Ocean Gardeners: Why Whale Poop Matters Now More Than Ever

Posted on Categories Discover Magazine

Against the backdrop of Southeast Alaska’s glacier-capped peaks, Dana Bloch leans over the side of a small boat and scoops up a clump of orange fecal matter floating in the ocean. “It’s my best sample yet,” she says, peering at the humpback whale poop in her net. “This one’s been feeding on krill instead of fish, so it’s pretty solid.”

Bloch is a fellow with the Alaska Whale Foundation and a graduate student at the University of Alaska Fairbanks. She’s also the first person to study how whale poop affects nutrients in the North Pacific Ocean.

The Significance of Whale Poop

What makes whale poop special? First, there’s a lot of it, since whales are the largest animals on Earth. Second, whales usually feed in deeper water and then poop when they surface to breathe; this cycles nutrients like nitrogen, phosphorus and iron — which naturally sink.

Third, their fecal plumes are buoyant, lingering in the sunny, uppermost layer of water. This means whale poop could help spur the growth of phytoplankton, tiny plants at the base of the marine food web.

“We know whales help in nutrient recycling and they help to maintain healthy oceans,” says Heidi Pearson, a marine biologist at the University of Alaska Southeast and the principal investigator for Bloch’s research project.

Read More: Is an Ancient Whale That Resembles a Massive Manatee the Heaviest Animal Ever?

How a Whale Pump Works

The recycling of nutrients via cetacean poop is called the “whale pump” and has been studied in other parts of the world, too.

In the North Atlantic, for example, researchers Joe Roman and James McCarthy found that whales and seals in the Gulf of Maine may be responsible for adding more nitrogen to the surface each year than all of the rivers combined.

And according to a different study co-authored by Roman, the vertical movement of phosphorus from the deep sea to the surface by marine mammals has been reduced by 77 percent worldwide since whaling drastically reduced cetacean populations.

Whales and Ocean Fertilization

In the Southern Ocean, feces from fin, sperm and blue whales replenish iron at the surface — a necessary ingredient for phytoplankton growth. A 2010 study found that the iron content in the fecal matter of baleen whales there was 10 million times higher than in background Antarctic seawater.

Whale poop likely plays an important role in fertilizing the cold waters of the North Pacific, too. An estimated 1,500 humpbacks migrate to Southeast Alaska every summer to feed, along with gray whales, orcas and other marine mammals.

Traditionally, people assumed the whales depleted fisheries by consuming species like herring — essentially competing with the humans who also fish these waters. Instead, whales may be benefiting the entire ecosystem by creating conditions that encourage fish populations to grow.

“Whales could be, in a sense, gardening by depositing nutrients on the surface,” says Bloch.

Read More: Humpback Whales Are Increasingly Giving Up on Singing

The Whale Pump and Climate Change

To test this theory, Bloch has been collecting fecal samples, usually with the help of a drone. Those samples are put to use in the lab, where Bloch compares how well phytoplankton grow in different types of feces versus plain seawater.

So far, she’s tested samples from humpbacks, harbor porpoises and gray whales. Results are still being analyzed but, “qualitatively, we did see more growth in some of the conditions with fecal matter,” she says.

As climate change intensifies and the water column becomes more stratified into cold and warm layers, “the whale pump may become increasingly important in bringing up nutrients from the deep,” says Pearson.

Read More: The Unique Relationship Between Whales and Dolphins

Why Are Phytoplankton Important?

In addition to boosting nutrients, whale poop may also play a role in sequestering carbon. “There’s this idea that phytoplankton are helping draw carbon out of the atmosphere and sink it into the deep ocean where it won’t return to the surface for thousands of years,” says Pearson.

Some scientists are even attempting to use artificial whale poo to boost both fish populations and phytoplankton growth, in hopes the marine plants absorb more carbon dioxide from the atmosphere.

Pearson co-authored a recent paper that estimates the amount of carbon sequestered by the whale pump. But she cautions that “to fully realize these benefits, we need to be talking about stringent conservation actions that allow whale populations to recover.”

Read More: Killer Whale Matriarchs Are Wise, Generous and a Little Disturbing

Are Whales Endangered?

It’s no secret that the number of whales on the planet right now is a fraction of the number that swam in the seas prior to large-scale industrial whaling.

While the North Pacific humpback whale population may be nearing record numbers, most species are still struggling. Antarctic blue whales represent less than 1 percent of the species’ historic population and northern right whales are on the brink of extinction.

One way to inspire more conservation is to help people “look at whales in a different light,” says Pearson. This includes putting numbers on how much they contribute to ecosystem health through nutrient cycling or carbon sequestration.

Which brings us back to Bloch in her small boat, scooping up bottles full of whale poop. She also hopes the findings will tell us more about how these gentle giants affect the food web, and give us even more reasons to protect whales.

Read More: A New Whale Species Is Fighting For Survival

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