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Study co-written by WWU’s Kathryn Sobocinski looks at impact of moon jellyfish’s voracious appetite

Moon jellyfish populations thrive in warmer conditions. They travel in groups called (fun fact) smacks. And they eat — a lot.

by Jennifer Nerad

University Communications

A congregation of moon jellyfish on the surface of the water during a 2021 sampling cruise. Photo by Haila Schultz/University of Washington

Jellyfish populations favor conditions associated with climate change, like warmer waters. In Puget Sound’s protected estuaries, moon jellyfish, or Aurelia labiata, sometimes take over an entire bay, filling the water with their delicate, translucent, bell-shaped bodies.

A new publication by UW’s Haila Schultz and Julie Keister, Western’s Kathryn Sobocinski, and Correigh Greene from the National Marine Fisheries Service looks at moon jellyfish predation on zooplankton and how this behavior could impact other species, like juvenile fish, who also rely on zooplankton as a food source. 

“Our study demonstrates that jellyfish are voracious predators that can draw down local zooplankton abundances,” said Sobocinski, the co-principal investigator on the project. Sobocinski is an associate professor in the Marine and Coastal Science (MACS) program and the Environmental Science department, and runs WWU’s Coastal and Marine Fish Ecology Lab.

Researchers use nets to capture and count moon jellyfish and zooplankton. Photo by Kathryn Sobocinski/WWU.

Jellyfish aggregations are called blooms, swarms, drifts, or “smacks,” a word that some say describes what it feels like when you bump up against one. Moon jellyfish have tentacles, but their stings are mild for humans. 

The smacks can be extremely dense and consume vast amounts of zooplankton, the tiny aquatic microorganisms essential to the marine food web. Jellyfish themselves are eaten by a variety of fish, especially when small.

Over the past few summers, Sobocinski and her students conducted lab studies in tanks and field sampling using large nets to sample and measure moon jellyfish and zooplankton densities in various locations around Puget Sound. In the field and in the lab, researchers observed the same dramatic reduction in zooplankton number in dense moon jellyfish aggregations.

“This project involves the environmental science ‘trifecta’ of lab, field, and modeling components to really understand the mechanisms through to the ecosystem impacts,” said Sobocinski.

Read more about this research in this open access article. 

This project was funded by a Washington Sea Grant. It included researchers from the University of Washington, Highline College, the National Ocean and Atmospheric Administration (NOAA) Northwest Fisheries Science Center, as well as Western Washington University.

Learn about WWU’s marine science degree options through the Marine and Coastal Science program and Environmental Sciences department.

Jennifer Nerad covers Western's College of the Environment for the Office of University Communications. Have a great story idea? Reach out to her at neradj@wwu.edu.