Scientists Dropped Three Alligator Carcasses to the Bottom of the Ocean, and Were Amazed by How Deep-Sea Creatures Reacted

Scientists who dropped alligator carcasses onto the ocean floor to see how deep-sea creatures would respond were surprised to find the reptiles were devoured within hours. The experiment also led to the team discovering a new species of worm.

American alligators, which are often found dead and alive on beaches and in coastal surf of their respective habitats, can sometimes end up offshore if they are carried along by a storm or hurricane, the authors explained in the journal PLOS One. So, the team wanted to find out if alligators could be a source of food for struggling benthos, or organisms which live on or near the seabed.

At such depths where there is no light, these creatures can't rely on the same processes to feed themselves as other animals. Study co-author River Dixon, a PhD Fellow in the McClain Lab at the University of Louisiana-Lafayette, explained to Gizmodo: "In the deep-sea, there is no light, so there is no photosynthesis.

"This means that the typical organisms that form the base of a food web, plants or plant-like organisms called phytoplankton in marine systems, are not present. Instead, food for animals in the abyss arrives via what we call 'marine snow,' aggregations of bits of decaying animals, faeces, and other detritus raining down from the overlying waters."

In the past, other researchers tried seeing how wood, plants and whales might help out the hungry deep-sea organisms. Building on that work, the authors of the new PLOS One study placed three American alligator carcasses around 2,000 meters deep (1.24 miles) along the continental slope of the northern Gulf of Mexico.

They expected the alligators' tough hide would stop scavengers from gobbling up the reptile's soft tissue. Instead, the organisms started eating one 198.2 centimeter (78 inch) alligator weighing 29.7 kilograms (65 pounds) 43 hours after it landed on the sea bed. After 51 days, the soft tissue of another alligator, 175.3cm (68in) and 19.5kg (42.9lbs), was totally gone.

Giant isopods were found nibbling the alligator remains, as well a fish known as a Macrouridae, and a type of crustacean known as an amphipod. The team also discovered a new species of bone-eating worm, which they haven't yet named. These creatures of the Osedax genus appeared as a sediment on the bones of the alligator.

Dixon explained to Gizmodo that Osedax feed on the fats inside the bones of many animals. These worms have never been spotted eating an alligator carcass, and this study also marks the first time these worms have been found in the Gulf of Mexico, the website reported. More tests are needed to confirm if the species only eats reptiles, or other animals in the Gulf, said Dixon.

A third alligator, measuring 172.7cm (68in) and 18.5kg (40.7lbs), "was missing completely after 8 days," the team wrote. The weight and harness used to deploy the body was found around 8m (26ft) away, and marks in the sea bed suggested its remains had been dragged away by a shark.

Dixon said the dimensions of the carcass made it "quite unwieldy." Therefore, "whatever did that had to be huge," he said.

"With some calculations we were able to figure out that the bite strength needed to cut cleanly through our rope was consistent with that of a large shark." The culprit is thought to be a Greenland or sixgill shark, which are capable of gobbling up an alligator whole.

Study co-author Clifton Nunnally, a
research scientist at Louisiana Universities Marine Consortium, told Newsweek:
"This study is significant because it emphasized that large food parcels are rapidly consumed in the food-limited deep sea."

He said the study also revealed that food parcels like the alligators "have many different fates, some slowly spread among scavenger communities, some existing long enough to support zombie worms and some that goes almost completely to a single individual."

Nunnally concluded: "Like much other deep-sea research it tells us that we have much to learn. Importantly it reinforces our ideas of competition for rare resources (food) in the deep-sea; reminding us that large or small food delivered to the ocean floor is quickly, efficiently and thoroughly utilized.

This article has been updated with comment from Clifton Nunnally.

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Scientists Dropped Three Alligator Carcasses to the Bottom of the Ocean, and Were Amazed by How Deep-Sea Creatures Reacted | Tech & Science