We used HPLC to test for a differential effect of atmospheric deposition on coastal phytoplankton of Barcelona and Blanes, a neighboring town subjected to a lower anthropogenic aerosol influence. We performed three microcosm experiments: one in winter (in Barcelona) and two in spring (one in Blanes and one in Barcelona). In each experiment, we incubated six containers with 15 L of coastal seawater pre-filtered through 150 μm at the temperature and light cycle of the respective time of the year. We added 0.8 mg L-1 of Saharan dust to two containers, 0.8 mg L-1 of anthropogenic dust to other two, and the remaining were used as controls. Samples for pigment analysis by HPLC were collected at the beginning and at the end of the experiments. In the two experiments from Barcelona, Fucoxantin was always the predominant pigment in both treatments, indicating the dominance of diatoms. However, in Blanes, Zeaxantin predominated initially, indicating the presence of Cyanobacteria, while Fucoxantin, 19’-butanoyloxyfucoxanthin and 19'-hexanoyloxyfucoxanthin, and Chlorophyll-c2 prevailed at the end. We discuss the results from both treatments in relation to the phytoplankton response
