Harmful blooming of Noctiluca scintillans in the southeast coastal waters of Iran, Oman Sea

Noctiluca is a dinoflagellate genus that causes algal bloom and is distributed in the tropical coastal waters of the Pacific and the Indian Oceans. The blooming of the species on the southeastern coast of Iran (the north part of the Oman Sea) is usually green and happens in the cold seasons. A dense harmful bloom of Noctiluca scintillans was reported in February and March 2020 along the coastal waters of Chabahar Bay (Iran) on a significant scale. Sampling was carried out from three stations located in the bloom areas. This study aimed to evaluate the distribution of the bloom in Chabahar Bay using field data and remote sensing, as well as examining N. scintillans cells and identifying the species that were present in the bloom area. The results of microscopic counting revealed a high density of N. scintillans. The bloom duration was about 22 days; with a density of 2.37 × 105 cells L-1. Apart from N. scintillans, 20 species of phytoplankton including 10 species of dinoflagellates, 9 species of diatoms, and 1 other phytoplankton species were identified. The bloom caused the mortality of marine organisms including jellyfish, crabs, and green sea turtles. Although N. scintillans is classified as a non-toxic species, it can lead to the mortality of marine organisms such as fish and invertebrates by causing severe hypoxia and ammonia release.