Zooplankton seasonal vertical migration in an optimality-based plankton ecosystem model.

The article focuses on simulating seasonal vertical migration (SVM) behavior of zooplankton in the high-latitude Labrador Sea using the OPtimality-based PLAnkton (OPPLA) ecosystem model. OPPLA treats SVM as a generic zooplankton trait, enabling analysis of its evolutionary stability and interactions with other plankton groups, including non-migrating microzooplankton and mesozooplankton ("Stayers"). The study finds that SVM amplifies seasonal variations in phytoplankton and zooplankton and reduces summer surface nutrient concentrations, with the timing of migrations—especially the day of ascent—being critical for SVM's success. Simulations indicate that SVM can be an evolutionarily stable strategy even without higher visual predators, although predators tend to suppress non-migrating Stayers, favoring migrators. This modeling approach highlights the ecological role of SVM in plankton community dynamics and carbon export in seasonal marine ecosystems.