Seasonal changes of potentially toxic epiphytic dinoflagellates in Chabahar Bay, Oman Sea

Harmful algal blooms caused by dinoflagellates have significant adverse effects on environmental and public health. This study aimed to investigate the effect of water physicochemical parameters on the annual cycle of epiphytic dinoflagellates in the northern Chabahar Bay coastal waters of the Oman Sea (Iran). The macroalgal samples with associated epiphytes were collected seasonally from 6 coastal sites in spring, summer, atumn 2019 and winter 2020. The water physicochemical parameters were measured, and the data were analyzed using a one-way ANOVA and the principal component analysis (PCA). Twelve potentially toxic dinoflagellate species from five genera were identified during the four sampling seasons. Amphidinium carterae with an average of 11.22% and A. operculatum with an average of 10.77% of the total abundance of epiphytic dinoflagellates were the dominant species, and Gambierdiscus australes showed an average of 6.48%.Based on the PCA, the abundance of certain species was found to be influenced by different environmental factors. The PCA revealed that NO2, NO3 and SiO4 values had the greatest impact at sites with high abundances of A. operculatum, Prorocentrum concavum, P. emarginatum, P. rhathymum and G. balechii. Furthermore, PO4 concentration had the greatest impact at the sites with high abundances of A. carterae, P. lima, Ostreopsis lenticularis, O. heptagona, G. balechii, G. toxicus, G. australes and Coolia monotis. The results obtained highlighted a significant impact of dissolved oxygen, pH, salinity, temperature and nutrients on the epiphytic dinoflagellate species abundances in the study area.