Bioassays with amendment of DIN, DIP, and various trace elements were conducted in short-term replicated bottle incubations to determine limiting elements for phytoplankton growth (Browning et al., 2017). Shipboard mesocosm experiments with a duration from 7 to 11 days were conducted on several cruises in the ETNA and ETSP and land-based on Cape Verde to determine the impact of N:P stoichiometry on the pelagic community (Franz et al., 2012b; Hauss et al., 2012; Meyer et al., 2016) and dissolved organic compounds (Loginova et al., 2015; Engel et al., 2015).