Roman, J., Abraham, A.J., Kiszka, J.J. et al. Migrating baleen whales transport high-latitude nutrients to tropical and subtropical ecosystems. Nat Commun 16, 2125 (2025). https://doi.org/10.1038/s41467-025-56123-2
Whales eat a lot!
Baleen whales are amongst the largest animals on earth. Their size means they need to eat a lot, and in turn that means they need to – well – poop a lot too. It turns out though, that this is a very good thing for the ocean! Recent research has revealed that some of the largest whales—blue whales, fin whales, and humpback whales—can play a remarkable role as nutrient transporters, helping fertilize vast stretches of the ocean and supporting entire ecosystems. Roman’s team focused on one part of this story: the relationship between whale-released nutrients and phytoplankton, the tiny, plant-like organisms at the base of the marine food web. Phytoplankton are not only important because they feed small fish and marine invertebrates—they also help produce much of the oxygen we breathe and absorb carbon dioxide from the atmosphere. That makes the nutrients whales release even more valuable.
These whales undertake extensive migrations, moving nutrients from nutrient-rich polar feeding grounds to nutrient-poor tropical and subtropical breeding areas. This process, dubbed the “great whale conveyor belt,” highlights whales as vital players in ocean nutrient cycles. As they travel across ocean basins, they act almost like long-distance delivery trucks, carrying important nutrients from one ecosystem to another—nutrients that would otherwise remain locked in colder waters.
Moving Nutrients
Roman and their team modelled feeding and breeding grounds using publicly available data. They estimated how many pregnant female whales would migrate from cold, food-rich waters to warm breeding areas, and calculated how much nitrogen each whale might release along the way. This nitrogen comes from sources like urea—a waste substance mammals make to safely remove extra nitrogen through urine—and the placenta, a temporary organ that supports the baby during pregnancy and is released after birth. Both urea and the placenta contain nitrogen, a key nutrient that helps fertilize ocean ecosystems.
The team estimates that migrating baleen whales transport approximately 3,800 tons of nitrogen annually to tropical coastal areas. These nutrients can stimulate the growth of phytoplankton, which forms the foundation of marine food webs and supports diverse ocean life. In regions like the Hawaiian Islands Humpback Whale National Marine Sanctuary, the amount of nitrogen supplied by whales during breeding seasons can be more than is provided by local nutrient sources.
During the summer months, baleen whales—like humpback and gray whales—feed heavily in cold, nutrient-rich waters in places like Alaska and Antarctica. There, they build fat stores to fuel their long migrations. When winter comes, they travel thousands of kilometers to warmer breeding grounds, such as Hawaii and Baja California. In these tropical waters, whales don’t feed—they live off the energy they stored during summer. But even while fasting, they continue to excrete waste, including nitrogen-rich urine, into the ocean. This is important because tropical waters are usually low in nutrients, so the nitrogen that whales release can help fertilize these ecosystems and support marine life like plankton, which form the base of the food web.
Historically, before industrial whaling significantly reduced whale populations, the levels of nutrient transport would have been even higher—potentially three times greater than current levels. Industrial whaling refers to the large-scale hunting of whales for products like oil, meat, and baleen, especially during the 19th and 20th centuries, when many species were pushed to the brink of extinction. The sharp decline in whale populations didn’t just affect whale species themselves—it may have disrupted entire nutrient cycles across the ocean. The decline in whale numbers has likely led to decreased nutrient availability in tropical and subtropical ecosystems, underscoring the importance of whale conservation for maintaining healthy oceanic nutrient cycles.
Ecological engineers
Their role in moving nutrients within the water column in feeding areas (also known as the whale pump) was already well documented, but this research emphasizes their impact on an even larger scale. It highlights how connected marine ecosystems are, and how important large migratory species like baleen whales are to keeping those systems functioning.
Protecting and restoring whale populations not only supports nutrient cycling but also helps maintain the productivity and stability of ocean environments. The more we learn about whales, the more we realize their influence stretches far beyond their immediate surroundings.
I am a post-doctoral researcher at the University of Hawaiʻi at Mānoa. My research interests cover many aspects of the ecology of marine mammals, in particular the factors that drive distribution and abundance of whales and dolphins, as well as the impacts of human activities on these animals. I’ve spent a lot of time in the field, conducting surveys (very lucky). When back at my desk, I use ecological modelling techniques to investigate relationships between animals and their environment.
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