Description: This dataset contains areas in the Chesapeake Bay with low amounts of oxygen. Excessive nitrogen and phosphorus pollution from human activities cause "dead zones"—or areas with low amounts of oxygen in the Bay. With little or no oxygen, fish, crabs, oysters, and other aquatic animals literally suffocate. Further, an excess in these nutrients also fuels the growth of dense algae blooms that block sunlight that underwater grasses need to grow in order to continue providing food for waterfowl and shelter for blue crabs and juvenile fish.