Morphological and molecular characterization of harmful algae species isolated from the Marmara Sea surface waters

Harmful algae species were identified by innovative molecular methods at eight stations in surface water of the Marmara Sea between April 2021 and February 2022. The semi-enclosed Sea of Marmara is directly exposed to rapid population growth, industrial activities and high pollution load as a result. The anthropogenic waste load and pollutants mixed with surface waters cause changes in nutrient salt ratios. Rapidly increasing primary production with nutrient input may cause harmful increases such as mucilage formation in 2020-2021. Toxic phytoplankton species, which are found in lower concentrations in surface waters under normal conditions, become dominant with the deterioration of environmental conditions and can be harmful to other living things and humans. In this thesis, it is aimed to determine the phytoplankton species that affect human health and cause harmful algae overgrowth (HAB) by phylogenetic analysis. As a result of the phylogenetic analyzes carried out within the scope of the the study, 7 species consisting of a total of 10 microalgae strains, three strains belonging to two species from Bacillariophyceae and seven strains belonging to five species from Dinophyceae class, were determined. Of the two isolated Pseudo-nitzschia strains, 63% P. pungens, one Cylindrotheca strain 97% C. closterium, two of the three Prorocentrum strains 100% P. cordatum, one 100% P. rhathymum, two Amphidinium strains 100% rate was found to be similar to A. carterae. Durinskia sp. and Biecheleria sp. strains could not be determined due to unsfufficient data. Prorocentrum rhathymum isolated in the study for Turkish coastal waters, Durinskia sp. is a new record for the Marmara Sea. The genus Pseudo-nitzschia was reported phylogenetically for the second time from Turkish coastal waters. The existence of cryptic species that have been overlooked or misidentified in detailed morphological studies has been shown, and the importance of using innovative molecular methods in biodiversity and taxonomy studies has emerged with this thesis.