Nutrients associated with internal waves are known to perturb
phytoplankton communities in oligotrophic oceans, but details of the
relevant processes and mechanisms are unclear. Here we report insights
about the impacts of internal waves on the phytoplankton community based
on 154-hour time-series of observations in an oligotrophic basin of the
South China Sea. We found that the temporal variations of phytoplankton
communities in the upper, middle, and lower layers of the euphotic zone
differ. We demonstrated that these changes probably resulted from the
perturbation caused by internal waves. These results suggest that the
structure of the phytoplankton community in oligotrophic oceans is best
described by a three-layer system at steady state and that the
perturbation caused by internal waves helps to reveal this structure. We
believe that the paradigm of this three-layer structure will provide a
new theoretical framework for the study of phytoplankton-based
biogeochemical processes in oligotrophic oceans.