Millions of Jellyfish Die from “The Blob”

Graphic: Annabel Driussi for Our Daily Planet

By Natasha Lasky, ODP Staff Writer

Julia Parrish, a University of Washington professor, using 20 years of data from citizens who reported on coastal conditions all along the West Coast, found that mass die-offs of sailor jellyfish correlated with “the blob,” a patch of unusually hot ocean waters in the Pacific, according to a new study. Normally, these jellyfish float through the ocean, letting the wind carry them towards new pockets of plankton where they can eat. But the wind can blow them onto the beach, where they become stranded, dry up, and die. Sometimes these mass die-offs can be catastrophic—like in New Zealand in 2006— with millions of jellyfish carcasses lining the country’s west coast. 

Why this Matters: The Blob became prevalent in 2013 when surface waters off the Pacific coast began getting especially warm.  As the ocean continued to warm in 2016, marine life at every part of the food chain suffered mass die-offs, from baleen whales to sea lions. Ironically, ocean warming led to a boom in the jellyfish population, but that led to a larger die-off when ocean conditions after warm winters pushed them to shore.  This drastic change in jellyfish populations could be an omen for what’s to come as oceans continue to warm. Parrish said in a statement, “A changing climate creates new winners and losers in every ecosystem. What’s scary is that we’re actually documenting that change.”

Climate Change “Winners”

The research team found that warming ocean surface temperatures allowed small fish like northern anchovies to have a longer spawning season. This gave the sailor jellies much more food, much earlier in the year, allowing the jellyfish population to increase right before the wind carried them to shore. In other words, these mass-die offs were actually symptomatic of a ballooning jellyfish population during years with warmer ocean waters. This research shows that even species that benefit from global warming may have negative impacts, as other species suffer and more jellyfish end up stranded on our beaches. 

Parrish and her colleagues published their study in the Marine Ecology Progress Series, showing 20 years of sailor jellyfish observations from the United States’ west coast. The Coastal Observation and Seabird Survey Team, COASST, an organization that trains citizen scientists to look for marine birds that have ended up stranded on shore, originally reported these observations. 

In the COASST database, which spans from northern California to the Arctic Circle, the researchers discovered nearly 500 reports of beached sailor jellyfish across 300 beaches. Most die-offs happened in the springtime from 2015 to 2019, and in those years, dead jellyfish covered over 620 miles of continuous coastline. 

This drastic change in jellyfish populations could be a sign of what’s to come.  With increasingly warm winters due to climate change, it could mean big booms and busts for this species of jellyfish, as well as for the fish they eat and the beaches where they blow in and die.

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