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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

Abstract
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.
Keywords: Hypoxia; Oxycline; Fish landings; Arabian Sea

Zooplankton of Oman Coastal Waters

Sergey A. Piontkovski1*, Asila Al-Maawali2, Ward Al-Muna Al-Manthri1, Khalid Al-Hashmi1, and Elena A. Popova3
1College of Agricultural and Marine Sciences, Sultan Qaboos University
P.O. Box 34, Al-Khod 123, Sultanate of Oman
2 Marine Science Fisheries Centre, Ministry of Agriculture and Fisheries Wealth
P.O. Box 227, Sultanate of Oman
3Institute of Biology of the Southern Seas, 2 Nakhmov av.-Crimea
99011,Sevastopol, Ukraine

ABSTRACT
Monthly sampling during daytime was carried out in 2007-2011 at Bandar Al-Khyran (23.51oN, 58.72oE) which is the largest semi-enclosed bay on the southern end of the Sea of Oman with about 4 km2 in surface area and an average depth of 10 m. Zooplankton were represented by Copepoda (79%), Cladocera (9%), Oikopleuriddae (7%), Chaetognatha (3%), and Decapoda (~2%) comprising the major part of the total zooplankton abundance. Among copepods, 27 species constituted ~75% of total copepod abundance. Changes of copepod abundance have not had a pronounced seasonal pattern. Instead, a multiple peak structure in monthly fluctuations was observed, on the level of genera as well as the abundance of species. Amplitudes and timing of the copepod peak abundance were markedly different during the studied years.

Keywords: Copepods, zooplankton, the Arabian Sea.

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