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The Omani shelf hypoxia and the warming Arabian Sea The Omani shelf hypoxia and the warming Arabian Sea

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Date added: 03/03/2015
Date modified: 03/03/2015
Filesize: 389.85 kB
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The Omani shelf hypoxia and the warming Arabian Sea
S.A. PIONTKOVSKI*† AND H.S. AL-OUFI‡
†Department of Marine Science and Fisheries, CAMS, Sultan Qaboos University, P.O. 34, Al-Khod 123, Sultanate of Oman; ‡Ministry of Agriculture and Fisheries Wealth, P.O. 467, Muscat 113, Sultanate of Oman
Interdecadal changes in oxygen depletion, with a special reference to artisanal landings of large pelagic fishes, were analysed. Data from 53 expeditions incorporating 29,043 vertical profiles of temperature and 2114 of dissolved oxygen implied an increase in temperature of 1.2 °C over the past 50 years in the upper 30 m layer of sea water during the south-west (summer) monsoon. The thermal stratification of the water column increased and the oxycline shoaled from 153 m in the 1960s to 80 m in the 2000s. Concentration of dissolved oxygen <3.5 mL L−1 is known to induce symptoms of stress for many tropical pelagic fishes, compressing them within upper layers and
exposing them to fishery. The habitat compression by the Oman shelf hypoxia has two components: a seasonal oxycline shoaling and an interdecadal trend.

Variability of dinoflagellates and diatoms in the surface waters of Muscat, Sea of Oman Variability of dinoflagellates and diatoms in the surface waters of Muscat, Sea of Oman

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Date added: 02/25/2015
Date modified: 02/25/2015
Filesize: 370.14 kB
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Variability of dinoflagellates and diatoms in the surface waters of Muscat, Sea of Oman: comparison between enclosed and open ecosystem
Khalid A Al-Hashmi(1)*, Joaquim Goes(2), Michael Claereboudt (1), Sergey A.
Piontkovski (1), Adnan Al-Azri (1) Sharon L Smith (3)

1-Khalid A Al-Hashmi* (Corresponding author); College of Agricultural and Marine Sciences, Sultan Qaboos University, P.O.Box: 34, Al-Khod 123, Sultanate of Oman.khalid99@squ.edu.om
2-Joaquim Goes; Lamont Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA goesgoa@gmail.com
1-Michael Claereboudt; College of Agricultural and Marine Sciences, Sultan Qaboos University, P.O.Box: 34, Al-Khod 123, Sultanate of Oman. michelc@squ.edu.om
1-Sergey A. Piontkovski; College of Agricultural and Marine Sciences, Sultan Qaboos University, P.O.Box: 34, Al-Khod 123, Sultanate of Oman. spion@squ.edu.om
1-Adnan Al-AzriCollege of Agricultural and Marine Sciences, Sultan Qaboos University, P.O.Box: 34, Al-Khod 123, Sultanate of Oman. adnazri@squ.edu.om
3-Sharon L Smith;The Rosenstiel School, University of Miami, 4600 Rickenbacker
Causeway, Miami, FL 33149 USA. sharon.smith@rsmas.miami.edu

We investigated the distribution patterns of phytoplankton species over a one year period (from April 2010 to February 2011) at an open ocean location off the coast of Muscat, Sea of Oman (OFF) and the other at Bandar Khayran (BK), a semi enclosed bay located downstream of the southeastward Sea of Oman coastal current. Although these two locations come under the influence of the semi-annually reversing monsoons, and experience nutrient influxes associated with the southwest (SWM, June-Sept.) and the northeast monsoons (NEM, Nov.-Feb.), they are hydrographically distinct. At both stations, a total of 133 phytoplankton taxa were identified and quantified over the sampling period. The two stations showed higher phytoplankton abundance, higher diversity and higher chlorophyll concentrations during the SWM and NEM seasons, a reflection of phytoplankton populations responding to injection of nutrients during these two seasons. Phytoplankton communities at both at BK and OFF were dominated by dinoflagellates and showed no significant differences in dinoflagellate community composition. In addition, no clear 138 Khalid A Al-Hashmi et al trend of dinoflagellate or diatom species succession was observed during the study period. Among the dinoflagellate population, Prorocentrum minimum,Gymnodinium sp., Scrippsiella trochoidea, Gymnodinium simplex and the mixotroph Noctiluca scintillans. On the other hand, Lauderia punctata, Bacteriastrum elongatum and Paralia moniliformis, Chaetoceros spp. Guinardia striata and Thalassiosira spp. were the most dominant diatoms.

Seasonal and Interannual Changes of Indian Oil Sardine, Sardinella longiceps Seasonal and Interannual Changes of Indian Oil Sardine, Sardinella longiceps

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Date added: 01/21/2015
Date modified: 01/21/2015
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Seasonal and Interannual Changes of Indian Oil Sardine, Sardinella longiceps Landings in the Governorate of Muscat (the Sea of Oman)
SERGEY A. PIONTKOVSKI, HAMED S. AL-OUFI, and SAUD AL-JUFAILI
Monthly data on Muscat’s landings of the Indian oil sardine, Sardinella longiceps, along with 23 environmental parameters ( sea surface temperature, temperature of the mixed layer, wind speed, kinetic energy of mesoscale eddies, concentration of nitrates, dissolved oxygen, chlorophyll-a, abundance of phytoplankton, zooplankton, and several others) were analyzed for the period 1994–2011.
Seasonal changes were associated with the time of the winter (Northeast) monsoon,with maximal landings in February.
The multiple regression analysis of the statistically signifi cant variables selected through the Principal Component
Analysis has implied that 51% of seasonal variability in sardine landings might be approximated by the seasonal variations
of the zonal component of wind speed and chlorophyll-a concentration in the coastal and open-sea regions. In terms of interannual changes, sardine landings exhibited a declining trend from 2001 to 2011 (the time covered by the most complete data set).
Rising sea temperature, thermal stratifi cation of the water column, and the trophic pressure imposed on sardine populations
by large pelagic predators (talang queenfi sh, Scomberoides commersonnianus; kingfish, Scomberomorus commerson; longtail tuna, Thunnus tonggol; and some others) might be the factors mediating this trend.

Oxygen Minimum Zone and Fish Landings along the Omani Shelf Oxygen Minimum Zone and Fish Landings along the Omani Shelf

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Date added: 09/26/2014
Date modified: 10/20/2014
Filesize: 949.74 kB
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Oxygen Minimum Zone and Fish Landings along the Omani Shelf
1Sergey A.Piontkovski and 2 Hamed S.Al-Oufi
1Department of Marine Science and Fisheries, Sultan Qaboos University, P.O.Box 34,Al-Khod, 123,Sultanate of Oman
2Ministry of Agriculture and Fisheries Wealth, P.O.Box 467, Muscat, 113,Sultanate of Oman

Historical data on vertical distribution of temperature, salinity, dissolved oxygen concentration, eco-soundings and artisanal fish landings were used, to investigate the relationship between characteristics of the oxygen minimum zone and fish landings along the Omani shelf (in the western Arabian Sea). It was shown that seasonal shoaling of the oxycline shifts the deepened layer of myctophids up to the surface and closer to the coast which in turn favors accumulation of pelagic predators in the same locality. Both phenomena lead to a compressing of the habitat and increasing artisanal landings. The factors mediating seasonal changes of the oxygen minimum zone are discussed here.

Long-Term Changes of Temperature in the Sea of Oman and the Western Arabian Sea Long-Term Changes of Temperature in the Sea of Oman and the Western Arabian Sea

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Date added: 05/12/2014
Date modified: 05/12/2014
Filesize: 1.5 MB
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Long-Term Changes of Temperature in the Sea of Oman and the Western Arabian Sea
S. A. Piontkovski1and T. Chiffings2
1Sultan Qaboos University, CAMS, PO 34, Al-Khod 123, Sultanate of Oman
2Center for Environmental Research, Sohar University, Sultanate of Oman

The NCEP-NCAR Reanalysis database (1948-2010), the Hadley Centre SST2 data (1850-2012), and historical data from 98 oceanographic expeditions (1950-2010) were used, in analyzing the long-term changes of temperature. In the western Arabian Sea in summer, the maximal gradient of temperature between the “oldest” mean vertical profile (1960-1970) and the newest one (2001-2010) was observed in the upper mixed layer.
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