I do 80% of my fishing in less than 7' of water. I can tell you for a fact that baitfish or their predators do not evacuate the shallow flats during high pressure days....I can see them!
In most places where I fish the deepest the plankton can go is 3-4ft. unless they burrow into the bottom.
I just don't think it's about plankton, but I could be wrong.
And if it was all about sunlight penetration then seeking out and fishing various degrees of shade would save the day. No, there are days when LAKE fish just flat shut down, simultaneously, over a large area, sometimes almost statewide.
River fish seem to be more reliable, possibly less effected by the atmosphere above the water surface, that is a fact.....but what does that tell us ?