Videos Capture The Strange World Of Deep-Sea Food Chains

This image of a gonatid squid eating a deep-sea bathylagid fish illustrates the old theory that squids and fishes (animals that are easily caught in nets) are the dominant predators in deep-sea food webs.© MBARI

The deep sea is one of the most fascinating, unknown, and downright weird ecosystems on Earth.

Fortunately, marine biologists at the Monterey Bay Aquarium Research Institute are working hard to unravel its mysteries. Recently, they have looked at food webs within the deep sea, including shrimp munching jellies and deep-sea fish eating squid. Their research was published this month in the journal Proceedings of the Royal Society B.

They started by looking at portions of the sea off the coast of central California, from the near-surface right down to 4,000 meters (13,120 feet). In this area alone, they managed to figure out at least 84 different predators and 82 different prey types that engaged in a total of 242 unique feeding relationships.

Many of these recent discoveries are based on 23,000 hours of video filmed by a remote-controlled sub. Best of all, you can check out the highlights of this stunning footage for yourself (below).

Jellies, of all creatures, appear to be one of the most instrumental predators of the deep sea, perhaps as important to the ecosystem as large fish.

“Our video footage shows that jellies are definitely not the dietary 'dead ends' we once thought,” Anela Choy, one of the three researchers leading the project, explained in a statement. “As key predators, they could have just as much impact as large fishes and squids in the deep sea!”

Scientists typically work out deep-sea food chains by collecting creatures, slicing them open, and looking at what’s in their guts. However, this method has its drawbacks. Scientists on this project, therefore, studied their diets by comparing the ratios of various natural elements in the deep-sea animals' tissues, paired with the video footage, to work out the intricate chains of predation.

“This direct approach has never been used systematically before," said co-author Bruce Robison. "Unlike other methods, it involves no guesswork and provides very precise information about who eats whom in the deep sea."

All deep-sea food webs were found to be ultimately fueled by processes in the sunlit surface waters, namely by phytoplankton-based organic matter that laps up the sunlight and produces energy through photosynthesis. These are then ingested by krill and other zooplankton or by gelatinous filter feeders. The web then spreads out with ever-gaining complexity through jellies, fish, squids, and beyond.

This food can also end up on our own dinner plates. Equally, it regularly ends up in the bellies of penguins, albatross, ocean sunfish, leatherback turtles, and all manner of creatures who don’t dwell in the deep sea.

It's a squid-eat-squid world down there, but it sure is interesting. 

This complex food web shows groups of animals (indicated by different colored circles and lines) that were observed eating each other during MBARI remotely operated vehicle dives. Thicker lines indicate more commonly observed predator/prey interactions. © 2017 MBARI



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