Is there a way to know how much to care? We do all sorts of things that displace species, so having some way of contextualizing and weighting the harm against the benefit would be helpful.
Seems to me it would initially be a narrowly scoped to the immediate outflow. As the brine dissipates I assume it will be normalized by the rest of the ocean as it's diluted.
However, as with all human endeavours, scaling up will scale up the problem. And we won't pay attention to that until it's a huge issue.
The Salton Sea in its current iteration was created by the failure of an irrigation canal. Before that there was no Salton Sea as we know it or tourist area.
This is necessarily a value judgment, isn't it? There are tools like lifecycle analyses and environmental impact reports and threatened species lists that can help estimate/enumerate impacts. But ultimately how much to care is a personal question, and people are going to disagree over whether some small fish or rare owl or fluffy panda is worth more or less than someone's job or a local industry or just some other charismatic species.
Species will always come and go, and they're going to die off faster than we can protect them, sadly. We only get to decide which ones to prioritize, at different personal, local, national, global levels etc.
I would start by wanting to know about the impact and benefit relative to other activities which we already do. Like how's it compare to various flavors of farming?
There's a database for California Environmental Quality Act reports, I think (Environmental Impact Reports? Statements? One is federal and the other is state, can't remember which is which). That probably have similar solar farms you can look at. Not sure about huge desal projects. Maybe overseas?
I'll try to find some analyses this weekend if I can.
However, as with all human endeavours, scaling up will scale up the problem. And we won't pay attention to that until it's a huge issue.