Seguimiento de un cultivo del dinoflagelado tóxico "Ostreopsis" cf. "ovata", procedente de una proliferación natural en el noroeste del Mediterráneo

Abstract

Ostreopsis cf. ovata is a toxic benthic dinoflagellate, which has been associated with harmful effects on human health and certain benthic organisms. The genus Ostreopsis includes so far nine species largely distributed in tropical and temperate regions worldwide. Microalgae blooms are natural processes and a key component of the structure and dynamics of the oceans. However, some species can cause negative impacts because they produce toxins. Ostreopsis cf. ovata can synthesize palytoxin and their analogues. In the Mediterranean Sea, the proliferation of this microalgae constitutes an emergent problem related to respiratory and skin irritations, moreover it has ecological problems like urchin and mussel’s massive mortalities. Therefore, it is important to conduct studies in the lab to characterise the behaviour of the benthonic microalgae and understand their dynamics in natural conditions. In this study, the cell forms and biomass related parameters (cells number, chlorophyll) were characterized along different physiological phases of an O. cf. ovata culture. The cells were isolated from field samples taken in the north-western Mediterranean coast. The most important limitation when working with this species is the mucilage production, a complex structure of organic fibres, produced by Ostreopsis to attach to surfaces and which aggregates a large number of cells. Moreover, the relationship between bacteria and microalgae was also analysed. The growth rate is calculated from the studied parameters and it is compared with field samples along a natural bloom in the same site where the cells were isolated (Sant Andreu de Llavaneres, Catalonia). The natural bloom has a growth rate slightly lower than the culture, likely due to higher cell losses associated to dispersion by water motion and to grazing pressure. Furthermore, the morphology and morphometry of the O. cf. ovata cells to be able to understand the variability observed in nature. The gained understanding contributed to a better monitoring and prevention of the impacts of Ostreopsis.

Ostreopsis cf. ovata is a toxic benthic dinoflagellate, which has been associated with harmful effects on human health and certain benthic organisms. The genus Ostreopsis includes so far nine species largely distributed in tropical and temperate regions worldwide. Microalgae blooms are natural processes and a key component of the structure and dynamics of the oceans. However, some species can cause negative impacts because they produce toxins. Ostreopsis cf. ovata can synthesize palytoxin and their analogues. In the Mediterranean Sea, the proliferation of this microalgae constitutes an emergent problem related to respiratory and skin irritations, moreover it has ecological problems like urchin and mussel’s massive mortalities. Therefore, it is important to conduct studies in the lab to characterise the behaviour of the benthonic microalgae and understand their dynamics in natural conditions. In this study, the cell forms and biomass related parameters (cells number, chlorophyll) were characterized along different physiological phases of an O. cf. ovata culture. The cells were isolated from field samples taken in the north-western Mediterranean coast. The most important limitation when working with this species is the mucilage production, a complex structure of organic fibres, produced by Ostreopsis to attach to surfaces and which aggregates a large number of cells. Moreover, the relationship between bacteria and microalgae was also analysed. The growth rate is calculated from the studied parameters and it is compared with field samples along a natural bloom in the same site where the cells were isolated (Sant Andreu de Llavaneres, Catalonia). The natural bloom has a growth rate slightly lower than the culture, likely due to higher cell losses associated to dispersion by water motion and to grazing pressure. Furthermore, the morphology and morphometry of the O. cf. ovata cells to be able to understand the variability observed in nature. The gained understanding contributed to a better monitoring and prevention of the impacts of Ostreopsis.