Effect of wind on the distribution of phytoplankton cells in lakes

Abstract

A model is developed that demonstrates how the tendency of phytoplankton cells to float or sink, coupled with wind‐induced circulation, leads to horizontal heterogeneity in phytoplankton concentrations in lakes. For the unstratified case after steady state conditions have been attained, modeled concentrations are approximately uniform in the vertical, but they increase (or decrease) at an exponential rate toward the downwind end of the lake if the plankton cells float (or sink). The rate of increase or decrease of concentration along the downwind axis of the lake is shown to depend simply on wind speed, rising or sinking velocity, and lake water depth. The degree of phytoplankton heterogeneity in a lake depends on the ratio of the spatial scale over which concentration varies to the length of the lake. Under certain conditions, the model can be extended to stratified lakes as well. Thus, the model can explain some observations of heterogeneity in plankton concentration within both unstratified and stratified lakes.