The Great Whales in the Fight against Climate Change

Our oceans are among the systems most affected by Climate Change. With rising of carbon dioxide (CO₂concentrations, rising temperatures, and acidification increase (due to the drop of the oxygen O₂sea levels have risen, leading to an increased risk of flooding in coastal communities, inducing other types of impacts.

To combat Climate Change, one of the big problems is finding effective ways to lower levels of CO₂Still, even if the solution to this situation is found, the problem arises in finding funds to support the costs. However, the simplest solution was always in front of us: increasing the world's whale populations.

Commercial whaling has drastically reduced the number of the world's whale populations, with researchers estimating that populations are now down to ¼ of what they were. Therefore, the benefits that Great Whales could be providing us are far less than they could be had it not been for whaling.

Great Whales include all species of Baleen Whales and Sperm Whales. Throughout their lives, these animals accumulate carbon in their large bodies, bodies that are abundant in fat and protein. Each whale can retain, on average, about 33 tons of CO₂. When these animals die, they sink, taking all the carbon absorbed in their lives to the ocean floor, which is trapped for centuries. Whale carcasses, in addition to retaining carbon, on the seafloor they can provide habitat and food for other organisms.

When looking for food, whales can influence the physical environment of the oceans through their vertical movement – diving and emerging – in the water column. This vertical movement, called the "Whale Pumpcan increase the upward transport of minerals and nutrient-rich deep waters. Although baleen whales often feed near the surface of the water, they sometimes dive a little deeper to find denser zones of fish and invertebrates.

Sperm whales, on the other hand, as they feed exclusively on prey from the ocean floor (e.g., giant squid), are constantly performing a vertical movement. This way the transfer of nutrients that occurs in the "Whale Pumpis simplified by feeding in depth and releasing faeces to the surface of the water. The faeces released by these animals are rich in iron (Fe) and nitrogen (N), which are two essential elements in phytoplankton fertilization, increasing photosynthesis and, therefore, carbon fixation.

On the other hand, there is also a horizontal movement called the Great Whales Conveyor Belt. This horizontal movement is due to the migration that these whales make through the ocean, transporting nutrients from high latitudes –high productivity zones (feeding areas) – to low latitudes – low productivity zones (breeding areas). Nutrients are transported through urea and faeces, which are rich in Fe and N.

This transfer of nutrients carried out by the Whale pump and the Great Whales Conveyer Belt, acts as a phytoplankton fertilizer. With the increase in phytoplankton production, there is an increase in carbon fixation, an increase in water productivity and, consequently, a greater abundance of prey. Therefore, phytoplankton plays an important role in this nutrient chain. These organisms contribute at least 50% of oxygen to the atmosphere and capture on average 40% of the carbon dioxide produced.

Although the contribution of Great Whales to the fluxes of carbon and nutrients is not very large, the continued recovery of these animals can help to control marine ecosystems, and their effect on nutrient levels can be important for the functioning of ecosystems (local and regional) and can increase the productivity of feeding and breeding areas.

This way, we can conclude that this solution of increasing whale populations would not only benefit marine life, but also terrestrial life, including our own.

This article was written by the biologist Gina Salazar of Picos de Aventura team.

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