Dynamics of potentially harmful phytoplankton in a semi-enclosed bay in the Sea of Oman

The dynamics of potentially harmful phytoplankton in relation to environmental parameters was investigated in the semi-enclosed Bay of Bandar Khayran (Sea of Oman) from April 2006 through April 2011. In total, 24 potentially harmful algal species were identified, including 11 species of dinoflagellates and eight species of diatoms. The dinoflagellates Prorocentrum minimum (Pavillard) Schiller, 1933, Scrippsiella trochoidea Balech ex Loeblich III, 1965, and Noctiluca scintillans (Macartney) Kofoid and Swezy, 1921 were most abundant during the Southwest Monsoon (SWM, July–September) and Northeast Monsoon (NEM, January–March) seasons, while other species occurred in low abundance and with no clear seasonal patterns. A dense bloom of Cochlodinium polykrikoides Margalef, 1961 that affected the distribution and abundance of other harmful algal species (HAB) was observed for the first time in the Sea of Oman during 2008–2009. Prorocentrum minimum increased in abundance during and after the decay of the Cochlodinium bloom while S. trochoidea was suppressed during this bloom, increasing thereafter once again. Noctiluca scintillans disappeared in the late SWM and NEM of 2008 and SWM of 2009, when blooms typically occur annually. Prorocentrum minimum and S. trochoidea persisted throughout the annual cycle of all years, enhancing their capability to bloom in the region under favorable conditions of high light intensities and relatively warm waters of low turbulence.