Long-term changes of Omani coastal ecosystems are a warning sign

Muscat: Marine scientists at the Sultan Qaboos University (SQU) have raised concerns at the rising temperatures in the upper 20-metre layer of the sea.

The SQU marine scientists have been focusing on the oceanographic database for the Sea of Oman for the three years. Their study has revealed that their pilot assessments of the inter-annual changes have implied a rising temperature in the upper 20-metre layer of the sea, which could result in strengthening thermal stratification of the water column, which is a warning sign.

Dr. Sergey Piontkovski, Associate Professor in the Department of Marine Sciences and Fisheries of the College of Agricultural & Marine Sciences at SQU, who is leading this research project, said that their findings are based on on-board measurements carried out during the past 60 years, and the satellite data available from the 1980s to the present.

"Pronounced thermal stratification would suppress the penetration of nutrients from the deep. This means less biological productivity in the upper layers and less food for fish. No wonder that recent statistical reports published by the Ministry of Agriculture & Fisheries of Oman implied a 40 per cent drop of sardine landing (from 2000 to 2009) in the Muscat region, in which sardines constitute about 50 per cent of total annual landing. It should be noticed that the number of fishing boats did not increase; for instance, the reported number was 1858 boats in 2004 versus 1624 boats in 2008 for the region", Dr. Piontkovski said.

The researcher further explained that the increased sea surface temperature automatically means reduced oxygen solubility, and this brought to us to the second warning sign- the rising number of fish kill incidents in the Sea of Oman, reported by the Ministry of Agriculture & Fisheries for the past 40 years.

"One of the reasons is the oxygen depletion in the water. In the Sea of Oman, the upper boundary of the oxygen minimum zone is recorded at the depth of about 50m," the SQU scientist explained. He added that overall, a simplistic picture of the hydrological structure of the sea would be a two-layered system; the upper layer is formed by the Indian Ocean waters. This layer is underlined by high-saline, oxygen-poor waters formed in the Arabian Gulf.

Due to the ocean-atmosphere interactions mediating physical dynamics of the upper layer, the oxygen depletion could resurface from time to time and could cause massive fish kill incidents along the coast, even within an hour.

"This is what has been recorded a number of times in the past," he pointed out, pointing out that hundreds of tons of fish were reported dead in the Omani coastal aqua farms.

"For instance, in November 2008, about 80 tons of the aquaculture fish perished in the Qurayat region, in one day."

The third warning sign is the sea level rise. Through the models, the experts from the Intergovernmental Panel of Climate Change have projected the rise from 10 to 90 cm, by 2100. The 90 cm level would mean tragic consequences for the economy of the Gulf countries because a lot of constructions, businesses and people would be altered.