Text: They include algal blooms that are potentially hazardous to human health, low dissolved oxygen concentrations, declines in the health of fish and shellfish populations, loss of seagrass beds and coral reefs, and ecological changes in food webs.
Entailment: Those algal blooms represent a potential threat to human well-being.
Contradiction: Marine life is completely unaffected, as both fish and shellfish populations are growing exponentially.