Fossils collected on board the JOIDES Resolution provide insight into modern Antarctic environment
The origin of the distinctive marine ecosystems found in today’s Southern Ocean can be traced back to the emergence of large ice sheets on Antarctica about 33.5 million years ago. Furthermore, the development of this sea ice ecosystem could have spurred the evolution of larger organisms such as whales and penguins. The results* appear in this week’s issue of the journal Science.
Integrated Ocean Drilling Program (IODP) Expedition 318 (Wilkes Land Glacial History) was the first to collect long, complete sediment cores from the seafloor along the Antarctic margin south of Australia. Previous studies on these same cores demonstrated that subtropical plants covered Antarctica about 53 million years ago. The current study focuses on a time period 20 million years later, during which time the climate gradually cooled, causing large ice sheets to appear on Antarctica 33.5 million years ago.
“Today, the seas around Antarctica play a critical role in the oceanic food web. Strong algal blooms only occur in summer, when the sea ice melts,” explains lead author Sander Houben of Utrecht University in the Netherlands. “These blooms are a key food source for both small single-cell organisms, such as certain species of dinoflagellates, and for larger organisms.”
The researchers found that when Antarctica was subtropical and ice-free, a diverse array of dinoflagellates characteristic of relatively warm climates inhabited the surrounding seas. However, when ice sheets first developed, many species died off, leaving only a handful of species – many of which still thrive in the sea ice environments of the Southern Ocean.
“Today the seasonal sea ice around Antarctica is there because of the regional cooling effect of the land ice, which is more than 10,000 feet thick with an area larger than the United States,” says co-author Sandra Passchier of Montclair State University in New Jersey. “Through laboratory analysis of the sediment around the fossils in the core, we were able to show that the ecosystems changed as the land ice appeared.”
“This [change] was not only critical for climate, but also for biology,” Houben explains. “Larger sea animals probably adapted their diet because the algal growth season became shorter and more intense. We therefore believe that it is no coincidence that the evolution of modern whales and penguins approximately corresponds with the emergence of the ice sheets.”
*A.J.P. Houben, et al. “Reorganization of Southern Ocean Plankton Ecosystem at the Onset of Antarctic Glaciation.” Science, April 19, 2013
The Integrated Ocean Drilling Program (IODP) is an international research program dedicated to advancing scientific understanding of the Earth through drilling, coring, and monitoring the subseafloor. The JOIDES Resolution is a scientific research vessel managed by the U.S. Implementing Organization of IODP (USIO). Together, Texas A&M University, Lamont-Doherty Earth Observatory of Columbia University, and the Consortium for Ocean Leadership compose the USIO. IODP is supported by two lead agencies: the U.S. National Science Foundation (NSF) and Japan’s Ministry of Education, Culture, Sports, Science, and Technology. Additional program support comes from the European Consortium for Ocean Research Drilling (ECORD), the Australia-New Zealand IODP Consortium (ANZIC), India’s Ministry of Earth Sciences, the People’s Republic of China (Ministry of Science and Technology), the Korea Institute of Geoscience and Mineral Resources, and Brazil’s Ministry of Education (CAPES). For more information, visit www.iodp.org.
For more information about IODP Expedition 318 (Wilkes Land Glacial History), visit http://iodp.tamu.edu/scienceops/expeditions/wilkes_land.html
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Dr. Sandra Passchier
Montclair State University
Montclair, NJ, USA
Consortium for Ocean Leadership
Washington, DC, USA
IODP Management International, Inc. (IODP-MI)