Morphology, Phylogeny and Discovery of the Antioxidant Potential of a Marine Dinoflagellate Karlodinium ballantinum (Kareniaceae, Dinophyceae) Isolated from Subic Bay, Zambales, Central Luzon, Philippines

Abstract

Morphological characteristics, phylogenetic analysis, and antioxidant activity of a marine unarmored dinoflagellate Karlodinium ballantinum were examined using a culture established from Subic Bay, Zambales in November 2022. Detailed examinations were based on light microscopy and molecular phylogeny inferred from internal transcribed spacer (ITS) and LSU rDNA sequences. Cells of K. ballantinum were small and ellipsoid, possessing a straight ASC, large central nucleus, accumulation bodies, and unequally distributed chloroplasts with internal pyrenoids. Cell size ranged from 7.2–13.7 μm in length and 5.4–9.0 μm in width. Phylogenetic analyses suggested that K. ballantinum has a close affinity to K. gentienii and K. zhouanum. Upscaling the culture into 20 L, the final cell density of the culture reached approximately 177.5×106 cells/mL, which produced 0.1 g of algal biomass. The antioxidant activity of K. ballantinum, as screened using the DPPH assay, showed a 23.39% antioxidative property. This result displayed the potential of K. ballantinum to be beneficial microalgae despite being known as a causative agent of HABs. The present study is the first record of K. ballantinum in Subic Bay, Zambales, and serves as the first report of the antioxidant activity of a species under the genus Karlodinium.