Whale pee transports thousands of tonnes of vital nutrients around the world’s oceans, study finds

Whales are not just big, they're a big deal for healthy oceans. Whale poo is responsible for moving tonnes of nutrients from deep water up to the surface.

Now new research shows that whales also move vast quantities of nitrogen thousands of kilometres in their urine - a process scientists have dubbed ‘the great whale pee funnel’.

These tons of nitrogen support the health of tropical ecosystems and fish, especially in areas where nitrogen is otherwise in limited supply. In some places, like Hawaii, the input of nutrients from whales is bigger than from local sources.

Whales transport 4,000 tonnes of nitrogen each year to low-nutrient coastal areas

In 2010, scientists revealed that whales, feeding at depth and pooing at the surface, provide a critical resource for plankton growth and ocean productivity.

A new University of Vermont-led study shows that whales also carry huge quantities of nutrients horizontally, across whole ocean basins, from rich, cold waters where they feed to warm shores near the equator where they mate and give birth.

Much of this is in the form of urine, though sloughed skin, dead whale carcasses, calf faeces, and placentas also contribute.

"These coastal areas often have clear waters, a sign of low nitrogen, and many have coral reef ecosystems," says Joe Roman, a biologist at the University of Vermont, who co-led the new research.

"The movement of nitrogen and other nutrients can be important to the growth of phytoplankton, or microscopic algae, and provide food for sharks and other fish and many invertebrates."

The study, published in March in the journal Nature Communications, calculates that in oceans across the globe, great whales - including right whales, gray whales, and humpbacks - transport around 4,000 tonnes of nitrogen each year to low-nutrient coastal areas in the tropics and subtropics. They also bring more than 45,000 tonnes of biomass.

Before the era of human whaling decimated populations, scientists believe these long-distance inputs may have been three or more times larger.

What is the great whale pee funnel?

One major example of this process can be seen in the thousands of humpback whales that travel from a vast feeding area in the Gulf of Alaska to a more restricted area in Hawaii where they breed each year.

There, in the Hawaiian Islands Humpback Whale National Marine Sanctuary, the input of nutrients - tons of pee, skin, dead bodies and poo - from whales is roughly double what is transported by local sources, the team of scientists estimate.

"We call it the 'great whale conveyor belt’," Roman says, "or it can also be thought of as a funnel because whales feed over large areas, but they need to be in a relatively confined space to find a mate, breed, and give birth.”

This means that nutrients spread out over the vast ocean get concentrated in much smaller coastal and coral ecosystems, "like collecting leaves to make compost for your garden," Roman says.

‘An impact on a planetary scale’

In the summer, adult whales feed at high latitudes (like Alaska, Iceland, and Antarctica), putting on tonnes of fat. According to recent research, North Pacific humpback whales gain about 14 kilos per day in the spring, summer, and fall.

They need this energy for their epic ocean journeys. Gray whales travel over 11,000 kilometres between feeding grounds off Russia and breeding areas along Baja California. Humpback whales in the Southern Hemisphere migrate more than 8,000 kilometres from foraging areas near Antarctica to mating sites off Costa Rica.

Once in their breeding spots, whales urinate vast amounts of nitrogen-rich urea. One study in Iceland suggests that fin whales produce nearly 1,000 litres of urine per day when they are feeding. For comparison, humans produce less than two litres of urine daily.

"Because of their size, whales are able to do things that no other animal does. They're living life on a different scale," says Andrew Pershing, one of ten co-authors of the new study and an oceanographer at the nonprofit organisation Climate Central.

"Nutrients are coming in from outside - and not from a river, but by these migrating animals,” he adds. “We don't think of animals other than humans having an impact on a planetary scale, but the whales really do."

Scientists push for increased whale conservation efforts

Before industrial whaling began in the 19th century, the nutrient inputs would have "been much bigger and this effect would've been much bigger," says Pershing.

In the Southern Ocean, blue whale populations are still greatly reduced after intense hunting in the 20th century. The study highlights the importance of pushing conservation efforts to boost populations around the globe.

"Animals form the circulatory system of the planet,” Roman says, “and whales are the extreme example."