Dead Or Alive?

Whale Falls: The Basics

Written by Helena Milazzo

Founder and CEO of LegaSea Ecology LLC Learn More About Helena

September 23, 2022

What are Whale Falls?

Whale Falls are a deep ocean phenomenon that occur when a whale dies and its carcass sinks to the ocean floor, attracting a community of species that feed off of everything, from the tissue down to the bone [1] 1.Haag, A. Whale fall. Nature 433, 566–567 (2005).. The first whale fall was discovered by Woods Hole Oceanographic Institution’s deep sea vehicle (DSV) Alvin when they came across an entirely intact skeleton of a 20 meter long whale at 1,240 meters on the seafloor [2] 2. Smith, C. R., Kukert, H., Wheatcroft, R. A., Jumars, P. A. & Deming, J. W. Vent fauna on whale remains. Nature 341, 27–28 (1989)..

Since the first discovery in 1987, it has been determined that whale falls generally tend to accumulate along migratory paths [3] 1.Haag, A. Whale fall. Nature 433, 566–567 (2005)., with the greatest number of whale falls between Alaska and the Gulf of California with one whale fall every 300 kilometers [4] 2. Smith, C. R., Kukert, H., Wheatcroft, R. A., Jumars, P. A. & Deming, J. W. Vent fauna on whale remains. Nature 341, 27–28 (1989)..

Evidence suggests that organisms that gather at whale falls are incredibly unique. In fact, 28 macrofaunal species were first discovered at whale falls and only 7 of those originally discovered exist elsewhere [5] 5. Smith, C. & Baco, A. Ecology of whale falls at the deep-sea floor. Oceanogr. Mar. Biol 41, (2003).. This finding also suggests that some of these organisms are whale fall specialists, meaning they rely upon and only exist in this ecosystem.

While there are organisms unique to whale falls, they share 11 species with hydrothermal vents and 20 species with cold seeps [6] 5. Smith, C. & Baco, A. Ecology of whale falls at the deep-sea floor. Oceanogr. Mar. Biol 41, (2003).. This has lead scientists to believe that whale falls potentially act as evolutionary stepping stones for certain species moving down the continental slope towards deep sea vent and seep communities [7] 5. Smith, C. & Baco, A. Ecology of whale falls at the deep-sea floor. Oceanogr. Mar. Biol 41, (2003)..

Decomposition Stages of a Whale Fall

Whale fall communities are the perfect example of zero-waste living, as not a single part of the whale carcass remains unconsumed. Certain species will go as far as extracting fats from the inside of the whale bone! Let’s walk through each phase of whale falls; their communities, duration, and importance to the decomposition process.

First is the mobile-scavenger stage. In this phase soft tissue is removed from the carcass of the whale by dense aggregations of large, active necrophages, which are organisms that obtain their nutrients from decomposing carcasses (think vultures of the oceans) [8]8. Smith, C. R., Glover, A. G., Treude, T., Higgs, N. D. & Amon, D. J. Whale-Fall Ecosystems: Recent Insights into Ecology, Paleoecology, and Evolution. Annual Review of Marine Science 7, … Continue reading. Some examples of necrophages are lithodid crabs (king crab), amphipods (varying crustaceans), Macrourid fish, small lyssianasids, Epatatgetus deani (Hagfish) and, on occasion, Somniosus pacificus (Pacific Sleeper Shark) [9] 9.Smith, C., Baco, A. & Glover, A. Faunal succession on replicate deep-sea whale falls: Time scales and vent-seep affinities. Cahiers de Biologie Marine 43, 293–297 (2002).. This stage can last anywhere between 4-5 months or 1-2 years depending on the size of the carcass [10] 5. Smith, C. & Baco, A. Ecology of whale falls at the deep-sea floor. Oceanogr. Mar. Biol 41, (2003)..

Following the mobile-scavenger stage is the enrichment-opportunistic stage. Once the soft tissue of the whale carcass is gone and a majority of the necrophage organisms leave, they are replaced by dense assemblages of heterotrophic macrofauna, specifically polychaetes and crustaceans, which respond to the organically rich sediment surrounding the mostly stripped skeleton [11]8. Smith, C. R., Glover, A. G., Treude, T., Higgs, N. D. & Amon, D. J. Whale-Fall Ecosystems: Recent Insights into Ecology, Paleoecology, and Evolution. Annual Review of Marine Science 7, … Continue reading. The polychaetes form white bacterial mats that resemble a white grass turf [12] 5. Smith, C. & Baco, A. Ecology of whale falls at the deep-sea floor. Oceanogr. Mar. Biol 41, (2003).. The enrichment-opportunistic stage can last from 4 months to 1.5 years on the seafloor [13] 5. Smith, C. & Baco, A. Ecology of whale falls at the deep-sea floor. Oceanogr. Mar. Biol 41, (2003).. It is also during this stage that organisms begin to dig into the lipid rich bones of the whale skeleton. Whale bone lipids can make up between 5-8% of the whale’s total body mass; in a whale that weighed 36,000 kilograms there may be up to 2,000-3,000 kilograms of lipids [14] 5. Smith, C. & Baco, A. Ecology of whale falls at the deep-sea floor. Oceanogr. Mar. Biol 41, (2003).!

Next is the suphophilic stage which is the most ambiguous phases of all and can last anywhere from 2 to 51 years [15] 5. Smith, C. & Baco, A. Ecology of whale falls at the deep-sea floor. Oceanogr. Mar. Biol 41, (2003).. During this stage chemolithoautotrophs (microbes that utilize chemosynthesis) colonize the bones and sediments as sulfide is emitted from the anaerobic tissue decay. This in turn fosters free-living or endosymbiotic bacterial methanotrophs (bacteria that feed on methane) [16]8. Smith, C. R., Glover, A. G., Treude, T., Higgs, N. D. & Amon, D. J. Whale-Fall Ecosystems: Recent Insights into Ecology, Paleoecology, and Evolution. Annual Review of Marine Science 7, … Continue reading. Macrofaunal communities during the suphophilic stage are large and can exceed 30,000-40,000 individuals [17] 5. Smith, C. & Baco, A. Ecology of whale falls at the deep-sea floor. Oceanogr. Mar. Biol 41, (2003).!

The final step of whale fall decomposition is the reef stage and it is the least understood stage of all, primarily due to how difficult it is to conduct any sort of research due to the suphophilic stage’s potentially long duration.

I hope you have enjoyed this brief overview of what I consider one of the most interesting phenomena of the deep sea! If you’re interested in learning more, make sure to head over to our Youtube channel @LegaSeaTV to watch our series on whale falls. If you have any questions or would like to learn more about individual aspects of this topic do not hesitate to leave a comment on one of our videos or reach out directly by emailing helena@yourlegasea.com. Catch you next time!

 

 

Helena Milazzo
Helena Milazzo

Founder and CEO of LegaSea Ecology LLC

Learn More About Helena

References

References
1, 3 1.Haag, A. Whale fall. Nature 433, 566–567 (2005).
2, 4 2. Smith, C. R., Kukert, H., Wheatcroft, R. A., Jumars, P. A. & Deming, J. W. Vent fauna on whale remains. Nature 341, 27–28 (1989).
5, 6, 7, 10, 12, 13, 14, 15, 17 5. Smith, C. & Baco, A. Ecology of whale falls at the deep-sea floor. Oceanogr. Mar. Biol 41, (2003).
8, 11, 16 8. Smith, C. R., Glover, A. G., Treude, T., Higgs, N. D. & Amon, D. J. Whale-Fall Ecosystems: Recent Insights into Ecology, Paleoecology, and Evolution. Annual Review of Marine Science 7, 571–596 (2015).
9 9.Smith, C., Baco, A. & Glover, A. Faunal succession on replicate deep-sea whale falls: Time scales and vent-seep affinities. Cahiers de Biologie Marine 43, 293–297 (2002).

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