Winter bloom of coccolithophore Emiliania huxleyi and environmental conditions in the Dardanelles

Abstract

Following a summer bloom of coccolithophore Emiliania huxleyi (Lohmann) Hay 81 Mohler, 1967, in 2003, a winter bloom was observed for the first time between late December 2003 and early January 2004 in the Dardanelles. Microscopic observations showed that the cell dimensions of £ huxleyi (Ehux) varied from 9.85 to 13.50 μm in diameter (mean: 11.20 ± 1.38 μm). while Ehux revealed a relatively small population density (1.60 x 104 cells L-1) in early December 2003, the bloom started in middle December 2003 (7.86 x 106 cells L-1) and then peaked in early January 2004 (5.03 x 107cells L-1) in the superficial layer. The peak dramatically decreased in late January 2004 (7.50 x 106 cells L-1). Ehux was the dominant species and represented about 90.0% of the phytoplankton assemblage. The bloom started flourishing after the diatom and dinoflagellate blooms under nitrogen depletion and moderate light, temperature and salinity conditions. Water temperature (10.31 ± 1.140°C) and salinity values (27.05 ± 0.88 ppt) were usually stabile. Surface chlorophyll-a concentrations ranged from 1.23 to 2.32 μgL-1 during the bloom. The ratios of N: P (mean: 4.12 ± 2.22) and Si: P (40.35 ± 16.25) of the bloom period were lower than those of the non-bloom periods. © IWA Publishing 2010.