Skip Links

USGS Home Contact USGS Search USGS

Ecosystem History of Biscayne Bay and the Southeast Coast

The U.S. Geological Survey is participating in a multi-institutional effort to assess, monitor, and restore the ecosystem of South Florida. Federal, State and local agencies are collaborating to establish a firm scientific basis for land management and water policy issues. Historical changes in South Florida related to rapid population growth in the early to middle 1900's have led to significant alteration of the natural hydrocycles and water quality of Florida and Biscayne Bays. These changes have affected the salinity and nutrient supply and introduced toxic components into Biscayne Bay. The Biscayne Bay ecosystem shows increasing signs of distress: declines in fisheries, increased pollution, and dramatic changes in nearshore vegetation. Northern and central Biscayne Bay are strongly affected by the urban development associated with the growth of Miami. Southern Biscayne Bay is influenced by drainage from the Everglades, which has been altered by canals and agricultural activities. Restoration and preservation of Biscayne Bay and Biscayne National Park are dependent on a comprehensive understanding of the linkages between the hydrologic system and the bay ecosystem, and of natural versus human-induced variability of the ecosystem.

The ecosystem of Biscayne Bay includes the marginal freshwater and saltwater wetlands, intertidal communities, and marine communities. The health of each of these communities can be linked to their interaction with the hydrologic regime of South Florida. Major factors that may affect these communities are:

• The alteration and control of freshwater flow entering Biscayne Bay.
• Urbanization of Dade County, thereby increasing storm runoff and pollutants into Biscayne Bay.
• Natural and artificial changes to vegetation associated with fires and urbanization.
• Natural disasters, including hurricanes, and prolonged wet or dry seasons.

In order for the restoration of Biscayne Bay to begin, it is necessary to have a comprehensive understanding of the evolution of the present ecosystem. The goals of this project are as follows:

• Assess the modern distribution of the plants and animals (biota) of the Biscayne Bay ecosystem with respect to present environmental conditions.
• Interpret the historical record of environmental change within Biscayne Bay by using biotic indicators.
• Determine agents (natural and (or) human-induced) that may be responsible for changes in the ecosystem of Biscayne Bay.
• Make recommendations concerning approaches for Biscayne Bay restoration and monitoring.

Modern biotic distribution and environmental data are gathered from surficial sediment and water samples collected throughout Biscayne Bay. The sediments are described and analyzed for animals (mollusks, foraminifera, ostracods) and plants (diatoms, pollen, and dinoflagellate cysts). Data from the water samples include temperature, salinity, dissolved oxygen, clarity, nutrients, and bacteria. These data are statistically compared to determine environmental conditions important to the distributions of the organisms.

The historical record is interpreted from the examination of biotic components from sediment cores collected on mudbanks within the bay. The interpretation of these biotic data, based on their modern distributions, allows us to reconstruct the ecosystem history of the bay. Dating of the core sediments is vital to our understanding of cause and effect relationships between changing environments and the ecosystem. Dating is accomplished by using several radiometric techniques that include Lead-210 and Cesium-137.

The U.S. Geological Survey, through collaboration with the National Park Service, South Florida Water Management District, and Metropolitan Dade County Environmental Resources Management, will gain a more comprehensive understanding of the evolution of the Biscayne Bay ecosystem and its components. This understanding will allow us to determine the impact of increasing human population and activities on the ecosystem and allow planners to make well founded decisions regarding restoration and land use policies for the future.

For more information contact:

Caribbean-Florida Water Science Center
U.S. Geological Survey
3321 College Avenue
Davie, FL 33314

Contact Pubs Warehouse