<p>Intra-annual and interannual variability of satellite derived chlorophyll-a concentration (Chl) is studied using wavelet analysis during 1997&ndash;2010 in tropical, subtropical and temperate zones of the Eastern North Atlantic (20&ndash;50&deg; N and 5&ndash;40&deg; W). It was found that during the period of observations the Chl dynamics was dominated by the four major periodicities: 0.5-year, 1-year, 2-year and 3&ndash;5-year cycles. The 0.5-year wavelet cycle predominantly is a function of the intensity of the secondary bloom (autumn or summer); it attains maximum of 80&ndash;100% of the fundamental seasonal (1-year) cycle in the subtropics and 30&ndash;60% in the southern tropics. The 2-year and 3&ndash;5-year wavelet cycles characterise the variations in the annual mean Chl concentrations and their amplitudes change in-parallel with the change of the amplitude of the 1-year cycle. Expressed as the percentage of the 1-year cycle, the interannual cycles play the most significant role in Chl variations in the southern tropics (40&ndash;50%). The 2-year and 3&ndash;5 year cycles are also present in the North Atlantic Oscillation Index (NAOI), but only the 3&ndash;5-year Chl cycle is closely coupled with the corresponding cycle in the NAOI. Weak correlations with the 2-year cycle are suggested to be a result of the NAOI variations that does not always directly translate into a biological response.</p>