Phytoplankton assemblages in the ballast water of the navigated ships from the Indian Ocean to Shahid Rajaee Port, Hormozgan, Persian Gulf, Iran

The present study has been conducted to identify and enumerate ballast water phytoplankton on 24 ships entering Shahid Rajaee Port (13 bulk carriers, 4 oil tankers, 6 general cargo and 1 container), in two cold and warm seasons in winter 2017 and summer 2018, from the four origins as the name the Persian Gulf, western, eastern, and northwestern Indian Ocean.The sampling of phytoplankton was conducted by passing 100 liters of sampling waters through a 20-micron plankton net, in compliance with the G2 standard method approved by MEPC.173 (58). In this manner, 108 phytoplankton species were identified in the ballast water tanks of the sampled ships, belonging to 4 phylum, 5 classes, 23 orders, and 38 families. In the warm season, Dinophyceae (54%) and in the cold season, Bacillariophyceae (60.96%) were prevalent among the samples. The identified species from the Persian Gulf had the highest similarity with the species from the western Indian Ocean, and the least similarity with the eastern Indian Ocean. Apart from Odontella longicruris, all other species had been reported in the waters of the Persian Gulf in previous studies. This result shows that the phytoplankton assemblages between Shahid Rajaee Port and other parts of the Indian Ocean have a high similarity and does not impose a real threat to the environment from the ballast water transfer. However, from the identified species, 28 species (25.9%) are known to cause red tide and death of other aquatic species in the region, which highlights the importance of continuous monitoring and discharge control in the marine environment of the region.