International Journal of Oceans and Oceanography ISSN 0973-2667 Volume 14, Number 1 (2020), pp. 9-16 © Research India Publications https://dx.doi.org/10.37622/IJOO/14.1.2020.9-16 Study on distribution of Cysts of Harmful Algal Blooms-forming algae at Sohar Industrial Port, Sea of Oman A. Al-Kharusi 1* , K.A. Al-Hashmi 2 , S. Dobrestov 1 Marine Science and Fisheries Center, Ministry of Agriculture and Fisheries 2 Sultan Qaboos University, Sultanate of Oman Abstract The current study focused on assessing the presence/absence of cysts of some harmful algal species in Sohar Industrial Port (SIP) and in the seawater intake basin of the desalination plant located in the Sea of Oman. A total of seven type’s species of potential harmful dinoflagellate cysts species were identified inside Sohar Port and in its surrounding area, while no cysts were found in the intake area of the desalination plant. The presence of cysts-forming algae in the port and their absence from the intake site of the desalination plant indicates that the port is providing a suitable environment for their survival. M. polykrikoides cysts were found during the two periods of sampling indicating their establishment of population and may well pose serious threat to the desalination plant in the future. Keywords: Harmful Algal Blooms; Sohar Industrial Port; Cysts of potential harmful dinoflagellate; Desalination plant; Sea of Oman 1. INTRODUCTION The most diverse and abundant variety of phytoplankton groups are the dinoflagellates. Most dinoflagellates are known to cause outbreaks of harmful algal blooms in coastal waters around the world, and can be very toxic, leading to an extensive ecological impacts as well as wildlife and human health issues (Boerlage & Nada, 2015; Pospelova