Active and resting harmful dinoflagellates in the highly productive mussel culture area of the Mar Piccolo (northern Ionian Sea)

The impact of HABs (Harmful Algal Blooms) on public health and aquaculture has increased in the last decades and the necessity of their detection and monitoring is urgent. The discovery of benthic resting stages (cysts) in the life cycle of many phytoplanktonic species, a strategy to escape unfavorable conditions in the water column, allows to investigate the plankton not only by classical methods of sampling in the water but also through the analysis of their dormant stages in the sediments. The Mar Piccolo of Taranto together with the Northern Adriatic Sea holds up to 50% of Italian mussel production. Since 1990, water sampling has been carried out at two sites in the basin by using a Niskin bottle. Moreover, since 1997, surface sediments were collected using small corers by a SCUBA diver to study the phytoplankton communities resting as cysts. More than 20 harmful dinoflagellates taxa were identified from the two domains of the ecosystem with some changes occurred during the years. This great number of harmful dinoflagellate species present in the Mar Piccolo of Taranto represents a potential threat for the aquaculture industry. Among the taxa identified in the water samples, many of them are not known as resting stage producers, but this aspect needs to be investigated, because in the sediments we found many cyst morphotypes that was not possible to identify at species level. This means that a greater number of harmful/toxic species could be present in the Mar Piccolo