Original scientific paper

Diel observations on populations of Dinophysis and Alexandrium spp. (Dinophyceae) from the NW Adriatic Sea

Maria Grazia Giacobbe ; Istituto Sperimentale Talassografico, CNR, Messina, Italy
Franco Bianchi ; Istituto di Biologia del Mare, CNR, Venezia, Italy
Giovanna Maimone ; Istituto Sperimentale Talassografico, CNR, Messina, Italy
Alessandra Puglisi ; Istituto Sperimentale Talassografico, CNR, Messina, Italy
Giorgio Socal ; Istituto di Biologia del Mare, CNR, Venezia, Italy

Abstract

Quanti-qualitative changes in Dinophysis and Alexatidrium populations from the Gulf of Venice NW Adriatic Sea - were studied on a short time scale (44 h cycles). Under hydrographic conditions of marked thermohaline stratification (July 1995), D. sacculus populations assembled in the surface waters (12 24 yt isopycnals). Division processes took place mostly in the early hours of the morning and at 14:00 h, 4 to 10 % of the population consisted of morphotypes of reduced size (possibly gametes resulting from successive cell divisions). Similar percentages were also observed in October for D. caudata, with a maximum division between 06:00 h and 10:00 h. During this month, coexisting populations of Alexandrium cf. fundyense and A. cf. tamarense displayed rhythmic changes in cell density that slightly differed from those exhibited in July by A. pseudogonyaulax, suggesting a circadian control of the cell cycle rather than a response to hydrographic changes.

Keywords

phytoplankton; toxic dinoflagellates; Alexandrium; Dinophysis; vertical migration; diel cycles; Gulf of Venice; Adriatic Sea

Hrčak ID:

160506

URI

https://hrcak.srce.hr/160506

Publication date:

31.12.1998.

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