Tiny Ocean Animals Get 'Drunk' on Algae, Act Crazy

Even tiny ocean animals get soused—and not just in seawater.  

A common species of plankton in the northern Atlantic Ocean becomes intoxicated when it slurps up toxic algae, a new study says. 

And just like drunk partygoers, "drunk" plankton take questionable risks. (Related: "Do Animals Get Drunk?") 

In contrast to the wobbly gait of inebriated people, plankton under the influence swim faster and on a straighter path, making them more susceptible to predators. 

The plankton’s reaction to the algae is the exact opposite of what Rachel Lasley-Rasher and her team expected. 

“We honestly thought we would see [the plankton] slow down," she says, but by speeding up and becoming less loopy, "they are encountering predators at a much higher rate," says Lasley-Rasher, a marine ecologist at the University of Maine in Orono.  

Toxic Red Tides

The plankton that can’t hold their sauce are a variety of copepod, tiny shrimp-like creatures that are a crucial foundation for the ocean's food web. 

Copepods, the most abundant multicelled creatures on Earth, serve as nutritious “baby food” to countless growing fish, including the kinds that people like to eat, Lasley-Rasher says.  

But the copepod species that Lasley-Rasher and her colleagues studied, Temora longicornis, has a potentially fatal weakness: An appetite for poisonous algae, Alexandrium fundyense, which lives in the waters off New England.  

Most of the time, the copepods eat other food, since the toxic algae is usually pretty rare. But occasionally—for instance, due to unusual weather and wind patterns—these toxic algae bloom profusely, producing so-called “red tides.”  

Strange Swimmers

To find out more about what happens to Temora during algae blooms, Lasley-Rasher and colleagues gave plankton the intoxicating brew at the Georgia Institute of Technology lab of Jeannette Yen. 

To their surprise, the copepods seemed to thrive after scarfing down the algae, even making babies. But they also began acting oddly.  

The tiny animals swam an average of 25 percent faster, and, rather than darting around, they swam in relatively straight lines. That’s the swimming style of copepods on the move. (Also see "Why Backyard Birds Are Getting Drunk on Fermented Berries.") 

The reaction was “weird,” Lasley-Rasher says. “If [the algae] doesn’t hurt them, it’s kind of strange that they’d want to get away.”  

By swimming faster, the copepods swim past more fish larvae and other potential predators. They also make a bigger wake, which can attract attention.  

This intoxicated swimming makes them 25 to 55 percent more likely to run into a predator, the scientists estimate in an April 27 study published in Proceedings of the Royal Society B: Biological Sciences. 

Skipping the Hangover

And there are reverberations up the food chain. If fish or shrimp eat enough drunk copepods, the toxic algae might persist longer in the water because there are fewer copepods to eat them, Lasley-Rasher says. 

Since the tiny animals are such an abundant and popular food, the toxins they eat could travel to higher levels of the food web, says David Fields of the Bigelow Laboratory for Ocean Sciences, who was not involved with the research.   

The results are reasonable but also surprising, adds the University of Delaware’s Jonathan Cohen. (See: "Flies Use Alcohol to Protect Their Young from Body Snatchers.") 

“I expected copepods to shown some degree of incapacitation,” he says via email. 

Perhaps this kind of copepod has gotten resistant to the toxin after a long co-existence, the study researchers say.  

The plankton certainly are not drunk or trying to get drunk, but Lasley-Rasher says it's a good parallel: "They’re eating something that is changing their behavior.”  

Lacking advanced brains, though, at least they won’t have a hangover.