Oyster Decline
Oysters are sea animals that have soft bodies and hard shells. An oyster is able to slightly open to let in water. Water brings in oxygen. The oyster feeds on bits of food that are brought in by the water. Two or three gallons of water may pass through the oyster in an hour.
Oysters filter water. In the Chesapeake Bay, oysters are important. Watermen harvest and sell them. They also keep the water in the Chesapeake Bay clean. Oysters help keep the water clean and clear for underwater grasses and other organisms. One oyster can filter more than 50 gallons of water in a single day.
A female oyster produces millions of eggs. But not all of them grow up. Some of the don't survive because the water is polluted. An egg hatches into a swimming larva. After two weeks of floating, the larva attaches itself to an object. Often the young oyster lands on an oyster bed. So oysters grow on top of oysters, forming an underwater structure. This underwater structure helps shelter small fish, crabs, and more. This underwater structure is important.
People eat oysters. So, many oysters are taken out of the Bay for food. Over the years too many have been taken out. This is called over-harvesting. It means there are not enough oysters to filter the water. This means that underwater plants won't get enough sunlight. This means there aren't enough oysters to make underwater structures that help other organisms. If people would be more careful about how many oysters they harvest, maybe there would be enough oysters.
MSX and Dermo are oyster diseases. Oysters catch them most when the water is warm. The earth's waters are getting warmer due to climate change (global warming). So, more oysters are dying from MSX and Dermo. It means there are not enough oysters to filter the water. This means that underwater plants won't get enough sunlight. This means there aren't enough oysters to make underwater structures that help other organisms. Scientists in Virginia are working to grow oysters that don't get the diseases.
When too much fertilizer gets into the water, the algae grows too fast. At night, the algae uses up too much oxygen. This makes the oyster larvae die. So, again, there aren't enough oysters. Governments can make rules about how farmers use fertilizer and how they store animal waste. This could cut down the amount of fertilizer getting in the Bay.
When people build houses near streams and when there is a lot of concrete instead of grass, dirt washes into the waterways. The bits of dirt are called sediment. When the sediment washes into the Bay, it kills some of the oysters. So, there aren't enough oysters to clean the water and to make underwater structures. When people plant grass, trees, and gardens, less sediment washes into the Bay.