{"id":37108,"date":"2021-12-21T00:05:34","date_gmt":"2021-12-21T08:05:34","guid":{"rendered":"https:\/\/hakaimagazine.com\/?post_type=custom_features&p=37108"},"modified":"2023-11-02T12:22:53","modified_gmt":"2023-11-02T19:22:53","slug":"bone-eating-worms-super-sized-isopods-and-other-surprises-from-dumping-alligators-in-the-sea","status":"publish","type":"custom_features","link":"https:\/\/hakaimagazine.com\/features\/bone-eating-worms-super-sized-isopods-and-other-surprises-from-dumping-alligators-in-the-sea\/","title":{"rendered":"Bone-Eating Worms, Super-Sized Isopods, and Other Surprises from Dumping Alligators in the Sea"},"content":{"rendered":"
\n

This story originally appeared in bioGraphic<\/em><\/a>, an independent magazine about nature, conservation, and regeneration powered by the California Academy of Sciences.<\/p>\n<\/div>\n

One bright morning in November 2018, state biologists in Louisiana loaded three dead and toothy alligators, each more than 1.5 meters long and weighing hundreds of kilograms, into the back of a pickup. The biologists bumped along Louisiana State Route 56, driving the carcasses as far south as one can go before plunging into the marsh at the outer mouth of the Mississippi River.<\/p>\n

Waiting at the end of the road was Craig McClain, a tall, bald, and bearded marine biologist who studies how living things get food at the bottom of the ocean. McClain leads a coastal research institute called the Louisiana Universities Marine Consortium, or LUMCON, that explores life at the interface of land and sea. Its main building hovers over the wetlands on big concrete pilings, driven deep into the muck.<\/p>\n

Coastal Louisiana teems with alligators (Alligator mississippiensis<\/em>)\u2014more than a million of them. They sit, mouths agape, on riverbanks and roadsides; they\u2019re crushed by cars; they swim in canals and bask in the sun on nearby barrier islands. McClain can look out the window at work and sometimes see them swim by. He wondered: what happens when they die? If they died at sea, or were washed out, might they provide food to the strange things that dwell in the depths of the Gulf of Mexico? Are they an important part of deep-sea energy cycles? He conjured up a plan to find out, but to carry it out, he would need dead alligators.<\/p>\n

When big alligators threaten pets, livestock, or humans\u2014charging, biting, eating\u2014the Louisiana Department of Wildlife and Fisheries considers them \u201cnuisance animals,\u201d and sends out hunters to remove them. In October 2018, McClain had asked the department if they could provide him with a few dead gators for an unusual research project. That November morning, he\u2019d gotten the call.<\/p>\n

\u201cThey said, \u2018Hey, we have three alligators for you. Are you prepared for them?\u2019\u201d McClain says.<\/p>\n

McClain\u2019s group unloaded the alligators, wrapped them in thick plastic sheets, and stashed them in a large freezer. They stayed there until February 2019, when the biologists transferred the alligators into another freezer on board the R\/V Pelican, <\/em>LUMCON\u2019s 35-meter research vessel, which houses four laboratories and can support 14 scientists for up to three weeks at sea. McClain\u2019s plan was to motor out into the Gulf to sink the alligators at various ocean locations and depths, to study what happens to their carcasses\u2014a kind of crocodilian burial at sea.<\/p>\n

The idea driving the experiment was simple: if you feed them, they will come. In this case, \u201cthey\u201d were the scavengers that float, swim, burrow, and crawl in the muck at the bottom of the Gulf of Mexico. These scavengers can\u2019t live without food, but because plants and phytoplankton cannot grow in the deepest ocean where there is no light, biologists believe that the organisms found there largely subsist on \u201cfood falls\u201d that drift down in the form of kelp or dead fish and other animals. McClain suspected that decomposing alligators might play a role in feeding the invertebrates that dwell at the bottom of the Gulf of Mexico. Understanding the fate of dead creatures\u2014like alligators\u2014on the seafloor would help to fill gaps in knowledge about both the food chain and the carbon cycle in the ocean depths.<\/p>\n

\"alligator<\/a>

A sunken alligator carcass attracts scavenging isopods in the Gulf of Mexico. Photo by LUMCON<\/p><\/div>\n

McClain\u2019s group was the first in the world, as far as he knows, to sink dead reptiles for research\u2014but not the first to study sunken carrion in the sea. In recent years, biologists have sunk whale carcasses, turkeys, shark craniums, pig carcasses, fish bones, and cow bones\u2014in waters deep and shallow, warm and cold, from California to the Mediterranean, Japan to Antarctica\u2014in order to draw out the exotic scavengers that hide in the deepest ocean and can\u2019t be studied in any other way. \u201cIt\u2019s mind-boggling,\u201d says McClain. \u201cYou can be two or three kilometers deep, and there\u2019s this whole set of animals that are just made to eat whatever carbon comes down.\u201d<\/p>\n

It\u2019s not just a quest for novelty that drives such research. Precise studies of the lives and genes of exotic worms, crustaceans, and other deep-sea denizens have expanded biologists\u2019 ideas about the diversity of marine life and how life evolves in the depths. Recent research<\/a>, for example, indicates that such scavengers emerged as far back as 100 million years ago, during the time of the dinosaurs, likely feasting on the remains of giant marine reptiles like plesiosaurs.<\/p>\n

Findings from food-fall experiments have also supported new hypotheses about how species that live in resource poor environments, like the deep ocean, evolve as their food sources change. Such research, McClain says, may ultimately help scientists better predict how deep marine life will respond to changes in carbon levels due to climate change. \u201cIf we give a little food, what happens? And then we give a little more, what happens then?\u201d he says. \u201cHopefully, we can predict what the losers and winners will be in future oceans.\u201d<\/p>\n

\n

A Waste of Utter Darkness<\/h2>\n

The deep ocean is the largest ecosystem on the planet, with more than half of Earth\u2019s surface submerged beneath at least two kilometers of water. It\u2019s also among the least hospitable to life.<\/p>\n

Indeed, until the mid-19th century, scientists believed that no life could survive at all below a certain depth. There was, they maintained, a \u201cbathymetrical limit to life,\u201d below which \u201cthe conditions became so peculiar \u2026 as to preclude any other idea than that of a waste of utter darkness, subjected to such stupendous pressure as to make life of any kind impossible,\u201d as Scottish zoologist and explorer Charles Wyvile Thomson explained in his 1873 book The Depths of the Sea.<\/em> That limit, according to 19th-century biologist Edward Forbes, resided at precisely 550 meters beneath the surface.<\/p>\n

But even back then, there were clues to the contrary. In 1810, for instance, French naturalist Antoine Risso identified and named a number of new fish species pulled from the bottom of the Mediterranean, including a boa dragonfish (Stomias boa boa)<\/em> caught on a line dropped 1,500 meters down. Based on this and other new finds, Risso introduced the idea of underwater zones, defined by depth, where different creatures flourished. In 1818, explorer John Ross, while scouting the Northwest Passage, found a brittle star wrapped around a kilometer-long sounding line\u2014the first evidence of deep-sea life in the colder North Atlantic Ocean. In the 1860s, engineers retrieved a broken North Atlantic telegraph line from a depth of two kilometers and found colorful corals, brittle stars, and other unusual invertebrates attached, further refuting the idea that life stopped at some set distance below the surface.<\/p>\n

\"boa<\/a>

The dragonfish was one of the first deep-sea animals known to science. French naturalist Antoine Risso named it in 1810. Photo by David Shale<\/p><\/div>\n

It was Thomson, however, who is generally credited with disproving the notion of a sterile, lifeless ocean bottom. From 1872 to 1876, he led an expedition on the HMS Challenger<\/em>, a British warship whose guns had been replaced with laboratories and workrooms. From the boat\u2019s deck, Thomson and his colleagues sank small traps attached to a rope 4.8 kilometers long and pulled up creatures that were, he wrote, \u201cexquisitely beautiful in their soft shades of colouring and in the rainbow-tints of their wonderful phosphorescence\u201d\u2014every bit as diverse and exquisite as fauna found in shallower waters. He dared future scientists to enhance our understanding of these creatures: \u201cTheir mode of life, and their relations to other organisms,\u201d he wrote, \u201cand the phenomena and law of their geographical distribution, must be worked out.\u201d<\/p>\n

\n

The Secret Taxonomy of the Deep<\/h2>\n

In the subsequent 150 years, oceanographers have endeavored to answer Thomson\u2019s challenge. Using increasingly sophisticated technologies, they have unearthed a vast diversity of species and begun to learn how energy moves in the deepest seas. They have learned that sunlight can usually penetrate only a few hundred meters below the ocean surface, which means that nothing living a kilometer underwater can use photosynthesis to turn sunlight into life. They have come to understand that while some surface-dwelling fish, kelp, and zooplankton do die and sink to the bottom, such \u201cmarine showers\u201d provide insufficient nourishment to support the wild diversity of life there. This suggests there must be other pathways for food to travel from the surface to the bottom, which is what experiments based on artificial food falls\u2014like McClain\u2019s alligators\u2014are designed to explore.<\/p>\n

Artificial food falls owe their origin, in large part, to another marine biologist named Craig\u2014Craig Smith, now at the University of Hawai\u2018i. In the 1980s, when Smith was a graduate student at Scripps Institution of Oceanography at the University of California San Diego, he found himself frustrated with how little scientists knew about life in the deep sea. They had discovered a growing catalog of wild species there, but had generated few ideas about how life could subsist in such an inhospitable environment. \u201cWe already recognized that [the ocean bottom] has high diversity, but ecological theory couldn\u2019t explain why,\u201d he says.<\/p>\n

A few years earlier, a navy bathyscaphe\u2014a bulky, self-propelled submersible built to withstand tremendous pressures\u2014had stumbled across a well-preserved whale skeleton off the coast of California, near Santa Catalina Island. Smith speculated that such whale falls might serve as living laboratories that could unlock the secret taxonomy of the deep, and in 1987, he had the good fortune to find one. He was exploring a 1,200-meter-deep undersea canyon with an ROV\u2014a remotely operated vehicle\u2014when he encountered a 20-meter-long whale carcass. Over five dives the following November, Smith and his colleagues identified an assemblage of bacteria, snails, clams, and other fauna, many of which hadn\u2019t been found in the area before or had never been known to science at all. His analysis, published in Nature<\/em> in 1989<\/a>, jump-started a new effort among marine biologists to document and analyze the ecosystems around fallen sea creatures.<\/p>\n