The Laboratory for Plankton and Shellfish Toxicity has carried out another extensive study of the genus Pseudo-nitzschia in the central Adriatic Sea.
Species of Pseudo-nitzschia are an important genus of marine diatoms found both in coastal areas and in the open sea, and they form a permanent component of the Adriatic phytoplankton community. However, certain Pseudo-nitzschia species are capable of producing domoic acid, a potent neurotoxin that causes Amnesic Shellfish Poisoning (ASP), thereby posing a risk to human health.
The species composition of Pseudo-nitzschia and their seasonal distribution were analyzed over a two-year period at four shellfish farming sites: the Velebit Channel, Šibenik Bay, Kaštela Bay, and Mali Ston Bay. Alongside seawater samples, in which the overall phytoplankton community was monitored under a light microscope, physical and chemical parameters (temperature, salinity, and nutrients) were measured at each station.
During the two years of research, species of this genus were present almost continuously across all sites, but in low abundance. Exceptions were two blooms recorded in the winter of 2022, when more than three and a half million cells per liter were observed in Mali Ston Bay, and two and a half million in Šibenik Bay, with Pseudo-nitzschia species accounting for up to 99% of the total phytoplankton community. Detailed species composition was determined using a Scanning Electron Microscope (SEM), since only at high magnification can the fine morphological characteristics necessary for distinguishing species within the genus Pseudo-nitzschia be observed. Eight different species were identified in natural samples, confirming a notable diversity of this genus in the central Adriatic. The analyses also revealed differences in seasonal distribution as well as in species composition among the study sites.
Our study represents the first detailed morphological analysis of Pseudo-nitzschia species composition from natural populations in relation to the corresponding environmental conditions. The results were published in the international scientific journal Estuarine, Coastal and Shelf Science.
The research was carried out within the project PSEUDOTOX, funded by the Croatian Science Foundation, with support from the Young Researchers’ Career Development Program – training of new doctoral students, in which our PhD candidate Tina Tomašević also participated.
