Some diatoms and dinoflagellates can produce marine toxins, which can accumulate in, e.g. filter-feeding bivalves, posing a potent treat to seafood consumers. In this study, concentrated net plankton samples were collected from mussel cultivation regions (Kavarna bay) and zones for wild catch (Varna bay) in two periods - winter to fall 2018 and spring 2019. A method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed to analyze domoic acid (DA), okadaic acid, dinophysistoxins, yessotoxin, pectenotoxin-2 (PTX2), gymnodimine A (GYM), 13-desmethyl spirolide C (SPX1), and goniodomin A (GDA). Paralytic shellfish toxins (PSTs) were investigated by high performance liquid chromatography with post-column derivatization and fluorescence detection. Results indicated the presence of DA, PTX2, SPX1 and GDA reaching maximum levels of 1.4 ng.NH-1.m-1 DA, 115.5 ng.NH-1.m-1 PTX2, 0.2 ng.NH-1.m-1 SPX1 and 8.6 ng.NH-1.m-1 GDA. No PSTs were detected in the investigated samples. The maximum toxin load of the samples was due to the presence of PTX2. Detection of DA, PTX2, SPX1 and GDA in the samples points to the possible toxigenic nature of phytoplankton species along the Bulgarian coast. These data may be used to evaluate the probability of potential risks to local aquaculture and seafood from wild catch.