A “dead zone” is a term often used to describe an area of the Chesapeake Bay that does not have enough dissolved oxygen to support life. Each summer, the Bay has a dead zone where fish, crabs and other animals cannot live because there is not enough oxygen in the water.

Global warming has led to sea level rise and increased temperatures in the Chesapeake Bay region and throughout the world. Other possible effects of global warming include habitat loss, increased precipitation and changes in wildlife patterns.

An estuary is a partially enclosed body of water where fresh water from streams and rivers mixes with salt water from the ocean. The Chesapeake Bay is an estuary.

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.

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

Bay grasses are a critical part of the Chesapeake Bay ecosystem because they provide food and habitat for countless species. They also help keep the water clear and healthy by absorbing nutrients, trapping sediments, reducing erosion and adding oxygen.

Plankton form the base of the Chesapeake Bay food web. All fish and shellfish depend on plankton for food during the early part of their lives, and some consume plankton their entire lives.

Poor water clarity is usually caused by a combination of suspended sediments, organic matter and excess nutrients that fuel the growth of water-clouding algae. Weather also plays a large role in water clarity. Rain storms can wash dirt and pollutants into the Bay and cause the water to look muddy. During drier conditions, the water is usually clearer.

Bay grasses are a critical part of the Chesapeake Bay ecosystem. Without bay grasses, underwater creatures such as fish and blue crabs do not have the shelter they need to survive, and migratory waterfowl do not have enough food to eat.

Another important role of bay grasses is to hold bottom sediments in place. If bay grasses are gone, waves can stir up bottom sediments and make the water cloudy. This can affect bay grass beds growing in other areas because they need clear water to survive.

People contribute pollution that can cloud the water and block sunlight from reaching bay grasses. This pollution comes from many sources, including farms, sewage, fertilizer and development.