Influence of current shear on Gymnodinium breve (Dinophyceae) population dynamics: A numerical study

Abstract

A time-dependent, 2-dimensional population dynamics model which incorporates current shear has been developed based on a time-dependent, 1-dimensional population dynamics model reported in an earlier study. Vertical shear in the horizontal velocity is shown to influence the cross-shelf distribution of a 2-dimensional filament of Gymnodinium breve (Dinophyceae) cells, which alters position in the vertical due to environmentally acclimated diel vertical migration. Three different vertical nitrogen distribution patterns are considered in the simulations: a surface nutrient plume, a bottom nutrient plume, and a uniform concentration in the water column. The simulations demonstrate that G. breve's vertical migratory behavior tends to maintain population coherency despite the tendency of shear in the current to disperse the population, and that the shear can contribute to predictable cell cycling within the aggregation. The simulations also show that the vertical distribution pattern of the external nutrient source has significantly influenced the horizontal advection, dispersion and cellular attributes of a G. breve population using the modeled swimming rules.