Do you have a source? I was not aware and would like to learn more.
"Brine can cut levels of oxygen in seawater near desalination plants"
https://www.reuters.com/article/us-environment-brine-idUSKCN...
We're already assuming far more electricity, so I'm not too concerned about the energy required to pump the brine many miles out, just worried about capital and repair costs.
This is very avoidable. Most extant desalination plants are in the Middle East and subject to relatively little environmental oversight. While desalination will always produce brine, introducing extra chemicals is something that can be solved at the technology level.