Mar 2008 • Graduate School of Oceanography • University of Rhode Island • www.gso.uri.edu
Diatoms: the ocean’s climate engineers
Dr. Tatiana Rynearson was recently awarded a National Science 
Foundation grant to study how plankton respond to the changing climate. Diatoms, admired for their intricate opaline shells, elegant spines, and multitude of forms since the Victorian era, are single-celled photosynthetic organisms.
They are tiny organisms that float within the ocean’s surface waters, but their size is deceiving–they remove the same amount of carbon dioxide from the atmosphere as all of the Earth’s rainforests combined. Because of this hefty role in the climate system, diatoms are key players in regulating atmospheric carbon dioxide concentrations.
Diatoms also 
have a global influence because they are able to thrive in an amazing range of habitats spread across the world’s oceans. They do this while simply floating at the surface layer of the ocean, drifting with the tides and currents. A challenge to oceanographers has been to identify whether diatoms are simply good at growing wherever the currents take them or whether there are populations of diatoms uniquely adapted to flourish in specific habitats.
GSO researcher Dr. Tatiana Rynearson plans to take on this challenge using DNA techniques to examine the genetic connections among diatoms sampled from across the globe.
Dr. Rynearson’s lab will use sensitive DNA fingerprinting techniques to examine how diatom populations are related to each other on local, regional and global scales. Since diatoms float passively in an open, boundless ocean, there are no clear physical barriers to the flow of individuals, and hence genes, as is common in many terrestrial ecosystems. The rates of genetic exchange among different marine habitats (e.g. estuaries and coasts) will help oceanographers understand whether diatoms have evolved special adaptations to each environment or whether they are generalists. The types of adaptations may ultimately be essential in predicting how these tiny and important organisms will respond to environmental change.
“The goal will be to discover the highways and by-ways of genetic exchange in the world’s oceans” says Dr. Rynearson. Her study represents the first large scale examination of diatom biogeography, and will likely initiate new hypotheses about diatom ecology and evolution, including mechanisms of bloom formation, the evolution of new species and responses to climate change.
in the ocean state