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Krill Paradox: More Whales, More Plankton, More Krill, More Fish.

Whales are not simply a major consumer of krill and fish, but play a critical role in sustaining the very krill and fish populations upon which they feed.


The Importance of Krill on the Food Chain

Krill are small crustaceans that look similar to shrimp and feed on phytoplankton and to a lesser extent zooplankton.


Krill are a vitally important link in the global food chain and are the main staple diet of hundreds of different animals including fish, whales, seals, penguins, albatrosses, petrels, squid and many others. Krill are the basis of the food web in the Southern Ocean around Antarctica and most marine species depend on krill for their survival.


Krill are among the species with the largest total biomass, estimated at around 400 million tonnes. Their daily vertical migration provides food for surface feeders at night and in deeper waters during the day.


The Krill Paradox

Next to man, whales are the largest consumer of small fish and krill. When millions of whales were removed from the ocean by commercial whaling, a huge increase in small fish and krill was expected. But the opposite happened. The loss of whales from the ecosystem caused a substantial loss in the volumes of krill and the fish that feed on them. This contradiction to seemingly valid reasoning became known as the "krill paradox".


The symbiotic whale, phytoplankton and krill loop.

The symbiotic loop relationship  between whales, phytoplankton and krill

The scientific evidence shows that whales increase (not decrease) the volumes of krill by enhancing their phytoplankton food source through faecal fertilisation. This is reported for the largest consumer of krill, the blue whale and the right whale (approximately 411 remaining) both currently endangered due to commercial whaling.


More whales = more nutrients = more phytoplankton = more small fish and krill

Population Biomass: Whales - versus - Krill


Whales are not simply a major consumer of krill and fish, but play a critical role in sustaining the very krill and fish populations upon which they feed.

Simply put: more whales = more nutrients = more phytoplankton = more small fish and krill.


A paper entitled Whales maintained a high abundance of krill; both are ecosystem engineers in the Southern Ocean shows the symbiotic relationship between whales and krill. This is shown in the graph left. The millions of whales killed due to commercial whaling resulted in a substantial decline in krill abundance.


More information about the krill paradox and how whales help the health of our oceans and atmosphere can be found here and at the Great Whales Conservancy.


Krill and Whales Under Threat

According to the U.S. National Oceanic and Atmospheric Administration, Antarctic krill populations have dropped an estimated 80 percent since the 1970s. Precisely why, scientists have not conclusively determined, but loss of sea ice due to ocean warming and commercial whaling is thought to be major factors.


LiveScience reports that the populations of large whales are estimated to have fallen to between 1% and 34%  of their pre-whaling levels. Accordingly, in the North Atlantic Ocean, the nutrient transport ability of whales is 14% of its historical value. In the North Pacific Ocean, just 10% and in the Southern Ocean, a paltry 2%. More detailed information on the Global Nutrient Transport in a World of Giants can be found here.


The Importance of Krill - As a Carbon Sink

According to a 2017 study by the British Antarctic Survey, krill play an important role in the transport of carbon within the oceans. Their movement between different depths can accelerate how atmospheric carbon moves into the deep ocean and can have a major impact on the world's climate.


A 2014 report by the International Union for the Conservation of Nature shows that krill take up 23,000,000 tonnes of carbon each year. That's equivalent to the weight of 15.2 million cars per year. (1.5 tonnes of carbon is equivalent by weight to a large family car). 5 years later, this figure had more than doubled to 35 million cars, as shown in a report published in March 2019 by Ocean Unite.


Peto's Paradox

Another paradox associated with whales and other large mammals is Peto's Paradox. This 2019 study describes how whales defy the cancer odds: Good genes. This research was also reported in Medical News Today.