The rivers of North America were molded by the Pleistocene glaciers and reinforced by their meltwaters. By the end of the Epoch, the massive Susquehanna River drained a large area of the eastern U.S.; with headwaters in south-central New York and northern Pennsyl-vania, this river and its numerous tributaries emptied into the ocean along the mid Atlantic Coast.
As the final Ice Sheets retreated into Canada, sea levels began to rise and, by 10,000 years ago, ocean waters had spead across the mouth of the Susquehanna. As the climate continued to warm and the glaciers continued to melt, the sea moved up the River's broad valley, creating Chesapeake Bay; the Bay stabilized at its current size about 3000 years ago, becoming the largest estuary in our country. Two hundred miles long and up to 35 miles wide, the Chesapeake has a shoreline of almost 11,700 miles and is home to more than 3600 plant and animal species; renowned for its blue crab, the Bay is inhabited by 350 species of fish.
Drawing from a watershed of 64,000 square miles, which covers parts of six States, the health of the Chesapeake has long been threatened by pollution. Industrial waste, agricultural runoff and sewage have all played a role, adding both toxins and exces-sive "nutrients" to the Bay waters; the latter trigger deadly algal blooms and foster outbreaks of Pfiesteria piscicida, a parasitic dinoflagellate that feeds directly on fish. Efforts to restore the health of this magnificent ecosystem have been spearheaded by the Chesapeake Bay Foundation since 1967; a link to their website is listed in the right column of this blog.
