But once seafloor scavengers swim and scurry away, the story isn’t over. Scientists aboard deep-sea submersibles have set out in search of whalefall skeletons and even experimentally sunk whale carcasses to predetermined locations to learn more. With enough replications and time, they found that whalefalls undergo successive phases, not unlike a forest ecosystem that changes in composition and size as it matures over decades.
Once defleshed, whalefalls undergo a second phase of colonization by snails, clams, and polychaete worms—some feeding off cartilage and the surfaces of the bone, others burrowing into the apron of sediment around the skeleton, enriched by the organic material leaching off the whale’s blubber and oil. The snails, clams, and polychaetes take months to a few years to consume all that they can, and afterward a third phase begins, which can last decades or more (no one knows because whalefalls have been studied for only 40 years). This presumably final climax stage involves two sets of bacteria living in or on whale bones: anaerobic bacteria that use sulfate in the seawater to digest oil locked in the whale’s bones; and then sulfur-loving bacteria that use the sulfide by-product of the anerobic bacteria to generate energy by combining it with dissolved oxygen.
Sulfophilic bacteria support a variety of true whalefall specialists at this stage, including some mussels, clams, and tube worms that have the bacteria living symbiotically within them, giving them the opportunity to generate their own energy in a world devoid of sunlight. At these depths, whale carcasses give a second life to an otherwise barren, abyssal world.
While the precise duration of these skeletons on the seafloor remains unknown, the upper bounds of some estimates suggest that a single whale carcass can provide up to one hundred years of sustenance. So little is known about the breadth and variation in whalefalls that new discoveries are being made all the time: one is an organism called Osedax—literally, Latin for “bone devouring”—a species of deep-sea worm whose entire life cycle depends on whalefall skeletons. Appearing as pinkish filaments only a few millimeters long covering the surfaces of bone, Osedax does not have a mouth or a gut, just wavy tendrils called palps facing outward. Instead of harboring symbiotic bacteria that use a sulfur-based pathway for decomposing bone lipids, its symbionts are a type of bacteria that mobilize proteins directly from the bone itself by dissolving it, using a tangled mat of bacteria-filled roots burrowed into the bones.
Not all whalefall colonizers are specialists; some are generalists that also make appearances on hot vents and methane cold seeps deep on the ocean floor. The range of the temperatures and environmental settings across these deep-sea habitats has led some scientists to argue that whalefalls, over millions of years, have served as evolutionary stepping-stones for invertebrates living in one habitat to leap to another. This idea remains hotly debated, with little known about all of the species that feast on fallen whales, or how often and where these skeletons are likely to appear on the seafloor.
- Abstract from the book Spying on Whales: The Past, Present, and Future of Earth’s Most Awesome Creatures by Nick Pyenson
Once defleshed, whalefalls undergo a second phase of colonization by snails, clams, and polychaete worms—some feeding off cartilage and the surfaces of the bone, others burrowing into the apron of sediment around the skeleton, enriched by the organic material leaching off the whale’s blubber and oil. The snails, clams, and polychaetes take months to a few years to consume all that they can, and afterward a third phase begins, which can last decades or more (no one knows because whalefalls have been studied for only 40 years). This presumably final climax stage involves two sets of bacteria living in or on whale bones: anaerobic bacteria that use sulfate in the seawater to digest oil locked in the whale’s bones; and then sulfur-loving bacteria that use the sulfide by-product of the anerobic bacteria to generate energy by combining it with dissolved oxygen.
Sulfophilic bacteria support a variety of true whalefall specialists at this stage, including some mussels, clams, and tube worms that have the bacteria living symbiotically within them, giving them the opportunity to generate their own energy in a world devoid of sunlight. At these depths, whale carcasses give a second life to an otherwise barren, abyssal world.
While the precise duration of these skeletons on the seafloor remains unknown, the upper bounds of some estimates suggest that a single whale carcass can provide up to one hundred years of sustenance. So little is known about the breadth and variation in whalefalls that new discoveries are being made all the time: one is an organism called Osedax—literally, Latin for “bone devouring”—a species of deep-sea worm whose entire life cycle depends on whalefall skeletons. Appearing as pinkish filaments only a few millimeters long covering the surfaces of bone, Osedax does not have a mouth or a gut, just wavy tendrils called palps facing outward. Instead of harboring symbiotic bacteria that use a sulfur-based pathway for decomposing bone lipids, its symbionts are a type of bacteria that mobilize proteins directly from the bone itself by dissolving it, using a tangled mat of bacteria-filled roots burrowed into the bones.
Not all whalefall colonizers are specialists; some are generalists that also make appearances on hot vents and methane cold seeps deep on the ocean floor. The range of the temperatures and environmental settings across these deep-sea habitats has led some scientists to argue that whalefalls, over millions of years, have served as evolutionary stepping-stones for invertebrates living in one habitat to leap to another. This idea remains hotly debated, with little known about all of the species that feast on fallen whales, or how often and where these skeletons are likely to appear on the seafloor.
- Abstract from the book Spying on Whales: The Past, Present, and Future of Earth’s Most Awesome Creatures by Nick Pyenson
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