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From High Mercury in Pythons to Sea-Level Rise to New Manatee Refuges
USGS at the Greater Everglades Ecosystem Restoration Conference
Released: 7/12/2010 1:11:56 PM

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The Greater Everglades Ecosystem Restoration Conference (Planning, Science, Policy) 2010 meets from July 12-16 in Naples, Fla. Below are a few USGS presentation highlights from the conference. For more information visit the conference website

High Mercury Levels Found in Burmese Pythons: Some invasive Burmese pythons have high levels of mercury, enough to merit concern from anyone interested in hunting them to eat, according to preliminary research by USGS researchers. Pythons are at the top of the food chain –they eat over 35 different species of mammals and birds, some of which are endangered and even alligators. As predators, these pythons are at a higher risk of mercury bioaccumulation because mercury builds up in organisms higher on the food web. One possible strategy to reduce the population of invasive pythons is to allow hunting; however, if the mercury content of the pythons is too high, the flesh of the pythons could present an unsafe level of mercury exposure to those humans who consume it. So far, the USGS Mercury Research Laboratory has analyzed over 50 python tail-tissue samples, with about equal numbers of adults and hatchlings.  These results show that on average, tissue from the adults contained high levels of mercury, and the hatchlings were on average 22 times lower in mercury levels than their mother. An additional 100 samples are scheduled for further examination. This study, Mercury Bioaccumulation in Everglades Pythons, will be presented on July 15 in the afternoon poster session. For more information, contact David Krabbenhoft at 608-335-4234 or atdpkrabbe@usgs.gov.

More Northern African Pythons Found in the Wild in South Florida:  When it comes to nonnative species, southern Florida is no stranger to big snakes, but recently there were 7 credible sightings of a newcomer called the Northern African python along the western border of Miami, alarmingly close to the eastern edge of the Everglades. A close relative to the invasive Burmese python, the African python can reach lengths of up to 20 feet and weigh over 150 pounds, although the largest one found in Florida was 14 feet and 138 pounds. In response to fears that a second large python species might establish itself in the Everglades, the Exotic Animal Strike Team organized an intensive 3-day search for the python in January of 2010, turning up five adult African pythons in the wild. Since then, several more African pythons have been removed from the same area. Scientists hope to assess the prospects for eradicating this new invader to help prevent it from becoming as widespread as the Burmese python. The Northern African Python in south Florida will be presented on July 13 from 5 to 7 p.m. in the exhibit hall.  For more information, contact Christina Romagosa at 334-844-8030 or at romagch@auburn.edu.

Florida Crocodile Would be Further Threatened by Sea-Level Rise: Predicted sea-level rise would likely inundate historical American crocodile nesting areas and increase salinity so that much of the habitat crocodiles now use would become less favorable, according to new modeling research by USGS researchers and their UF colleagues. Everglades restoration alone would have little effect on the crocodile population, but in combination with sea-level rise, restoration will significantly help offset the negative effects of climate change on the American crocodile population. This study, Using a Spatially Explicit Crocodile Population Model to Predict Potential Impacts of Sea Level Rise and Everglades Restoration Alternatives, will be presented on July 15 at 4 p.m. in Royal Palm III. For more information, contact Tim Green at 352-317-7506 or at tgreen@usgs.gov.

Manatees Take Shelter Below the Cold: Manatees in the Ten Thousand Islands and Everglades National Park do not have access to springs or power plants that provide warm water in other parts of the state. This may account for the high manatee mortality during the especially severe winter of 2010 in the Everglades National Park, but in the Ten Thousand Islands, scientists discovered that artificial canal systems provided manatees with warm water refuges beneath the colder surface water. These warm- water pockets occur beneath the cold surface water because freshwater is lighter than saltwater and can flow over it, forming a sharp freshwater-saltwater gradient that scientists call a halocline. This prevents the cold water from sinking and the warm water from rising, allowing the manatees to stay warm along the bottom. This study highlights a previously unappreciated mechanism, amenable to management actions that can provide thermal protection for manatees and other cold-sensitive species. Manatees, Restoration, and Severe Winters: How Haloclines Shelter Manatees from Cold in Southwest Florida, will be presented on July 15th at 11:40 a.m. in Royal Palm IV-V. For more information, contact Brad Stith at 352-264-3529 or at bradley_stith@usgs.gov.

Pet or Threat? Invasive Species May be Both: In a risk assessment to determine which reptile species are most likely to invade South Florida, USGS scientists and their University of Florida colleagues found four factors effectively predict whether a nonnative species can establish itself: what kind of animal it is, temperatures the animal can live in, manageability, and sale price. Since most invasive wildlife species originate from the pet trade, the scientists suggest that screening imported wildlife using these criteria could prevent future invasion. To test this, models based on the four factors were applied to the 33 most frequently imported reptiles in Florida, 12 of which the model predicted as potential invaders. Adapting these new prediction and modeling procedures to screen the South Floridian pet and aquarium trade might help to slow down the addition of nonnative, invasive species to the Everglades. This study, Risk Assessment of Invasive Wildlife Species in South Florida, will be presented on July 13 at 9:40 a.m. in Royal Palm III. For more information, contact Kristen Hart at 954-577-6335 or at kristen_hart@usgs.gov.

Cuban Treefrogs Dining on Florida’s Native Treefrogs: South Floridians have noticed that in areas where the invasive Cuban treefrog is present, fewer or no native treefrog species are around. A USGS study is adding to mounting evidence that Cuban treefrogs are a threat to native green treefrogs and squirrel treefrogs. While the exact ecological consequences of the invasion are still being unraveled, the study found that sites occupied by Cuban treefrogs were 9 times less likely to have green treefrogs and 16 times less likely to have squirrel treefrogs. Other studies indicate that Cuban treefrogs are outcompeting native treefrogs for resources and also preying upon the native treefrogs, which are considerably smaller than the Cuban treefrog – a 6-inch adult Cuban treefrog can easily dine upon the 2 1/2 –inch green treefrog and the even smaller 1 1/2 –inch squirrel treefrog. With predicted climate change, the Cuban treefrog may even be able to invade more northern areas of the United States. The study revealed that already the Cuban treefrogs seem to be invading farther eastward in the state. This study, Presence of Invasive Cuban Treefrog Reduces Probability of occurrence of Native Treefrog Species in Southern Florida, will be presented on July 13 at 5 p.m. in the exhibit hall. For more information, contact Susan Walls at 352-264-3507 or at swalls@usgs.gov.

Disappearing Islands and Mangrove Forests Documented in South Florida: By using historical charts and aerial photos, USGS scientists based in Florida documented that between 1928 and 2004, 80 islands have disappeared from Whitewater Bay, likely because of hurricanes, sea-level rise, and storm surges. Traditionally the coast has been dominated by mangrove forests, but since 1910 seven major hurricanes have devastated the mangroves, converting them to intertidal mudflats. Meanwhile, the combination of saltwater-bearing canals, storm surge, and sea-level rise has caused an increase in water salinity and coastal erosion, converting substantial marshland to open water and causing the disappearance of islands in Whitewater Bay, and the shrinking in size of numerous other islands. Understanding the cause of island loss in Whitewater Bay may assist in management and conservation efforts of the more than 145,000 acres of mangrove forest from Cape Romano to Cape Sable. This study, The Disappearing Islands of Whitewater Bay, Everglades National Park, will be presented on July 13 at 6 p.m. in the exhibit hall. For more information, contact Paul R. Nelson at prnelson@usgs.gov or at 727-803-2032.

 Sea-Level Rise, Storms, Freezes, and Fire: Change in the Coastal Everglades: By using historical charts and aerial photos, USGS researchers were able to show changes that have occurred in the coastal Everglades since the early 20th century. They found that sea-level rise, major storms, altered fire regimes and artificial canals have caused numerous changes, including the conversion of the intertidal area, historically dominated by mangrove forests, to intertidal mudflats. On Cape Sable, the combination of canals from the gulf into freshwater marshes and storm surges has increased salinity and coastal erosion, leading to the conversion of thousands of hectares of marsh to open water or to mangrove forests. In more upstream marsh locations, mangroves are migrating into and replacing marsh. As sea-level continues to rise, these shifts are likely to be permanent with consequences for numerous at-risk species, such as the Cape Sable seaside sparrow, a species first found in the now-vanished marshes. Not all consequences are harmful, though – the endangered small-tooth sawfish and roseate spoonbill, for example, use the newly formed open-water habitats.  This research reveals that as restoration proceeds, it is clear that climate change and other factors must be considered. This study, Vectors of Change in the Coastal Everglades: Sea Level Rise, Storms, Freezes and Fire, will be presented on July 15 at 2:40 p.m. in Royal Palm III. For more information, contact Tom Smith at Tom_J_Smith@usgs.gov or at 727-803-8747 ext. 3130.

Wildlife, Fish, and Toxic Mercury: Considerations for Restoration: Two years of surveys of surface water and forage fish from about 70 sites across Everglades National Park show several regions of elevated methylmercury – the most toxic form of mercury -- in the head of Shark River Slough, the C111 Basin, and the mouths of the Shark River and Taylor sloughs. Scientists from the USGS and the National Park Service found that large-scale factors, including land use, water use and management, disturbances such as fires and droughts, and atmospheric mercury levels all play a role in controlling mercury accumulation across the Everglades. Consequently, these factors are vital to address in the Everglades Restoration Program, especially since almost all of the mercury in top predators is the toxic methylmercury. Since the methylation process occurs on a much smaller scale, scientists must link large-scale land and water-use factors and small-scale biogeochemical processes to inform decision makers on how various restoration efforts may affect future methylmercury production and potential exposure to wildlife, fish, and humans. This study, The Influence of Canal Water Releases on the Distribution of Mercury, Methylmercury, Sulfate, and Dissolved Organic Carbon in Everglades National Park: Implications for Ecosystem Restoration, will be presented on July 13 at 4:40 p.m. in Royal Palm III. For more information, contact David P. Krabbenhoft at 608-335-4234 or at dpkrabbe@usgs.gov.

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