Whales give back… incredibly well

You should know: whales are tremendous givers. What must go, must go well.

The mystery began when a marine biologist, Victor Smetacek, thought something was missing with the phytoplankton-krill-whale food pyramid. He thought, of course, prior to massive whale hunting, the Southern Ocean was simply teeming with whales. Consequently, there must be billion tons of krill if whales were to flourish [1]. After all, a single whale feasts on tons of krill every single day [5].

The problem, however, is that Southern Ocean, centuries ago, has a short supply of iron that a billion tons of krill is unfathomable [1]. Iron, an electron carrier, is a crucial nutrient in photosynthesis. If iron were insufficient, phytoplankton can’t grow, there is less krill, and whales will starve. [5]. It is either the whales get by with a modest dinner or substantial amount of iron must have come from somewhere.

Until a plausible explanation surfaces: whales poop, and that they do it tremendously well. Smetacek was then credited for his “whale poop hypothesis” [1].

Baleen whales’ favorite food is Antarctic krill (Euphausia superba) [8]. Having consumed humongous amounts of krill, a whale defecates a highly concentrated iron-rich deposit, which is, on average, 10 million times as much iron as Antarctic seawater. Nicol’s team validated this by analyzing 27 fecal samples from four species of baleen whales. Huge portion of iron in the poo, indeed, came from the krill [1,2,8].

Great whales – the baleen and sperm whales – are smart enough to poo near the ocean’s surface, just where it is needed [1,4,5]. Sperm whales (Physeter microcephalus) alone in the Southern Ocean sequestered around 400,000 tons of carbon dioxide every year [3], with every individual recycling 50 tons of iron. Rich plumes of iron means phytoplankton bloom, a big dinner for the krill, and viola, a feast for the whales! [1]. Scientists might have overlooked whales for a long time, but now, with great certainty and respect, whales are indeed great ‘recyclers’ [1,3].

Today, there are only around 8,000 whales, compared to an estimate of 200,000 blue whales in the Antarctic alone in the early 1900 [3]. The decimation of great whales to 66 to 90 percent “likely altered the structure and function of the oceans”, according to Joe Roman [4,6,7]. It is not all grim, though. Hope is in line as scientists propose for re-stabilizing our oceans against warming climate through enhanced iron levels. The sound bet? Restore whale populations in the Southern Ocean [5,8].

How? Well, the powerful whale poo speaks for itself.

To know more about whales, visit SeaLifeBase.

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[1] Krulwich, R. (2014, April 5). The power of poop: a whale story. Retrieved from http://www.npr.org/sections/krulwich/2014/04/03/298778615/the-power-of-poop-a-whale-story

[2] Zukerman, W. (2010, April 22). Whale poop is vital to ocean’s carbon cycle. New Scientist. Retrieved from https://www.newscientist.com/article/dn18807-whale-poop-is-vital-to-oceans-carbon-cycle/

[3] Keim, B. (2012, August 9). The hidden power of whale poop. Wired.  Retrieved from http://www.wired.com/2012/08/blue-whale-poop/

[4] Metcalfe, J. (2014, July 7). The incredible thing about whale poop is that it fights climate change. Mother Jones. Retrieved from http://www.motherjones.com/environment/2014/07/incredible-whale-poop-might-help-fight-climate-change

[5] Jenner, M. (2014, August 4). Bottoms up: how whale poop helps feed the ocean. The Conversation. Retrieved from http://theconversation.com/bottoms-up-how-whale-poop-helps-feed-the-ocean-27913

[6] Añonuevo, M. (2014, July 11). Scitech: Whale poop shapes marine ecosystems. GMA News Online. Retrieved from http://www.gmanetwork.com/news/story/369837/scitech/science/whale-poop-shapes-marine-ecosystems

[7] Roman, J., Estes, J. A., Lyne, M., Smith, C., Costa, D., McCarthy, J.,… & Smetacek, V. (2010). Whales as marine ecosystem engineers. Frontiers in Ecology and the Environment 12(7), 377-385. doi:10.1890/130220

[8] Nicol, S., Bowie, A., Jarman, S., Lannuzel, D., Meiners, K. M., & Van Der Merwe, P. (2010). Southern Ocean iron fertilization by baleen whales and Antarctic krill. Fish and Fisheries, 11(2), 203-209. doi: 10. 1111/j.1467-2979.2010.00356.x


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