Moon jellies appear to be gobbling up zooplankton in Puget Sound

This aerial view shows the RV Rachel Carson inside a moon jelly aggregation on August 25, 2021, in Quartermaster Harbor. The concentration of tiny marine life known as copepods inside the moon jelly aggregation was as low as a quarter of the levels in other parts of the bay.

Swarms of jellies have been seen more frequently in Puget Sound over the past several decades, and some biologists speculate these fast-growing jellyfish will do especially well in the warmer oceans of the future.

Moon jellies, or Aurelia labiata, are unique among the various jellyfish species inhabiting Puget Sound in that they form vast blooms. When populations spike, they can take over a single bay — creating a dramatic sight.

University of Washington-led research suggests moon jellies are feasting on zooplankton, the various tiny animals that drift with the currents, in the bays they inhabit. This could affect other hungry marine life, like juvenile salmon or herring — especially if predictions are correct and climate change will favor fast-growing jellyfish.

The team, which included researchers at Highline College, Western Washington University and the National Oceanic and Atmospheric Administration, presented this work March 2 as a poster at the Ocean Sciences Meeting.

“These aggregations can contain thousands to millions of individuals, and they can cover a broad range of space,” said lead author Haila Schultz, a UW graduate student in oceanography. “It’s kind of really amazing to see these aggregations when you run into them, oftentimes in protected bays.”