Deep in the North Sea off Norway, a jelly-feast is under way – and it's the last thing researchers expected to find.
Daniel Jones of the National Oceanography Centre in Southampton, UK, and his colleagues lowered dead jellyfish down to the seabed on a platter fitted with a time-lapse camera. Previous observations of large blooms of jellyfish dying suggested that the creatures are so unpalatable that they pile up in heaps called jelly lakes, which slowly rot away. These observations were quite limited, however, so Jones's team wanted to find out if they were reliable.
The time-lapse footage was a revelation. It showed a host of scavengers, including hagfish, crabs and lobsters, tucking into the free meal of dead jellyfish, suggesting that scavengers like eating jellyfish after all. The carcasses were polished off in as little as 2½ hours, with barely a scrap remaining. At the height of the feeding frenzies, more than 1000 scavengers joined the feast, including transparent prawns and tiny crustaceans called amphipods.
"The results were very surprising, as we expected slow bacterial degradation, not rapid scavenging by fish and crustaceans," says Jones.
Jellyfish recycled
The finding is important for modelling the effects of jellyfish blooms
"Our results show that much of this carbon in jellyfish could, in fact, make it into deep-sea food webs, fuelling these systems and increasing the numbers and diversity of fish and seabed creatures," says Jones.
One downside of the discovery, however, is that jelly-falls may not make effective sinks for human-produced carbon emissions as some researchers had thought.
Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2014.2210
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