"I have never seen so many whales in one place and I was totally fascinated by watching these huge groups eating," says Bettina Meyer, a biologist at the Helmholtz Centre for Polar and Marine Research in Bremerhaven. The researcher and her team saw up to 70 fin whales at the same time while hunting krill around Elephant Island in the Antarctic Weddell Sea: one of the largest accumulations of the second largest marine mammal species on Earth after the blue whale, as the team reports in "Scientific Reports". A follow-up expedition even counted up to 150 of the large whales at this location when feeding.
The working group originally wanted to investigate how climate change affects the Antarctic krill. The small crabs are quite far down in the food chain; However, their mass deposits feed large whales such as seals or seabirds. If your number shrinks through the warming or catch, this has a negative impact on many other species.
In addition, the participants also counted the local large whales on their helicopter flights. In total, they sighted 100 fin whales, mostly in smaller groups of up to four animals. But on two occasions near the Elephant Islands they observed large gatherings of the animals with 50 and 70 individuals. For Meyer and Co, this is a sign that the stocks of fin whales have finally recovered since the hunting stop in 1976. "Even if we do not know the total number of fin whales in Antarctica due to the lack of synchronous observations, it could be a good sign that the fin whale population is recovering, " says the biologist.
The whales not only eat the krill, they use it and the entire ecosystem: the feces of the whales fertilizes the ocean, because the nutrients contained therein such as the iron hardly existing in antarctic waters are vital for the growth of the phytoplankton. Phytoplankton, in turn, forms food for krill. »When the whale population increases, the animals recycle more nutrients and as a result the southern Ocean can become more productive. In this way, more algae can grow from the atmosphere through the photosynthesis of carbon dioxide and thereby lower the CO2 content in the atmosphere, «says Meyer.
