Nature up close: Chesapeake Bay

By “Sunday Morning” contributing videographer Judy Lehmberg.

Chesapeake Bay, at about 200 miles long and between 2.8 and 30 miles wide, is the largest bay in the United States. It formed about 35 million years ago when a meteor hit the Earth, but it didn’t become a bay until 10,000 years ago, when the Susquehanna River valley was flooded as sea levels rose during the last ice age. More than 150 rivers and creeks run into the bay, including the Susquehanna, Patuxent, Potomac, Rappahannock and James Rivers.

The Chesapeake Bay is actually an estuary, an area where fresh and salt water meet. Estuaries are extremely productive and therefore important habitats, since they act as nurseries for many saltwater-dwelling organisms, including oysters, shrimp, crabs, and many fish species.

Because of the large human population around Chesapeake Bay, tons of sewage and other pollutants are dumped into it. Many of these pollutants, especially sewage, contain nitrates and phosphates which stimulate algal blooms. As the algae die, bacteria feed on them. Most bacteria species absorb oxygen from the water, so as the bacteria population increases, the oxygen levels in the water drops, sometimes to the point where life cannot be sustained. This causes “dead zones,” where fish, crabs, oysters and other organisms die. In fact, in the 1970s the Chesapeake Bay was one of the first places on Earth where a marine dead zone ever occurred.

The pollutants in Chesapeake Bay and the resulting dead zones are the main reason (along with over-harvesting) that a once-thriving oyster fishery that produced from 14 to 20 million bushels of oysters in the 1880s now produces less than one percent of its former harvest. Chesapeake Bay oysters used to filter all of the bay’s water and remove excess nutrients in the algae they captured within three to four days. Now it takes them about a year, exacerbating the results of human-caused pollution.

Much time and money have gone into trying to improve the bay’s water quality. The state of Maryland has spent more than $100 million to restore Chesapeake Bay, but conditions still continue to worsen. Twenty years ago the bay supported more than 6,000 oystermen; that number has dropped to less than 500 today. There are still ongoing efforts to improve water quality by federal, state and local governments, as well as the Chesapeake Bay Program and the Chesapeake Bay Foundation, along with other environmental groups. There has been some improvement in the last 30 years. The amount of nitrogen has decreased from highs of 350 million pounds per year in 1985, to about 250 million pounds per year in 2015.

One of the bay’s more prominent inhabitants is the great blue heron, the largest heron in North America, which can be found along rivers, lakes, estuaries, marshes and coastlines across the continent. Their diet consists primarily of fish, but they will eat anything they can catch, including snakes, rats, salamanders, gophers and crabs. They normally feed by walking slowly in shallow water. When they see a prey species, they freeze until the prey moves closer. Then they strike rapidly, grabbing or impaling their dinner with their bill.

Great blue herons nest colonially in bird rookeries, where they build stick nests -- usually in trees, although they will use buoys, bushes, artificial platforms, and even the ground. Most rookeries are in areas difficult to access, such as islands, and can contain anywhere from five to five hundred nests.

Great blue herons were one of the bird species whose feathers were used over a century ago to make women’s hats. During that time, their population declined. Around the year 1900 the National Audubon Society was formed primarily to raise awareness to declining bird populations. As a result, the use of bird feathers declined in the millinery trade, and bird populations increased.

Another important species in the Chesapeake Bay is the striped bass, designated the official fish of the State of Maryland. Its numbers have recovered from the lows of the 1980s due to better management, allowing fishing to resume after a moratorium, and now attracting large numbers of sports fishers to the bay.

The bay, which continues to attract boating enthusiasts, enjoying the waters in all manner of watercraft (from sailing yachts and paddle boards), is a welcome asset to the densely-populated East Coast.

Judy Lehmberg is a former college biology teacher who now shoots nature videos.

For more info:

• Judy Lehmberg (Official site)
• Judy Lehmberg’s YouTube Channel

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