It's going to be dumped near the shoreline, where sea life is very different from what is supported in the open ocean. If the shoreline is made uninhabitable, the marine life there might not have anywhere else to go.
Near in this case would need to basicly be directly into. Actual desalination plants don’t do this.
Further by parking lot I mean an actual parking lot. Dump it even 1000 feet from the shoreline and you would have trouble detecting the extra salt in the surf.
Shoreline is also highly variable and localized, and effects to the shoreline have staggering effects even if the region affected is small. I'd recommend looking at mangrove forests, coral reefs, and the mouths of rivers.
Further by parking lot I mean an actual parking lot. Dump it even 1000 feet from the shoreline and you would have trouble detecting the extra salt in the surf.