This blog continues the discussion about what happens after a whale passes away. Find out more in Part I, here.
What happens to a whale’s body after it dies?
Decomposition begins almost immediately after death and there several processes begin to break down various parts of a cetacean’s body. Autolysis (the process in which cells or tissues are broken down by naturally occurring enzymes), bacterial decomposition, putrification (the process of breaking down proteins and is responsible for organ liquefaction), and fermentation all occur and all produce noxious gases such as CO2, methane, hydrogen sulfide, and ammonia.
Gases accumulate in the body cavity of a deceased cetacean causing, in some cases, extreme bloating. An estimated 3-5 atmospheres of pressure can build inside the whale, equivalent to the pressure experienced diving 40 metres underwater. Eventually, these gases find a means of escaping the body through weak points in the connective tissue, skin, and blubber. This process can occur rapidly, resulting in an explosive event, where gases and organs may be propelled several metres from a whale upon release, or slowly if several points of escape are present.
Once the bloating has ceased, decomposition will continue to occur until all tissue has been broken down and only the skeleton remains.
What happens when a dead whale sinks?
When a floating dead cetacean is no longer bloated, the body usually slips below the surface and falls to the ocean floor, creating a “whale fall.” Almost immediately, scavengers like hagfish, sleeper sharks and amphipods begin to prey on the whale’s flesh, consuming an estimated 40-60 kg a day. Within months, the carcass is stripped down to its skeletal frame.
Soon after, polychaete worms and invertebrates colonize the skeleton, feasting on any organic material contained within the bones. Little is known about many of these creatures, most of whom seem to appear as deep-sea whale fall specialists.
Within a year, most of the organic material is consumed, and bacteria move in to consume fats and oils embedded deep within the bones of the whale. This process releases hydrogen sulfide, which attracts sulfur-loving creatures. At this stage of decomposition the whale fall tends to resemble an active deep sea vent community. One whale fall was found with 190 unique species living on or around it.
Researchers estimate whale falls can be found every 5-16 kilometeres along the ocean floor, a distance that would be easily travelled by marine creatures that rely on whale falls. That said, whale falls have been known to support communities for up to 200 years, eliminating the need for dependent species to travel often.
Although much research still needs to be done to understand the extent of a whale’s legacy after it dies, there is no doubt that through both life and death, cetaceans play a key role in their ecosystems.
If you find a dead, distressed, sick, or injured marine mammal in British Columbia, call the Marine Mammal Response Network immediately at 1.800.465.4336.
Bhatia, A. (2014). What’s the pressure inside an exploding whale?. Wired Magazine online. Retrieved June 10, 2014 from the internet: http://www.wired.com/2014/05/exploding-whale-physics/
Fulton-Bennett, K. (2002). Whale falls—islands of abundance and diversity in the deep sea. Monterey Bay Aquarium Research Institute News. Retrieved June 10, 2014 from the internet: http://www.mbari.org/news/news_releases/2002/dec20_whalefall.html
Perrin, W. F., Wursig, B., & J. G. M. Thewissen (Eds.). (2002). Encyclopedia of Marine Mammals. San Diego, USA: Academic Press. – See more at: http://reffor.us/index.php#sthash.LIAqA6h2.dpuf
Zeidner Russo, J. (2004). This Whale’s (After) Life. NOAA’s Undersea Research Progarm. Retrieved June 10, 2014 from the internet: http://www.nurp.noaa.gov/Spotlight/Whales.htm