**4. Conclusions**

Silica skeletons of planktonic marine silicoflagellates were found in honey samples from Greece, Morocco, Poland, Romania, and Tunisia. In Tunisia, the source of silicoflagellate content of honey is suspected to be the wind erosion of microfossils from the Tripoli Formation of Messinian age in nearby Sicily. In Poland, the source is similarly shown in the Polish Outer Carpathians, but with low diversity of silicoflagellata species. Atmospheric trajectory analysis confirmed the possibility of atmospheric transport of deflated grains in the harvesting period. Therefore, silicoflagellates could be used as indicators of the geographical origin of honeys collected in areas characterized by diatomite outcrops. It was demonstrated that the diatom content of honey can have both natural (wind) and artificial (filters) sources.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/10 .3390/foods10020421/s1, Supplement 1: The studied honey samples. Data are organized by collection code, botanical origin, type and location.

**Author Contributions:** Conceptualization, observation of silicoflagellates, research concept, supervision, writing—original draft preparation, photos, spore identification: D.M.; identification of silicoflagellates and writing: P.D.; laboratory works, writing—review and editing: A.M.-M.; identification of pollen grains: Z.M.; trajectory analysis, funding acquisition: Á.L.; identification of diatoms, conceptualization and writing: S.S.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** The atmospheric transport analysis presented in this research was supported by the National Research, Development and Innovation Office of Hungary (No. K128818).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data is contained within the article or supplementary material.

**Acknowledgments:** The authors are thankful to Szilvia Babinszkyné Nagy (Hungarian Institute for Forensic Sciences, Budapest, Hungary) for gifting the Tunisian honey and for the translation of French and Arabic texts; Francesca Grillenzoni (Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria, Centro di Ricerca Agricoltura e Ambiente, Italy) for gifting several honey samples; Magdalena Wójcik (University of Rzeszów, Poland) for gifting a honey sample from Poland; Jakub Alexandrowicz (Geology and Palaeogeography Unit, Faculty of Geosciences University of Szczecin, Poland) for the consultation on diatomites in Poland; and Ágnes Schütz and Zsuzsanna Udvardi (National Public Health Center, Budapest, Hungary) for their kind technical help in the laboratory.

**Conflicts of Interest:** The authors declare no conflict of interest.
