You’ve heard of the butterfly effect — the idea that a tiny flap of wings can trigger a hurricane on the other side of the world. Now, imagine a whale effect.

Previous studies have found that whale poop helps fertilize the ocean, moving nutrients from deep water to the surface. But new research suggests whale pee might be just as crucial. Every time a whale urinates, sheds skin, gives birth, or even dies, it releases nitrogen, phosphorus, and other nutrients that fuel entire ecosystems — sometimes thousands of miles from where they were first consumed.

Scientists call this the “great whale conveyor belt.” According to a new study led by Joe Roman and colleagues from the University of Vermont, whales transport nearly 4,000 tons of nitrogen each year, acting like migrating fertilizer tanks for tropical and subtropical oceans. But here’s the thing: before industrial whaling decimated their populations, the impact could have been three times greater.

Whale pee is an ocean fertilizer

“Whales are the largest animals ever to exist on the planet, and they have the longest migration of any mammal,” Roman says. It’s clear that they’d have a significant impact. Great whales (a group that includes gray whales, right whales, and humpback) feed in high latitudes like Alaska in the summer and burn these energy reserves on their breeding grounds such as Hawaii.

“They release essential nutrients, such as nitrogen, through their pee, and also via placentas, sloughing skin, and carcasses. These nutrients can then be picked up by marine algae — thousands of miles from where they were consumed,” Roman adds.

To estimate just how much nitrogen whales contribute, the researchers had to get creative. Whales can’t (and shouldn’t) be studied in captivity, Roman emphasizes. Instead, co-author Dan Costa analyzed the urine output of northern elephant seals, a species with similar physiology, to calculate how much nitrogen a whale might excrete daily. Their results were staggering: migrating gray, humpback, and right whales transport an estimated 3,784 tons of nitrogen per year.

What does this mean for ecosystems?

This natural fertilization process is particularly important in tropical and subtropical waters, where nutrients are often scarce. In places like Hawaii, the nitrogen transported by whales can exceed the amount brought in by natural physical processes, such as ocean upwelling.

“It depends on the area,” Roman says. “Low-nutrient systems, like Hawaii or the Caribbean likely show the biggest impact.”

This study shows that oceans could be even more connected than we thought. There’s a nutrient “highway” in the oceans that supports ecosystems through a delicate balance of inputs and outputs. Without a steady influx, marine food webs struggle — algae grow more slowly, fish populations decline, and entire ecosystems become less productive.

In this system, whales act as living pipelines. By moving nutrients across vast distances, whales don’t just sustain themselves — they engineer entire ecosystems, making the ocean richer, more resilient, and more capable of supporting life.

“Beyond urine, whale carcasses also serve as nutrient deposits. When a whale dies, its massive body sinks to the ocean floor, creating a ‘whale fall’ — an event that supports entire deep-sea communities. Scavengers like sharks, hagfish, and deep-sea invertebrates feast on the remains, recycling nutrients back into the ecosystem.”

Whaling could have been even more damaging than we thought

Commercial whaling, which peaked in the 19th and 20th centuries, drastically reduced populations of whales. Without realizing it, whalers severed this natural nutrient flow. Scientists estimate that before industrial whaling, whales transported over two times more nitrogen.

The loss of whales and other large migratory animals, such as bison, cut off these nutrient corridors, affecting everything from phytoplankton to scavenging sharks in the sea, to grasslands and rivers on land. Commercial hunting was a vast, and tragic experiment.”

But there is hope. Humpbacks are a great success story, Roman says. “Now that they’re back, these arteries have been revived, a beneit for tropical ecosystems and the many animals and plants that live there.”

As whale populations hopefully continue to recover, scientists are optimistic that these migratory giants will restore their role in shaping marine ecosystems. Whales aren’t just passive ocean wanderers. They’re ecosystem engineers, shaping marine environments in ways we are only beginning to understand.

The study was published in Nature Communications 10.1038/s41467-025-56123-2.