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
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
SERGEY PIONTKOVSKI*, ADNAN AL-AZRI and KHALID AL-HASHMI
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.
Seasonal Changes of Chlorophyll a and Environmental Characteristics in the Sea of Oman
Al-Hashmi, Khalid A. Claereboudt*, Michel R. Al-Azri, Adnan, R. Piontovski, Sergey. A.
Sultan Qaboos University, Department Marine Science and Fisheries College Agricultural and Marine Sciences, Box 34
Al-Khod 123 Sultanate of Oman
Monthly estimates of chlorophyll a, temperature, salinity, and nutrients were collected through sampling at two stations from January 2001 to January 2002, in and near Bandar Al-Khyran, the largest semi-enclosed bay on the southern coast of the Sea of Oman. Although the sampling location was at the limit of the tropical range, the seasonal changes of the coastal phytoplankton were more related to temperate dynamics, showing seasonal fluctuation of more than 10o C.
Sharp temperature drops observed in August and July were likely due to rises of the thermocline under the influence of coastal upwelling events or to deep water injections along the north coast of Oman generated by changes in the coastal wind patterns. Overall, small phytoplanktonic cells [0.7-5 μm] dominated the phytoplankton community of the mixed layer with an average of 69.7 % and 73.5 % of the extracted chlorophyll a at the station "Inside" and "Outside" the bay, respectively.
Keywords: Arabian Sea, picoplankton, chlorophyll a, coastal upwelling, phytoplankton blooms.