Chesapeake Bay - A Global Ecoregion


Healthy mix of freshwater and marine organisms

Horseshoe, Sanibel Island, Florida, USA.

Snapshot: Ecoregion 202

Size:
N/A

Habitat type:
Temperate Shelf and Seas

Geographic Location: Eastern North America

Conservation Status:
Vulnerable

Quiz Time!

Is it true that the Chesapeake Bay once had abundant oyster populations?

Answer:
When Europeans first arrived in the Chesapeake Bay nearly 400 years ago, oysters were so plentiful that oyster reefs posed navigation problems! Earlier, the oysters could have filtered all the water clean in the Chesapeake Bay in just a few days, but today so few oysters remain that it takes months for today's populations to filter that much water.

About the Area
The Chesapeake and Delaware Bay complex is one of the largest estuaries on Earth. Large rivers feed the ecoregion, including the Susquehanna, James, Potomac, Patuxent, and Chester, each bringing nutrients that help make this bay one of the most productive areas on earth.

It contains diverse habitats, each perfectly suited to different plants and animals, making it commercially vital for fisheries, particularly for blue crabs and historically for oysters.

Local Species
Characteristic of this ecoregion is the Atlantic blue crab (Callinectes sapidus), American oyster (Crassostrea virginica), Horseshoe crab (Ilynassa polyphemus), Soft-shelled clam (Mya arenaria), Hard clam (Mercenaria mercenaria), Marsh periwinkle (Littorina irrorata), and Northern diamondback terrapin (Malaclemys terrapin).

Anadromous fish species (those that migrate from freshwater to the ocean and back to freshwater) include American shad (Alosa sapidissima), Atlantic herring (Clupea harengus), Alewife (Alosa pseudoharengus), and Striped bass (Morone saxatilis). Other fish species include the Oyster toadfish (Opsanus tau), Sheepshead minnow (Cyprinodon variegatus), and Marsh killifish (Fundulus confluentes).

Among the many bird species are Clapper rail (Rallus longirostris), Tundra swan (Cygnus columbianus), Atlantic brant (Branta bernicla), Wood duck (Aix sponsa), Hooded merganser (Lophodytes cucullatus), Oldsquaw (Clangula hyemalis), Bufflehead (Bucephala albeola), Green-backed heron (Butorides virescens), Black-crowned night heron (Nycticorax nycticorax), and numerous shorebirds.

Threats
High levels of urban development and pollution from agriculture introduce contaminants and cause eutrophication and anoxic conditions (lack of oxygen) in the bay. Introduced species like the Rapa whelk (a large snail originally from Asia) threaten native species, and toxic algal blooms can harm fish and people. Overfishing and habitat destruction represent other disturbance factors.

Resources
• NationalGeographic.com


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