Most dinoflagellate produce resting cysts during their sexual lifecycle as well as under unfavorable
environmental conditions and from water column settle in the sediments substratum. The evaluation of
diversity and distribution of dinoflagellate cysts is very important in environmental studies, because cysts act
as seed in sea bed that can cause red tide with excystment. This study was performed to determine the
diversity and distribution of dinoflagellate cysts in the sediments of Gwatar Bay in 2013 by sediments
sampling from five stations. Sediment sampling was made by Ekman grab with covering area of 0.225
square meters with three replicates at each station in two seasons before and after the monsoon. In total of
sampling 16 samples in species level belonging to 9 genera of dinoflagellate cysts were identified. The
highest and lowest abundances are related to the genus Protoperidinium (52%) and the genus
Zygabikodinium (1%), respectively. The results showed the average dinoflagellate cysts diversity from 2.22
before monsoon have decreased to 2.06 after monsoon.