What is the effect of air and water pollution caused by mining on a food chain in a habitat?

Heavy metals build up in concentration as you move up in the food chain. The fish ingest the heavy metals, but it doesn't cause them to die because it is only a small amount of heavy metals. When the crocodiles eat the fish, they eat a lot of fish, each containing a little heavy metal. This adds up to a lot of heavy metals in the crocodile, eventually poisoning and killing it.