Text: Once mercury is deposited in lakes, rivers, and oceans, it bioaccumulates in the food chain, resulting in high concentrations in predatory fish.
Entailment: Once mercury finds its way into bodies of water, it bioaccumulates in the food chain, and that results in high concentrations being found in predatory fish.
Contradiction: Mercury is never found in any fish, even when highly concentrated in lakes, oceans and rivers.