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Summit to the Sea:
information for k-12 education what is an estuary? | habitat | climate | geology |
hydrology Animals and Plants: Common Atlantic Oyster (Crassotrea virginica) An oyster is a soft-bodied animal that lives within a hard shell that it builds around itself through secretions. Oysters live underwater in large colonies called "beds" that are attached to hard surfaces on the river bottom. They feed by filtering algae, small pieces of detritus, and other nutrients from the water. Filtering is an important activity because it helps improve the water quality of the estuary. Being a filter feeder, however, can create problems. Because oysters ingest everything that is suspended in the water, they sometimes ingest dangerous disease organisms and pollutants that are carried by rivers into the ocean. Clean rivers are important so people do not get sick from eating raw oysters. Occasionally, a small particle will get embedded in the flesh of an oyster. When this happens, oysters build a protective wall around the particle. This is how a pearl is formed! It is rare, however, for pearls of great value to be found in oysters in the waters around North America. Oysters have an unusual life cycle. They are born "male" and produce sperm in the first year of life. Afterwards, they become "female" and produce eggs. When the water gets warm in summertime, males and females release the sperm and eggs at the same time. The eggs are fertilized in the water. The young oysters float for a few weeks, before settling to the bottom and attaching to another oyster shell. Oyster populations have declined tremendously in the last 100 years due to over-harvesting and habitat destruction. |
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