Big Performance Hit With Particles on iOS

I have a scene with one particle effect, a waterfall, with an emission rate of 120. In the Editor on MacOS, whether or not the particles are in frame or not has no effect on frame rate. However on iOS, whenever the camera moves to a view where the particles are visible, the frame rate drops significantly. It's very obvious because as soon as the particles come into view, the camera's movement gets slow and jerky. I assume it will be even worse on older iPads.

I've used particles in iOS apps...

Big Performance Hit With Particles on iOS