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•Climate-driven increase in winter sea surface temperatures in the area contributes to the temporal shift in phytoplankton blooms (including HABs).•The total number of taxonomically diverse phytoplankton blooms and their abundance decreased compared to the previous reports.•The increase in diatoms, the most important contributors to the total chlorophyll a, suggests an improvement in the environmental status of the investigated region.•Phytoplankton production periods observed in mid-spring and late summer periods in the region in previous years partly moved to the early summer and late autumn / early winter period.

This investigation focused on weekly variations in cell density and volume of the dinoflagellate Noctiluca scintillansbetween March 2001 and January 2004 in the Dardanelles. March–June and October–December periods were excessive bloom periods. During the bloom periods the density of N. scintillansreached 2.20× 105cells L−1with a volume of 1.32×1012μm3L−1. In addition to the high surface density, there was an increase in subsurface waters during the blooms. The bloom of N. scintillans, like that of diatom and other dinoflagellate blooms, was associated not only with eutrophication, but also with stable temperatures and salinities.