Transparent Exopolymer Particles play a central role in marine carbon cycling,acting as a bridge between dissolved and particulate organic carbon and contributingto the formation of marine snow. This study investigates strain- and growthphase-specific differences in TEP concentration among five picophytoplanktonstrains from the Baltic Sea to better understand their contribution to the biologicalpump. These consist of three picocyanobacteria (KAC 102, 106, 108) and twopicoeukaryotes (KAC 117, 123). Over a series of controlled experiments, growthrates, cell abundances, particulate organic carbon (POC) and TEP concentrationswere measured. Results show that while TEP concentrations per liter generallyincreased over time, TEP concentration normalized per cell was highest during earlygrowth phases and declined thereafter. This suggests a compensatory response whenlower in abundance, individual cells produce more TEP. Significant differenceswhen comparing concentrations per liter were found over time independent ofstrain, but none when comparing concentrations normalized per cell. TEP can beutilized by some species to form microcolonies, but the substance is also theby-product of various types of stress response as well as excreted at all stages ofgrowth. The various reasons that originate production raise questions such as underwhat conditions it is formed. Understanding this will help uncover why it is theocean’s most abundant gel particle and how it shapes the environment for microbiallife in the ocean through food web-interactions.