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The zooplankton community was analyzed in ten Adriatic ports as part of the port biological baseline surveys carried out within the framework of the BALMAS project. We provide the first inventory of resident zooplankton taxa and five detected non-indigenous zooplankton species (NIS), and their spatial and seasonal distribution patterns. Copepoda and meroplankton larvae, particularly of Mollusca, dominated the zooplankton in all sampled ports. We recorded a total of 76 indigenous copepod species and five NIS, among which Parvocalanus crassirostris detected in Šibenik and Rijeka ports and Oithona davisae in Venice port, are new for the Adriatic. All detected NIS were widely distributed within the recipient ports. Co-occurrences of NIS were observed in the ports of Venice, Bari, Ancona and Trieste. The results are expected to contribute to the quality of practical monitoring of zooplankton NIS and facilitate the synchronization of efforts in creating NIS- related policies for the Adriatic sub-region.

The paper presents a database of information on wrecks, natural and artificial reefs located in the Adriatic Sea, collected within the framework of the Interreg Italy-Croatia project ADRIREEF – Innovative exploitation of Adriatic Reefs in order to strengthen Blue Economy. The data collection lasted more than one year and comprehended three surveys and a wide literature review. After being collected, data were harmonized and, where possible, made machine-readable. Moreover, data were widely metadated, published in a webGIS (https://adrireef.github.io/sandbox3/) and shared as Open Data in EMODnet (European Marine Observation Data network) through the SEANOE repository (Ferrà et al., 2020; http://doi.org/10.17882/74880). The database is composed of 285 three-dimensional records, each one described by 51 attributes. Parameters are clustered in four main groups: identification, reef and site description, management/exploitation information. Available literature (scientific and/or grey) was also included in the database and linked to the corresponding site.

Harmful algal blooms represent a severe issue worldwide. They affect ecosystem functions and related services and goods, with consequences on human health and socio-economic activities. This study reports new data on paralytic shellfish toxins (PSTs) from Sardinia and Sicily (Italy), the largest Mediterranean islands where toxic events, mainly caused by Alexandrium species (Dinophyceae), have been ascertained in mussel farms since the 2000s. The toxicity of the A. minutum, A. tamarense and A. pacificum strains, established from the isolation of vegetative cells and resting cysts, was determined by high performance liquid chromatography (HPLC). The analyses indicated the highest toxicity for A. pacificum strains (total PSTs up to 17.811 fmol cell−1). The PSTs were also assessed in a strain of A. tamarense. The results encourage further investigation to increase the knowledge of toxic species still debated in the Mediterranean. This study also reports new data on microcystins (MCs) and β-N-methylamino-L-alanine (BMAA) from a Sardinian artificial lake (Lake Bidighinzu). The presence of MCs and BMAA was assessed in natural samples and in cell cultures by enzyme-linked immunosorbent assay (ELISA). BMAA positives were found in all the analysed samples with a maximum of 17.84 µg L−1. The obtained results added further information on cyanotoxins in Mediterranean reservoirs, particularly BMAA, which have not yet been thoroughly investigated.

Dinophysis spp. blooms and related shellfish toxicity events of diarrhetic shellfish poisoning (DSP) have been the most reported toxicity event through the Croatian National monitoring program. With the aim to characterize the DSP toxin profile in shellfish farmed in Croatia, for the first time a complete analysis of the toxin profile of Croatian mussels has been carried out using the LC-MS/MS technique. The obtained results showed okadaic acid (OA) as the main toxin contaminating Croatian mussels at that time. The maximum concentration of OA in shellfish tissue was recorded 12 days after the Dinophysis fortii bloom, thus suggesting that rapid growth of the toxin level in the shellfish occurred in the first week after the bloom while it was slower in the second week. Furthermore, the presence of only OA at concentrations which could endanger human health suggests D. fortii as the main organism responsible for the toxic event that occurred in Lim Bay. The presence of gymnodimine and spirolides in Croatian mussel has been detected for the first time, while the presence of yessotoxin and pectenotoxin-2 is confirmed.

The formation of massive amounts of suspended mucilaginous organic matter which periodically affects the Adriatic Sea, has been regarded as a complex physico-chemical phenomenon resulting from the production of extracellular material by phytoplankton. Although the exact cause has remained obscure, the mechanism of its formation has usually been considered to be a long-term process, starting after the late winter-early spring blooms, and involving the participation of various algal species, mainly within the diatom group. In this paper we report on the results of a phytoplankton monitoring programme in northern Adriatic seawaters off the Emilia-Romagna coast of Italy which revealed the constant concomitant presence of the dinoflagellate Gonyaulax fragilis (Schutt) Kofoid and mucilaginous formations. In the early stages of the phenomenon the dinoflagellate was clearly observable by microscopic examination in the mucilage, but as the mucilage aged this alga almost completely decomposed and diatom cells increased in number and became predominant. Although characterized by a slow growth rate in culture, in natural seawater G. fragilis was observed to reach cell densities of up to 7.0×10 6 cells l −1 . The results of this study lead us to propose the hypothesis that the appearance of mucilage in the water column of the Adriatic Sea is the consequence of a seasonal growth of this dinoflagellate favoured by specific environmental circumstances.

The Northern Adriatic Sea is the area of the Mediterranean Sea where eutrophication and episodes related to harmful algae have occurred most frequently since the 1970s. In this area, which is highly exploited for mollusk farming, the first occurrence of human intoxication due to shellfish consumption occurred in 1989, nearly 10 years later than other countries in Europe and worldwide that had faced similar problems. Until 1997, Adriatic mollusks had been found to be contaminated mostly by diarrhetic shellfish poisoning toxins (i.e., okadaic acid and dinophysistoxins) that, along with paralytic shellfish poisoning toxins (i.e., saxitoxins), constitute the most common marine biotoxins. Only once, in 1994, a toxic outbreak was related to the occurrence of paralytic shellfish poisoning toxins in the Adriatic coastal waters. Moreover, in the past 15 years, the Adriatic Sea has been characterized by the presence of toxic or potentially toxic algae, not highly widespread outside Europe, such as species producing yessotoxins (i.e., Protoceratium reticulatum, Gonyaulax spinifera and Lingulodinium polyedrum), recurrent blooms of the potentially ichthyotoxic species Fibrocapsa japonica and, recently, by blooms of palytoxin-like producing species of the Ostreopsis genus. This review is aimed at integrating monitoring data on toxin spectra and levels in mussels farmed along the coast of the Emilia-Romagna region with laboratory studies performed on the species involved in the production of those toxins; toxicity studies on toxic or potentially toxic species that have recently appeared in this area are also reviewed. Overall, reviewed data are related to: (i) the yessotoxins producing species P. reticulatum, G. spinifera and L. polyedrum, highlighting genetic and toxic characteristics; (ii) Adriatic strains of Alexandrium minutum, Alexandrium ostenfeldii and Prorocentrum lima whose toxic profiles are compared with those of strains of different geographic origins; (iii) F. japonica and Ostreopsis cf. ovata toxicity. Moreover, new data concerning domoic acid production by a Pseudo-nitzschia multistriata strain, toxicity investigations on a Prorocentrum cf. levis, and on presumably ichthyotoxic species, Heterosigma akashiwo and Chattonella cf. subsalsa, are also reported.

This paper reports on the determination of toxin profile of mussels (Mytilus galloprovincialis) collected in November-December 2003 along the Emilia Romagna coasts (Italy) when a high concentration of Alexandrium ostenfeldii cells was detected in sea water. Detailed liquid chromatography-mass spectrometry (LC-MS) analyses were performed on the crude extracts in both selected ion monitoring (SIM) and multiple reaction monitoring (MRM) modes. They revealed that M. galloprovincialis had accumulated the three major spirolides produced by the alga, namely 13-desMethyl spirolide C, 13,19-didesMethyl spirolide C and 27-hydroxy-13,19-didesMethyl spirolide C, which fully accounted for toxicity of lipophilic extracts shown in mouse bioassay. Interestingly, yessotoxin (YTX) and its analogues were still present in mussel polar extracts but YTX itself was not the major toxin contained in mussels. The presence of pectenotoxin-2 seco acid (PTX-2sa) and its putative epimer was also assessed. The presence of azaspiracids, never reported from the Adriatic sea, as well as of diarrhetic shellfish poisoning toxins (okadaic acid, dinophysistoxins and OA esters) and domoic acid, long known as contaminants of Adriatic mussels, was also investigated.

The north-western coasts of the Adriatic sea have long been subjected to recurring cases of harmful algae blooms and concomitant mussel contamination. In 1995, yessotoxins (YTXs) were detected for the first time in Adriatic mussels and their presence was subsequently linked to the presence of Protoceratium reticulatum and occasionally Lingulodinium polyedrum in seawater. Since then, farmed molluscs are yearly found to contain YTXs for long periods with a severe impact on aquaculture activities. In 2004, unusually high amounts of homoYTXs were detected in mussels. In this period, a careful look at the phytoplankton composition highlighted that P. reticulatum and L. polyedrum were nearly absent in seawater whereas the dinoflagellate Gonyaulax spinifera was present at high densities. G. spinifera has been recently associated with YTX production in New Zealand. The present work was performed in order to ascertain whether Adriatic G. spinifera was a toxic species. Determination of the toxin content of natural samples (mussels and net haul plankton samples) as well as monitoring of the dinoflagellate species present in seawaters allowed us to correlate the presence of G. spinifera to that of homoYTX in mussels. Cultures of G. spinifera were set up which gave us the opportunity to investigate toxin content and profile of the dinoflagellate, for the first time, by liquid chromatography–mass spectrometry (LC–MS) and to perform a molecular characterization of the species through rDNA sequencing. Two G. spinifera isolates, sampled in different years, were analyzed and resulted to be different in both toxin content and gene sequence: the isolate sampled in 2005 produced only low levels of YTX (5.4 pg cell−1) while that sampled in 2006 contained higher toxin amounts, namely 33.4 pg cell−1 of homoYTX and 3.6 pg cell−1 of YTX; the two isolates also differed in 111 and 176 nucleotide positions, respectively, in the SSU and partial LSU rDNA genes. Comparing similar sequences of G. spinifera strains contained in GenBank, divergences among the Adriatic strains and strains of different geographical origin emerged; on the contrary, a good similarity was evidenced (1.3%) between the Adriatic isolate sampled in 2006 and two New Zealand strains; the similarity was confirmed also by the presence in all strains of YTXs, although the New Zealand strains were analyzed by ELISA which could not distinguish among the different YTX analogues. Due to an originally confusing description of the species and to the availability of very low number of deposited sequences the doubt arises whether the studied G. spinifera strains belong to the same species. However, although the taxonomy of the species complex G. spinifera remains largely unresolved, this study allowed to unambiguously link the presence of G. spinifera to recurring mussel toxicity episodes.