity to disturbances of the long living macroalga Ascophyllum nodosum was analyzed by the determination of growth, recruitment, mortality, and production of biomass in a population near its southern distribution limit. Recruitment, survival and growth rates of <2 yr old individuals were determined in a new population growing in experimentally denudated squares. Demographic data for >2 yr old individuals were obtained from individuals in the original population after estimating their age from the number of gas bladders in the thallus. Growth and survival were described as continuous non-linear functions of age applied to the population and were further used to make demography-based production estimates. Recruitment of A. nodosum in denudated substrates required a previous cover of other macroalgae (as Fucus vesiculosus) but subsequent settlement of new recruits was not observed, as only one cohort was detected during the 26 month-period of the study. The low production estimates (2,033 g m-2 for a 10 yr period) and poor recruitment indicates high sensitivity of this population to denudation. However, the large variability observed in the growth curves of different populations along this southern distribution area suggest a large potential for adaptation to local conditions that may overcome environmental changes at regional scales.

proyecto ANILE (CTM2009-08396 y CTM2010-09904-E) Plan Nacional de I+D+I (España)

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