Vertical distribution of the toxic epibenthic dinoflagellates Ostreopsis cf. ovata, Prorocentrum lima and Coolia monotis in the NW Mediterranean Sea

Abstract

The present work is one of the first studies investigating the vertical distribution of the benthic toxic dinoflagellates Ostreopsis cf. ovata, Prorocentrum lima and Coolia monotis in the NW Mediterranean Sea. Relatively low epiphytic abundances of the three species were detected up to 30 m depth in late August-early September, suggesting that higher abundances may be found earlier in summer. Ostreopsis cf. ovata was more abundant than the two other species at very shallow depths, while P. lima and C. monotis were more present than O. cf. ovata at depths deeper than 3 m. The decrease of O. cf. ovata with depth likely reflected the temperature and light intensity depletion. Determination and understanding of vertical patterns require defining the ecological niche of each species, including their responses to light, temperature and nutrients. Nutritional mode and chemical defense of dinoflagellates may also affect their ecological niches. A better assessment of the vertical distribution of toxic microalgae could be very useful for a suitable management and an effective anticipation of HAB events.