Scientists surveying the submerged Macquarie Ridge, which stretches from New Zealand almost to the Antarctic Circle, have discovered a water world teeming with life. Tens of millions of starfish-like creatures live on an underwater mountain dubbed “Brittlestar City,” whose unique shape and location make it possible for these animals to survive in such crowded conditions.

Scientists affiliated with the Census of Marine Life found hundreds of brownish brittlestars living arm tip to arm tip in each square yard of the seamount’s flat top, about 2,500 feet above the ocean floor and 300 feet below the ocean surface. Larger orange-red brittlestars (shown in photo) cling to the seamount’s flanks, and fish hide below rock ledges and in the folds of coral. Aboard a ship operated by New Zealand’s National Institute of Water & Atmospheric Research, the scientists “flew” a towed imaging system over the seamount to capture photos and video of the animals and their home.

A massive ocean current, known as the Antarctic Circumpolar Current, swirls clockwise around Antarctica. The current passes over Brittlestar City at a brisk speed of about 2.4 miles per hour. To catch a passing meal, the filter-feeder brittlestars simply lift their arms. The current also helps protect the brittlestars from fish and other predators.