POSTER SESSION 2
10:30–12:30, Tuesday, September 15
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ABSTRACT 1381 | POSTER 218
DUNALIELLA SP.: NATURE’S REMARKABLE SOLAR COLLECTOR FROM EXTREME HYPERSALINE ENVIRONMENTS
The unicellular green flagellate algae of the genus Dunaliella exhibit remarkable adaptability to hypersaline environments, producing high levels of β-carotene to protect themselves from intense sunlight and salinity. This pigmentation contributes to the characteristic “red color” of salt brines during peak summer periods. The primary objective of this study was to examine the physiological adaptations and optical signatures of Dunaliella sp. isolated from this hypersaline habitat. In August 2025, we sampled crystallization and evaporation ponds from Pag Saltern in Croatia, one of the oldest Mediterranean salterns, located in Northern Dalmatia, known for its hot summers, high solar radiation, and the Bora wind. Nutrient analysis of the crystallization pond revealed high concentrations of nitrates, while orthophosphates, nitrites, and ammonium were extremely low. High-performance liquid chromatography (HPLC) pigment analyses indicated that the crystallization pond (salinity > 233) had the highest β-carotene levels, underscoring the adaptation of Dunaliella to extreme salinity. The isolated Dunaliella sp. was cultured in filtered seawater (salinity = 38) that had been passed through a 0.22 μm pore filter and enriched with F/2 nutrients, maintained at 18 °C with shaking, and subjected to a 12:12 light-dark cycle. Cell viability, color, and density were analyzed using light microscopy. Confocal microscopy revealed intense chlorophyll fluorescence at 630–750 nm in intact cells. Carotenoid signals were clearly visible at 495–550 nm only in ghost vesicles; removal of interfering intracellular material revealed a distinct yellow emission previously obscured in intact cells, providing insights into their acclimatization strategy in extreme conditions.
Manuela Spevec*, University of Zagreb, Faculty of Science, Department of Biology, Croatia, [email protected]
Lina Kovačević, University of Zagreb, Faculty of Science, Department of Biology, Croatia, [email protected]
Antonija Matek, University of Zagreb, Faculty of Science, Department of Biology, Croatia, [email protected], https://orcid.org/0000-0002-2063-3417
Zrinka Ljubešić, University of Zagreb, Faculty of Science, Department of Biology, Croatia, [email protected], https://orcid.org/0000-0001-5502-3662
Nadica Ivošević DeNardis, Division for Marine and Environmental Research, Ruđer Boškovic Institute, Croatia, [email protected], https://orcid.org/0000-0002-3635-4869
Nives Novosel Vlašić, Division for Marine and Environmental Research, Ruđer Boškovic Institute, Croatia, [email protected], https://orcid.org/0000-0002-7528-017X
Romina Kraus, Center for Marine Research, Ruđer Bošković Institute, Croatia, [email protected], https://orcid.org/0000-0003-4626-1161
Petar Žutinić, University of Zagreb, Faculty of Science, Department of Biology, Croatia, [email protected], https://orcid.org/0000-0002-9836-9636
Marija Gligora Udovič, University of Zagreb, Faculty of Science, Department of Biology, Croatia, [email protected], https://orcid.org/0000-0002-1982-2528
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