New study reveals the crucial role of jellyfish in Greenlandic waters

Eye on the Arctic
Posted: Tuesday, August 27, 2024 at 16:18
0 Comments

An atolla jellyfish., a prey of the blue wolffish. “[Jellyfish] play a significant but previously overlooked role in the subarctic food web,”said Annkathrin Dischereit, the lead author of a new study. (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research)

A new study is challenging old assumptions about the role of jellyfish in marine ecosystems and suggests it may be more significant than previously thought.

Scientists have commonly regarded jellyfish as a secondary food source for predatory fish, due to their low energy density and nutritional value, typically consumed only as a last resort or in emergency situations.

But a team of scientists from the Alfred Wegener Institute and the Thünen Institute in Germany has discovered that fish in Greenlandic waters consume jellyfish much more frequently than previously thought.

Their study, published in Royal Society Open Science, suggests the need to reconsider the role of the invertebrates in the broader marine ecosystem, particularly around Greenland.

“It is important that we rethink and understand how jellyfish and gelatinous zooplankton generally fit into marine food webs,” Charlotte Havermans, the head of the ARJEL junior research group at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, said in a statement.

“Our results raise the question of why fish seem to eat jellyfish surprisingly frequently.”

Researchers collecting and photographing gelatinous zooplankton gathered in plankton nets and trawls to compare it with the species found in the stomach contents of fish. (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research)

To conduct the research, the team analyzed the stomach contents of seven fish species, including Atlantic cod and haddock, using DNA metabarcoding. This technique enables researchers to precisely identify the dietary contents of the fish.

“We found DNA of jellyfish in the stomachs of all examined fish species, although in varying quantities,” said Annkathrin Dischereit, the study’s lead author. “For some species like the greater silver smelt and the northern wolffish, jellyfish made up a significant portion of their diet.

“We detected up to 59 species of gelatinous invertebrates in the stomachs of the fish. This clearly shows that they play a significant but previously overlooked role in the subarctic food web.”

Siphonophores, a marine animal made up of different types of small animals that are all connected, was the most important prey for several fish species, including large smelt and haddock. Siphonophores are like jellyfish, but where a jellyfish is one organism, Siphonophores are made up of many, each one which has a specific role in the colony. (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research)

Dischereit noted that jellyfish have likely been overlooked in studies because their tissue is digested quickly, causing them to rarely be recorded as prey.

Climate change expected to drive jellyfish further north

Havermans said more research is needed as it’s increasingly important to understand the role of jellyfish in marine environments, particularly as global warming drives their populations further north, which could significantly impact Arctic ecosystems

“Understanding the role of jellyfish in these ecosystems is crucial,” she said. “We need to collect continuous samples throughout the year and link these to how the gelatinous zooplankton communities change over this period of time.

“The results of our current study raise doubts about how well we understand subpolar ecosystems and how the recently observed increase in gelatinous zooplankton might affect them.”