This experimental study implies: (1) isotopic
compositions of phytoplankton lipids are heterogeneously generated through different cell growth phases, likely
dependent on cell physiological states, medium conditions, and relative proportions of intracellular components;
and (2) microbial degradation plays a more important role in altering isotopic compositions of lipid compounds
than cell respiration, probably related to different labilities of lipids between different cellular components.