SCIENTIFIC EDUCATIONAL CENTER science idea

Today, the ocean is home to 14 species of baleen whales, including blue whales, which reach a mass of more than 150 tons. These are the largest animals on Earth, and their appetite is appropriate. Filtering water through the horn plates of the "whalebone", they consume several tons of food daily - mainly shrimp and other small marine crustaceans. However, these figures have so far been only approximate, obtained from indirect data.
Only recently, American biologists have completed a multi-year project to more accurately assess the biomass absorbed by whales — and it turned out to be many times more than previously thought. Such quantities make baleen whales key to the functioning of marine biosystems.
Between 2010 and 2019, scientists were able to track the nutrition of a total of 321 baleen whales of seven different species, including blue, humpback, bowhead and striped (fin whales) living in the Pacific, Atlantic and Southern Oceans. The work was dangerous: while on the boats, biologists caught the moment when the animals surfaced for a breath of air. Using long poles, they fixed tags on the whales in the form of strong vacuum suckers, which were held for about a day on average, collecting data using GPS sensors, accelerometer, video and cameras. In parallel, they were shooting with the help of drones, which made it possible to accurately measure the size of the whales themselves.
The work showed that baleen whales consume two to three times more food than was thought. So, one studied bowhead whale ate six tons of zooplankton per day, and another blue whale ate 16 tons each. Extrapolating these figures into the past, scientists calculated that until the populations of huge animals were almost destroyed by whalers, they "wrapped" 430 million tons of krill per year.
This also explains the well-known paradox associated with the disappearance of krill, which has been observed since the second half of the last century. It would seem that after humans destroyed most of the whales (and their numbers fell by more than 80 percent in the twentieth century and continue to decline today), crustaceans should have multiplied in even greater numbers. However, in fact, krill populations have also declined sharply and have not recovered so far. The authors of the new work associate this effect precisely with the huge volumes of biomass that baleen whales absorb.
By transferring nutrients from one part of the ocean to another and from the surface to the depth, sea giants provide suitable conditions for the growth of phytoplankton, small algae that feed on zooplankton. Since humans have practically removed one of the elements of this chain — whales - the entire cycle of nutrient movement has been disrupted. Many important substances — such as iron - simply settle to the bottom and do not return to circulation. Phytoplankton quantities are falling, preventing krill from reproducing on the same scale.
The article was published in the journal Nature
PHOTO: Scientists examine a humpback whale near Antarctica © Duke University Marine Robotics and Remote Sensing, NOAA
Source: naked-science.ru, sci-dig.ru