I dont think even the scientists know about salt turnover and replenishment. I think you'd be looking at small amounts at any one time. I did look it up with my research but what's out there is very minimal to be perfectly honest! My guess is that the more active a carp is, means the more salt it needs?
Research out there suggest that things like caddisfly, mayfly, etc larvaes are not tolerant of salinity at all whereas shrimps, snails, etc. actually can tolerate it. This study actually found that at low salinity levels and at over 8ppt all freshwater inverts sampled had higher mortalities however at levels between 1.5 - 2.2ppt there was no more moralities than at freshwater. Again the tests are done with salt water, not salt laid bare on the ground. I am with you and think that a large deposit of salt crystals laid direct on the lake bed will basically burn it and create a dead zone.