"The other way is when toxic species of algae bloom"
and other versions of this kind of thing, such as new forms of superbugs proliferating for exmaple, courtesy "Corexit", if anyone still remembers... I don't think we have any idea what's actually going on under the surface of waters. (Or in the sky)
Sadly, the big mystery (to me) is that there aren't more birds dying, (and more dead fish floating), considering the many possible stresses that could cause "internal injuries" such as some have exhibited.