A thousand feet below the Antarctic seas’ surface, a breeding colony of icefish, 60 million active nests across 92 square miles observed during a series of deep dives. Credit... PS118, AWI OFOBS team
As soon as the remotely operated camera glimpsed the bottom of the Weddell Sea, more than a thousand feet below the icy ceiling at the surface, Lilian Boehringer, a student researcher at the Alfred Wegener Institute in Germany, saw the icefish nests. The sandy craters dimpled the seafloor, each the size of a hula hoop and less than a foot apart. Each crater held a single, stolid icefish, dark pectoral fins outspread like bat wings over a clutch of eggs.
Aptly named icefishes thrive in waters just above freezing with enormous hearts and blood that runs clear as vodka. Their blood is transparent because they lack red blood cells and hemoglobin to transport oxygen throughout the body. Icefishes’ loss of hemoglobin genes was less an evolutionary adaptation than a happy accident, one that has allowed them to absorb the oxygen-rich Antarctic waters through their skin.
The sighting occurred in February 2021 in the camera room aboard a research ship, the Polarstern, which had come to the Weddell Sea to study other things, not icefish. It was 3 a.m. near Antarctica, meaning the sun was out but most of the ship was asleep. To Ms. Boehringer’s surprise, the camera kept transmitting pictures as it moved with the ship, revealing an uninterrupted horizon of icefish nests every 20 seconds.