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Along the Italian coasts, toxins of algal origin in wild and cultivated shellfish have been reported since the 1970s. In this study, we used data gathered by the Veterinary Public Health Institutes and the Italian Environmental Health Protection Agencies from 2006 to 2019 to investigate toxicity events and relate them to the distribution of toxic species. Among detected toxins (OA and analogs, YTXs, PTXs, STXs, DAs, AZAs), OA and YTX were those most frequently reported in cases of seafood contamination. Levels of those toxins exceeding regulatory limits for OA were associated with high abundances of Dinophysis spp. and for YTX with blooms of Gonyaulax spinifera, Lingulodinium polyedra, and Protoceratium reticulatum. Seasonal blooms of Pseudo-nitzschia spp. occurred all along the Italian coast, but DA was only occasionally found in shellfish, at concentrations consistently below the regulatory limit. Alexandrium was recorded in many more areas than STXs, which only rarely exceeded the regulatory limit. Azadinium was sporadically recorded, and AZAs were sometimes detected in low quantities. Among the emerging toxins, PLTX-like toxins often accumulated in wild mussels and sea urchins due to the occurrences of Ostreopsis cf. ovata. Overall, Italian coastal waters harbour numerous potentially toxic species, with a few HAB hotspots related to DSP toxins. Still, rare cases of intoxications have occurred so far, reflecting the whole Mediterranean Sea conditions., Corresponding author's email: s.accoroni@univpm.it

In Italy Alexandrium minutum is recurrently found at low concentrations in mussel farming areas, such as the Western Adriatic and the Sardinia coasts; mussels positive to PSP toxins have occasionally been detected but rarely exceeded the legal limit for commercial sale. Conversely, in South Italy, the Sicilian coast represents a hot spot of A. minutum blooms, repeatedly occurring in high densities. This study shows the presence of extensive blooms detected for the first time on the Jonian coast of Calabria at Roccella Jonica; the first bloom occurred in 2018, followed by a larger event in 2020. Both blooms occurred in March in the harbour dockyard, an area not monitored for toxic algae due to the absence of mussel farms. The blooms caused a yellow/brown water discoloration, but no PSP symptoms were reported. In order to understand if these blooms can cause harmful consequences, five Alexandrium strains were isolated from the 2018 event for molecular identification at the species level and analysis of the toxin content and profile. All strains were confirmed to belong to the A. minutum group and produce PSP toxins, with four out of five clones displaying higher toxin levels. The toxin profile displayed slight differences among strains, however, GTX 1,4 were the prevalent analogues, as previously observed in the Mediterranean region. Despite A. minutum blooms being rare events historically, intensive toxic blooms are increasing, especially on the South Italian coasts. This poses some concerns and highlights the need for better monitoring and management of the new identified spot and of nearby areas.

Besides being a highly sensitive ecosystem, the Adriatic Sea is also an important seaway for international and local shipping, which poses a serious risk on the transfer of harmful aquatic organisms and pathogens (HAOP) by ships. Monitoring programs and surveillance activities would be of limited efficacy if carried out on a local scale only. The first step in setting up a common Adriatic approach towards unwanted threats to the environment from the transfer of HAOP was to prepare an inventory of organisms in ports. Phytoplankton diversity was determined through the port baseline survey in twelve Adriatic ports in years 2011, 2014 and 2015. Phytoplanktonic HAOP were identified as species, either native or non-indigenous (NIS) that can trigger harmful algal blooms (HAB). A list of 689 taxa was prepared and among them 52 were classified as HAB and five as NIS. Records of toxigenic NIS (Pseudo-nitzschia multistriata, Ostreopsis species including O. cf. ovata) indicate that the intrusion of non-native invasive phytoplankton species has already occurred in some Adriatic ports. The seasonal occurrence and abundance of HAOP offers a solid baseline for a monitoring design in ports in order to prevent possible expansion of HAOP outside their native region.