Poor water clarity does not allow sunlight to reach bay grasses growing at the bottom of shallow waters. These underwater grasses provide food and habitat for many animals, including fish, crabs and birds. Without bay grasses, these animals may not have the food and habitat they need to survive.

Water clarity improves when less pollution washes off the land and into streams, rivers and the Chesapeake Bay. You can help improve water clarity by fertilizing your lawn less and planting a buffer of trees and shrubs around your property. Also, when boating, make sure you obey wake laws so you don’t stir up bottom sediments in shallow areas.

Scientists use a device called a Secchi disc to measure water clarity. A Secchi disc is a simple, black-and-white circle attached to a rope. The Secchi disc is lowered into the water until it disappears, then pulled up until it can just barely be seen. Scientists note the water line on the rope and measure the distance between the Secchi disc and the water line. The measurement is the water’s clarity: the depth that sunlight is able to penetrate through the water.

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.

Bay grasses usually die because the water is too cloudy for sunlight to reach them. Cloudy water is most often caused by pollution from excess nutrients and sediment. Extreme temperatures and certain human activities can also cause bay grasses to die.

Just like any other plant, bay grasses go through photosynthesis, so they need sunlight to grow. This means that the water that bay grasses grow in must be clear enough for the sun’s rays to pass through.