Jellyfish to thrive in warming arctic waters, study reveals

Jellyfish are one of the few organisms that might benefit from climate change. According to the latest research, cnidarians are already spreading further north, and by the end of the 21st century, they may dominate the waters of the Arctic Ocean.

Progressive climate change negatively impacts many marine organisms. However, jellyfish may benefit from rising water temperatures, especially in the Arctic. Scientists at the Alfred Wegener Institute for Polar and Marine Research (AWI) in Germany published their findings in the journal Limnology and Oceanography.

Researchers used computer modeling to investigate how marine ecosystems will change in the future. They introduced eight Arctic jellyfish species into the simulation and examined how rising temperatures, the retreat of sea ice, and other environmental changes affect their occurrence. The modeling used a climate scenario in which greenhouse gas emissions remain moderate to high.

In the future, gelatinous zooplankton (composed of simple invertebrates such as predatory cnidarians, comb jellies, and filter-feeding tunicates) may be one of the few groups of organisms to benefit from global warming. Numerous studies have confirmed that these animals thrive due to rising water temperatures, overfishing, and excess nutrients in seas and oceans. Combined, these three factors may cause marine ecosystems to be dominated by jellyfish. Many researchers have warned of the impending "gelification of the oceans."

"Climate change may give gelatinous zooplankton an advantage over their food competitors, such as fish. This will affect the entire food web and fish populations," explained the study's lead author, Dmitrii Pantiukhin, from the Arctic Jellies (ARJEL) research group at the Alfred Wegener Institute.

He added that many jellyfish feed on fish larvae and eggs, which can slow down or prevent the recovery of fish populations already dwindling due to global warming and intensive fishing. "The Arctic Ocean is warming the fastest of all the oceans in the world. About 10 percent of the world's fish catch comes from the Arctic," he reminded.

"Anyone interested in the fate of fish should keep an eye on jellyfish," noted Pantiukhin.

During the study, the AWI team combined three-dimensional species distribution models with oceanographic data from the Earth’s climate model (MPI-ESM1.2) developed at the Max Planck Institute (Germany).

"Simulations of species distribution in the ocean are often two-dimensional, like a map. However, jellyfish population sizes depend on water depth. So, we created three-dimensional species occurrence models. By combining them with the Earth's climate model, we calculated how the distribution of the eight main jellyfish species might change by 2050-2099," explained Dr. Charlotte Havermans, head of the ARJEL research group.

The modeling results indicated that the habitats of seven out of the eight studied species could significantly expand towards the North Pole—they will occupy twice as large areas. Most significantly, the habitat of the lion's mane jellyfish (Cyanea capillata) may increase nearly threefold.

Only one species included in the study, Sminthea arctica, would occupy a slightly smaller area than today by the end of the 21st century. Rising Arctic Ocean temperatures would force this jellyfish to retreat to greater depths.

"The predicted expansion of jellyfish habitats could have a huge, cascading impact on the entire food web," warned Dmitrii Pantiukhin.