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Penilia avirostris: Regional and Global Patterns of Seasonal Cycles

S.A. Piontkovski1, S. Fonda-Umani2, A. De Olazabal3 and A.D. Gubanova4
1Sultan Qaboos University, CAMS, PO 34, Al-Khod 123, Sultanate of Oman
2Department of Life Sciences, University of Trieste,
v. Valerio 28/1 34123 Trieste, Italy
3Department of Biological Oceanography, OGS, v. Piccard, 42, Italy
4Institute of Biology of the Southern Seas, 2 Nakhimov Pr.,
Sevastopol 99011, Ukraine
*Corresponding Author E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Seasonal cycles of the Penilia abundance were compared, over five coastal regions-the north-western part of the Black Sea (Sevastopol Bay), the northern
part of the Adriatic Sea (Gulf of Trieste), the north-eastern Atlantic (Vigo coast), the north-western Mediterranean basin (Barcelona coast), and the
north-western part of the Arabian Sea (the Gulf of Oman). Satellite derived monthly data were used, to analyze coupling between the Penilia abundance,
sea surface temperature, and chlorophyll a concentration over these regions. Two types of seasonal dynamics were noticed: (1) a unimodal type of population dynamics with one peak lasting 3-4 months in summer to fall (in Vigo, Sevastopol, and Trieste regions) and (2) all year round persisting
population in subtropical highly productive waters of the Arabian Sea (Gulf of Oman). A regional link between abundance and temperature was also reflected
by the global geography of the Penilia habitats. As far as the global aspect is concerned, a general relationship representing the abundance as the linear function of two environmental variables-sea surface temperature and chlorophyll a concentration was proposed.

Keywords: Zooplankton; Arabian Sea; Black Sea; Mediterranean Sea

Seasonal and interannual variability of chlorophyll-a in the Gulf of Oman compared to the open Arabian Sea regions
Department of Marine Science and Fisheries, College of Agricultural and Marine Sciences, Sultan Qaboos University, CAMS, P.O. 34, Al-Khod 123, Sultanate of Oman

Field sampling, remote sensing and modelling were employed to understand the seasonal and interannual changes of chlorophyll-a concentrations in the Gulf of Oman in comparison to open sea regions. In these regions, maximal chlorophyll concentrations were reported during the summer monsoon (with peaks in June and August), while in the Gulf of Oman, the chlorophyll maximum was observed during the winter monsoon (February–March). From 1997 through to 2008, the interannual variability in chlorophyll-a concentrations in the Gulf of Oman has not exhibited pronounced trends and neither have the other two (oceanic) regions in the western Arabian Sea. However, an increase of the annual variation in chlorophyll concentrations over the years was noticed. The diatom biomass decreased two-fold from 1997 to 2007. Nitrate concentration and mixed-layer depth also declined. In comparison to the seasonal blooms driven in the Gulf of Oman by the dinoflagel- late Noctiluca scintillans, the year 2008 was markedly different. The summer bloom was shifted to September; it was gradually extended in time and formed by the other species. An applicability of the concept of ecosystem regime shift is discussed.

Mesoscale Eddies of Arabian Sea: Physical-biological Interactions

S.A. Piontkovski1 , N.P. Nezlin2
1Sultan Qaboos University, CAMS, P.O. 34, Al-Khod 123, Sultanate of Oman
2Southern California Coastal Water Research Project, 3535 Harbor Blvd., Costa Mesa, CA 92626, USA

Satellite derived (SeaWIFS, TOPEX/Poseidon) products for chlorophyll-a concentration, sea surface heights, and calculated kinetic energy of eddies were employed, to analyze physical-biological coupling from 1997 to 2008. It was shown that, when cyclonic eddies dominated throughout the year, the chlorophyll-a concentration was positively related to the kinetic energy of eddies.
For the other years, when the total annual balance of negative to positive sea surface heights was dominated by anticyclonic eddies, the correlation was negative. The evaluated switch contributes a useful detail to the understanding of the mechanism mediating variability of the chlorophyll-a in regions with vigorous eddy fields.

Mesoscale eddies; Arabian Sea; Chlorophyll-a; Remote sensing

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