Conducted largely at Georgia Tech’s marine lab in Savannah, Ga., the research was sponsored by the U.S. National Science Foundation and the U.S. Environmental Protection Agency.
Phaeocystis has two primary predators: small grazers such as ciliates, which prefer to eat small solitary cells that are four to six microns in diameter, and the larger shrimp-like copepods, which prefer to eat large, ball-shaped colonies.
When copepods are attacking the phytoplankton, therefore, the best survival strategy of Phaeocystis is to form solitary cells. When ciliates are attacking, the best strategy is to form colonies that are too large for those predators to consume.
Lead author Jeremy D. Long, along with collaborators Gabriella W. Smalley, Todd Barsby, Jon T. Anderson and Mark Hay found that’s just what Phaeocystis does. Chemicals that signaled attacks from copepods suppressed the formation of colonies by 60 to 90 percent, while signals from ciliates enhanced colony formation by more than 25 percent.
The transformations took place over periods of three to six days, and the overall size difference could be dramatic. “When one of these cells changes to the biggest colony form, although it takes a while, it’s like changing from a mosquito to 76 blue whales or 3,000 bull elephants,” Hay explained. “That’s a pretty dramatic difference.”
Defensive responses are often seen in higher plants, but this is believed to be the first report of such a complex and species-specific response in marine phytoplankton. Hay suspects scientists may find other examples of complex defensive strategies when they look more closely at other single-celled organisms.
The response of Phaeocystis could be important to scientists studying climate change because the predator that ultimately consumes the phytoplankton determines the fate of the carb
Source:Georgia Institute of Technology Research News