Rev. biol. mar. oceanogr. 49(2): 267-277Article |
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The phytoplankton communities in two eutrophic areas on the Alexandria coast, Egypt |
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Hanan Mohamed Khairy1, Nabila Ragab Hussein1, Hayat Mohasseb Faragallah2 and Mohamed Moussa Dorgham3 |
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1Hydrobiology Laboratory, Marine Environmental Division, National Institute of Oceanography and Fisheries, Kayet Bay, Alexandria, 21556, Egypt
2Marine Chemistry Laboratory, Marine Environmental Division, National Institute of Oceanography and Fisheries, Kayet Bay, Alexandria, 21556, Egypt
3Department of Oceanography, University of Alexandria, Alexandria, 21511, Egypt
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The phytoplankton community was studied in historically and ecologically important area on the southeastern Mediterranean coast at Alexandria, Egypt. Monthly samples were collected during January-December 2009 from 2 areas [Bahia Oriental (EH) and Kayet Bey (KB)]. A total of 162 phytoplankton species were identified in the EH and 110 species in the KB, dominated by diatoms in both areas (100 and 64 species, respectively). The phytoplankton count showed an annual average of 1.387 x 106 cells L-1 in the EH and 0.108 x 106 cells L-1 in the KB, and biomass (Chlorophyll a) of 2.4 and 2.0 mg L-1, respectively. Diatoms and dinoflagellates demonstrated clearly different roles in the phytoplankton cycle in the 2 areas, with the persistent occurrence of several toxic species, sometimes in high count, like the diatom Pseudo-nitzschia delicatissima and the dinoflagellates Scrippsiella trochoidea, Pyrophacus horologium, Prorocentrum micans, Prorocentrum triestinum, Prorocentrum cordata, Gonyaulax catenata and Protoperidinium subinerme. Regardless of the stopping of great part of the discharged wastes to the study area, it is still suffering from eutrophication all the year round, as indicated from high nutrient concentrations and intensive phytoplankton growth.
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Key words: Alexandria harbour, nutrients, diatoms, toxic algae, dinoflagellates |
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