[mciboroTamarindo]

Fish kills do occur under certain naturally occurring (or human exacerbated) environmental conditions, and low oxygen is often the cause of death of the fish. Turtles, breathing air, are not affected in the same way by low oxygen in the water. Not sure what the original post meant by "other wildlife". For instance: tadpoles, yes; adult frogs, no, as to low oxygen vulnerability.
Chemicals could be a problem, and can sometimes move "up" the food chain. But eating something that died from a lack or oxygen should not, in and of itself, be fatal to the animal doing the eating.