But the whales not only eat the krill; they also benefit them: whale excrement fertilises the ocean, since the nutrients it contains – like iron, which is comparatively sparse in the Antarctic – are essential for the growth of phytoplankton (microalgae) in the water. In turn, phytoplankton is a food source for the krill. “When the whale population grows, the animals recycle more nutrients, increasing the productivity of the Southern Ocean. This boosts the growth of algae, which for their part absorb carbon dioxide from the atmosphere through photosynthesis, reducing the atmospheric CO2 concentration,” Bettina Meyer explains.
The recovery of the fin whale stocks seems to be a trend: one year after the Polarstern expedition, the whale research team and the BBC returned to Elephant Island with a chartered ship and observed up to 150 animals. “Even if we still don’t know the total number of fin whales in the Antarctic, due to the lack of simultaneous observations, this could be a good sign that, nearly 50 years after the ban on commercial whaling, the fin whale population in the Antarctic is rebounding,” says Bettina Meyer.