Algal blooms pose threat to fish, desalination plants

MUSCAT, NOV 19 – Harmful algal blooms (HABs) are increasingly becoming a concern in the Sultanate as they cause economic losses and disruption of work in desalination plants. This startling revelation is made in a thesis by a student in the Marine Science and Fisheries Department of the College of Agricultural and Marine Sciences (CAMS) at Sultan Qaboos University. “In Oman, HABs lead to economic losses due to deaths of large number of fish and disruption of desalination plants’ work because of membrane clogging,” points out Ahlam al Kharousi, a Master of Science student in her thesis. HABs are a concern for desalination plants due to high algal biomass present in sea water and toxin production by some HABs species. In severe cases, desalination plants have to be taken off line.

To drive home her point, Ahlam cites the example of the desalination plant in the Barka site which ceased its operation for 55 days during HABs incident in 2008-2009. Arid countries around the world, particularly in the Middle East, rely on sea water desalination process to produce fresh water. The increase in the construction of the sea water reverse osmosis desalination plants has been accompanied with the expansion of HABs. According to the thesis, HABs is a common phenomenon in Oman waters usually detectable by the presence of green or red colour of sea water. This is due to high density of microscopic photosynthetic organisms, such as diatoms and dinoflagellates.

It is estimated that in the US only, HABs result in economic loss of $82 million each year. Some of these harmful species can have resting stages called cysts that propagate when the environmental conditions are favourable. There has been only limited information about the composition of HABs species and their cysts in Oman waters in particular in the areas near desalination plants, Ahlam reveals in the thesis “The effect of environmental factors on harmful algal blooms at Majis desalination plant, Suhar industrial area, Sea of Oman”. For the first time, the presence of cysts was studied in sediments of Suhar industrial area and the port.

“No cysts were found near the desalination plant. In opposite, cysts of seven HABs forming species were observed in sediments of Suhar industrial port,” Ahlam points out. Most of these species belonged to potentially toxin producing dinoflagellate species. This finding revealed that this area provides suitable environmental conditions for HABs-forming algae. Presence of cysts also can be one of the reasons for HABs in the studied area. Finally, the study of Ahlam provides important recommendations for the desalination plant to mitigate and prevent HABs.