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Revista chilena de historia natural

Print version ISSN 0716-078X


MARTINEZ, GINGER; MOLINA, XIMENA; OLMEDO, MARIA ISABEL  and  MONTECINO, VIVIAN. Susceptibility to ultraviolet-B radiation of the dinoflagellate Alexandrium catenella Kofoid Balech, and the diatom Phaeodactylum tricornutum Bohlin. Rev. chil. hist. nat. [online]. 2000, vol.73, n.2, pp.323-330. ISSN 0716-078X.

Differential susceptibility to ultraviolet B (UV-B, 280 - 320 nm) radiation among microalgae generates patterns of dominance in phytoplankton assemblages. However, despite some events of harmful algal blooms (HAB's) of the dinoflagellate Alexandrium catenella have been coincident with high UV-B radiation episodes in the southern region of Chile, a causal relationship has not been found among these processes. Through the population parameters, intrinsic growth rate (µ) and carrying capacity (K), the UV-B effect over the population dynamic of A. catenella cultures was determined, and compared with the demographic response of cultures of the UV-B-susceptible diatom, Phaeodactylum tricornutum. Results showed that both species exhibit a significant decrease in µ faced with an increased UV-B radiation. Nevertheless, while response of A. catenella exhibited a threshold dose after which growth decreased down to 0.03 d-1, µ-values in P. tricornutum showed a proportional decrease down to 0.34 d-1. Notwithstanding, the parameter K showed a similar decline in both species under a RUV-B gradient, A. catenella exhibited a significant inhibition at 2.9 KJ m-2 d-1, meanwhile in P. tricornutum K was affected under doses equal to or higher than 4.1 KJ m-2 d-1. Contrary to prediction, results indicated that with an increase in the UV-B radiation dose, A. catenella presented a higher susceptibility compared with P. tricornutum, granting a week causality to this factor in determining the dominance pattern of A. catenella during HAB's

Keywords : UV-B radiation; Alexandrium catenella; Phaeodactylum tricornutum; growth; carrying capacity.

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