Whales and krill fundamental for our planet
New research published today in the journal Nature concludes that giant mammals – such as blue whales, humpback whales, orcas – eat an average of three times more food per year than scientists previously calculated.
Between 1910 and 1970 alone, hunting these mammals wiped out more than 1.5 million specimens in Antarctic waters and their population has not recovered since then, but why is there less and less krill? (crustacean they eat).
Today, a study conducted by Stanford University and published in Nature concludes that the relationship between the disappearance of whales and krill is not only related, but is an example of the extent to which these marine giants are important to marine ecosystems.
“Fifty years after we stopped whaling, we are still learning what impact it has had. The system is not the same,” says Matthew Savoca, a researcher at Stanford’s Hopkins Marine Station and lead author of the work.
To find out why Antarctic krill continues to decline, the researchers wanted to know how much whales eat, and to do so, they collected data from 321 Atlantic, Pacific and Pacific whales between 2010 and 2019. oceans. South.
The whales were tagged with a miniature device – with a camera, microphone, GPS, and an accelerometer that tracks motion – that captured their activity in three dimensions.
The dataset was completed with drone photographs of 105 whales that were used to measure their length and create accurate estimates of their body mass and the volume of water each whale filtered with one shot.
In collaboration with NOAA’s Environmental Research Division and the University of California, Santa Cruz, the researchers also used a device called a depth sounder – which Savoca likens to “a fantastic fish finder” – which uses sound waves at different frequencies to measure the amount of prey there are.
Thus, for ten years, they have collected information on how often whales feed, the amount of prey they consumed and the catches available.
Analysis of the data revealed that Southern Ocean whales eat about twice as much krill as previously thought, and that krill-eating blue and humpback whales off the coast of California eat two to three times. more than estimated. .
From these consumption data, the researchers calculated that in the early 20th century, krill in the Southern Ocean had to be about five times more abundant than it is now in order to feed the whale population at the time.
This shows that whales “play a complex role in their ecosystems and that their decline or recovery is strongly linked to productivity and overall ecosystem functioning,” the authors point out.
Additionally, a second part of the study points out that the Southern Ocean is one of the most productive ecosystems on earth, largely due to the abundance of phytoplankton (microscopic algae) which is a vital food source for krill and a vital tool. for the storage of carbon in the oceans.
By eating krill and defecating, the whales return the iron stuck in the krill to the water, making it available to the phytoplankton, which needs it to survive. Whales have this incredible ability to strengthen the system, the study points out.
We at Myblue4you are very sensitive to the health of the marine ecosystem. Fauna and marine flora are essential for the survival of our species and for the health of our beautiful world. Many whales pass through Panama, we are on their favorite route. Every year, we observe them with extreme attention, with their puppies and their majestic size. They will always be worthy of our seafaring bow.