<p>Although the surface of Antarctica is almost completely white, a field of green and brown algae clings to the underside of the sea ice around the frozen continent.</p>
<p>Previously, this underwater forest of algae was accessible only to marine creatures or specially trained divers. But now, researchers are using pioneering drones to scout out and map the miles of algae mats.</p>
<p>The Antarctic algae begin growing in early spring and rely on the small amount of sunlight that penetrates the ice to survive. They play a key role in the Antarctic food chain by supplying food for krill and other tiny animals.</p>
<blockquote>with a radiometer that measures how much light each clump of algae absorbs. Based on the measurements, scientists can predict the total amount of algae growing under the ice.</blockquote>
<p>The diving drones are 8.2 feet (2.5 meters) long and are shaped like torpedoes. The devices are deployed from holes that the researchers cut into the thick ice using an oil burner and a steam drill. The carefully carved holes also happen to be an ideal entry point for hunting seals, and sometimes, the researchers have to share their space with seals and sea lions that crowd around the heaters set up to keep the holes from icing over.</p>
<p>Algae growing on the bottom of sea ice absorb light at different wavelengths. Each torpedo-shaped drone is equipped with a radiometer that measures how much light each clump of algae absorbs. Based on the measurements, scientists can predict the total amount of algae growing under the ice.</p>