Rev. biol. mar. oceanogr. 50(2): 347-352

Research Note

Removal of the toxic dinoflagellate Alexandrium tamarense (Dinophyta, Gonyaulacales) by Mnemiopsis leidyi (Ctenophora, Lobata) in controlled experimental conditions

Sergio Bolasina^1,2, Hugo Benavides^1,4, Nora Montoya¹, José Carreto^1,4, Marcelo Acha^1,3,4 and Hermes Mianzan^1,3,4

¹Instituto Nacional de Investigación y Desarrollo Pesquero - INIDEP, Paseo Victoria Ocampo N°1, Escollera Norte, (7602), Mar del Plata, Buenos Aires, Argentina

²Núcleo em Ecologia e Desenvolvimento Sócio-Ambiental de Macaé -NUPEM/UFRJ, Rua São José do Barreto 764, Macaé, Rio de Janeiro, Brasil. (Present address)

³Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina

⁴Universidad Nacional de Mar del Plata, Funes 3350 (7600) Mar del Plata, Buenos Aires, Argentina

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The objective of the present study is to estimate the removal capability of the ctenophore Mnemiopsis leidyi (Ctenophora, Lobata) on cultures of the toxic dinoflagellate Alexandrium tamarense (Dinophyta, Gonyaulacales). For this purpose, observations on its clearance and survival rates were made in controlled experiments, using different A. tamarense cell concentrations. Mnemiopsis leidyi is able to remove dinoflagellates actively from the water column only at the lowest density tested (150 cells mL^-1). Animals exposed to 300 cells mL^-1 presented negative clearance and removal rates (survival= 67%). All ctenophores exposed at the highest concentrations of toxic dinoflagellates (600 cells mL^-1) died after 4 h. Removal may occur mainly by incorporating and entangling cells in the mucus strands formed by the ctenophore, and in a lesser way by ingestion. Results indicate that higher concentrations of A. tamarense are fatally toxic to M. leidyi and that this ctenophore could control only the initial development of this dinoflagellate bloom.

Key words:  Removal capability, Mnemiopsis leidyi, Alexandrium tamarense