“This could alter the flow of energy and nutrients from deep to shallow, depending on what might be trying to eat it, and how the organism responds to the chemical signals of what’s attacking it,” Hay said.
Experimentally, the researchers attempted to separate the chemical signals from the actual predators. They grew Phaeocystis in the presence of either ciliates or copepods. They then filtered out both the phytoplankton and predators, leaving only water containing the chemical signals of attack.
Water samples containing signals from the two predators were then separately introduced into Phaeocystis cultures that had not been attacked. The scientists then studied how the different chemical signals affected the percentage of Phaeocystis living in colonies or as solitary cells. Finally, they examined whether this response affected how much the predators ate to determine if the change conferred a survival advantage.
“We found that these organisms were making the right choice,” Hay said. “They were shifting to the shape that made them largely immune to whichever predator was attacking, and this shift suppressed either the feeding or growth and reproduction of the consumer to which they were responding.”
The role of this phytoplankton has been controversial in the scientific community, with some arguing that Phaeocystis makes a good food source for higher creatures in the cold oceans, while others contend its food role is small. While this paper won’t resolve the dispute, Hay believes it shows that both points of view could be correct – depending on
Source:Georgia Institute of Technology Research News