The impact of fine‐scale turbulence on phytoplankton community structure

Abstract

Lay AbstractThe mechanisms that maintain the great diversity of marine phytoplankton are not well understood. In particular, the widespread distribution and survival of large phytoplankton cells in the ocean are paradoxical, as they are at a distinct competitive disadvantage compared with smaller cells. The growth of large phytoplankton is typically limited by the diffusive supply of essential nutrients, whereas smaller cells have a greater surface‐area‐to‐volume ratio and are thus able to acquire sufficient resources more effectively via diffusion. Here, we employ a model of the diverse marine phytoplankton community to show that fine‐scale turbulence, a defining and ubiquitous feature of the ocean environment, aids the survival of large cells by increasing their effective supply of critical nutrients. This ecological impact of turbulence becomes most important in regions with established grazer populations, with high inputs of turbulent kinetic energy, and where nutrients have been exhausted, such as in the middle and high latitudes in summer and the trade wind latitudes of the tropics and subtropics. Our work shows that the presence of turbulence can have profound impacts on the size structure of the marine phytoplankton community.