A magnificent humpback whale, Megaptera novaeangliae, breaches out of the blue waters of the Caribbean Sea.

1192968104

A magnificent humpback whale, Megaptera novaeangliae, breaches out of the blue waters of the Caribbean Sea.

Photo by: Ethan Daniels/Stocktrek Images

Ethan Daniels/Stocktrek Images

Whale and Krill Populations are the Secret to Healthier Oceans

By: Robin Fearon

Oceans rely on their largest species, especially whales, to recycle and regenerate ecosystems. Studies at Stanford University identify the whale as an animal that recharges its own food sources and recycles carbon. Now researchers think they have found a way to seed plankton and krill numbers that will boost whale populations and restore fading sea life.

December 08, 2021

Krill is the chief food source of baleen whales including the blue whale. Reddish in appearance, the tiny crustaceans are swallowed in vast quantities by the whales, sieved out of seawater using the bristly baleen plates in their mouths.

Whales in turn sustain phytoplankton – a vital food source for krill, small fish, and crustaceans – by eating krill and then defecating. This releases iron in the whale’s krill diet back into the water to boost both phytoplankton numbers and krill. Healthy whale populations support the recycling of resources and if numbers drop it has a negative impact.

Krill, Euphausia superba, is an important food source to animals living in the Antarctic.

528711192

Krill, Euphausia superba, is an important food source to animals living in the Antarctic.

Photo by: Roger Tidman

Roger Tidman

Researcher Matthew Savoca of Stanford’s Hopkins Marine Station studied feeding data from baleen whales – blue, fin, humpback, and minke – and found that they eat at least twice as much krill as previously thought. Blue whales can eat up to 16 metric tons per day – with each gulp their mouths can swell to gather up a volume of water larger than their own body.

Using drones to photograph and measure feeding whales, and echo sounders to size up krill swarms, Savoca and his team estimated that before commercial whaling, baleen whales would have eaten around 430 million metric tons of krill each year. By comparison that is more than twice the worldwide annual fish and seafood caught today.

Whale populations are only now recovering from centuries of hunting and re-establishing an essential role in ocean health. But many species including six out of the 13 baleen species are still endangered.

Known as a mating group also called a heat run when then female is moving and being chased by the males.

1171706426

Known as a mating group also called a heat run when then female is moving and being chased by the males.

Photo by: by wildestanimal

by wildestanimal

Baleens were killed on an industrial scale for their meat, oil, and whalebone. The arrival of explosive harpoons and factory ships, which stripped whale carcasses at sea, in the twentieth century massively impacted their numbers. Between 1910 and 1970 around 1.5 million baleen whales were caught and killed in Antarctic waters.

In six decades the blue whale population was reduced from 360,000 to 1,000. After the US banned commercial hunting in 1971 and the International Whaling Commission (IWC) followed in 1982, whale numbers recovered slowly. The IWC estimates there are 1.7 million whales total with between 5,000 and 10,000 blue whales.

Accelerating their recovery should have been a ready over-supply of krill-rich waters, hundreds of millions of tons of their favorite food. Instead, the decline of baleen whales also impacted krill numbers. Factors like climate change and commercial overfishing have further reduced krill populations by 80 percent since the 1970s.

Savoca said the drop-off in whale numbers badly affected all ocean ecosystems including the food they rely on. “Fifty years after we stopped hunting whales, we’re still learning what impact that had. The system is not the same.”

bryde's whale eating small fish,many of bird, whale watching in thailand

1183299798

bryde's whale eating small fish,many of bird, whale watching in thailand

Photo by: boonchai wedmakawand

boonchai wedmakawand

Whales are ecosystem engineers because the way they eat supports the ocean food web. As well as recycling nutrients from krill, they dive to bring nutrient-rich deep water to the surface, and when they bottom-feed they stir up sediments and crustaceans that other species eat. Finally, when they die their carcasses are food for a rich variety of creatures including killer whales, sharks, fish, and ocean floor organisms including invertebrates and bacteria.

All of the whale’s productive input could be realized again, according to the Stanford research group, if phytoplankton and krill are stimulated using one simple input: iron. Adding iron particles, it said, could stimulate plankton blooms, and their growth would, in turn, soak up carbon dioxide and fuel krill populations.

Stimulating krill in areas where whale numbers are recovering would positively boost local food webs and lead them to self-regenerate – a form of rewilding. The team is planning a small, controlled experiment to see if adding precise amounts of ironworks, based on their data showing how much krill whales actually eat.


If they are successful it could begin to mend a hole created by human plundering of one of the ocean’s most important species, restoring some balance. These giants of the sea are responsible for recycling carbon and sustaining ocean food chains. In effect, healthy whale populations make a healthier planet.

Next Up

Manatee’s Cousins Have Vanished from the Ocean

Dugongs, the peaceful ‘sea cows’ of the ocean have been declared functionally extinct in China. The vegetarian mammal has vanished from the coastlines of Asia and Africa.

The Highest Animal on the Food Chain: Megalodon Sharks

The now-extinct megalodon and its ancestors may have been "hyper apex predators," higher up on the food chain than any ocean animal ever known.

How Frogs Boost Their Sex Appeal

Male frogs form ‘boy bands’ to serenade females and woo them into their mating pool.

If A Bat Were To Bite You In Your Sleep, You'd Probably Never Know

Rabies is rare, but most cases are associated with bats.

Coral Reef Survival Relies on Gene Science and Lower Emissions

Coral reefs across the world are under threat as global warming raises sea temperatures and the oceans become more acidic from absorbing carbon dioxide. While nations work to reduce industrial greenhouse gases, including carbon dioxide, helping coral to adapt to changing conditions could provide welcome relief for affected reefs.

99% of Sea Turtles are Now Born Female. Here's Why.

Global warming is creating a crisis in sea turtles' gender ratios, where 99% of them are being born female. Sea turtle populations have been facing a significant population decline further exasperated by climate change.

An Otterly Adorable Awareness Week

Our southern sea otters at Georgia Aquarium are furry, energetic, and (of course) adorable. They spend most of their days swimming, playing, and eating, but most importantly they inspire our guests to care for our world’s waters.

Channel Islands: A Tale of Two Worlds

Channel Islands National Park is one of the least visited national parks in the United States, yet it is only about 20 miles from the coast of Los Angeles and the bustling surf and sand lifestyle of Southern California.

There is Hope for the Future of Polar Bears Threatened by Climate Change

Scientific researchers have recently identified a sub-population of polar bears in southeastern Greenland that survive by hunting on glacial slush. The discovery of their unique behaviors is helping scientists understand the future of this species whose habitats are threatened by climate change.

Two Orcas Are Hunting Great White Sharks in South Africa

A killer whale duo has been killing great white sharks off the Gansbaai coast, causing them to flee the area. These orcas have developed a taste for shark livers, transforming the local marine ecosystem.