Estuaries: Chesapeake Bay

By: Allen Kim, Harrison Kim, and Yeongmin Ko11/6/13

What is an Estuary?

An estuary is a partially enclosed body of water formed where freshwater from rivers and streams flows into the ocean, mixing with the salty sea water. Estuaries and the lands surrounding them are places of transition from land to sea, and from fresh to salt water. Although influenced by the tides, estuaries are protected from the full force of ocean waves, winds, and storms by the reefs, barrier islands, or fingers of land, mud, or sand that define an estuary's seaward boundary.

Estuary Zones

Estuary Locations

Species

Estuaries can include oyster reefs, coral reefs, rocky shores, submerged aquatic vegetation, marshes, and mangroves. There are also different animals that live in each of these different habitats. Fish, shellfish, and migratory birds are just a few of the animals that can live in an estuary.

Today we will be specializing in Chesapeake Bay

Biodiversity/Food Web

Light Penetration

The increased "muddiness" of estuarine waters reduces water clarity and has a number of adverse effects on estuarine and coastal ecosystems. These include limiting the feeding options of predators like snapper and seabirds that rely on their eyesight to find food. Reduced light penetration also adversely impacts the growth of submerged aquatic plants

Light Penetration Example

Estuary Temperature

There is no average temperature in Estuaries. The temperature can vary greatly depending on the depth of the water, the location and the season. Chesapeake Bay

Salinity/Oxygen

Under laboratory conditions, pure water contains only oxygen and hydrogen atoms, but in the real world, many substances are often dissolved in water, like salt. Salinity is the concentration of salt in water, usually measured in parts per thousand (ppt). The salinity of seawater in the open ocean is remarkably constant at about 35 ppt. Salinity in an estuary varies according to one's location in the estuary, the daily tides, and the volume of fresh water flowing into the estuary.

Salinity also affects chemical conditions within the estuary, particularly levels of dissolved oxygen in the water. The amount of oxygen that can dissolve in water, or solubility, decreases as salinity increases. The solubility of oxygen in seawater is about 20 percent less than it is in fresh water at the same temperature.

Chesapeake Bay

Chesapeake Bay is located in-between Maryland/Virginia and Delaware

Chesapeake Bay is the largest estuary in the United States

The Bay and its rivers, wetlands and forests provide homes, food and protection for diverse groups of animals and plants. Fish of all types and sizes either live in the Bay and its tributaries year-round or visit its waters as they migrate along the East Coast.

Location

Doomsday Situation

Chesapeake Bay used to support many crabs, oysters, and watermen, but is now becoming empty and slowly losing biodiversity from over-harvesting and another issue.

In the 1970s, the Chesapeake Bay was discovered to contain one of the planet's first identified marine dead zones, where hypoxic waters were so depleted of oxygen that they were unable to support life, resulting in massive fish kills. Today the bay's dead zones are estimated to kill 75,000 tons of bottom-dwelling clams and worms each year, weakening the base of the estuary's food chain and robbing the blue crab in particular of a primary food source

Dead Zone