A Catch of Another Kind

When Miami fisherman Tim O’Neill went fishing off Key Biscayne one morning in search of swordfish he returned with a much rarer specimen than he had in mind. When he finally reeled in the big chunk of ocean bottom he realized he had hooked a giant tooth.

“I couldn’t grab the rock fast enough,” said O’Neill, captain of the F/V Cacique.

Sharktooth_closeup

What he reeled in that day from 1800 feet below was an exceptional find – a crustal rock from the ocean floor with a large fossilized shark tooth jutting out. He contacted UM Rosenstiel School scientists to help him identify his unusual find.

According to Rosenstiel School scientists the fossilized upper front tooth encased in rock he caught is from the now extinct relative of the great white shark, Carcharodon megalodon, which is known for its “mega teeth” and estimated to be 10-15 million years old.

“The great white shark that exists today is more closely related to the prehistoric Mako shark than the megalodon,” says Rosenstiel research assistant professor Neil Hammerschlag and director of the RJ Dunlap Marine Conservation Program.

Rosenstiel School marine geology professor Gregor Eberli examined the rock first hand to discover that the black-colored megalodon tooth was well preserved in the limestone rock coated with a mixture of iron and manganese.

Eberli

O’Neill caught his one-of-a kind find about 10 miles off the coast of Miami in an area known as the Miami Terrace. University of Miami scientists conducting an echo-sounding survey first discovered the region in 1958. The area is of interest to scientists for its mix of geological and biological finds.

“At approximately 1800 feet depth, the Miami Terrace is a large, current-swept submarine plateau whose flank down to the floor of the Straits of Florida at 2600 feet is covered with 100 foot ridges, which provides habitat for deep-water corals, sponges, lobsters and fish,” said Eberli.

Tim O’Neill pulled the rock off the edge of the Terrace. He is planning to keep his million-year-old ocean treasure at home as a reminder that great whites once roamed the Straits of Florida.

– RSMAS Communications

– Photos: Diana Udel

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The disappearing of the largest lake in the Middle East

U5The world’s third largest hypersaline lake, Urmia Lake is located 1267 meters above sea level in a closed continental drainage basin in northwestern Iran. The lake and its associated wetlands are home to 27 species of mammals, including the endangered Mesopotamian Fallow Deer, 212 species of birds, 41 reptiles and 7 amphibians. High levels of salinity – 200 ppt, which is 5.5 times more than average seawater – limits the fauna and flora that can survive within the lake. The most dominant flora is a green algae and the only marine zooplankton is a unique brine shrimp; Artemia urmiana, which plays a key role in the lake’s food chain, in particular as the primary source of food for migratory birds such as flamingos.

RSMAS_scientistsAlthough the unique and fragile environment of Urmia Lake is protected under the United Nations Ramsar Convention and registered as a UNESCO Biosphere Reserve location, the lake and its surrounding wetlands have been subject to extensive disturbances since the early 1980s. One of the main developments that severely impacted the lake’s environment was construction of the dyke-type “Kalantari” highway to connect two major cities across the lake. As a consequence, natural water circulation, sedimentation pattern and evaporation rates have been significantly altered and high levels of heavy metal contaminants have been introduced to the lake environment.

Lake UrmiaOur study of the elemental distribution patterns in the lake’s sediments reveals high mercury contamination near the Kalantari highway. Moderate mercury contamination is also detected in the main rivers that supply water to the lake, indicating progressive human development in the Lake’s catchment basins. Another major anthropogenic disturbance comes from excessive damming on the Urmia Lake’s tributaries and poor water management in their watershed areas. As a result, the lake’s water level has dropped by as much as 9 meters over the last two decades. The lake has also been losing water to enhanced evaporation in its southern “sub-basin” due to construction of the Kalantari highway.

IMG_8204Covering an area of 5000 km2, Urmia Lake is one of the largest bodies of water in west Asia and plays a crucial role in conditioning regional climate. Rapid shrinkage of the lake not only changes climate conditions in northwest Iran, but it also has a transboundary climatic effect on the neighboring countries such as Turkey, Azerbaijan and Armenia.  Decreasing the lake’s surface area leads to expansion of salt planes with high albedo and affects the thermal balance of the atmosphere above the lake. Freshly exposed salt planes become new point-sources of toxic slat aerosols into the atmosphere, and can cause serious agricultural and health complications across the region. While enhanced global climate change cannot be ruled out as a contributor to higher evaporation rates at Lake Urmia, it is clear that anthropogenic sources have played a far more significant role in the graduate demise of the largest continental lake in the Middle East. The fate of Lake Urmia and the demand for saving it has increased tension between people and state authorities in a way that an environmental disaster has turned into a national security concern (“The Guardian” September 5, 2011).

600px-Urmia_lake_1984_to_2011Another important aspect of our research is the study of abrupt climate change in the history of the Lake Urmia. Long-term climate data can be used to assess the natural trends in regional climate and their effect on the lake’s water and sedimentary regime. During September of 2012, in collaboration with the Iranian National Institute for Oceanography, we conducted a field campaign in Urmia National Park and collected more than 20 meters of split cores from different locations around the Lake.  The preliminary results of our study has revealed possible abrupt variations in past climate condition of the region, but the severity of such variability and its impact on Lake Urmia is the subject of our ongoing investigation.

By: Assistant Professor Ali Pourmand and graduate student Arash Sharifi of the Division of Marine Geology and Geophysics at RSMAS