Nitrogen and phosphorus from industrial farming and chicken factories is washing into the Chesapeake Bay and Gulf of Mexico and over-fertilizing algae. The enormous algae blooms take over fish habitats and consume all the oxygen, making hypoxic zones where no aquatic life can survive.
The primary source of the chemicals is industrial corn farms in the Midwest, and factory chicken farms in the Mid-Atlantic.
Industrial corn farms over-apply fertilizers to their fields. The crops cannot absorb the entire amount, and rains carry the residual chemical from the corn farms into the Mississippi, which deposits them in the Gulf of Mexico, where they feed the algae bloom.
The chicken factories on the Delmarva Peninsula produce a huge amount of nitrogen- and phosphorus-rich manure, too much of which is washed into the Chesapeake Bay.
I think the title of the linked article sums it up nicely. If you, like me, enjoy Maryland crab cakes or Louisiana shrimp gumbo, stop eating factory-farmed chicken and processed corn-containing products!