Occurrence of epibenthic dinoflagellates in relation to biotic substrates and to environmental factors in Southern Mediterranean (Bizerte Bay and Lagoon, Tunisia): An emphasis on the harmful Ostreopsis spp., Prorocentrum lima and Coolia monotis.

•First time detection of potentially toxic epibenthic dinoflagellates on macrophytes from the Bizerte Bay and Lagoon.•First description of the seasonal distribution of epibenthic dinoflagellates, hosted by macrophytes from the Bizerte area.•Positive correlation between Ostreopsis spp. abundances and temperature in the Bizerte Bay and Lagoon.•Cymodocea nodosa and Zostera noltei: suitable substrates for the settlement of C. monotis and Ostreopsis spp., respectively.