I wonder if the salt extracted during desalination could be dumped on top of underwater salt domes? Salt domes are one of the sources of the salt in the ocean [1].

The idea is that our salt would cover part of the salt dome, preventing that part of the salt dome from providing salt to the water. Instead, the salt that would have come from that part of the dome comes from our salt.

[1] https://oceanservice.noaa.gov/facts/whysalty.html