Investigation of the Flood Effect on Environmental Parameters of Gorgan Bay

Abstract In mid-March 2019, severe floods occurred in the northern provinces of Iran (Golestan and Mazandaran). Coastal areas, wetlands and bays are strongly influenced by water inputs from land. In this study, the nutrients (nitrate, nitrite, phosphate, silica and ammonium) and other physicochemical parameters (salinity, pH, dissolved oxygen and water temperature) at 8 selected stations in the Gorgan bay were measured and compared before (February, 2019) and after (April and May, 2019) the floods. The nutrients were measured using the standard MOOPAM method. Other physicochemical parameters were measured on-site by means of Hack multimeter. The results of this study showed that the amounts of all nutrients in the Gorgan bay have decreased after the floods. In particular, ammonium and nitrate showed a decrease of about 8.30 and 3.13 times, respectively. This dilution of nutrients are due to rainfall, as well as the entry of water from Gorganrod and Qareso rivers to the Gorgan bay. Compared to other nutrients, nitrate had a higher percentage before and after the floods. Furthermore, the average salinity amounts of the bay before and after the floods were 14.79 psu and 9.27 psu, respectively. These changes in hydrochemistry can affect the ecosystem of Gorgan bay.