Scientists at the University of Rhode Island’s Graduate School of Oceanography have made the first observation of a predator avoidance behavior by a species of phytoplankton, a microscopic marine plant. Susanne Menden-Deuer, associate professor of oceanography, and doctoral student Elizabeth Harvey made the unexpected observation while studying the interactions between phytoplankton and zooplankton.
Their discovery will be published in the September 28 issue of the journal PLOS ONE. The paper can be viewed at http://dx.plos.org/10.1371/journal.pone.0046438.
“It has been well observed that phytoplankton can control their movements in the water and move toward light and nutrients,” Menden-Deuer said. “What hasn’t been known is that they respond to predators by swimming away from them. We don’t know of any other plants that do this.”
While imaging 3-dimensional predator-prey interactions, the researchers noted that the phytoplankton Heterosigma akashiwo swam differently in the presence of predators, and groups of them shifted their distribution away from the predators.
In a series of laboratory experiments, Menden-Deuer and Harvey found that the phytoplankton not only flee when in the presence of the predatory zooplankton, but they also flee when in water that had previously contained the predators. They found only a minimal effect when the phytoplankton were exposed to predators that do not feed on phytoplankton.
“The phytoplankton can clearly sense the predator is there. They flee even from the chemical scent of the predator but are most agitated when sensing a feeding predator,” said Menden-Deuer.
When the scientists provided the phytoplankton with a refuge to avoid the predator – an area of low salinity water that the predators cannot tolerate – the phytoplankton moved to the refuge.
Funding for this research was provided by the National Science Foundation, the National Oceanic and Atmospheric Administration, and the U.S. Department of Agriculture. The study was conducted, in part, at the URI Marine Life Science Facility, which is supported by the Rhode Island Experimental Program to Stimulate Competitive Research.
For more information, see the full press release at https://www.uri.edu/news/releases/?id=6406
Predatory zooplankton Favella sp. (left) and its algal prey Heterosigma akashiwo.
Photo by researcher, Elizabeth Harvey.