Beyond the Plankton Ecology Group (PEG) Model: Mechanisms Driving Plankton Succession

TLDR

Plankton seasonal succession is an annually repeated community assembly process, historically described by the PEG model, which has since expanded to include overlooked interactions such as overwintering, microbial food webs, parasitism, food quality, and higher‑order predators. The PEG model attributes phytoplankton dynamics to physical conditions, grazing, and nutrient limitation, while zooplankton dynamics are driven by food limitation and fish predation. Recent reviews indicate that these novel interactions minimally alter overall biomass patterns but substantially influence species replacement during succession.

Abstract

The seasonal succession of plankton is an annually repeated process of community assembly during which all major external factors and internal interactions shaping communities can be studied. A quarter of a century ago, the state of this understanding was described by the verbal plankton ecology group (PEG) model. It emphasized the role of physical factors, grazing and nutrient limitation for phytoplankton, and the role of food limitation and fish predation for zooplankton. Although originally targeted at lake ecosystems, it was also adopted by marine plankton ecologists. Since then, a suite of ecological interactions previously underestimated in importance have become research foci: overwintering of key organisms, the microbial food web, parasitism, and food quality as a limiting factor and an extended role of higher order predators. A review of the impact of these novel interactions on plankton seasonal succession reveals limited effects on gross seasonal biomass patterns, but strong effects on species replacements.