Ecophysiological responses of the toxic dinoflagellate Ostreopsis cf. ovata under different water motion conditions

Abstract

Hydrodynamic conditions affect marine microalgae. In the case of some harmful epiphytic species, field observations suggest that water motion and wave action play a selective role in determining their spatial distribution and ecology and regulating cell physiology. In order to obtain new insights on this topic, laboratory experiments were performed with Mediterranean strains of Ostreopsis cf. ovata. Monospecific cultures were exposed during 3 weeks to the turbulent motion generated by an orbital shaker at 50 rpm in order to simulate the wave movements in their natural habitat. The growth curve and toxin concentrations in the shaken cultures were compared to those maintained under still, control conditions. Shaken O. cf. ovata populations entered stationary phase earlier, reached lower cell yield and had 30% lower ovatoxin-a intracellular content compared to control ones. In the two treatments, the cell toxin content in the exponential phase was lower than in the stationary phase. These results contribute to understand the dynamics of benthic HABs and their impacts to the ecosystem and human health