Sperm whale poo is ideal phytoplankton fertiliser. During their hour-long dives into the ‘twilight zone’ ocean layer, chasing after squid, the whales’ digestive systems temporarily shut down to save energy.

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When they return to the surface they release a liquid, iron-rich slick which floats at the surface and can stimulate the growth of carbon-fixing plankton.

Each year, sperm whales around Antarctica release roughly 50 tonnes of iron from their deep-sea diet, triggering phytoplankton blooms that capture about 400,000 tonnes of carbon from the atmosphere – enough to offset the carbon released by the whales when they breathe out, making them carbon neutral.

Before commercial whaling, sperm whale waste matter helped capture more like 2 million tonnes of carbon.

This profound impact on other wildlife in the ecosystem has led to sperm whales being described as marine ecosystem engineers.

Hippopotamus rising from a lake.

As well as faeces, the digestive system of sperm whales also produce a substance called ambergris. This is a solid and waxy substance, which gains a sweet, earthy substance as it ages.

It has long been used in perfumes, as well as being served as food or in a medicinal purpose – being considered an aphrodisiac in some cultures, and used to treat a range of ailments by Europeans in the Middle Ages.

Because it is hard to come by naturally, and whaling has mostly stopped around the world, ambergris is worth a fortune when found.


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Main image: A sperm whale swimming in the Atlantic Ocean. © Thomas Haider/Getty

Authors

Dr Helen Scales is a marine biologist, broadcaster and science writer. She is the author of Spirals in Time and The Brilliant Abyss.

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