Of local, regional, national and international importance, Biscayne Bay is a sub-tropical shallow estuary that is home to two state aquatic preserves, a critical wildlife area, a national park and national marine sanctuary.
Due to its unique habitat, Biscayne Bay is designated an aquatic park and conservation area by Miami-Dade County. Cradled by the mainland to the west and barrier islands to the east, its 428 square miles continue to be a source of sustenance and economic vitality, while also providing for countless recreational opportunities enjoyed by residents and visitors alike. Its spectacular natural beauty is widely recognized and enjoyed by nearly 2.8 million residents and millions of visitors every year.
Similar to many other ecosystems in Florida, Biscayne Bay has undergone a significant change over time due to dredging and filling activities, construction of major drainage canals, land development, reduction of natural mangrove shorelines, tourism and commerce. Since 1890, over 20 percent of the North Bay area was filled and replaced by 30 islands and six causeways. The Miami River and North Bay canals were dredged in order to improve navigation.
Early recognition of the impact human-induced changes on the Biscayne Bay environment led to the establishment of the Biscayne Bay Aquatic Preserve by the State of Florida and Miami-Dade County government declared the Bay an "Aquatic Park" in 1974.
In 1981, the Biscayne Bay Management Committee was created to counteract the substantial loss of Bay resources. The Committee’s goal was to oversee restoration projects that provided aesthetic, recreational and ecological value to the Bay.
The restoration plan succeeded in returning the Bay to a more ecologically stable condition. The Division of Environmental Resources Management is responsible for the enhancement, restoration and protection of Biscayne Bay.
Historically, Miami-Dade County has used a combination of regulation, environmental monitoring and habitat restoration projects to help protect and preserve Biscayne Bay. This includes programs such as the County’s artificial reef program, surface water quality monitoring program, and Biscayne Bay restoration and enhancement program.
This approach has now been expanded to promote greater awareness regarding the health of Biscayne Bay through the hiring of a Chief Bay Officer, and through implementing the recommendations from the Biscayne Bay Task Force Report. With its governmental, academic and community partners, the County remains committed to improving the health of this fragile yet resilient ecosystem for current and future generations.
Biscayne Bay was historically a highly productive subtropical estuary fueled by large volumes of freshwater from the Everglades. This clean freshwater was the bay’s lifeblood, mixing with ocean water to create low salinities on the western side of the bay that promoted extensive growth of mangroves, oysters and seagrass beds.
Historically, Biscayne Bay received freshwater along its shoreline as water traveled south and east, mixing with water from the Atlantic Ocean. Today, natural freshwater flows have been replaced by pulsed, point source discharges from dredged canals, intended to offer flood protection and move water away from inland areas.
Canals can intercept groundwater, and more than half of the freshwater received by the Bay enters via the northernmost canals where the most notable seagrass losses have occurred. Runoff from the land, impacted by the activities taking place on land, degrade the quality of the water entering canals and Biscayne Bay. The timing, source and quality of freshwater delivered to the Bay can and has influenced the health, diversity and distribution of the flora and fauna that comprise the Biscayne Bay ecosystem.
While there may be a general awareness in South Florida of the importance of the Biscayne Aquifer and the need to protect the quality of the groundwater in this aquifer as our sole source of drinking water, what is less known is the connection of this aquifer to Biscayne Bay and the Bay’s dependence on large volumes of clean, fresh water for its ecological health.
Hydrological changes, water management practices, upland development, and aged infrastructure have contributed to degraded water quality, seagrass die-offs and algal blooms as determined in part through data collected via the County’s surface water quality and benthic habitat monitoring programs and those data from other agencies and institutions.
The reduction of freshwater flows and the pulsed pattern of stormwater discharge through floodgates has changed the natural estuarine character of the Bay. Areas along the western shoreline of the Bay that historically received more consistent flow of freshwater off the everglades also supported lower salinities which provided important nursey habitat for the Bay’s fish and wildlife.
Over time, the disruption of this historic flow of freshwater has impacted the Bay and its ecosystem. Today, much of the freshwater that reaches the Bay from drainage canals also carries nutrients and other pollutants that impact the Bay. Nutrients flowing into the Bay can promote algal blooms and can lead to the loss of productive seagrass beds.
Historically, the shoreline of Biscayne Bay was lined with a thick green forest of mangroves. These trees, with their complex system of prop roots, help stabilize the shoreline and provide shelter for animals, birds and marine life. Their leaves become a vital part of the food chain when they fall into the water. Many mangrove forests have been lost to development. Remaining mangrove resources are protected from destruction.
The lush seagrass beds found throughout Biscayne Bay form another major part of the food chain. The Florida spiny lobster depends on this rich food chain and the Bay has been designated a sanctuary where the lobsters are protected year-round. Shrimp, fish, sea turtles and manatees also utilize these productive underwater pastures.
On the Atlantic side of the islands outside the Bay lie the most diverse of the underwater communities: the coral reefs. The reefs support a kaleidoscope of life. Fish, plants and other animals abound in a variety of colors. However, as human impacts increase, damage to the reefs has had nearly irreparable effects.
- Biscayne Bay is in trouble. Hydrological changes, water management practices, upland development and aged infrastructure have contributed to degraded water quality, seagrass die-offs and algal blooms as determined in part through data collected via the County’s surface water quality and benthic habitat monitoring programs and those data from other agencies and institutions.
Today, natural freshwater flows have been replaced by pulsed, point source discharges from dredged drainage canals, constructed to provide flood protection and move water off inland areas. These drainage canals can intercept groundwater, and more than half of the freshwater received by the Bay enters via the northernmost canals where the most notable seagrass losses have occurred.Runoff from the land, impacted by the activities taking place on land, degrade the quality of the water entering canals and Biscayne Bay. The timing, source and quality of freshwater delivered to the Bay can and has affected the health, diversity and distribution of the flora and fauna that comprise the Biscayne Bay ecosystem.Seagrass, the foundation of all life in Biscayne Bay, has declined significantly in several basins. Seagrasses provide habitat for ecologically and economically important fisheries such as shrimp, lobster, and various fish species and provide services such as stabilizing sediments and attenuating wave energy from storms.
Within the past decade, the scientific community began to better understand and quantify the role that coastal and submerged plants such as seagrasses, mangroves and other tidal wetlands play in sequestering and storing carbon, surpassing the capacity of their upland tree counterparts.
While notable coverage of seagrasses occurs in central and southern Biscayne Bay, seagrass losses over the past decade have been identified in the north, central, and southern regions of the Bay.
In the south, Barnes Sound and Manatee Bay basins have experienced a decrease in seagrass of approximately 93 percent. In the central portion of the Bay, an area along the eastern shoreline near Coral Gables, has seen a decrease in seagrass of approximately 85 percent. In the basins north of the Rickenbacker Causeway, seagrass losses range from approximately 66 percent to 89 percent.
The County’s water quality and seagrass survey data, as well as review of scientific literature and academic studies, indicate that chronic, low-level nutrient loading and/or acute, pulsed nutrient loading is likely linked to seagrass loss in Biscayne Bay.
Excess nutrients can lead to a shift from a seagrass-dominated habitat with clear water, low turbidity, and low levels of algae in the water column, to an algae-based ecosystem that is turbid and reduces habitat essential for fish, birds, marine mammals and other marine species.
Sources of nutrients can include pet waste, fertilizers and yard clippings and can be conveyed by stormwater outfalls. Other sources may include leaky sewer infrastructure and septic tank effluent. Unique challenges presented by storms and sea level rise compound and complicate these existing issues.
All of these factors contribute to larger ecological problems, such as seagrass decline, algal blooms, coral disease and other issues. Water quality impacts, habitat degradation, climatological changes and other factors can even lead to fish kills. Biscayne Bay has already experienced these, and until the Bay’s health is restored, the threat of more sea life dying in great quantities remains.