Drones have served science in myriad ways, from planting trees to vacuuming marine debris to predicting tornadoes. Now, a team of researchers has used one to measure the size of a massive bloom of jellyfish off the coast of British Columbia, Canada. And it's a monster: According to a new paper in the journal Marine Ecology Progress Series, the huge swarm weighed more than 70 tons.

That's at least 150,000 individual jellies.

"The size of the bloom surprised me. What was exciting was going from not being able to see the bloom easily, if at all, to instantly being able to find them from the air," says co-author Brian Hunt, the Hakai Professor in Oceanography at the University of British Columbia in Vancouver, B.C. "It is remarkable how tightly they group together."

Keith Holmes, Hakai Institute

The bloom is comprised of five species in the Aurelia genus, also known as moon jellies. They're found worldwide (and in aquarium exhibits), often gathering in quiet harbors and bays to feed on plankton, fish larvae, crustaceans, and mollusks.

Hunt and colleague Jessica Schaub conducted their survey in Pruth Bay, a peaceful waterway edged with dense forests, near Calvert Island on the province's central coast, roughly 375 miles north of Seattle. The Hakai Institute, a scientific research institution that supported the survey, faces the bay. The area is within the First Nations territories of the Heiltsuk and Wuikinuxv Nations.

This is the first time a drone has been used to locate and study jellyfish blooms, Hunt tells Mental Floss. Previously, scientists viewed the groups at water level, which provided a limited perspective on their true size and density. The aerial view can help researchers estimate the biomass of jellyfish more accurately and reveal aggregations' behavior, such as their movements in currents or tides.

The team deployed the drone from a research vessel positioned within the mass of invertebrates. While the drone captured aerial images, the researchers also sampled the waters with nets. Then, they compared the drone data and sampling, and estimated that the bloom could weigh anywhere from 70 to as much as 128 tons.

Keith Holmes, Hakai Institute

There isn't much long-term data about the blooms, Hunt says, but those living in the area are familiar with the jellies' appearances in the waterways. "I wouldn’t call these events common, but they are definitely consistent in their timing. We see this happening every four or so years, particularly the local fisherman who catch them as bycatch in their nets," William Housty, chair of the Heiltsuk Integrated Resource Management Department's board of directors, tells Mental Floss.

In the future, drones might help scientists interpret the blooms based on where, when, and how often they occur—as well as how they affect the surrounding ecosystem. Housty says these jellyfish may be following the pattern of warmer waters along the coast.

"We did notice higher numbers during the 2015 marine heatwave and the 2016 El Niño [also a warm event]," Hunt says. "It is possible that changes in the seasonal timing of the jellyfish life cycle might be as or more important than increasing numbers. For example, if jellyfish are more advanced in their life cycle in the spring, they might have a bigger predation impact on herring larvae."

Soon, thanks to aerial imagery, we might know more about the jellies' secret lives.

This story was made possible in part through the Institute for Journalism and Natural Resources.