The Chesapeake Bay’s salinity gradually decreases as you move north and increases as you move south. Salinity also varies widely from season to season and from year to year, depending on the amount of fresh water flowing from the Bay’s rivers.

Scientists generally agree that the Bay’s creatures need dissolved oxygen concentrations of 5.0 mg/L or more to live and thrive. However, the amount of oxygen an animal needs varies depending on how large or complex the animal is and where it lives.

A subwatershed is a small watershed contained within the larger Chesapeake Bay watershed. Each of the streams, creeks and rivers in the Bay watershed has its own watershed. For example, the Potomac River watershed is a subwatershed of the Chesapeake Bay watershed.

Altogether, more than 100,000 streams, creeks and rivers thread through the Chesapeake Bay watershed.

The Chesapeake Bay watershed spans six states and the District of Columbia. Within this watershed are several large cities, including Cooperstown, N.Y.; Harrisburg, Pa.; Baltimore, Md.; Washington, D.C.; and Norfolk, Richmond and Charlottesville, Va.

Blue crabs do not eat more to prepare to winter hibernation (like, for instance, a black bear might). While blue crabs are heavier in the fall, this is because the crabs have gone through several molts and grown in size.

The Choptank, James, Nanticoke, Patapsco, Patuxent, Potomac, Rappahannock, Susquehanna and York rivers are just a few of the many rivers that flow into the Chesapeake Bay. These rivers are fed by hundreds of thousands of streams and creeks that flow throughout the Chesapeake Bay watershed.

An oyster reef is an example of a benthic community.

Shad are anadromous, which means they migrate from the ocean to spawn in freshwater rivers and streams.

Epifauna and infauna are both types benthic, or bottom-dwelling, organisms. Epifauna live attached to a surface and infauna live within the Bay’s bottom sediments.