The phytoplankton community of open oligotrophic oceans is dominated by prokaryotic Prochlorococcus spp., Synechococcus spp., and eukaryotic picoand nanophytoplankton [1-3]. The competitive success of these phytoplankton species depends on different factors, including the response to the (dynamic) irradiance conditions encountered in the water column. With the occurrence of different ecotypes, picophytoplankton species such as Prochlorococcus spp., Synechococcus spp., and Ostreococcus spp. can grow over a broad range of irradiance conditions [4-7]. For example, the low light adapted ecotypes of Prochlorococcus are well adapted to the irradiance intensity and spectral composition of the deep chlorophyll maximum with high chlorophyll b/a ratios and low optimal growth irradiances [4,5,8]. In contrast, the high light adapted ecotypes of Prochlorococcus spp. can competitively grow in the (upper) mixed layer with low chlorophyll b/a ratios and higher optimal growth irradiances [4,5,8]. Similar differ‐ ences in pigmentation, absorption, and photosynthetic characteristics have been found in ecotypes of marine Synechococcus spp. [9-11] and Ostreococcus spp. [7,12,13]. In addition to the genetically defined (photo)physiology of the different ecotypes, the photoacclimation poten‐ tial of specific (pico)phytoplankton species may play an important role in the response to (dynamic) irradiance conditions [11].