Trophic interactions drive the emergence of diel vertical migration patterns: a game-theoretic model of copepod communities

Diel vertical migration (DVM), the daily movement of organisms through oceanic water columns, is mainly driven by spatio-temporal variations in the light affecting the intensity of predator–prey interactions. Migration patterns of an organism are intrinsically linked to the distribution of its conspecifics, its prey and its predators, each with their own fitness-seeking imperatives. We present a mechanistic, trait-based model of DVM for the different components of a pelagic community. Specifically, we consider size, sensory mode and feeding mode as key traits, representing a community of copepods that prey on each other and are, in turn, preyed upon by fish. Using game-theoretic principles, we explore the optimal distribution of the main groups of a planktonic pelagic food web simultaneously. Within one single framework, our model reproduces a whole suite of observed patterns, such as size-dependent DVM patterns of copepods and reverse migrations. These patterns can only be reproduced when different trophic levels are considered at the same time. This study facilitates a quantitative understanding of the drivers of DVM, and is an important step towards mechanistically underpinned predictions of DVM patterns and biologically mediated carbon export.