New technology helps researchers study unknown Arctic comb jellies

October 28, 2016

About the series: This is the third part of a three-part series on a recent research cruise to better understand species and processes in the Chukchi Borderlands, the complex transition area from the shallow Chukchi Sea shelf to the deep Arctic Basin. Currently, the region is not well understood. The cruise supported international researchers, including a team of professors and graduate students from the University of Alaska Fairbanks, on the U.S. Coast Guard Cutter Healy, an icebreaker capable of conducting extreme Arctic research. The research was funded by a National Oceanic and Atmospheric Administration Ocean Exploration grant, which sends researchers to explore the unknown and ask new questions.

UAF researchers may soon describe six new species of comb jellies revealed by high-resolution underwater cameras during a summer 2016 cruise on the USCGC Healy icebreaker.

The Beroe abyssicola is a species of comb jelly that the Global Explorer ROV collected during the expedition. Photo courtesy of Caitlin Bailey, GFOE, The Hidden Ocean 2016: Chukchi Borderlands.

UAF College of Fisheries and Ocean Sciences marine biology professor Russell Hopcroft led the group that focused on collecting and describing Arctic zooplankton. The team chose to focus on studying and collecting comb jellies, or ctenophores, with a remotely operated vehicle (ROV) because they are a bit larger than the region’s jellyfish, so they are easier to spot and collect. The species collected ranged from about 1 centimeter to 15 centimeters.

Hopcroft said that prior to a similar research cruise in 2005, only six species of ctenophores had been documented in the Arctic. In 2005, the team saw a number of comb jellies that hadn’t been identified before, but they didn’t have the means to successfully collect them. Since then, the resolution on ROV cameras has increased dramatically, making it much easier to find and collect new species underwater.

“The new data could help double our documented number of Arctic comb jellies,” Hopcroft said.

Jellyfish and comb jellies have similar squishy, delicate bodies. But while a jellyfish is commonly umbrella-shaped with long tentacles hanging off the edges, a comb jelly is shaped more like a lightbulb, with lots of tiny strings, called ctens, attached to the outside. These ctens help comb jellies swim.

Ctenophores are important drivers of the arctic food web. “Comb jellies are probably consistently the largest predators in the water column,” Hopcroft said. “Their behavior has an influence on the whole Arctic system.”

Typically, collecting water column species is done with a plankton net, which has limitations. “It’s blind sampling technology,” Hopcroft said. “You tend to get the stuff that’s most abundant, that you can routinely collect, in a probability sense.”

The researchers named this mystery ctenophore Mr. Pumpkin. Specimens of Mr. Pumpkin collected by the Global Explorer ROV allow scientists to look at the ctenophores’ structure and take DNA samples. Photo courtesy of Caitlin Bailey, GFOE, The Hidden Ocean 2016: Chukchi Borderlands.

Because comb jellies are soft and gooey, plankton nets tend to destroy them. Additionally, some of the comb jellies most intriguing to Hopcroft’s team live on or close to the seafloor, outside of the range of the plankton nets.

Hopcroft used an ROV with a suction device and 12 containers for collecting species of interest that are spotted along the way. An ROV allows operators to see what is around them. They can hunt for what is being collected, explore different areas of the ocean floor, get up close to something if they want to take a more detailed look, and collect sensitive species more carefully than with a plankton net. This maneuverability increases the ability to target species during the sampling process.

The researchers have not processed their jellyfish data yet, but they are excited to see what they can learn about the six collected comb jellies.

The data collected on the 2016 cruise will provide important baseline information for many aspects of the biology and productivity of the Chukchi Borderlands. With the new insight from the cruise, the researchers look forward to further investigating the organisms and their habitat.

Read the first part of this series on the mysterious seafloor biology and the second part on what lives in the sea ice.

More information from this research cruise, including photos and videos, can be found on the NOAA Ocean Explorer website.