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Frequently Asked Questions
Why study the south Florida ecosystem?
South Florida is a unique but endangered ecosystem. Prior to significant human activity in the area (mid-1800's), south Florida constituted one of the largest wetlands in the continental United States. The Everglades, referred to by Marjory Stoneman Douglas as the "River of Grass", historically encompassed an area of approximately 4,500 square miles.
In the last few decades, algal blooms, seagrass die-off, declining shellfish numbers, mercury buildup in the animals, contamination by pesticides, and the widespread invasion of exotic plants have occurred in the ecosystem. Scientists want to find out if these changes are due to natural changes in the system or if they were influenced by human development, or a combination of factors.
If scientists can determine what the ecosystem was like before significant human activity began in the region, then the land-managers responsible for the restoration can set realistic goals. In other words, these studies can help answer the questions "what was the system like before the land was altered?" and "what do we need to do to restore the system to its natural state?" In addition, these studies can determine what portion of the recent changes are due to natural causes, such as hurricanes or El Niño events, and thus can save tax-payer's money by preventing the "correction" of a change brought about by natural events.
Where is the study area?
There are three primary areas which we study in south Florida: Florida Bay, Biscayne Bay, and terrestrial south Florida (including the Everglades). Florida Bay is located between the mainland of Florida and the Florida Keys, Biscayne Bay is located between the coast near Miami and the Atlantic Ocean, and terrestrial south Florida includes most of Florida south of Lake Okeechobee, including the wetlands of the Florida Everglades.
How do scientists study South Florida?
In Biscayne Bay and Florida Bay, 1-2 meter cores are taken from mud banks, and areas of sediment buildup to examine materials deposited over approximately the last 100-200 years. Scientists also collect samples from modern sites around the bays to show current distributions of the plants and animals. After the samples are taken, the mud is washed off; leaving the remains of tiny organisms that lived in the bay. These organisms are mollusks, ostracodes, diatoms, and foraminifera. The bottom-dwelling or benthic organisms can provide information about the floor of the bay and whether or not seagrasses or algae were present.
All of the organisms can provide information about the salinity of the bay waters so scientists can tell how salty the water was. In addition, pollen grains that were carried by the wind or currents are deposited in the sediments. These are examined in order to tell what was happening on land at approximately the same time.
What have scientists learned from the study so far?
Scientists studying the south Florida ecosystem have learned that invading cattail plants increased in number and are slowly displacing the native sawgrass communities along the margins of the canals. This may be due to increased nutrients entering the system through the canals. Also, scientists have learned that the amount of sawgrass present has fluctuated naturally over time.
In Florida Bay, the studies have shown that salinity and seagrass distribution have fluctuated a great deal over the last 100-200 years. Before 1940, these fluctuations seem to match natural cycles. After 1940, the fluctuations are much greater, and they no longer match natural cycles. The timing of this change coincides with a large part of the canal construction in the Everglades, so it seems that this human activity has had a big influence on Florida Bay. The studies also have shown that seagrass and macro-benthic algae were much less abundant in the 1800's and early 1900's, than in the last half of this century.
Our data provide strong evidence for region-wide ecosystem disturbance in the late 20th century that was accelerated by human activities. Research is continuing to find additional evidence, and to develop a better understanding of the relationships between salinity, seagrass, fresh-water input, and the plants and animals of the region.
If you have other questions about the South Florida Ecosystem History Project, please feel free to email Lynn Wingard.
U.S. Department of the Interior, U.S. Geological Survey, Center for Coastal Geology
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