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Interannual Changes in the Sea of Oman Ecosystem

Sergey A. Piontkovski*,1, Hamed M.H. Al-Gheilani2, Barry P. Jupp3, Adnan R. Al-Azri1 and Khalid A. Al-Hashmi1
1Department of Marine Science and Fisheries, Sultan Qaboos University, P.O. Box 34, Al-Khod 123, Sultanate of Oman
2Marine Science and Fisheries Center, Ministry of Agriculture and Fisheries, P.O. Box 467, Muscat 113, Sultanate of Oman
3GEO-Resources Consultants, P.O. Box 175, Mina Al Fahal, Muscat 116, Sultanate of Oman

Abstract
Historical data were used to estimate interannual tendencies for the Sea of Oman over the past 50 years. Declining trends were shown for the atmospheric surface level pressure in the region affected by the Siberian High atmospheric anomaly, the zonal component of wind speed, concentration of nitrates, biomass of diatoms and sardine landings. Changes in Zooplankton biomass showed no clear trend. These trends were associated with and accompanied by rising atmospheric temperature, sea surface temperature, annual variability of the kinetic energy of mesoscale eddies, frequency of fish kills (along with the death of other animals- dolphins, turtles, and sea birds) and harmful algal bloom incidents. In terms of interannual coupling between physical and biological processes, the evaluated trends imply that the weakening of the Siberian High atmospheric anomaly results in the decline of the zonal wind speed and a regional increase of air temperature. This in turn increases the temperature in the mixed layer which strengthens thermo-haline stratification of the water column. Increasing stratification prevents the penetration of nutrients into the mixed layer and does not favor the interannual increase of biological productivity, although annual variation of biological productivity has increased, from 1997 to 2008.
Keywords: Gulf of Oman, long term changes oceanography, chlorophyll a, climate change.

Interannual changes of the Arabian Sea productivity

SERGEY A. PIONTKOVSKI* & MICHEL R. CLAEREBOUDT
Department of Marine Science and Fisheries, Sultan Qaboos University, Al-Khod, Sultanate of Oman

Abstract
Inter-annual changes in temperature and chlorophyll a across the Arabian Sea (subdivided into 61 2-degree regions) were analysed. For each 2-degree region, from appropriate databases, remotely sensed chlorophyll a, sea surface temperature, and wind speed time series were retrieved. Spatial and temporal trend analysis showed physical - biological oscillations with dominant periods of 12 and 6 months (reflecting the seasonality of monsoonal winds) with a globally warming trend, but no overall increase in chlorophyll during the period 1997 - 2009. Variation coefficients of the inter-annual time series of chlorophyll a implied high variability in western regions of the sea in comparison to eastern regions. The basin-wide maps of chlorophyll distribution did not show the enlargement of the productive area over time and overall, not only did the Arabian Sea not get more productive, but several regions in its eastern basin showed a decline in chlorophyll a concentration.

Key words: Arabian Sea, chlorophyll a, global changes, marine ecosystems

Mesoscale eddies and variability of chlorophyll-a in the Sea of Oman

SERGEY A. PIONTKOVSKI*, NIKOLAY P. NEZLIN, ADNAN AL-AZRI and KHALID AL-HASHMI
Department of Marine Science and Fisheries, Sultan Qaboos University, Al-Khod 123,
Sultanate of Oman
Southern California Coastal Water Research Project, Costa Mesa, CA 92626, USA

Abstract
Satellite-derived (TOPEX/Poseidon, Jason-1, Jason-2, SeaWIFS (Sea-Viewing Wide Field-of-View Sensor) and MODIS (Moderate Resolution Imaging
Spectroradiometer) Aqua) weekly and monthly products for sea surface height, sea surface temperature (SST) and chlorophyll-a (CHL) concentration were used to analyse the trends of physical–biological coupling. In the variability of chlorophyll, no interannual trends were found for the Sea of Oman (1997–2008). However, the variation of chlorophyll within the annual cycle has increased. A similar tendency was evaluated for the variability of the energy of mesoscale eddies. Themedian level of kinetic energy and the coefficient of variation of this energy within the annual cycle both increased from 1997 through 2008.

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