Red tides have naturally occurred since oceans were formed, but today increasing due to human influence. Red tide is considered one of the earliest phenomena which dates back to Jurassic period where several geological changes occurred on earth and led to a major bloom of phytoplankton. It is believed that first written reference of a red tide appears in Bible. In Japan, one of the old historical books entitled “The History of Great Japan” (Dai Nippon Shi),edited more than 300 years ago, described 16 cases of red tide, seven in freshwater and the rest in the marine environment. The oldest was an occurrence in 731 AD. Red tides have been documented along Florida's gulf coast since the 1840's and probably occurred much earlier. The Red tide phenomenon was reported in India in 1935.
The following table shows a record of Red tide phenomenon in the Arabian Gulf and the Sea of Oman.
||Bahrain and Saudi Arabia
||Mammals, birds and starfish
||Fish and starfish
The fish and other marine organisms kill has been witnessed in the Arabian Gulf since 1986 due to oil and chemical pollution, rise of temperature, lack of oxygen in water and increase in chloride concentration resulting from power stations.
Red tide in UAE waters in 2008-2009
The outbreak of Red tide was first witnessed by fishermen in Kalba area on 28 August 2008. The occurrence of Red tide continued to extend along the Eastern Coast and was reported in Dibba, Al Hussin in September 8, 2008. It was also reported in the Coasts of Ras Al Khaimah Emirate with beginning of November 2008, But subsequent red tide effect repeated in Ras Al Khaimah emirate with the beginning of December 2008.
According to the reports and observations of fishermen and satellite images sent by (ROPME) as well as the track of the technical team of the ministry the phenomenon of red tide that appeared again in RAK in the beginning of December 2008, and spread to most of the UAE coastal areas through Umm Al Quwain, Ajman, Sharjah to parts of Dubai coasts within February to may 2009. Another outbreak of red tide occurred during the period from 1-9 September 2009 and spread to almost all regions all along the Eastern Coasts.The phenomenon was extensively concentrated in Dibba from Dibba Al Hussin port to Faqeet natural protect area, Khorfakkan, AlFujairah from Merbeh port to Al Rughylat and Kalba ports where it existed as intermittent sightings with low density in the coastal area and with high density in the ports, however no cases of fish or marine organism kills. Also from the period of 10 September 2009 an outbreak of red tide was noticed and spread to some of the coastal areas in the eastern coasts, however no fishes and other marine organisms kills were observed.
The Red tide was started to disappear along the eastern coast during the period from 11-13 September 2009
- The temperature of water averaged to 220 C-340 C along the UAE coastal areas where the red tide appeared, concentration of dissolved oxygen level ranged between 4.5-5 mgl-1, pH "is a measure to specify acidity or basicity of an aqueous solution" averaged between 8.1-8.3 . Salinity ranged between 39-40 ppt.
Analysis of toxicity did not shown any toxic species of phytoplankton that cause Red tide, moreover, no cases of fishes and other marine organisms kills were observed.
Factors contributing to Red tide during 20008-2009:
The red tide may occur due to climate change and its consequence such as:
- Monsoon season and Upwelling "Upwelling is an oceanographic phenomenon of movement of cooler nutrient rich dense water towards the ocean surface associated with divergence of currents" , cyclone El Niño and La Niña phenomenon "is global climate phenomenon in which ocean surface water temperature are becoming more warmer than normal rates with a global impact on weather patterns" effect which cause changes in sea water condition of Indian Ocean, the Arabian Sea, Sea of Oman and the Arabian Gulf.