Algal Population in Light-Limited Conditions*

 

We investigate the population dynamics of phytoplankton (photosynthetic, one-celled algae) in turbulent waters, in conditions where light can be considered as the limiting factor for growth¹. In such conditions, the negative buoyancy characterizing most phytoplankters, would condemn the population to sinking out of the photic zone at the top of the ocean, towards the dark deep waters. Turbulence may resuspend them long enough to reproduce and reach a stationary population.  While classic models for the development of algal blooms are one-dimensional and purely diffusive, recent numerical investigations point to the relevance of the different flow scales for bloom conditions^3,4. We perform numerical simulations of a turbulent flow to study how the population correlates with the flow and how the large-scale and small-scale components of turbulence influence the vertical profile and horizontal inhomogeneity of the population and its fluctuations.

¹ De Lillo et al. (in preparation, 2022).

² Huisman et al.,  Limnol. Oceanogr. 44, 1781 (1999).

³ Tergolina et al., Phys. Rev. E 104, 065106 (2021).