Wednesday, 26 July 2017

Changes in Omani Coastal Ecosystems

Changes in Omani Coastal Ecosystems

Horizon
Department of Public
Relations and Information
Sultan Qaboos University
https://www.squ.edu.om/Portals/33/almasar/Horizon1.pdf

Marine Scientists at SQU, who have been focusing on the oceanographic database for the Sea of Oman for the past three years, revealed that their pilot assessments of the inter-annual changes have implied a rising temperature in the upper 20 meter 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 onboard 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% drop of sardine landing (from 2000 to 2009) in the Muscat region, in which sardines constitute about 50% 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 them 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. 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 had happened a number of times; 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”.

What would happen to the oxygen minimum zone during the next decades?
Would it expand and start moving towards the surface or, would it just move up and down (fluctuate) in a water column over the years?
Dr. Piontkovski said that in order to answer these questions, we need to study the processes driving the extension and location of the oxygen minimum zone along the coast. In order to do that, regular field surveys are required. The later ones are not feasible at the moment, due to the absence of research vessels capable of carrying out regular oceanographic surveys.

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.

Dr. Piontkovski made it clear that the oceanographic data currently available for the Sea of Oman do not represent the issue of the marine ecosystem and climate change, in a proper way. “In order to do that, we need the time series with observations dated back, by hundreds and thousands of years.
In this sense, we have bits and pieces of information so far, retrieved by the scientists in the field of paleoclimate, through the analysis of sediment cores. Some of the samples were taken in the western Arabian Sea, right across the Sea of Oman- at the Murray Ridge. The analysis of these cores enabled the scientists to evaluate the long-term fluctuations of productivity on the scale of the past 100 000 years, with highest productivity in interglacial periods. So the question is, which productivity wave are we surfing, in the long run- the rising or the declining?”, he added.

1700km Omani coast is surrounded by the waters of different physicalchemical and biological properties, which depend upon the coast considered- the oceanic or the gulf-oriented. This means that the long-term changes of marine ecosystems along these coasts might be different, on the time scale, ranging from decades to thousands of years. As far as the Sea of Oman is concerned, the hydrological regime of the basin has a complicated structure mediated by high-saline waters of the Arabian Gulf (coming from the west) and less saline waters of the Arabian Sea from the east. Geomorphology of Omani mountains contributes this complexity by imposing a specific mode of winds affecting surface circulation in the sea. The atmosphere- ocean interactions result in gradual differences in the productivity of the Sea of Oman versus the western Arabian Sea.

Oceanographic research of the Sea of Oman may be dated back to 1950s, then the first reports on hydrological surveys were compiled.
Dr. Piontkovski aid that currently, the scientists studying long-term changes of physical, chemical, and biological processes in the Gulf aim to assemble the database incorporating all historical data.
“This would enable us to assess the changes that have happened in the past six decades and to project the ecological future of the Gulf. Unfortunately, the future is not looking good. According to the reports of the Intergovernmental Panel on Climate Change, by the end of the current century, the Gulf countries will face an increase in temperature (up to 2oC), drop of water run-off by 30%, decline in precipitation, and increase in severity of extreme weather events” he revealed.

 

 

General contact:   Prof. Sergey Piontkovski spiontkovski@gmail.com
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