I'm not sure if this comment is sarcasm or not? But it would get saltier as time goes on. Seawater goes in, water evaporates out. There is more salt at that point . But that is fine. Hypersaline lakes are everywhere. As long as they are kept wet it isn't a big deal.
The lake is currently more saline than seawater, so adding more seawater would dilute it. True, over time it would get saltier as the water in the seawater evaporates out. But then just add more seawater to dilute more haha...