As jellyfish blooms decay, their remains serve as food for a number of seawater bacteria, contributing and even changing the water column food web.
A team of researchers from Austria, Slovenia, and the Netherlands has observed a new impact of jellyfish blooms - which is becoming a more frequent occurrence - in marine ecosystems. The details of their study are published in the journal Frontiers in Microbiology on Friday, October 30.
The Need to Understand Jellyfish Blooms
"When jellyfish blooms decay, the sinking detritus is likely to be a temporary but significant source of food for marine microorganisms," explains Dr. Tinkara Tinta, research author from the Marine Biology Station Piran at Slovenia's National Institute of Biology. She added that their work shows the organic matter from decaying jellyfish is eaten by fast-growing bacteria, which in turn are eaten by other marine creatures in the column.
Jellyfish blooms, or the rapid increase in jellyfish populations around the world, has been attributed to climate change and the continuous deterioration of underwater ecosystems. Researchers are working to better understand the extent these blooms have on the marine life around them.
"Large jellyfish blooms block cooling intakes of coastal power and desalinization plants, interfere with ship operations, and cause damage to the tourism, fishing and aquaculture industries," explained Gerhard J. Herndl, co-author of the study from the Department of Functional and Evolutionary Ecology at the University of Vienna. He stressed the importance of understanding these blooms, adding that very few efforts focused on the effect of jellyfish detritus on marine ecosystems.
Investigating the Composition of Jellyfish Detritus
Researchers inquired into a detailed composition of a decaying bloom, using samples from Moon Jellyfish (Aurelia aurita), taken from the northern Adriatic Sea - which separates Italy from the Balkans. They then tested how seawater bacteria responded to the detritus as a food source.
Dr. Tinta explains that the microbes that consumed the moon jelly detritus rapidly multiplied in the process, adding that the microorganisms that fed on the jellyfish will then serve as food for planktons, being consumed by other, larger organisms. They also observed that the organic material from the jellyfish detritus in the water column is significantly reduced by a few species of bacteria before reaching the seabed.
On the other hand, Professor Herndl reminds the need for additional studies, despite their work bridging some of the previous gaps about the effect of blooms on food webs in water columns.
A 2018 study from marine biologists at the National Institute of Oceanography and Applied Geophysics and the Arctic University of Norway, Narvik campus also inquired about the marked increase in jellyfishes in different parts of the world - addressing the presence of "much uncertainty" regarding this phenomenon, mainly due to the lack of reliable data.
To help address the issue, researchers provided an overview of online databases that offered data for interested ecosystem modelers. They then summarized how jellyfish species have been characterized in existing ecosystem models, identifying patterns that might be of significant interest for future studies in relation to the increasingly frequent jellyfish blooms.
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