Biscayne Bay


Biscayne Bay is a lagoon with characteristics of an estuary located on the Atlantic coast of South Florida. The northern end of the lagoon is surrounded by the densely developed heart of the Miami metropolitan area while the southern end is largely undeveloped with a large portion of the lagoon included in Biscayne National Park.
The part of the lagoon that is traditionally called "Biscayne Bay" is approximately long and up to wide, with a surface area of. Various definitions may include Dumfoundling Bay, Card Sound, and Barnes Sound in a larger "Biscayne Bay", which is long with a surface area of about.

Etymology

related in the 16th century that a sailor from the Bay of Biscay called the Viscayno or Biscayno had lived on the lower east coast of Florida for a while after being shipwrecked, and a 17th-century map shows a Cayo de Biscainhos, the probable origin of the name for Key Biscayne. The lagoon was known as "Key Biscayne Bay" in the 19th century, finally shrinking to "Biscayne Bay" late in the 19th century.

Other names

The lagoon has been known by several names. Juan Ponce de León called it Chequescha in 1513, and Pedro Menéndez de Avilés called it Tequesta in 1565. Those names are variant spellings of "Tequesta", the name of the people who lived around the lagoon at the time. The British, during their occupation of Florida, called the lagoon "Cape River", "Dartmouth Sound", and "Sandwich gulph".

Geography

Biscayne Bay is a semi- or subtropical lagoon extending most of the length of Miami-Dade County, from North Miami Beach to the upper Florida Keys. Biscayne Bay, in the strictest sense, extends from a point between North Miami Beach and Sunny Isles Beach south to the Arsenicker Keys and the Cutter Bank just to the east of those islands. Many discussions about the lagoon include Dumfoundling Bay, a small lagoon just north of North Miami Beach, as part of Biscayne Bay, and include Card Sound and Barnes Sound, in southern Miami-Dade County adjacent to Key Largo, as either part of a system of connected lagoons including Biscayne Bay, or as part of Biscayne Bay itself. The lagoon is bordered on its west by the mainland of Florida, and is separated from the Atlantic Ocean to the east by a string of barrier islands in the northern part of the lagoon, a large shoal in the central section, and the northernmost of the Florida Keys in the south. The lagoon is about long from Dumfoundling Bay to Card Sound, and another to Jewfish Creek, if Card Sound and Barnes Sound are included in the lagoon. The lagoon is across at its widest point. The lagoon, from Dumfoundling Bay to the Arsenicker Keys, has a surface area of about. The larger lagoon, including Card Sound and Barnes Sound, has a surface area of about. It has an average depth of and, except where channels have been dredged, a maximum depth of.
The eastern rim of the lagoon is based on an ancient coral reef which existed along the southeastern edge of the Florida Platform about 100,000 years ago. The ensuing Wisconsin glaciation lowered sea levels, leaving the reef above water. The dead reef became fossilized, forming the Key Largo Limestone. Key Largo Limestone underlies the Eastern edge of the barrier islands and the shoals along the northern and middle part of the lagoon. It makes a brief appearance at Soldier Key, in the middle of the [|Safety Valve], and rises above sea level to the south to form the upper Florida Keys.
The western side of the bay has characteristics of an estuary, with 16 waterways, the largest of which is the Miami River, flowing into it. All of the waterways have saltwater intrusion control structures, which restrict the flow of saltwater inland, and regulate the flow of fresh water into the lagoon. Some fresh water enters the lagoon as groundwater flow from the Biscayne Aquifer. All of the bedrock under the lagoon west of the ancient reef, and the adjacent mainland, consists of Miami Limestone, an oolitic limestone that formed in a lagoon behind the ancient reef that became the Key Largo limestone, and is the same age as the Key Largo limestone. The limestone bottom of the lagoon is overlain by of sand, carbonate mud, and coral rubble sediments.
For purposes of discussion and analysis, Biscayne Bay is often divided into three sections: North Bay, Central Bay, and South Bay.

North Bay

The North Bay of Biscayne Bay principally lies between Miami Beach on a barrier island and Miami on the mainland, from Dumfoundling Bay on the north to the Rickenbacker Causeway to the south. Other municipalities on the western shore of the lagoon include Aventura, North Miami Beach, North Miami, and Miami Shores. Municipalities bordering the lagoon on the barrier islands north of Miami Beach include Sunny Isles Beach, Bal Harbour, Bay Harbor Islands, Surfside, and Indian Creek Village. North Bay Village is located on two artificial islands in the middle of the lagoon. North Bay is the part of the lagoon that has been most modified by human works, including channels and other dredged areas, and spoil banks and artificial islands created with material dredged from channels. More than 40% of the area of North Bay had either been dredged or filled to form artificial islands, and more than half of the remaining lagoon bottom is barren. Coastal wetlands have been almost eliminated in North Bay. Turbidity is high in North Bay due to erosion from spoil islands and banks, and the lack of vegetation on the lagoon bottom. The spoil islands host large quantities of invasive plant species.
North Bay is separated from the Atlantic Ocean by barrier islands. Freshwater sources flowing into North Bay include Oleta River, Arch Creek, Biscayne Canal, Little River and Miami River. Tidal flow between North Bay and the ocean is through Baker's Haulover Inlet, Government Cut, and Norris Cut.
Northeast 163rd Street, or Sunny Isles Boulevard, connects North Miami Beach and Sunny Isles Beach across the section of the Intracoastal Waterway running between Dumfoundling Bay and Biscayne Bay proper. Five causeways cross North Bay between Northeast 163rd Street and the Rickenbacker Causeway, including:
More than 20 islands in North Bay north from the MacArthur Causeway have been created, in whole or in part, with material dredged from the lagoon bottom. Most of the islands, such as the Venetian Islands, are residential. Brickell Key, another residential island, is just south of the mouth of the Miami River. Dodge Island, across the main ship channel to the south of the MacArthur Causeway, was enlarged in the 1960s when the Port of Miami was moved there from the mainland north of Bayfront Park. The Miami Marine Stadium was built on the north side of the Rickenbacker Causeway extending from the east side of Virginia Key in the early 1960s. There are also many undeveloped spoil islands in North Bay, such as Sandspur Island and the Picnic Islands.

Central Bay

Central Bay is the largest part of the bay. It extends from the Rickenbacker Causeway and Virginia Key on the north to the Featherbed Bank, which runs across the bay from Black Point to Boca Chita Key. It is separated from the Atlantic Ocean by Key Biscayne, the Safety Valve, and the Ragged Keys, the northernmost of the Florida Keys. It is bordered on the western shore by the municipalities of Miami, Coral Gables, Palmetto Bay, Cutler Bay, and a portion of unincorporated Miami-Dade County. Key Biscayne occupies the middle third of the island on the eastern side of Central Bay.
Fresh water sources for Central Bay include the Coral Gables Waterway and Snapper Creek. Tidal flow between Central Bay and the ocean is through Bear Cut between Virginia Key and Key Biscayne and across the Safety Valve. The development that has so transformed North Bay has spread over much of the northern shores of Central Bay. Miami Seaquarium and the University of Miami's Rosenstiel School of Marine, Atmospheric, and Earth Science are located on the southern end of Virginia Key, the only part of that island bordering on Central Bay. Grove Isle, near the Miami neighborhood of Coconut Grove, is an artificial island in Central Bay. The large marina at Dinner Key is also in Coconut Grove. Central Bay has been adversely affected primarily by bulkheading, urban runoff discharged by canals, and the loss of natural fresh water flow.

South Bay

South Bay is nearly as large as Central Bay, and is defined as extending from the Featherbed Bank to the Arsenicker Keys, or to Cutter Bank, which is to the east of the Arsenicker Keys. It is separated from the ocean by the northernmost of the Florida Keys, from Boca Chita Key to Old Rhodes Key. Fresh water sources for South Bay include Black Creek, Goulds Canal, North Canal, Florida City Canal, and Model Land Canal. Tidal exchange with the ocean occurs through Sands Cut, Caesar's Creek and Broad Creek. Boca Chita Key, Elliott Key, and Old Rhodes Key were all enlarged by dredging in the first half of the 20th century. Boca Chita Key was the site of some construction in the early 20th century. Mark C. Honeywell bought the key in 1937, and built a large retreat on the island, including a tall faux lighthouse. South Bay is the least affected by human activities, although it also suffers from the loss of natural fresh water flow. The Turkey Point Nuclear Generating Station is a significant presence on the mainland shore.

Card Sound and Barnes Sound

Card Sound is an extension of Biscayne Bay to the south of South Bay. Little Card Sound is the next south, separated from Card Sound by Card Bank. The causeway of the Card Sound Bridge now separates Barnes Sound to the south of Little Card Sound. Manatee Bay is to the west of Barnes Sound. Card Sound and Barnes Sound are bounded on the east by Key Largo. South Biscayne Bay is sometimes defined as including Card Sound and Barnes Sound. Barnes Sound is connected to Florida Bay through a few small channels.
Manatee Bay is partially separated from Barnes Sound by Short Key and Main Key. In 1994, it was described as having particularly undisturbed habitat for a location in the Florida Keys. Due to its distance from the open ocean and the restrictive passages between other components of Biscayne Bay, Manatee Bay experiences low tidal exchange, while the C-197 canal allows fresh water from the C-111 canal to flow into Manatee Bay. Salinity levels in Manatee Bay range from 14 parts-per-thousand to 45 ppt. In July 2023, the bay was in the news when a bouy there recorded a water temperature of.