EFFECT OF WIND ON THE DISTRIBUTION OF PHYTOPLANKTON CELLS IN LAKES REVISITED

Experimental evidence suggests that winds having speeds >2-3 m s-1 are required to mix floating phytoplankton cells (or colonies) away from the water surface. We consider theoretical, steady state distributions of phytoplankton in a lake caused by turbulence and circulation patte rns induced by winds having speeds above this critical level. The mode l incorporates an eddy diffusivity which varies with position in the w ater column. It predicts concentration variations in the downwind dire ction which are more in accord with experiment than a previously prese nted model having an eddy diffusivity uniform in the vertical. If the windspeed is less than the critical value, then a floating phytoplankt on scum is expected to remain on the surface. The horizontal distribut ion of a phytoplankton population will be very different depending on whether the windspeed is greater or less than the critical speed.