What makes whales fin-tastic nature champions?

Whales are the largest living creatures on the planet. In fact, blue and fin whales are the two largest animals that have ever existed. But this massive stature is not their only superpower: whales play an important role when it comes to ocean productivity that could, by extension, influence the climate.

Scientists have discovered in recent years that great whales (baleen whales and sperm whales) can have a significant impact on nutrient cycling in the ocean which can indirectly impact planet-heating carbon from the atmosphere.¹ This is critical as climate change is an existential crisis impacting our planet in startling ways from sea to shore.

Whales also have some of the longest migrations of any mammal on Earth. Along these oceanic journeys, or "blue corridors," whales fertilize the marine ecosystems they move through and support the marine life inhabiting them.

Superpower: phytoplankton multiplier

Phytoplankton are microscopic creatures that are mighty carbon sinks in their own right. They are primary producers like trees and grasses, meaning they can convert light energy into chemical energy and food by taking in carbon dioxide from the atmosphere and releasing oxygen. They capture about 37 billion metric tons of carbon dioxide (that's an estimated 40% of all CO₂ produced!) and produce at least 50% of all oxygen in our atmosphere, regulating the climate and the formation of clouds.² This amount of carbon dioxide is four times the amount captured by the Amazon rain forest.³

Phytoplankton are the ocean's gardens and are the foundation of all marine life. Whales have a multiplying effect on phytoplankton numbers wherever they travel. They do this in a couple of different ways:

1. The "whale pump"
   All whales dive underwater to feed and return to the surface to breathe. As whales swim through the water column, they stir up minerals deep in the ocean and bring them to the surface through this vertical movement. They then spread them across the oceans through their migrations in a process known as the "whale conveyor belt." These physical activities essentially fertilize the ocean with the nutrients needed to help phytoplankton grow.
   
   
2. Nutrient-rich waste
   Whale excrement contains iron, phosphorus, and nitrogen, which are substances that phytoplankton need to grow. Whale fecal plumes are 10 million times more iron-rich than the surrounding seawater.⁴ This feeds and nourishes the phytoplankton.

When phytoplankton and zooplankton excrement sinks to the ocean floor, it accounts for 70% of total global carbon export.⁵ Climate change is already a major stressor on phytoplankton, so maintaining this nutrient cycling from whales is critical for ensuring their survival.

Every hero has a villain

There are around 1.3 million whales today, but this number stands in stark contrast to pre-commercial whaling when around 4 million to 5 million whales traversed the high seas.

"While a global ban on commercial whaling has virtually eliminated this threat, whales still face significant threats to their survival," says Leigh Henry, director of wildlife policy at WWF. "This is largely from entanglement in fishing gear and nets, ship strikes, plastic and noise pollution, and climate change." Six out of the 13 great whale species are either endangered or vulnerable.

The big fight

As a migratory species, whales can exert their nutrient-cycling superpower around the globe. To help whale populations recover, the threats impacting their survival must be addressed.

There is growing evidence that whales play a role in the carbon cycle, and there is so much more to discover. They, along with many other valiant marine species, play vital roles in the larger web of life that allows our ocean to thrive, and they need us on the same team, now more than ever. 

Learn more about other wildlife champion nature and fight climate change.

^[1] https://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(22)00279-8
^[2] McCoy, D.T., Burrows, S.M., Wood, R., Grosvenor, D.P., Elliott, S.M., Ma, P.L., et al. 2015. Natural aerosols explain seasonal and spatial patterns of Southern Ocean cloud albedo. Science Advances, 1 (6): e1500157. DOI: 10.1126/sciadv.1500157
^[3] https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0012444#pone-0012444-t001
^[4] Ratnarajah, L., Lannuzel, D., Townsend, A.T., Meiners, K.M., Nicol, S., Friedlaender, A.S., et al. 2017. Physical speciation and solubility of iron from baleen whale faecal material. Marine Chemistry, 194 (20): 79-88. DOI: 10.1016/j.marchem.2017.05.004 
^[5]  Nowicki, M., DeVries, T., and Siegel, D.A. 2022. Quantifying the Carbon Export and Sequestration Pathways of the Ocean's Biological Carbon Pump. Global Biochemical Cycles, 36 (3): e2021GB007083. DOI: 10.1029/2021GB007083.