Gulf of Oman
When large numbers of fish began dying in droves off the northern coast of Oman in the Persian Gulf in late August 2000, the local media reported that the deaths were due to the release of contaminated ballast water from a U.S. tanker visiting the area. Meanwhile, Omani authorities feared that a toxic algal bloom was killing the fish, raising concerns about health and food security for their nation’s fishing industry.
Neither was true, say a collaborating team of oceanographers and marine biologists from the Marine Science and Fisheries Centre (MSFC) in Oman, North Carolina State University, and the University of Miami. Using data from two NASA Earth Observing System (EOS) satellites, the team of researchers demonstrated that the fish kill was due to a series of natural environmental changes that severely reduced the oxygen content of the surface waters.
Ironically, at the time of the fish kill in early September 2000, Dr. John M. Morrison, professor of oceanography at North Carolina State University, was already in Oman working with scientists from the Ministry of Agriculture and Fisheries. He was helping the Ministry upgrade their local capability to use satellite remote sensing techniques to allow them to process imagery in near real time as part of an ongoing effort by the Ministry to forecast conditions in the Gulf of Oman.
“With support from the Ministry, a satellite data downlink station was installed in Oman in 1996 as part of an international program to study the role of the Indian Ocean in the ocean carbon cycle,” explains Morrison. “This station enables them to receive AVHRR and SeaWiFS data transmitted directly from the overpassing satellites. Since that time we have had an ongoing program to train local scientists in operating the station as well as in processing and interpreting satellite images, both for scientific use and as a part of their fisheries advisory program.” (“AVHRR” is NOAA’s Advanced Very High Resolution Radiometer and “SeaWiFS” is Orbital Sciences Corporation’s Sea-viewing Wide Field-of-view Sensor.)
Shortly after Morrison arrived in Muscat on September 2, the Ministry’s Assistant Director General for Fisheries and Guidance Eng Saud Bin-Humud al-Habsi informed the team that a large fish kill was taking place off the Batinah region of Oman’s northern coast. There was a heightened sense of urgency given that the fish kill was happening during the peak harvest time of the fishing season. Fisheries exports are one of Oman’s chief sources of revenue.
“The Ministry wanted satellite imagery to help them define the extent of the problem and help resolve whether the problem was caused by a toxic plankton bloom or red tide, or whether it was an oxygen problem,” Morrison states. “The imagery would help them resolve whether there was upwelled water in the area of the fish kill.”
Occurrences of red tide blooms are a common phenomenon in the coastal waters of Oman. The abnormal production of all groups of phytoplankton (diatoms, dinoflagellates, and blue-green algae) lead to discoloration of surface waters there and unfortunately some of these phytoplankton are toxic, causing mass mortality of marine organisms. Another common cause of fish kills in this region is oxygen-depleted water upwelling to the surface. Each cause carries vastly different implications. Oxygen depletion raises no concerns about food security, while concerns about toxic blooms can seriously damage Oman’s fish exports and local consumption.
