A preliminary study on a strain of Pseudo-nitzschia delicatissima (Cleve) Heiden isolated from the Golden Horn Estuary (Sea of Marmara, Türkiye): Morphology, phylogeny and toxicity

The diatom Pseudo-nitzschia delicatissima (Cleve) Heiden, 1928 is known a potential producer of domoic acid (DA), a neurotoxin which can cause Amnesic Shellfish Poisoning (ASP). The specific objectives of this study are to reveal the identification, based on morphological characterization via Scanning Electron Microscopy (SEM) and molecular phylogeny, and toxicity of a P. delicatissima strain (DEB132304) isolated from the Golden Horn Estuary (Sea of Marmara, Türkiye). SEM analysis revealed characteristic frustule features consistent with the general morphological description of P. delicatissima. Molecular and phylogenetic analyses based on ribosomal gene sequences from the LSU and ITS regions further supported the identification of the strain as P. delicatissima, with congruent phylogenetic placements obtained from both markers. The strain was harvested during the stationary growth phase and analysed for DA and its isomers; however, none were detected above the limit of detection (LOD) of 0.39 pg cell-1. Considering that the Pseudo-nitzschia species have previously formed blooms in the study area, regular monitoring of these species is essential. Further studies investigating the ecophysiological characteristics of different strains of P. delicatissima isolated from the same study area and the influence of environmental factors on DA production are needed to better understand its toxinological potential.