History and Ecology

In 1513 explorer Juan Ponce de Leon sailed south from St. Augustine and found a “bright nameless great bay…and fresh springs in the rocks.” The bright great bay came to be called Biscayne Bay – named, many believe, after the Bay of Biscay north of Spain and west of France. Other theories hold that the bay was named after one of several Spaniards called El Biscaino or El Viscaino, including one gentleman who served as Keeper of the Swans at the Spanish court before settling on one of the islands in the bay.

Whatever its name’s origins, Biscayne Bay is and always has been a bright, great bay, attracting countless explorers, adventurers, tourists and new residents. Not only is it a source for food, transportation and commerce, it also offers boundless opportunities for recreation, education and spiritual nourishment to those who visit and live near it.

Biscayne Bay is the largest estuary on the coast of southeast Florida and is contiguous with the southern Florida Everglades and Florida Bay. It encompasses a marine ecosystem that totals approximately 428 square miles. Its drainage area is 938 square miles, of which 350 are freshwater and coastal wetlands in Miami-Dade, Broward, and Monroe counties. It is home to Biscayne National Park, the largest marine park in the U.S. national park system, and to Oleta River State Park, Bill Baggs Cape Florida State Park, the Biscayne Bay Aquatic Preserve, Barnacle State Historic Site, and numerous local parks.

The bay is also the location of the Port of Miami, one of the largest passenger and commercial ports in the world.

The Miami River, one of the largest tributaries to the bay, is a major port in its own right – Florida’s fifth largest port and the primary service area of international trade to the Caribbean. The Miami River is also home to some of Miami’s most historic and interesting neighborhoods.

Biscayne Bay is many things to many people. It supports important sport and commercial fisheries. It is a source of environmental education and recreation. Its waters and shores are favored for sailing, boating, snorkeling, swimming, bay viewing and sunbathing. More importantly, the bay is ecologically significant, supporting and nurturing an enormous variety of wildlife.

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Biscayne Bay is part of a large south Florida ecosystem and relies on water that flows directly from the Everglades, through the watershed and into the bay. The recent passage by the United States Congress of the Comprehensive Everglades Restoration Plan, and the planning and implementation of other regional land and water management efforts, have focused attention and resources on problems facing the Everglades and the South Florida ecosystem. These efforts are critically important to the future of our region.

Five thousand years ago, there was no Biscayne Bay. Sea level was about 20 feet lower than today, so the places we call Miami and Miami Beach formed one continuous expanse of land. The bay formed between 5,000 and 2,400 years ago as sea level rose to fill a depression in the limestone. During and since that time, sandy barrier islands, banks of sand and mud, and coastal wetland swamp and marsh deposits have grown and evolved to give the bay its present form.

Especially critical was the relatively slow rise in sea level during the past 2,400 years – less than two inches per century. During that time, shallow sand and mud banks formed along the eastern margins of the bay, partitioning the bay into natural divisions.

The natural, unaltered Biscayne Bay was a magnificent shallow subtropical estuary characterized by clear water and dominated by diverse and productive bottom communities of sea grasses, corals and sponges. Mangrove wetlands rimmed the bay margin with limestone reaching the coast in only a few places. The bay was once noted for freshwater springs that were visited by ships seeking drinking water. The clear waters were maintained by the sediment filtering and trapping activity of the bottom (or “benthic”) communities of plants and animals and by coastal swamps. The benthic communities, in turn, were able to flourish because of the clear waters.

Landward, freshwater sheet flow, natural tributaries and shallow depressions that cut through the coastal ridge (known as transverse glades), fed water from the Everglades to the margins of the bay. Freshwater also entered the bay through springs in the limestone. The seaward margin of the bay was a series of sandy barrier islands to the north, channel-dissected shallow marine sand and mud banks along the central portion, and islands of coral limestone to the south.

The entire South Florida coastal ocean ecosystem, including Biscayne Bay, has undergone major environmental change due to a century of huge regional population growth that has accelerated development, pollution and habitat loss. When Miami began to grow at the beginning of the 20th century, Biscayne Bay became the site of one of its most important population centers.

By 1917 four canals sliced through the Everglades from Lake Okeechobee to the Atlantic Ocean, including the channelization of the Miami River. Later, Baker’s Haulover was constructed and other ocean inlets across Biscayne Bay’s barrier islands were stabilized. Alterations continued throughout this period, culminating with significant changes that resulted from the Central and Southern Florida Project for Flood Control, beginning in 1948. This project dramatically lowered freshwater levels in the Biscayne Aquifer by approximately four feet by cutting drainage canals to drain surface and groundwater to prevent intermittent coastal flooding and expand agricultural production.

A century of modifications to its hydrology has changed Biscayne Bay from a subtropical estuary fed by coastal rivers, tidal creeks, and groundwater seepage, including submarine springs, to a pulsed system that alternates between marine conditions and extreme low salinity conditions near canal discharge sites. Fresh water now enters the bay as an intense point source rather than as distributed input over time and space.

Today, Biscayne Bay is an estuarine lagoon with salinity, circulation and water quality that vary, dependent on freshwater flow, wind driven circulation and ocean exchange in each of three distinct areas.