The case study of Ceratium hirundinella as a sign of an environment changes in the center of Iranian coasts of Caspian Sea (Farah Abad-2018)

Ceratium hirundinella is considered as a biological indicator in the environmental and climate changes. In the summer of 2018, the presence of Ceratium hirundinella reported in the Iranian region of the Caspian Sea. So the present study conducted to survey trend of Ceratium hirundinella fluctuations in the Iranian basin of the Caspian Sea during the last 3 decay. The study showed that in the winter of 1995, Ceratium contained very little percentage of phytoplankton density. In the summer of 2013, contribution of the species in dinoflagellates and total phytoplankton biomass reported 34 and 31% respectively. The percentage of Ceratium participation in phytoplankton biomass increased to 70% in summer of 2018. The study also showed that the increasing of water temperature and pH coincided to the Ceratium presence recorded, compared to the same time in the study area. Meanwhile, the trophic state changed from oligotrophic to mesotrophic condition. The annual changes of ceratium (presence and abundance) in the phytoplankton composition may be a response to increase of the regional warming and anthropogenic activity. The Ceratium bloom affects the feeding of planktivore organisms and causes water oxygen decreasing, which it led to fishes killing. Recently, the tendency of aquaculture has been increased in the Caspian Sea, so the monitoring and control methods of Ceratium hirundinella should be considered in the area.