In 2010, two researchers in the U.S. demonstrated that whale poop redistributes crucial amounts of nitrogen from deep waters to shallow coastal regions. A new study shows that whale pee plays a similar role, ferrying nutrients horizontally across oceans.
Researchers have discovered that whales carry thousands of tons of nutrients across thousands of miles when they migrate from their cold feeding grounds to warmer mating waters. The majority of this traveling nutrient is in their pee, but dead skin, carcasses, and placentas also contribute to the so-called whale conveyor belt, as detailed in a study published March 10 in the journal Nature Communications.
“Because of their size, whales are able to do things that no other animal does. They’re living life on a different scale,” Andrew Pershing, co-author of the new study and an oceanographer at the nonprofit organization Climate Central, said in a University of Vermont statement. “Nutrients are coming in from outside—and not from a river, but by these migrating animals. It’s super-cool, and changes how we think about ecosystems in the ocean. We don’t think of animals other than humans having an impact on a planetary scale, but the whales really do.”
Whales undertake the longest migration routes of any mammal. For example, humpback whales in the Southern Hemisphere travel over 5,000 miles (8,000 kilometers) from Antarctica to Costa Rica, and gray whales travel nearly 7,000 (11,200 km) miles from Russia to Baja California. The extensive migration patterns of whales including right whales, gray whales, and humpback whales redistribute around 4,000 tons of nitrogen and 45,000 tons of biomass to low-nutrient coastal areas every year, according to the study.
“These coastal areas often have clear waters, a sign of low nitrogen, and many have coral reef ecosystems,” said Joe Roman, a University of Vermont biologist who co-led the study. “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 warm waters where whales travel to mate and give birth are usually smaller regions than their extensive feeding grounds. As a result, their redistribution of nutrients through pee is “like collecting leaves to make compost for your garden,” Roman explained, when we rake leaves across a wide lawn and deposit them in a single garden bed. For instance, humpback whales migrating from the vast Gulf of Alaska to Hawaii deposit nearly twice as many nutrients in the Hawaiian Islands Humpback Whale National Marine Sanctuary as other local physical processes, according to the researchers.
The whale conveyor belt. © A. Boersma & Nature Communications“We call it the ‘great whale conveyor belt,’” Roman added, “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. At first, the calves don’t have the energy to travel long distances like the moms can.”
Furthermore, the study does not account for nutrients redistributed by blue whales, some of the largest animals to ever exist, since many aspects of their behavior remain a mystery to scientists. That means the true amount of nutrients that whales ferry across the world is likely much higher than the researchers calculated—not to mention the amounts they would have redistributed before 20th-century whaling activities decimated many of their populations.
“Lots of people think of plants as the lungs of the planet, taking in carbon dioxide, and expelling oxygen,” Roman said, “For their part, animals play an important role in moving nutrients. Seabirds transport nitrogen and phosphorus from the ocean to the land in their poop, increasing the density of plants on islands. Animals form the circulatory system of the planet—and whales are the extreme example.”
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