▎ WuXi AppTec content team editor
Blue whales are one of the largest creatures on Earth, and recently, scientists at Stanford University discovered that these "big stomach kings" are more eatable than previously thought, eating on average three times more food per year than researchers previously estimated! As the largest known animal in the world today, blue whales can eat an average of 16 tons per day during their feeding period. In addition, several baleen whales, such as the North Pacific humpback whale and the fin whale, can eclipse up to 9 tonnes and 8 tonnes respectively during the feeding period.
By underestimating their "appetite," people may have previously underestimated the importance of these marine behemoths to the health and productivity of marine ecosystems. For example, the decline in the number of baleen whales in the Southern Ocean caused by whaling will lead to a decline in the number of krill, their main food. By restoring whale populations, in addition to increasing the productivity of the oceans by influencing the cycle of nutrients, it will also make a huge contribution to global carbon emission reduction.
▲The relevant research was published in the famous academic journal Nature
Between 1910 and 1970, about 1.5 million baleen whales in the Southern Ocean were killed by humans, severely disrupting marine ecosystems. "50 years later, we're still learning what effect this behavior has had." Dr. Matthew S. Savoca, lead author of the paper, explains, "We are looking at how we can use this information to understand the impact of whale populations on marine ecosystems. We hope that this will bring benefits to biodiversity conservation, fisheries production, carbon emission reduction and so on. ”
However, some basic biological problems related to whales need to be addressed first. For example, how much do they eat per day? Top predators directly affect the living structure of their prey, which in turn indirectly affects ecosystems.
Image source: wikipedia, CC BY anim1754, Author: NOAA Photo Library
To accurately calculate their food intake, the team used data from 321 whales from seven species in the Atlantic, Pacific and Southern Oceans, including blue whales, humpback whales, fin whales, bowhead whales, right whales, Antarctic minke whales and Brucellow whales.
The researchers tracked the whales from 2010 to 2019 using electronic tag devices that resemble "miniature smartphones" attached to the backs of the whales (functions including cameras, microphones, GPS locators, and motion trackers, among others), and used drone photographs to assess the whales' body length and mouth size, and to accurately estimate the amount of food they could swallow at a time, while assessing the number of prey near them through a small boat equipped with an echo detector to calculate the amount of food that could be caught.
Researchers used a variety of methods to accurately estimate whale food intake (Image source: Reference[1])
The study found that baleen whales, which mainly feed on krill, eat 2 to 3 times more than previously expected. Whales, who use fish as their main food source, eat about the same amount as previously estimated. In addition , most whales eat intensively for only about 100 days of the year , mainly during the summer breeding season. For example, blue whales eat an average of 16 tons a day during their feeding period, and they eat about 1600 tons a year.
Based on this information, the researchers further deduced that before whaling, the southern ocean krill population density was about 5 times that of now, which means that whales play a complex role in their ecosystems. Changes in whale populations are closely related to the productivity and function of the entire marine ecosystem. ,
▲ There is a correlation between food density and the amount of food required by whales, which require more krill to get the same energy than fish (Image: Reference[1])
The oceans are among the most productive ecosystems on Earth, and the researchers note that restoring whale populations restores ocean productivity, thereby increasing the amount of carbon dioxide absorbed by phytoplankton. Phytoplankton are an important food source for krill, small fish and crustaceans. By eating krill and excreting, whales release the iron locked in the krill back into the water, providing the phytoplankton with the iron they need to survive. It is estimated that baleen whales in the Southern Ocean before whaling could circulate 12,000 tons of iron per year, compared with 1,200 tons today.
Pre-whaling whale populations are estimated to increase marine productivity by about 11 per cent in the Southern Ocean through trophic cycling and reduce the amount of carbon uptaken and stored by marine ecosystems and organisms by at least 215 million metric tonnes, with the potential to lead to cumulative carbon reduction benefits over the years.
Dr Nicholas D. Pyenson, one of the paper's authors, concluded: "Our findings suggest that, in terms of scale, whales' impact on global productivity and carbon reduction may be comparable to that of forest ecosystems across continents. And if we restore whale populations to pre-20th-century levels, we will restore much of the lost function of marine ecosystems and provide a natural climate solution. ”
Resources:
[2] Researchers Find Whales Are More Important Ecosystems Engineers Than Previously Thought. Retrieved November 3, 2021, from https://news.stanford.edu/press-releases/2021/11/03/researchers-findles-eat-expected/
[3] World's Largest Whales Eat More Than Previously Thought, Amplifying Their Role As Global Ecosystem Engineers. Retrieved November 3, 2021, from https://phys.org/news/2021-11-world-largest-whales-previously-thought.html
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