Short-term variations of phytoplankton communities in response to Noctiluca scintillans bloom in the Chabahar Bay (Gulf of Oman)

The abundance, distribution, and species composition of phytoplankton were investigated in Chabahar Bay located in the Gulf of Oman during 2016-2017. The number of 114 phytoplankton species belong to 4 main phylum (Bacillariophyta, pyrrophyta, Cyanophyta and Chromophyta) were identified of which the most dominant phytoplankton group was pyrrophyta with a relative abundance of 94%. A significant difference of the density of phytoplankton between different sampling months was observed (non-parametric Kruskal-Wallis analysis, p≤0.05). Clear alignment between phytoplankton abundance and nutrient contents was observed during study period. The results showed that increasing the concentration of nutrients by the mid-autumn resulted in phytoplankton blooms. Noctiluca scintillans blooms were observed in October, January and February with the highest abundance in February while, disappeared in the rest of the sampling months. The maximum values of nutrients were observed in Oct (0.73, 5.59 and 3.66 µM of phosphate, nitrate and silicate, respectively) followed by a sharp decrease during Jan and Feb which is probably due to the phytoplankton blooms started from Oct. Diatoms (Bacillariophyta) with a relative abundance of 5.3%, were present in all sampling times with the minimum and maximum abundance in October and February, respectively.