Three-dimensional turbulence effects on plankton dynamics behind an obstacle

TL;DR

This study uses numerical simulations to analyze how three-dimensional turbulence influences plankton population dynamics behind an obstacle, revealing that while overall behavior is similar across dimensions, 3D turbulence reduces localized plankton structures and biomass.

Contribution

It demonstrates that the qualitative biological dynamics are largely unaffected by spatial dimensionality, highlighting the role of flow and biological timescale relations in plankton blooms.

Findings

Biological dynamics are similar in 2D and 3D turbulence.

Spectral properties of plankton are akin to inert tracers.

3D turbulence destroys localized plankton structures, reducing biomass.

Abstract

We study a predator-prey model of plankton dynamics in the two and three-dimensional wakes of turbulent flows behind a cylinder, focusing on the impact of the three-dimensional character of the carrying velocity field on population variance spectra and spatial distributions. By means of direct numerical simulations, we find that the qualitative behavior of the biological dynamics is mostly independent of the space dimensionality, which suggests that only the relation between the typical flow and biological timescales is crucial to observe persistent blooms. Similarly, in both cases, we find that the spectral properties of the planktonic populations are essentially indistinguishable from those of an inert tracer. The main difference arising from the comparison of the two and three-dimensional configurations concerns the local spatial distribution of plankton density fields. Indeed, the three-dimensional turbulent dynamics tend to destroy the localized coherent structures characterizing the two-dimensional flow, in which the planktonic species are mostly concentrated, thus reducing the phytoplankton biomass in the system.